Table 4 The second polynomial equations for quality prediction of Cudrania tricuspidata calculated by SAS program

Response1)	The second polynomial equations	R²	Significance
TPC	Y=10.877500-0.019000X₁-0.061125X₂+0.110208X₃-0.000021441X₁²	0.9161	0.0395
TPC	+0.000261X₂X₁+0.000441X₂²+0.000155X3X₁-0.000948X₃X₂-0.000547X₃²	0.9161	0.0395
TFC	Y=-90.351250-0.034101X₁+3.216875X₂+5.601424X₃-0.000320X₁²	0.9186	0.0286
TFC	+0.001166X₂X₁-0.020683X₂²+0.001274X₃X₁-0.052177X₃X₂-0.049242X₃²	0.9186	0.0286
DPPH	Y=76.027500-0.027608X₁-1.867438X₂+0.932222X₃+0.000137X₁²	0.9303	0.0200
DPPH	+0.000599X₂X₁+0.014211X₂²-0.001337X₃X₁+0.010271X₃X₂-0.024708X₃²	0.9303	0.0200
E	Y=-23.338750-0.035212X₁ +0.915500X₂ -0.161840X₃ -0.000025029X₁²	0.9782	0.0012
E	-0.000281X₂X₁-0.006107X₂²+0.001516X₃X₁+0.009875X₃X₂-0.005281X₃²	0.9782	0.0012

TPC, total polyphenol content; TFC, total flavonoid content; DPPH, DPPH radical scavenging activity; ΔE, Color difference.