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1. Introduction
Solanum macrocarpon L. is a tropical perennial plant from the Solanaceae family. Known in Vietnamese as “cà pháo” and in English as the “Vietnamese white eggplant,”. This species is notable for its rich nutritional profile and pharmacological properties, making it an important component of traditional medicine and diets in many tropical regions, particularly in West Africa (Chinedu et al., 2011). With beneficial phytochemical compounds, such as tannins, alkaloids, phytates, phenols, saponins, flavonoids, and steroids (Edeoga et al., 2005; Sood et al., 2012), S. macrocarpon is a potent natural antioxidant with diverse biological activities, protecting the body from the harmful effects of free radicals and diseases related to inflammation, cardiovascular issues, and cancer.
In West Africa, S. macrocarpon is cultivated as a fruit-bearing plant and serves as a significant food source in the form of leafy vegetables, contributing to the daily diet of local populations. The leaves are considered a valuable nutritional source, rich in protein, fats, fiber, calcium, and zinc (Oboh et al., 2005). These leaves are commonly prepared in dishes, such as soups and stews, providing essential nutrients for the body. Additionally, other parts of the plant, including flowers, fruits, and seeds, have valuable applications in agriculture and pharmaceuticals.
The morphological characteristics of S. macrocarpon are diverse, spanning from its leaves to flowers, fruits, and seeds, creating a rich and valuable ecosystem (Fig. 1). The leaves range from 10 to 30 cm in length and 4 to 15 cm in width, with an oval shape and undulating margins, growing alternately along the stem. The flowers are clustered in small inflorescences containing 2-7 flowers, with a diameter of about 3-8 cm. The flowers in the lower part of the inflorescence are typically hermaphroditic, while those in the upper part tend to be male. The fruit is round, with a flattened, grooved surface at the top and bottom, measuring 5-7 cm in length and 7-8 cm in width. The seeds have an asymmetrical structure with a smooth surface and intricate patterns that enhance the distinctiveness and identification of this plant species (Wahua and Sam, 2016).
These physiological characteristics not only make S. macrocarpon easily recognizable but also contribute to its wide applications in the agriculture and food industries. For example, in addition to direct consumption, various parts of the plant can be utilized in the food processing and pharmaceutical industries. S. macrocarpon leaves are widely used in cooking and traditional medicine, especially in tropical African regions, such as Nigeria, where the plant is cultivated and integrated into daily meals. In addition to their nutritional value, leaves are known for their strong pharmacological effects. They are used to treat a range of conditions in traditional medicine, including asthma, allergic rhinitis, rhinitis, and skin diseases, such as infections and ulcers (Bello et al., 2005). The plant is regarded as an important medicinal herb in many indigenous medical practices across Africa and other tropical regions.
Thus, advancing and expanding research on S. macrocarpon is crucial. Beyond its traditional uses, improving the cultivation of this plant through advanced agricultural techniques can help increase its yield, quality, and commercial value. Novel studies on its bioactive compounds may open opportunities for the development of health-promoting and therapeutic products derived from nature, contributing to the growth of sustainable agriculture and economic development in regions where the plant is grown. Therefore, this comprehensive review aims to systematically compile and analyze current scientific literature on the phytochemical composition, nutritional value, and diverse biological activities of S. macrocarpon. Specifically, we seek to highlight its potential applications in both the food and pharmaceutical industries, identify existing knowledge gaps regarding its safe consumption and full utilization, and propose future research directions to optimize its sustainable development and maximize its benefits for public health.
2. Chemical composition of S. macrocarpon
S. macrocarpon is not only an important food plant but also possesses remarkable nutritional and pharmacological value, as highlighted in numerous studies. This plant contains a high concentration of essential minerals, including calcium, iron, potassium, and magnesium, which offer various health benefits. Jaeger and Hepper (1986) found that S. macrocarpon was a nutritious food source that could support important bodily functions, such as maintaining bone health, improving neurological functions, and maintaining the electrolyte balance.
According to the data presented in Table 1, the calcium and potassium content in S. macrocarpon leaves and fruit are particularly impressive. Specifically, the calcium and potassium levels in the fruit are 23.30-37.70 and 374.10 mg/100 g, respectively, indicating a moderate concentration of these essential minerals. However, in the leaves, the levels of both calcium and potassium are significantly higher, with concentrations reaching 1,704-1,965 mg/100 g for calcium and 2,289-4,596 mg/100 g for potassium (Ojo et al., 2015; Sereno et al., 2018). This stark difference highlights the leaves as a much richer source of these vital nutrients, which are crucial for various physiological functions, including bone health, muscle function, and maintaining fluid balance. The higher mineral content in the leaves suggests that they could be a valuable part of the plant, not only for their potential medicinal uses but also as a dietary supplement to enhance nutrient intake. These figures highlight the plant’s superior nutritional profile compared to many other foods, particularly in providing essential nutrients that support bone health, the nervous system, and the normal functioning of bodily organs.
1) Data from Ojo et al. (2015), Sereno et al. (2018).
2) Data from Dougnon et al. (2012), Gbeyonron and Ortswen (2023).
