Table 4. Significant individual phenolic compounds in the skin of Meili grapes based on density classes (μg g-1 skin).
| Phenolic compounds | Density level | ||
|---|---|---|---|
| D3 | D4 | D5 | |
| Nonflavonoid phenolics | |||
| Hydroxybenzoic acids | 27.61(40.21%) | 33.52(42.79%) | 34.90(44.18%) |
| Gallic acid | 3.48 ± 0.08(a) α | 4.14 ± 0.10(b) | 4.34 ± 0.06(b) |
| Benzoic acid | nd β | nd | nd |
| Vanillic acid | 4.41 ± 1.49(a) | 5.38±0.23(a) | 6.06 ± 0.87(a) |
| Syringic acid | 6.16 ± 1.95(a) | 8.11±0.66(a) | 8.17 ± 0.93(a) |
| p-Coumaric acid | 0.44 ± 0.12(a) | 0.51±0.03(a) | 0.52 ± 0.01(a) |
| Salicylic acid | 13.12 ± 0.73(a) | 15.38±0.79(b) | 15.81±0.19(b) |
| Hydroxycinnamic acids | 0.08(0.12%) | 0.09(0.11%) | 0.09(0.11%) |
| Chlorogenic acid | nd | nd | nd |
| Caffeic acid | 0.08 ± 0.01(a) | 0.09 ± 0.02(a) | 0.09 ± 0.02(a) |
| Ferulic acid | nd | nd | nd |
| Stilbenes | 1.48(2.16%) | 1.63(2.08%) | 1.75(2.22%) |
| trans-Resveratrol | 1.48 ± 0.12(a) | 1.63 ± 0.05(a) | 1.75 ± 0.18(a) |
| Benzopyrone | 13.73(19.99%) | 14.05(17.93%) | 13.84(17.52%) |
| Coumarin | 13.73 ± 0.66(a) | 14.05 ±0.88(a) | 13.84 ± 0.89(a) |
| Sum of individual nonflavonoid phenolics | 42.90(62.47%) | 49.29(62.92%) | 50.58(64.03%) |
| Flavonoids | |||
| Flavan-3-ols | 12.87(18.74%) | 13.55(17.30%) | 13.13(16.62%) |
| (+)-Catechin | 10.59 ± 0.14(a) | 11.04 ± 0.29(a) | 10.13 ± 0.75(a) |
| (-)-Epicatechin | 2.28 ± 0.59(a) | 2.51 ± 0.32(a) | 3.00 ± 0.44(a) |
| Flavonols | 12.90(19.79%) | 15.50(20.89%) | 15.28(20.47%) |
| Rutin | 1.74 ± 0.03(a) | 3.76 ± 0.11(b) | 4.23 ± 0.86(b) |
| Morin | nd | nd | nd |
| Quercetin | 6.56 ± 0.11(a) | 7.45 ± 1.25(a) | 6.88 ± 0.60(a) |
| Kaempferol | 4.60 ± 0.38(a) | 4.29 ± 0.14(a) | 4.17 ± 0.22(a) |
| Hesperetin | nd | nd | nd |
| Sum of individual flavonoid phenolics | 25.77(37.53%) | 29.05(37.08%) | 28.41(35.97%) |
| Sum of individual phenolics | 68.67 ± 2.54(a) | 78.34 ± 1.77(b) | 78.99 ± 2.95(b) |
α Values are the mean ± standard deviation (n = 3) and are based on the fresh weight of skin. Within lines, significant differences according to the Fisher’s LSD test at the P≤0.05 level are indicated by different letters.
β nd: not detected.