A Dissipation Pattern of Gibberellic Acid and Its Metabolite, Isogibberellic Acid, during Tea Planting, Manufacturing, and Brewing

Abstract

As a widely used plant growth regulator, the gibberellic acid (GA₃) residue in tea has potential risk for human health. Herein, the degradation of GA₃ and its conversion into main metabolites were investigated during tea planting, manufacturing, and brewing using ultrahigh-performance liquid chromatography tandem mass spectrometry. The metabolite iso-GA₃ was first discovered during the tea production chain and identified using Q-Exactive Orbitrap mass spectrometry. GA₃ dissipated following first-order kinetics in tea shoots with half-lives ranging from 2.46 to 2.74 days. It was degraded into iso-GA₃ in tea shoots, which had a longer residual period than GA₃. Meanwhile, external application of GA₃ could increase the proportion of growth-promoting endogenous phytohormones and lead to rapid growth of tea plants. During tea manufacturing, iso-GA₃ was quickly and massively converted from GA₃. Fixing (heat at 220-230 °C) played an important role in the dissipation of GA₃ and iso-GA₃ during green tea manufacturing, but there were high residues of iso-GA₃ in black tea. High transfer rates (77.3 to 94.5%) of GA₃ and iso-GA₃ were observed during tea brewing. These results could provide a practical reference for food safety in tea and other agricultural products and the guidance for scientific application of GA₃ in tea planting.