Compared to sesame seeds and bananas, which are common foods with lower calcium and potassium contents, S. macrocarpon offers superior nutritional value. Sesame seeds and bananas contain only 1,450 mg of calcium/100 g and 261.66-546.66 mg of potassium/100 g, respectively (Athira et al., 2019; Siji and Nandini, 2017). In contrast, S. macrocarpon provides significantly higher levels of these essential minerals in its leaves (Table 1), making it especially valuable for individuals who need to supplement their daily calcium and potassium intake.
Beyond these general comparisons, when examining Solanum species like S. torvum, S. melongena L., S. incanum, and S. sessiliflorum D., S. macrocarpon generally demonstrates a superior or at least comparable mineral content. For instance, S. macrocarpon fruit shows remarkably higher calcium levels compared to S. torvum (22.15 mg/100 g; Akoto et al., 2015), S. incanum (15.00 mg/100 g; Sambo et al., 2016), and S. sessiliflorum D. (1.82 mg/100 g; Sereno et al., 2018), which only contain trace or very low amounts of calcium (Table 2). Similarly, S. macrocarpon’s potassium content in its fruit far surpasses that found in S. torvum (9.153 mg/100 g; Asante et al., 2024), S. incanum (215.45 mg/100 g; Sambo et al., 2016), and S. sessiliflorum D. (0.55 mg/100 g; Sereno et al., 2018), and even the reported ranges for S. melongena L. (159-274.48 mg/100 g; Arivalagan et al., 2013). This trend extends to iron (e.g., S. macrocarpon fruit with high values vs. S. torvum 7.68 mg/100 g, S. melongena L. 0.170-0.846 mg/100 g, S. sessiliflorum D. 0.18 mg/100 g) and copper (e.g., S. macrocarpon fruit vs. S. torvum 0.26 mg/100 g, S. melongena L. 0.024-0.178 mg/100 g, S. sessiliflorum D. 40 mg/100 g), where S. macrocarpon (specifically its fruit) also exhibits substantially higher concentrations when compared to most of the Solanum species listed. While some Solanum species, like S. incanum, show high levels of certain minerals (e.g., phosphorus 1,082.50 mg/100 g and magnesium 38.99 mg/100 g), S. macrocarpon stands out for its consistently high concentrations of multiple key minerals, especially calcium and potassium in its fruit. This comparative analysis further underscores S. macrocarpon’s potential as a highly valuable source of essential dietary minerals within the Solanum species.
1) Data from Akoto et al. (2015), Asante et al. (2024).
2) Data from Arivalagan et al. (2012), Arivalagan et al. (2013).
3) Data from Sambo et al. (2016).
4) Data from Sereno et al. (2018).
Additionally, in Nigeria, during the rainy season, S. macrocarpon thrives and becomes an important vegetable source in the local diet. However, in the dry season, the availability of this vegetable decreases, making preservation methods crucial to ensure its availability year-round. Traditional preservation techniques, such as sun-drying fresh or processed leaves, have been developed to extend the shelf life of vegetables. While these methods help preserve food for extended periods, the drying and cooking processes can result in nutrient losses, particularly in essential minerals and vitamins. Studies have noted nutrient degradation during vegetable processing, especially when they are dried or cooked for extended periods (Khachik et al., 1992; Yadav and Salgel, 2007). This can affect the nutritional value of the food, reducing the bioavailability of minerals, such as calcium, potassium, and magnesium, which are crucial for health.
Oboh et al. (2005) showed that S. macrocarpon leaves are rich in nutritional value, particularly in protein, fat, and carbohydrate content (Table 3). Regarding moisture content, the data indicate a broad range across the plant’s parts, with the fruit exhibiting the highest levels, typically between 90.54 and 92.50 g/100 g. Leaves also contain a substantial amount of moisture (85.87-88.6 g/100 g), while roots show the lowest moisture content at 62.62 g/100 g (Chinedu et al., 2011; Gbeyonron and Ortswen, 2023; Ilodibia et al., 2016).
| Nutrients | Fruits1) | Roots2) | Leaves3) |
|---|---|---|---|
| Moisture | 90.54-92.50 | 62.62 | 85.87-88.6 |
| Protein | 1.33-1.52 | 2.89 | 4.78-27.16 |
| Fat | 0.11-0.17 | 0.38 | 0.77-2.16 |
| Ash | 0.47-1.36 | 0.93 | 1.77 |
| Carbohydrates | 3.92-4.42 | NT4) | NT |
1) Data from Chinedu et al. (2011), Gbeyonron and Ortswen (2023).
2) Data from Ilodibia et al. (2016).
3) Data from Dougnon et al. (2012).
When compared to Solanum species, S. macrocarpon’s moisture content falls within a similar range to S. torvum (86.23-95.79%; Akoto et al., 2015), S. melongena L. (90.86-94.08%; Khan et al., 2015), S. incanum (91.40%; Sambo et al., 2016), and S. sessiliflorum D. (91.42-91.94%; Andrade-Júnior and Andrade, 2012), indicating that high moisture content is a common characteristic across many members of this species, suggesting their potential as fresh food sources.
