Effect of ultrasound-assisted extraction on total phenolics, flavonoids, 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 evaluate 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. At the same time, 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 optimum 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, antioxidant activity of 2,507.19±26.62 mg/L (IC50 of DPPH assay), and 133.50±0.71 mg/L (IC50 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.