Ultrasound-assisted extraction optimization and antioxidant activity of Adenostemma lavenia leaves

Abstract

Adenostemma lavenia has been reported to possess significant value in traditional medicine and exhibit therapeutic potential. This study aimed to optimize the extraction conditions of A. lavenia leaves using an ultrasound-assisted technique. A completely randomized factorial design with two factors (extraction time and ethanol concentration) was implemented. Total phenolic content (TPC) and total flavonoid content (TFC) were determined using the Folin-Ciocalteu and AlCl₃ complex assays, respectively, while antioxidant activity was assessed using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and cupric ion reducing antioxidant capacity (CUPRAC) assays. The Rank Spearman test evaluated the correlation between TPC, TFC, and antioxidant activity. The results indicated that the optimal conditions were 45 minutes of extraction time and 90% ethanol concentration, yielding a TPC of 11.94±0.11 mg tannic acid equivalents (TAE)/g extract, a TFC of 0.51±0.00 mg quercetin equivalents (QE)/g extract, an antioxidant activity of 2,507.19±26.62 mg/L (IC₅₀ of DPPH assay), and 133.50±0.71 mg/L (EC₅₀ of CUPRAC assay). Antioxidant activity (CUPRAC assay) was significantly correlated with TFC in A. lavenia leaves. This study suggests that A. lavenia could be explored as a natural antioxidant.