The protein content in S. macrocarpon shows a clear trend, with leaves being the richest source. Specifically, the protein content in the leaves is 4.78-27.16 g/100 g, suggesting that the leaves of this plant serve as a significant source of plant-based protein. Notably, the protein concentration in the leaves is approximately four times higher than that found in the fruit (1.33-1.52 g/100 g) and considerably higher than in the roots (2.89 g/100 g), making leaves particularly useful for vegetarians or those needing to supplement their protein intake from plant sources. In comparison, the protein content of brown rice and black beans is 7.23% and 10.56 g/100 g, respectively (Anjum, 2007; Mary et al., 2021). Furthermore, S. macrocarpon fruit exhibit a comparable protein content when compared to Solanum species (Table 4), for example, S. melongena L. (1.30-1.51 g/100 g; Arivalagan et al., 2013) and S. sessiliflorum D. fruit (1.09-2.72 g/100 g; Vargas-Arana et al., 2024); while protein content of S. torvum (5.08 g/100 g) and S. incanum fruit (7.80 g/100 g) is significantly higher (Asante et al., 2024; Sambo et al., 2016).
1) Data from Akoto et al. (2015), Asante et al. (2024).
2) Data from Arivalagan et al. (2012), Arivalagan et al. (2013), Khan et al. (2015).
3) Data from Sambo et al. (2016).
4) Data from Andrade-Júnior and Andrade (2012), Vargas-Arana et al. (2024).
In addition to protein, the leaves of S. macrocarpon also contain notable amounts of fat and carbohydrates, providing energy for the body and supporting its physiological functions. These components are essential in maintaining stable energy levels and supporting metabolic processes.
The fat content in different parts of S. macrocarpon has been studied, showing clear differences between the fruit, roots, and leaves. There is a discernible trend of increasing fat content from the fruit to the roots, and then to the leaves. Specifically, the fat content is in the range of 0.11-0.17 g/100 g in fruit, 0.38 g/100 g in the roots, and is highest at 0.77-2.16 g/100 g in the leaves (Chinedu et al., 2011; Gbeyonron and Ortswen, 2023; Ilodibia et al., 2016). The increasing fat content from fruit to leaves is similar to the trend observed for ash content, which also increases from fruit (0.47-1.36 g/100 g) to roots (0.93 g/100 g) and leaves (1.77 g/100 g) (Chinedu et al., 2011; Gbeyonron and Ortswen, 2023; Ilodibia et al., 2016). When compared with Solanum species, S. macrocarpon’s fat content in fruit (up to 2.16 g/100 g) is generally higher than that of S. melongena L. (0.28-0.31 g/100 g; Khan et al., 2015) and comparable to S. sessiliflorum D. (1.08-2.72 g/100 g; Vargas-Arana et al., 2024). However, it is notably lower than the high fat content reported for S. torvum (10.50 g/100 g; Asante et al., 2024) and S. incanum (12.50 g/100 g; Sambo et al., 2016). Regarding ash content, S. macrocarpon fruit (1.77 g/100 g) appears to have a lower ash content than S. torvum (6.51%; Asante et al., 2024) and S. incanum (21.20%; Sambo et al., 2016), though it is comparable to or slightly higher than S. sessiliflorum D. (0.71-0.94%; Vargas-Arana et al., 2024). Although the fat levels in these parts are not particularly high, they still play a significant role in the plant’s biological effects. Scientific studies have demonstrated that Solanum species can regulate blood lipoprotein levels, specifically reducing low-density lipoprotein (LDL) - the “bad” cholesterol - while increasing high-density lipoprotein (HDL), the “good” cholesterol, thereby protecting the cardiovascular system. This effect has been clearly demonstrated in rabbits with hypercholesterolemia (Igwe et al., 2003; Odetola et al., 2004), suggesting that S. macrocarpon may reduce the risk of cardiovascular disease.
Regarding carbohydrates, current research primarily focuses on the fruit, showing a range of 3.92-4.42 g/100 g. However, there is a notable lack of detailed studies on carbohydrate content in the leaves and roots of S. macrocarpon (Chinedu et al., 2011; Gbeyonron and Ortswen, 2023), indicating a gap in current knowledge.
Reported nutritional values for S. macrocarpon can vary due to environmental factors (soil, climate, light), plant variety, and post-harvest processing (drying, cooking). Consequently, these elements directly influence nutrient content and can explain conflicting research findings. Recognizing these variables is key for a more accurate understanding of the plant’s true nutritional profile and for standardizing future research.
In general, S. macrocarpon is a versatile plant that provides rich nutrition and has numerous important medical applications for treating common diseases. Research and development related to appropriate preservation methods to maintain the plant’s nutritional and pharmacological value are essential to maximizing the benefits of this plant in the community. Furthermore, studies on the biological effects of S. macrocarpon will provide opportunities for the development of additional natural health products, particularly in the context of the increasing demand for natural medicinal therapies.
