Comparative analysis of chemical constituents and antioxidant activity in tea-leaves microbial fermentation of seven tea-derived fungi from ripened Pu-erh tea

Ripened Pu-erh tea is a traditional microbial-fermented tea with multiple beneficial effects and the genus Aspergillus were considered as the dominant fungi. In this study, six Aspergillus and one Penicillium fungi, abbreviated as AniPT1, AsyPT2, ApaPT3, AsePT4, PmaPT5, AusPT6 and AtaPT7, were inoculated into sun-dried green tea-leaves for the microbial fermentation. Based on 42 chemical components belonging to several classes as polyphenols, amino acids and purine alkaloids, PCA and HCA revealed the significant differences in tea-leaves microbial fermentation of seven tea-derived fungi. Most of catechins, flavonoids and free amino acids were decreased highly significantly (p < 0.001), while theabrownins, theaflavins and gallic acid contents were increased highly significantly (p < 0.001) in all microbial fermentation. Additionally, several tea-derived fungi contributed to the accumulation of (+)-catechin, (-)-epicatechin, kaempferol, myricetin, theophylline, Lmethionine, L-tryptophan, L-cysteine, L-histidine and gamma-aminobutyric acid, and the improvement of antioxidant activity in tea-leaves after inoculated fermentation. Particularly, AsyPT2 converted caffeine into theophylline mainly. The bivariate correlation analysis confirmed the extremely significantly (p < 0.001) positive correction of gallic acid and kaempferol to antioxidant activity in fermented tea-leaves. This study provided reference for the application of tea-derived fungi in ripened Pu-erh tea.

Automated summary

The study demonstrates that microbial fermentation by different fungi derived from tea leaves can significantly alter the chemical composition of tea leaves and enhance the antioxidant activity of tea leaves.