Suyoung Kang

Wuyi rock tea (WRT) is one of the most famous subcategories of oolong tea, exhibiting distinct aroma characteristics with the application of different cultivars. However, a comprehensive comparison of the characteristic volatiles among WRTs with different cultivars has rarely been carried out. In this study, non-targeted analyses of volatile fragrant compounds (VFCs) and targeted aroma-active compounds in WRTs from four different cultivars were performed using chemometrics and gas chromatography olfactometry/mass spectrometry (GC-O/MS). A total of 166, 169, 166, and 169 VFCs were identified for Dahongpao (DHP), Rougui (RG), Shuixian (SX), and Jinfo (JF), respectively; and 40 components were considered as the key differential VFCs among WRTs by multivariate statistical analysis. Furthermore, 56 aroma-active compounds were recognized with predominant performances in “floral & fruity”, “green & fresh”, “roasted and caramel”, “sweet”, and “herbal” attributes. The comprehensive analysis of the chemometrics and GC-O/MS results indicated that methyl salicylate, p-cymene, 2,5-dimethylpyrazine, and 1-furfurylpyrrole in DHP; phenylethyl alcohol, phenethyl acetate, indole, and (E)-β-famesene in RG; linalool, phenethyl butyrate, hexyl hexanoate, and dihydroactinidiolide in JF; and naphthalene in SX were the characteristic volatiles for each type of WRT. The obtained results provide a fundamental basis for distinguishing tea cultivars, recombination, and simulation of the WRT aroma.

Purpose: To investigate the anti-melanogenesis effect of green tea compound, (-)-epigallocatechin-3- gallate (EGCG), on B16 murine melanoma cell irradiated by ultraviolet A (UVA) in the search for natural skin-lightening alternative agents. Methods: B16 murine melanoma cells by UVA (9.0 J/cm²) for 0 to 32 min and then incubated in Dulbecco's Modified Eagle's Medium (DMEM) with EGCG (0-200 μg/mL) for 2 days. Cell viability was determined by MTT method and cell protein was quantified using a PA102 Bradford protein assay kit. Activity of tyrosinase (TRY) was determined based on the oxidation rate of 3,4-dihydroxy phenylalanine (DOPA). The ultra-structure of the melanosomes was observed by transmission electron microscopy (TEM). Results: TRY activity and melanin concentration were increased to 146.70 ± 10.28 % (p < 0.05) and 157.06 ± 6.37 % (p < 0.05), respectively, by 9.0 J/cm² UVA irradiation for 8 min, compared to blank control without UV A and EGCG. EGCG inhibited the UV A induced increase in TRY activity and melanin level, and the optimum concentration of EGCG was 25 μg/mL. TRY activity and melanin concentration were decreased to 64.71 ± 4.41 (p < 0.05) and 86.24 ± 5.15 % (p < 0.05), respectively, compared to blank (control) which was neither treated by UVA nor by EGCG. TEM showed that UVA induced the formation of melanosomes while EGCG inhibited UVA-induced melanosome maturation. Conclusion: EGCG inhibits UVA-induced melanogenesis via suppression of TRY activity and melanosome maturation and is thus a potential alternative to melanogenesis inhibitor. Keywords: Green tea, Catechins, Melanin, Melanosome, Tyrosinase, Cell proliferation