3. Phytochemicals in S. macrocarpon
Table 5 shows that the fruit and leaves of S. macrocarpon are rich in bioactive compounds, including tannins, alkaloids, saponins, polyphenols, flavonoids, phytosterols, and triterpenoids (Chinedu et al., 2011; Oyessola et al., 2022). The potential of these bioactive compounds suggests that S. macrocarpon may offer new beneficial properties for the fields of medicine and pharmacology.
| Phytochemical | Fruits1) | Leaves2) | Roots3) |
|---|---|---|---|
| Tannins | +4) | + | + |
| Alkaloid | + | + | + |
| Saponin | + | + | + |
| Polyphenol | + | + | NT |
| Flavonoid | + | + | - |
| Quinone | NT | NT | NT |
| Steroid | - | + | NT |
| Triterpenoids | + | - | NT |
| Phytosterols | + | NT | NT |
1) Data from Chinedu et al. (2011).
3) Data from Ilodibia et al. (2016).
Table 5 highlights the significant differences in the biological activities between the leaves and fruit of S. macrocarpon. Specifically, the leaves contain compounds such as alkaloids, pyrogallic tannins, mucilage, saponins, and reducing compounds. Although S. macrocarpon is widely consumed, particularly in regions such as Nigeria, no comprehensive studies have yet confirmed the long-term safety of consuming the leaves, especially regarding the impact of the compounds found in the leaves on human health.
On the other hand, tannins, particularly hydrolysable pyrogallic tannins, have been identified as potentially having negative effects at high doses, such as reducing growth and inhibiting protein digestion in experimental animals. Additionally, research has shown that certain cancers, such as esophageal cancer, may be linked to the consumption of foods rich in tannins, as tannins negatively affect cells and, in some cases, contribute to carcinogenesis (Ross et al., 2020). Therefore, excessive consumption of this vegetable, particularly the leaves, should be carefully controlled to avoid potential health risks.
Emebu and Anyika (2011) noted the presence of tannins in S. macrocarpon, showing that tannins are found in both the leaves and fruit but in different concentrations. S. macrocarpon fruit contains a moderate number of hydrolysable tannins, while the leaves have a higher concentration, which explains the more common consumption of the leaves than the fruit in many African countries. Sodipo et al. (2008) clarified the astringent properties of tannins and highlighted their role in traditional medicine as a treatment for wounds. However, the strong presence of tannins in the leaves can have an opposite effect if consumed excessively. Chinedu et al. (2011) also confirmed the presence of tannins in S. macrocarpon fruit but in more moderate amounts compared to the leaves.
In addition to tannins, S. macrocarpon leaves and fruit contain several other bioactive compounds with pharmacological effects. The presence of alkaloids (which are found in low concentrations in the leaves and higher concentrations in the fruit) suggests potential analgesic, anti-inflammatory, and immunostimulant properties as well as stress-reducing effects (Gupta, 1994). The mucilage in leaves and fruits, which consists of polysaccharides, is known for its antioxidant properties (Lin et al., 2005), indicating the potential of S. macrocarpon as a food and medicinal plant capable of protecting cells from free radical damage.
Furthermore, S. macrocarpon is a rich source of reducing compounds, including monosaccharides and disaccharides, which are found in the fruit (Otshudi et al., 2000). Saponins, a group of glycosidic compounds, are also present in leaves and are known for their expectorant properties, which are helpful in treating respiratory infections (Sodipo et al., 2008).
Notably, phytochemical analysis reveals that S. macrocarpon fruit is rich in key bioactive compounds such as tannins, alkaloids, saponins, polyphenols, flavonoids, triterpenoids, and phytosterols (Chinedu et al., 2011). The presence of tannins, alkaloids, and saponins is a notable commonality when compared to the fruits of S. incanum, S. melongena L., S. torvum, and S. sessiliflorum D., indicating these are widespread phytochemical groups within the Solanum species (Table 6). Similarly, polyphenols and flavonoids are also frequently found in these species, reinforcing their antioxidant roles. However, a distinction emerges with triterpenoids: while present in S. macrocarpon and some species like S. torvum (Kannan et al., 2012) and S. sessiliflorum D. (Mascato et al., 2015), they are notably absent in S. melongena L. (Contreras-Angulo et al., 2022; Solanke et al., 2019). Overall, the rich phytochemical profile of S. macrocarpon fruit, with significant similarities to Solanum species, underscores its potential as a valuable source of beneficial compounds for health and medicinal purposes. However, it’s crucial to acknowledge that differences in cultivation region, climate, and soil composition can also influence the specific phytochemical concentrations reported across studies for these Solanum species.
1) Data from Sambo et al. (2016).
2) Data from Solanke at al. (2019), Contreras-Angulo et al. (2022).
3) Data from Kannan et al. (2012).
4) Data from Mascato et al. (2015).
Overall, the research findings suggest that while S. macrocarpon has significant nutritional and pharmacological value, its consumption should be carefully managed to avoid unwanted effects due to the presence of compounds, such as tannins, alkaloids, and coumarins. Moreover, the differences in chemical composition between the plant’s leaves and fruit highlight the need for clear distinctions in their use, as excessive consumption of the leaves can have adverse effects. Further research is needed to better understand the long-term effects and safety of using S. macrocarpon in both dietary and medicinal contexts.
