Structural features, antioxidant and tyrosinase inhibitory activities of proanthocyanidins in leaves of two tea cultivars

Figures & data

Figure 1. Chemical structure of proanthocyanidin polymers: R₁, R₂ = H, propelargonidins; R₁ = OH, R₂ = H, procyanidins; R₁, R₂ = OH, prodelphinidins.

Figure 2. MALDI-TOF positive reflectron mode mass spectra of the proanthocyanidins in leaves of A: Huangjingui and B: Qilan cultivars.

Figure 3. Reversed-phase HPLC chromatograms of thiolytic products of the proanthocyanidins in leaves of A: Huangjingui and B: Qilan cultivars. Peaks 12 and 13 represent excessive benzyl mercaptan and thiolytic by-product, respectively.

Table 1. Antioxidant activities of the proanthocyanidins in leaves of Huangjingui and Qilan cultivars using the DPPH radical scavenging, ABTS radical scavenging and the FRAP assays.

Cultivar	Antioxidant activity
	IC50 of DPPH radical (µg/mL) ^a	IC50 of ABTS radical (µg/mL) ^b	FRAP (mmol AAE/g)
Huangjingui	87.36 ± 0.83c	43.57 ± 0.25c	4.83 ± 0.03a
Qilan	97.33 ± 0.61b	55.01 ± 0.22b	3.97 ± 0.02b
BHA	117.57 ± 1.43a	97.43 ± 0.49a	4.76 ± 0.09a

Values are presented as means ± standard deviation (n = 3).

Different letters in the same column show significant differences from each other at p < 0.05 level.

^aThe antioxidant activity was evaluated as the concentration of the test sample required to decrease the absorbance at 517 nm by 50%.

^bThe antioxidant activity was evaluated as the concentration of the test sample need to decrease the absorbance at 734 nm by 50%.

^cFRAP values were expressed in mmol ascorbic acid equivalent (AAE)/g sample in dry weight.

Figure 4. Antioxidant activity of the proanthocyanidins in leaves of Huangjingui and Qilan cultivars: (A) DPPH radical scavenging activity; (B) ABTS radical scavenging activity; (C) Ferric reducing antioxidant power (FRAP).

Figure 5. (1) Inhibitory activity, (2) inhibitiory mechanism, and (3) inhibitiory type and constants of the proanthocyanidins in leaves of A: Huangjingui and B: Qilan cultivars against mushroom tyrosinase. The concentrations of the proanthocyanidins for curves 0-3 were 0, 6.66, 33.3, 66.6 µg/mL for Huangjingui cultivar, and 0, 13.3, 53.3, 80.0 µg/mL for Qilan cultivar, respectively.