Geographical origin identification of Chinese white teas, and their differences in tastes, chemical compositions and antioxidant activities among three production regions.

The producing area of Chinese white tea has been expanded to Xinyang and Yunnan from Fuding region. In this study, six sensory tastes and fifty-one chemical components including seventeen phenolic compounds, three purine alkaloids and twenty amino acids were determined in eighteen Bai mudan sub-type of white tea by electronic tongue, high performance liquid chromatography and amino acid analyzer for geographical identification, respectively. Additionally, in vitro antioxidant activities were evaluated by five various assays. Multivariate statistical analyses such as PCA, HCA and PLS-DA, completely divided these white teas into Xinyang, Yunnan and Fuding groups, indicating the feasibility of white tea classification by the production region. Twelve characteristic compounds (VIP > 1.0, P < 0.05) like gallic acid, theaflavin and L-glutamic acid contributed to the geographical identification. In conclusion, this study explored the chemical, taste and antioxidant capacity differences among three main production regions, and revealed their potential relations in white tea.

Impact of prolonged withering on phenolic compounds and antioxidant capability in white tea using LC-MS-based metabolomics and HPLC analysis: Comparison with green tea.

Contents of 20 bioactive compounds in 12 teas produced in Xinyang Region were determined by high performance liquid chromatography. Ultra-high performance liquid chromatography-quadrupole time of flight-mass spectrometry was developed for untargeted metabolomics analysis. Antioxidant activities were measured by 4 various assays. Those teas could be completely divided into green and white tea through principal component analysis, hierarchical cluster analysis and orthonormal partial least squares-discriminant analysis (R2Y = 0.996 and Q2 = 0.982, respectively). The prolonged withering generated 472 differentiated metabolites between white and green tea, prompted significant decreases (variable importance in the projection > 1.0, p-value < 0.05 and fold change > 1.50) of most catechins and 8 phenolic acids to form 4 theaflavins, and benefited for the accumulation of 17 flavonoids and flavonoid glycosides, 8 flavanone and their derivatives, 20 free amino acids, 12 sugars and 1 purine alkaloid. Additionally, kaempferol and taxifolin contributed to 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging ability of white tea.

Region identification of Xinyang Maojian tea using UHPLC-Q-TOF/MS-based metabolomics coupled with multivariate statistical analyses.

Xinyang Maojian tea is a kind of famous roasted green tea produced in the middle of China. Ultra-high performance liquid chromatography-quadrupole time of flight-mass spectrometry (UHPLC-Q-TOF/MS)-based metabolomics coupled with multivariate statistical analyses, including principal component analysis (PCA) and hierarchical cluster analysis (HCA), were carried out in XMMJTs collected from Luoshan, Shangcheng, and Shihe Counties, respectively. Additionally, seven catechins, four flavonoids, two purine alkaloids, and gallic acid contents were determined by HPLC. Differential metabolites were selected by p-value <0.05, and fold change >1.50 or < 0.66 among 745 detected metabolites in metabolomics analysis. The results showed significant (p < 0.05) differences of three catechins including (-)-epicatechin, (-)-epicatechin gallate, and (-)-gallocatechin gallate, four flavonoids (i.e. quercetin, kaempferol, myricetin, and rutin), and theobromine among three various regions, and significant (p < 0.05) differences of (-)-epicatechin gallate, (-)-epigallocatechin, (+)-catechin, gallic acid, and kaempferol between Shuchazao and Group cultivar. The HCA showed that, except for two samples (i.e. LS 2 and SH 2) of Shuchazao cultivar clustered together, others could be clustered completely according to production place. The 63 relevant differential metabolites could achieve the purpose of region identification through PCA. Kyoto encyclopedia of genes and genomes (KEGG) metabolic pathway analysis elaborated the impact of geographical origin and tea cultivar on physiological metabolism in tea tree. PRACTICAL APPLICATION: Ultra-high performance liquid chromatography-quadrupole time of flight-mass spectrometry (UHPLC-Q-TOF/MS)-based liquid chromatography-tendem mass spectrometry (LC-MS/MS) metabolomics coupled with multivariate statistical analyses, such as principal component analysis (PCA) and hierarchical cluster analysis (HCA), revealed 63 differential metabolites related to production place, which contributed to the region identification of Xinyang Maojian teas.

3-Methylxanthine production through biodegradation of theobromine by Aspergillus sydowii PT-2.

BACKGROUND: Methylxanthines, including caffeine, theobromine and theophylline, are natural and synthetic compounds in tea, which could be metabolized by certain kinds of bacteria and fungi. Previous studies confirmed that several microbial isolates from Pu-erh tea could degrade and convert caffeine and theophylline. We speculated that these candidate isolates also could degrade and convert theobromine through N-demethylation and oxidation. In this study, seven tea-derived fungal strains were inoculated into various theobromine agar medias and theobromine liquid mediums to assess their capacity in theobromine utilization. Related metabolites with theobromine degradation were detected by using HPLC in the liquid culture to investigate their potential application in the production of 3-methylxanthine. RESULTS: Based on theobromine utilization capacity, Aspergillus niger PT-1, Aspergillus sydowii PT-2, Aspergillus ustus PT-6 and Aspergillus tamarii PT-7 have demonstrated the potential for theobromine biodegradation. Particularly, A. sydowii PT-2 and A. tamarii PT-7 could degrade theobromine significantly (p < 0.05) in all given liquid mediums. 3,7-Dimethyluric acid, 3-methylxanthine, 7-methylxanthine, 3-methyluric acid, xanthine, and uric acid were detected in A. sydowii PT-2 and A. tamarii PT-7 culture, respectively, which confirmed the existence of N-demethylation and oxidation in theobromine catabolism. 3-Methylxanthine was common and main demethylated metabolite of theobromine in the liquid culture. 3-Methylxanthine in A. sydowii PT-2 culture showed a linear relation with initial theobromine concentrations that 177.12 ± 14.06 mg/L 3-methylxanthine was accumulated in TLM-S with 300 mg/L theobromine. Additionally, pH at 5 and metal ion of Fe2+ promoted 3-methylxanthine production significantly (p < 0.05). CONCLUSIONS: This study is the first to confirm that A. sydowii PT-2 and A. tamarii PT-7 degrade theobromine through N-demethylation and oxidation, respectively. A. sydowii PT-2 showed the potential application in 3-methylxanthine production with theobromine as feedstock through the N-demethylation at N-7 position.