4. Antioxidant capacity, total polyphenol content (TPC), and tannin content of S. macrocarpon
The antioxidant concentration required to reduce the initial concentration of 2,2-diphenyl-1-picrylhydrazyl (DPPH) by 50% (IC50) is an important and commonly used parameter to measure the antioxidant activity of plant extracts. A lower IC50 value indicates a higher antioxidant capacity, meaning the substance can neutralize free radicals more effectively (Brighente et al., 2007). According to Ojo et al. (2015) and Eletta et al. (2017), the antioxidant capacity of various parts of S. macrocarpon varies significantly, with the lowest IC50 value found in the fruit (IC50=3.9-33.56 μg/mL) and the highest in the leaves (IC50=47.06 μg/mL) (Table 7). This suggests that fruit extracts are more potent in scavenging free radicals than leaf extracts, reflecting a higher concentration of antioxidant compounds in the fruit than in the leaves.
| Parts | Antioxidant (IC50, μg/mL) | TPC (mg GAE/g) | Tannin content | References |
|---|---|---|---|---|
| Leaves | 47.06 | 61.93 | 6.39 mg/g | Ojo et al. (2015), Oyessola et al. (2022) |
| Roots | NT | NT | 0.77% |
Ilodibia et al. (2016)
Eletta et al. (2017) Oaa et al. (2017) |
| Fruits | 3.9-33.56 | 8.13 | 0.65% |
Beyond its antioxidant properties, S. macrocarpon is notably rich in its TPC, reflecting its significant contribution to human health. Studies have shown a clear trend in TPC distribution: it is most abundant in the leaves, reaching levels as high as 61.93, highlighting leaves as a prime source of natural antioxidants. Conversely, the fruit contains the lowest TPC, at 8.13. Interestingly, current literature does not extensively detail or report the presence of TPC in the roots of S. macrocarpon, indicating an area for future research. This plant also contains other important compounds, such as tannins, found in all parts of the plant (leaves, roots, and fruit). The concentration of tannins also exhibits a distinct trend across the plant’s various parts: it is highest in the leaves with 6.39 mg/g, followed by the roots at 0.77 %, and lowest in the fruit at 0.65% (Eletta et al., 2017; Ilodibia et al., 2016; Ojo et al., 2015). Tannins are phenolic compounds with strong antioxidant properties that inhibit the development of free radicals and protect the body from oxidative damage. Furthermore, some studies have reported the presence of steroid compounds in these plants, particularly in their leaves, though other research may present differing results (Dougnon et al., 2012). These steroid compounds are closely related to sex hormones, such as testosterone and estrogen, and play a crucial role in the synthesis of these hormones in the body (Okwu, 2001). This explains why S. macrocarpon leaves are commonly used in Vietnam as a nutritious vegetable for pregnant or breastfeeding women to help balance hormones in the body and support fetal development.
In conclusion, the presence of tannins, flavonoids, polyphenols, and other compounds in various parts of S. macrocarpon is responsible for the plant’s positive physiological effects and antioxidant properties. These compounds can help reduce free radical accumulation, thereby protecting the body from damage caused by oxidative stress. However, further detailed studies are needed to isolate and clearly identify the active components in each part of the plant to fully exploit the potential of S. macrocarpon in medicine and practical applications. These studies also help clarify the mechanisms of action of these compounds and expand their potential uses in the treatment and prevention of diseases related to oxidative stress and chronic inflammation.
5. Antibacterial activity of S. macrocarpon
Table 8 indicates that different S. macrocarpon parts, including the leaves, roots, and fruit, exhibit good antibacterial activity against various test bacteria. Specifically, the minimum inhibitory concentration (MIC) values of the ethanol extract from these plant parts against different bacteria are outlined in the table. Leaf extracts have shown strong antibacterial activity. For S. macrocarpon leaves, the aqueous extract demonstrated significant inhibition against Staphylococcus aureus with a zone of 23.56±0.46 mm at 200 mg/mL, and against Escherichia coli with 21.33±0.70 mm at 150 mg/mL. It was also effective against Klebsiella pneumoniae, showing 20.00±0.71 mm at 200 mg/mL (Enyinta et al., 2024). These results indicate strong efficacy, particularly against Gram-negative bacteria, based on the agar diffusion method. In contrast, the fruit extract exhibited activity against E. coli and S. aureus at concentrations ranging from 100 to 200 mg/mL. However, its antibacterial efficacy was generally lower compared to the leaves. For S. macrocarpon fruit aqueous extract, the highest recorded inhibition zone against Salmonella sp. was 21.67±0.20 mm at 200 mg/mL, against E. coli was 18.97±0.43 mm at 200 mg/mL, and against S. aureus was 16.58±0.33 mm at 200 mg/mL (Enyinta et al., 2024).
| Microorganism | Leaves1) | Roots2) | Fruits1) |
|---|---|---|---|
| Staphylococcus aureus | +3) | + | + |
| Escherichia coli | + | + | + |
| Candida albicans | + | + | + |
| Aspergillus niger | + | + | + |
| Klebsiella pneumonia | + | NT | + |
| Salmonella sp. | + | NT | + |
1) Data from Ilodibia et al. (2016), Enyinta et al. (2024).
2) Data from Ilodibia et al. (2016).
