Impact of Altitude, Seasonal Variation, and Processing Parameters on Bioactive Compounds and Antioxidant Potential of Darjeeling Tea

Abstract

The study aims to explore the influence of processing parameters, altitude, seasonal variations, and soil conditions on the metabolite composition and antioxidant activity of Darjeeling tea. The Camellia sinensis var. sinensis were sampled from different processing stages of two Darjeeling tea gardens situated at different altitudes representing different environmental conditions and investigated for targeted metabolomics using high-performance thin layer chromatography (HPTLC) techniques where eight key bioactive compounds were chosen for the analysis. The antioxidant activity demonstrated a positive association with altitude, with elevated levels of total phenol (25.7 μg GAE/g), total flavonoid (4253.09 μg QEA/g), DPPH (94.09%), and H2O2 (95.94%) observed in the final processed tea from the higher elevation garden. Conversely, seasonal transitions exhibited a detrimental effect on antioxidant activity, with a decline from 94.09 to 78.65% (DPPH) and 95.94 to 84.98% (H2O2) during the shift from spring to summer and autumn in the higher elevation garden. Soil analyses unveiled significant positive correlations between pH (r= +0.98) and total flavonoid, carbon (r = +0.85), and potash (r = +0.99) with H2O2, and sulfur (r = +0.98) with total phenol. The study highlights the complex interplay of altitude, seasonality, processing parameters, and soil characteristics in shaping the accumulation of bioactive compounds in tea.