Optimization of tea-leaf saponins water extraction and relationships between their contents and tea () tree varieties.

Resulting from the year-on-year increase in tea plantations and the saturated consumption of tea leaves, the relative overcapacity in China's tea-leaf production appears. Discovering the new utilization of tea leaves is helpful to alleviate this phenomenon. The feasibility of extracting saponins from aged tea leaves was investigated and confirmed; three major variables in water extraction were optimized by Box-Behnken designs. The significant variable found in Box-Behnken designs, liquid-solid ratio, was went through single-variable experiments for a more accurate optimization. Seventy-five ml/g, 1 hr, and 80°C were optimal values and tea-leaf saponins yield of tea tree variety Longjing 43 reached 12.19% ± 0.0030% after optimizations, higher than the yield of tea-seed saponins from seed meals using the same extraction method (water extraction based on optimizations). According to correlation analyses, tea tree's leaf type and germination stage affected tea-leaf saponins contents positively, indicating tea trees with larger leaves and later germination stage would have a higher content of tea-leaf saponins with a higher yield of tea-leaf saponins under the same extraction method.