Regarding the root extract, while it did not show a significant inhibition zone in agar diffusion assays (Ilodibia et al., 2016), further studies using different methods confirmed its antimicrobial potential. The root extract demonstrated activity against E. coli with a MIC of 50 mg/mL and a Minimum Bactericidal Concentration (MBC) of 100 mg/mL. Similarly, it was effective against S. aureus with an MIC of 50 mg/mL and an MBC of 100 mg/mL (Ilodibia et al., 2016). Compared to the leaf and fruit extracts, which exhibited clear inhibition zones, the root extract’s efficacy, as measured by MIC/MBC, requires relatively higher concentrations for inhibition compared to the lower end of the active concentration ranges of leaf/fruit extracts in agar diffusion (e.g., leaf at 50 mg/mL in study of Enyinta et al. 2024). This difference may be related to the evaluation methods, distribution and concentration of bioactive compounds, such as alkaloids, flavonoids, saponins, and polyphenols, in each part of the plant (Hassan et al., 2009). These compounds are known for their strong antibacterial properties, particularly against common pathogenic bacteria, such as E. coli and K. pneumoniae. These findings suggest that the various parts of S. macrocarpon are valuable natural resources for developing antibacterial products that contribute to public health protection.
The previous results highlighted the similarity in antibacterial potential among species within the Solanum species. Ihodibia et al. (2016) demonstrated that leaf and fruit extracts from S. aethiopicum and S. macrocarpon exhibited bactericidal and fungicidal activities (minimum bactericidal/fungicidal concentration, MB/MFC) ranging from 25 to 100 mg/mL against the tested organisms, indicating strong antibacterial potential within Solanum species. This similarity may be attributed to the presence of bioactive compounds, such as alkaloids, flavonoids, and saponins, which are known for their ability to inhibit the growth of bacteria and fungi. Additionally, Tegegne et al. (2021) affirmed the antibacterial activity of S. anguivi, particularly against E. coli and K. pneumoniae. This further supports the hypothesis that Solanum species contain potent bioactive compounds that help protect the plant from pathogenic attacks while also providing opportunities for the development of natural antibacterial products. The similarities among these species emphasize the value of Solanum plants as a valuable resource in the research and production of plant-derived pharmaceutical products.
Thus, these findings not only highlight the diverse antibacterial potential of the various parts of S. macrocarpon but also contribute to expanding the scientific foundation for the use of natural plants in medicine. This provides a basis for further research into the biological activities and application potential of these extracts in developing therapeutic products, especially in the context of the growing issue of antibiotic-resistant bacterial and fungal infections today.
6. Pharmacological properties of S. macrocarpon
Table 9 indicates that S. macrocarpon fruit extracts inhibit tracheal contractions, suppress nitric oxide (NO) production, protect against air pollution-induced oxidative stress, and prevent obesity in mice at doses of 46.8 μg/mL, 200 μg/mL, 75 mg/kg, and 200 mg/kg, respectively (Akinwunmi and Ajibola, 2018; Bello et al., 2005; Ng et al., 2015; Olajire and Azeez, 2012). Excessive NO production can increase chronic inflammatory responses, contributing to the development of severe conditions (Ng et al., 2015). Therefore, inhibiting NO production is a key strategy in chronic inflammatory disease treatment.
| Part | Subjects | Dosage | Effects | References |
|---|---|---|---|---|
| Fruits | Hartley guinea pigs | 46.8 μg/mL | Brochial spasm inhibition | Bello et al. (2005) |
| RAW 264.7 | 200 μg/mL | No inhibition | Ng et al. (2015) | |
| Adult male albino rats | 75 mg/kg | Anti-stress due to air pollution | Olajire and Azeez (2012) | |
| Adult female Wistar | 200 mg/kg | Obesity | Akinwunmi and Ajibola (2018) | |
| Leaves | Adult Wistar rats | 600 mg/kg | Treatment of acute renal toxicity due to acetaminophen | Sood et al. (2012) |
| Male albino rats | 500 mg/kg | Anti-stress | Elasoru et al. (2018) | |
| Spontaneously hypertensive rats | 100 mg/kg | Antihypertensive | Oluwagunwa et al. (2019) | |
| Male Wistar rats | 550 mg/kg | Reduce anxiety | Mary et al. (2020) | |
| Male Wistar rats | 49.8 mg/kg | Reduce kidney disease | Ekakitie et al. (2021) | |
| Diabetic rats | 100 mg/kg | Improve cardiomyopathy | Osukoya et al. (2022) | |
| Female albino rats | 800 mg/kg | Enhance fertility | Ezechukwu et al. (2024) |
Olajire and Azeez (2012) demonstrated that S. macrocarpon can mitigate toxicity caused by exposure to urban air pollution. Specifically, their study found that oral administration of a S. macrocarpon fruit extract at a dose of 75 mg/kg body weight in rats significantly reduced oxidative stress markers and improved histopathological changes in affected organs. This finding supports the broader understanding that urban air pollution can cause severe toxic effects on vital organs, such as the lungs, liver, and kidneys (Mary et al., 2020).
Moreover, beyond its protective effects against pollution, S. macrocarpon leaf extracts have also been studied for their potential to treat acute nephrotoxicity induced by acetaminophen (also known as paracetamol) at a dose of 550 mg/kg, a widely used pain reliever and antipyretic agent. Although paracetamol is very effective in treating pain and fever, it can also cause acute tubular necrosis, one of the leading causes of acute kidney failure (Cobden et al., 1982). S. macrocarpon leaf extracts can reduce kidney damage and aid in the recovery of kidney function, highlighting their potential application in treating kidney toxicity-related issues.
