Impact of harvest season on bioactive compounds, amino acids and in vitro antioxidant capacity of white tea through multivariate statistical analysis

Abstract

To explore the impact of harvest season in white tea, high-performance liquid chromatography (HPLC) and amino acid analyzer were developed for the determinations of 17 phenolic compounds, 3 purine alkaloids, 19 amino acids, γ-aminobutyric acid (GABA) and 4 main quality components in 18 Bai mudan sub-type of Xinyang white teas harvested in spring, summer and autumn seasons, respectively. Additionally, the in vitro antioxidant capacity was evaluated by 5 various assays. Principal component analysis (PCA), hierarchical cluster analysis (HCA) and partial least squares-discriminant analysis (PLS-DA) could completely classify these white teas by the harvest season, and indicated its profound impact on chemical composition in white tea. 14 Characteristic compounds (VIP ≥1.0), such as (−)-epigallocatechin (EGC), gallic acid, caffeine, l-theanine, conduced to identify the harvest season of white tea. Through comparison, the spring tea was observed to possess the highest amino acids, catechins contents and in vitro antioxidant capacity. (−)-Epicatechin (EC), EGC, (−)-epicatechin gallate (ECG) and (−)-epigallocatechin gallate (EGCG) were considered as the major antioxidants in white tea due to their highly significantly (p < 0.01) positive correlations. Overall, the research results provided support for the identification of harvest season in white tea.