Response Surface Optimized Extraction of Total Triterpene Acids from Eriobotrya japonica   (Thunb) Lindl (Loquat) Leaf and Evaluation of their In vitro Antioxidant Activities

Purpose: To optimize extraction of total triterpene acids from loquat leaf and evaluate their in vitro antioxidant activities.
Methods: The independent variables were ethanol concentration, extraction time, and solvent ratio, while the dependent variable was content of total triterpene acids. Composite design and response surface method were used to optimize the extraction process, while antioxidant activity was evaluated in vitro using α,α-diphenyl-β-picrylhydrazyl (DPPH) and pyrogallol autoxidation methods.
Results: The optimum extraction conditions were as follows: 81 % ethanol, extraction time 160 min, and extraction cycles 2, ratio of solvent to sample 14mL/g. Under these conditions, the yield of total triterpene acids reached 3.41 %. Furthermore, total triterpene acids exhibited strong reducing power, as well as radical scavenging activity against DPPH (IC₅₀, 203.41 mg/L) and superoxide anion free radical; when the concentration was > 274.64 mg/L, scavenging ability increased significantly.
Conclusion: Total triterpene acids from loquat leaf possess an antioxidant activity in vitro, but further studies are required to develop them into effective drugs and health foods for human applications.

Keywords
Eriobotrya japonica (Thunb.) Lindl.,; Triterpene acids; Extraction optimization; Response surface methodology; Antioxidant