Furthermore, S. macrocarpon leaf extracts have been reported to have various therapeutic effects, including reducing stress (Elasoru et al., 2018), alleviating diabetic nephropathy (Ekakitie et al., 2021), improving diabetic cardiomyopathy (Osukoya et al., 2022), and enhancing fertility (Ezechukwu et al., 2024). These effects reflect the broad range of biological activities of S. macrocarpon.
The research findings suggest that S. macrocarpon has significant anti-inflammatory and health-protective potential. However, all these studies were conducted in animal models, primarily in mice, and no clinical evaluations in humans have been reported. This presents a major challenge in translating these findings into practical applications. Therefore, to better understand the effectiveness and safety of S. macrocarpon for human health, more detailed clinical studies are required. Further research and human trials will help clarify the plant’s potential in health protection, particularly in the context of increasing air pollution-related diseases and drug toxicity.
7. Applications of S. macrocarpon fruit in food in Vietnam
S. macrocarpon, commonly known as “cà pháo” or eggplant, is a plant of significant culinary and medicinal value in Vietnamese culture, particularly in traditional dishes. Not only is S. macrocarpon an essential ingredient in various foods, but it also contains numerous nutrients that have health benefits. One of the most popular traditional dishes made from S. macrocarpon is pickled eggplant. Each preparation method highlights the vegetable’s natural sweetness, which, when combined with simple spices, enhances the flavor of the dish.
In recent years, several processed products made from S. macrocarpon have been commercialized, offering convenience to consumers. Products such as pickled eggplant (Fig. 2), sour and spicy eggplant (Fig. 3), and traditional fermented shrimp sauce-based eggplant preparation (Fig. 4) are now available on the market, catering to the growing consumer demand. The prices of these products range from USD 1.08 to 1.50 for 400 g, depending on the type and quality. This indicates a promising market, reflecting the widespread popularity of S. macrocarpon in Vietnamese cuisine and the increasing demand for its consumption. These products are easy to make and can be produced on a small or industrial scale. Some processing processes of Vietnamese white eggplant fruit are described as follows:
Ingredients: Soak the eggplants in a diluted salt solution (1 tablespoon of salt per 500 mL of water) for 10-15 minutes. Mix 1,000 mL of water with 3-4 tablespoons of salt, 1-2 tablespoons of sugar, and 2-3 tablespoons of vinegar (or lemon juice), and stir well. Remove 1 kg of eggplant, rinse it under clean water, and place it in a glass jar. Pour the pickling liquid over the eggplant until it is fully submerged. Seal the jar and leave it in a cool place for 2-3 days. Once the eggplants absorb the flavors and become crisp, they are ready to be eaten with white rice, braised meat, or other dishes.
Clean the eggplant, remove the stem, and make small cuts on each fruit. Soak the eggplant in a diluted salt solution for 10-15 minutes, then drain it and let it cool. Boil water with vinegar, fish sauce, sugar, and salt, stirring until the ingredients dissolve completely, and then let it cool. Chop garlic and slice chili. Place the eggplants in a jar, add garlic and chili, and pour the prepared pickling liquid over them to fully submerge the eggplant. Seal the jar and let it sit at room temperature for 1-2 days. The eggplants have a tangy, spicy flavor and crisp texture.
Cut the eggplant into halves or quarters, and soak it in a lemon salt solution for 30 min. Rinse the eggplant several times. Mix 200 g of fermented shrimp paste, 100 g of water, and 100 g of sugar in a pot, and heat while stirring until the shrimp paste boils. Remove the mixture from the heat and let it cool. Add the eggplant, mix well, and place it in a glass jar to allow it to absorb the flavors overnight.
Depending on the culinary characteristics of the different regions, preparation methods vary significantly. However, most products made from these ingredients are still primarily produced on a small scale. Therefore, it is essential to promote and introduce these unique dishes globally.
With immense potential in both culinary and medicinal applications, S. macrocarpon could become a key product in the agricultural economy if developed sustainably with a strategic approach. As the demand for organic and healthy food continues to rise, S. macrocarpon has the opportunity to expand both domestically and internationally.
8. Toxicity of S. macrocarpon and potential solutions in the future
While S. macrocarpon offers several benefits, such as fast growth and high nutritional value, it also contains glycoalkaloids – a group of compounds that can be harmful to health if consumed in high quantities. According to Moreau et al. (2002), S. macrocarpon fruit and leaves contain glycoalkaloids, which protect the plant from pests and fungi. However, if these compounds accumulate in food, they can have negative health effects. Despite this, there is still limited research on the levels of glycoalkaloids in S. macrocarpon fruit, and detailed studies on their concentrations are necessary.
