Table 1. Experimental data for total extract yield (TY), total anthocyanin contents (TAC), total phenolic contents (TPC), and antioxidant activities of eggplant powder extracts using microwave-assisted extraction (MAE) under different conditions based on CCD of response surface methodology
| Exp. No1) | Independent variables | | Response variables |
| Ethanol conc. (%) | Microwave power (W) | Extraction time (sec) | TY(%) | TAC (mg CE/L) | TPC (mg GAE/100 mL) | DPPH RSA (mg TE/100 mL) | ABTS RSA (mg TE/100 mL) | FRAP activity (mg TE/100 mL) |
| 1 | 65 (-1)2) | 50 (-1) | 60 (-1) | | 1.67±0.023)ab4) | 5.03±0.09h | 40.14±0.56d | 37.06±0.29f | 34.38±0.32f | 54.50±0.34abcde |
| 2 | 65 (-1) | 50 (-1) | 120 (1) | | 1.56±0.06bcde | 6.37±0.11f | 43.13±0.39c | 39.67±0.08d | 37.70±0.32e | 60.11±0.82ab |
| 3 | 65 (-1) | 150 (1) | 60 (-1) | | 1.60±0.00abc | 7.10±0.05d | 43.13±0.55c | 39.84±0.42d | 40.17±0.69c | 60.41±0.41def |
| 4 | 65 (-1) | 150 (1) | 120 (1) | | 1.72±0.11a | 9.07±0.09b | 48.75±1.50a | 44.15±0.39b | 44.30±0.98b | 69.22±0.34a |
| 5 | 85 (1) | 50 (-1) | 60 (-1) | | 1.46±0.01cdef | 1.74±0.02n | 30.38±0.19f | 26.70±0.04k | 20.15±0.11k | 39.38±0.67ef |
| 6 | 85 (1) | 50 (-1) | 120 (1) | | 1.45±0.01def | 2.93±0.01k | 34.22±0.71e | 29.23±0.22j | 24.70±0.15j | 44.03±0.34bcdef |
| 7 | 85 (1) | 150 (1) | 60 (-1) | | 1.41±0.15f | 3.30±0.04j | 34.61±0.29e | 30.85±0.20i | 27.49±0.37h | 45.58±0.58bcdef |
| 8 | 85 (1) | 150 (1) | 120 (1) | | 1.43±0.01ef | 6.99±0.07e | 39.10±2.78d | 37.89±0.22e | 37.89±0.22e | 55.47±0.82abcde |
| 9 | 75 (0) | 100 (0) | 90 (0) | | 1.59±0.00abcd | 6.93±0.03e | 42.13±0.08c | 39.49±0.36d | 39.00±0.15d | 57.02±0.89abcd |
| 10 | 75 (0) | 100 (0) | 90 (0) | | 1.63±0.01ab | 7.79±0.13c | 43.22±0.26c | 40.48±0.23c | 40.66±0.52c | 57.98±0.34abc |
| 11 | 55 (-2) | 100 (0) | 90 (0) | | 1.65±0.00ab | 1.23±0.02o | 45.89±1.29b | 31.74±0.24h | 33.39±0.66g | 55.47±0.58abcde |
| 12 | 95 (2) | 100 (0) | 90 (0) | | 1.19±0.12g | 1.99±0.06m | 25.07±2.57g | 19.88±0.12l | 13.37±1.62m | 31.43±0.34f |
| 13 | 75 (0) | 0 (-2) | 90 (0) | | 1.46±0.02cdef | 3.80±0.03i | 36.21±0.34e | 33.38±0.44g | 27.95±0.16h | 46.94±0.89bcdef |
| 14 | 75 (0) | 200 (2) | 90 (0) | | 1.64±0.01ab | 9.55±0.17a | 47.56±1.33ab | 45.95±0.34a | 46.74±0.69a | 65.54±0.34a |
| 15 | 75 (0) | 100 (0) | 30 (-2) | | 1.21±0.06g | 2.21±0.06l | 21.13±0.39h | 13.88±0.39n | 17.26±0.40l | 33.15±0.63f |
| 16 | 75 (0) | 100 (0) | 150 (2) | | 1.43±0.05ef | 5.87±0.08g | 28.68±0.37f | 17.58±0.04m | 25.46±0.66i | 43.13±0.60cdef |
1)The number of experimental conditions by central composite design.
2)Coded level of independent variables.
3)The values are the means of three replicates±SD.
4)The values within the same column with different small letters (a-m) are significantly different at p<0.05 based on Duncan’s multiple range test.