Indeed, alkaloids have been reported in both the leaves (Ezechukwu et al., 2016) and fruit (Sánchez-Mata et al., 2010) of S. macrocarpon. Notably, the levels of these compounds in S. macrocarpon fruits were found to be much higher than those reported for the common eggplant (S. melongena) and scarlet eggplant (S. aethiopicum), reaching values of 1.4-2.2 mg/g fresh weight, which is far beyond the safety level (Sánchez-Mata et al., 2010). However, it is also acknowledged that other reports suggest a much lower content, indicating that this plant characteristic can vary intraspecifically (Sánchez-Mata et al., 2010). A study on the toxicity of fresh leaves of tropical vegetables demonstrated the relatively low toxicity of S. macrocarpon leaves when compared to other plant species (Oboh, 2005). The presence of cholesterol in plants from the Solanaceae family is typically linked to the biosynthesis of glycoalkaloids (Hartmann, 1998). Therefore, the analysis of glycoalkaloid content in the leaves is crucial for a proper evaluation of the potential toxicity of S. macrocarpon leaves, as well as edible parts of other underutilized Solanum species (Haliński et al., 2012).
Beyond glycoalkaloids, another aspect of potential toxicity relates to the plant’s cuticular waxes. While plant long-chain hydrocarbons found in these waxes are generally believed to be non-toxic for mammals (Kolattukudy and Hankin, 1966), there have been past reports of massive deposits of plant n-alkanes in the livers and lungs of animals (Halse et al., 1993) and humans (Salvayre et al., 1988). The hydrocarbon content in S. macrocarpon leaf waxes is relatively low, being 6-13 times lower than in the closely related eggplant (S. melongena). Specifically, the alkane content in Solanum species can vary, with reported values for S. macrocarpon ranging from 3.4 mg to 4.0 mg per 100 g fresh weight, while in eggplant leaves, it ranged from 23 to almost 45 mg per 100 g (Haliński et al., 2012). Despite these relatively low levels in S. macrocarpon, the potential risk associated with consuming large amounts of long-chain hydrocarbons of plant origin necessitates further complex studies involving Solanum species.
To ensure consumer safety, international organizations have established guidelines for total glycoalkaloid (TGA) content in food, primarily based on extensively studied crops like potatoes. The World Health Organization (WHO) considers TGA levels below 100 mg/kg fresh weight (FW) in potatoes as not concerning (WHO, 2023). Some broader assessments also suggest an acceptable upper safety limit of up to 200 mg/kg FW for TGA in products (Knuthsen et al., 2009).
To address the issue of glycoalkaloid toxicity in edible forms, various strategies can be considered, focusing on processing methods.
Processing Methods: Glycoalkaloids are generally considered quite heat-stable, with significant degradation typically occurring only at very high temperatures (e.g., above 200°C) (Friedman, 2006). However, standard food processing techniques can still effectively reduce their levels. Peeling is highly effective as glycoalkaloids are primarily concentrated in the skin or outer layers (Friedman, 2006). While not destroyed by typical boiling temperatures, glycoalkaloids are somewhat water-soluble; thus, boiling can reduce their concentration by leaching them into the cooking water, especially from peeled plant parts. Therefore, discarding the cooking water after boiling is recommended (Ojo et al., 2024). Deep-frying at high temperatures (e.g., above 170°C) can also lead to partial decomposition of glycoalkaloids, contributing to their reduction in the final product (Elżbieta, 2012). Furthermore, fermentation or prolonged soaking (with subsequent discarding of soaking water) may also contribute to glycoalkaloid reduction through enzymatic degradation or leaching. However, their specific efficacy for S. macrocarpon requires further investigation (Friedman, 2006). Implementing appropriate processing methods during food preparation is a practical approach to enhance the safety of S. macrocarpon for consumption. This would benefit both human health and increase the economic value of S. macrocarpon, especially in markets with stringent food safety standards.
Currently, despite initial insights into the chemical composition and potential toxicity of S. macrocarpon based on in vitro models (such as brine shrimp larvae) and data on the content of harmful compounds (glycoalkaloids) as well as heavy metals, there remains a critical lack of in-depth toxicity studies specifically on human subjects. Therefore, future research should focus on determining safe dosages, evaluating long-term health impacts, and exploring cultivation and processing methods to minimize toxins, thereby ensuring maximum consumer safety.
9. Conclusions
S. macrocarpon provides numerous benefits to human life, both economically and medicinally, through its various parts. Scientific studies have shown that the plant contains valuable nutrients, such as carbohydrates, proteins, minerals, and bioactive compounds, including phenolics, saponins, tannins, and steroids. These compounds exhibit anti-inflammatory, antimicrobial, antioxidant, blood pressure-regulating, blood sugar-stabilizing, and potential anticancer properties. While S. macrocarpon is widely used in cooking and traditional medicine, its medicinal potential extends to pharmaceuticals and health products, utilizing not only the fruit and leaves but also other parts like flowers and roots. However, it is important to acknowledge that S. macrocarpon contains glycoalkaloids, which can be toxic if consumed in excessive amounts. These compounds may cause adverse effects such as gastrointestinal disturbances and, in severe cases, neurological symptoms. Therefore, future research should focus on determining safe consumption levels and developing effective detoxification methods to minimize health risks. Additionally, further studies should explore innovative applications of S. macrocarpon in functional foods and nutraceuticals while ensuring safety and efficacy. By addressing these challenges, S. macrocarpon can contribute more effectively to sustainable development in the food and pharmaceutical industries, ultimately improving public health and quality of life.
