Evaluation of the Effect of Excipient-free Processing on Total Phenolic Content and Antioxidant Activity of Fallopia multiflora Thunb.

Introduction: Fallopia multiflora Thunb., a valued herb in traditional medicine, is rich in phenolics, primarily anthraquinones and stilbenes, contributing to its potent antioxidant activity. The ratio between two chemical markers, emodin (EM, an anthraquinone) and 2,3,5,4′-tetrahydroxystilbene-2-O-β-D-glucoside (THSG, a stilbene), is crucial in determining the herb's toxicity. A previous study established a processing method for Fallopia multiflora Thunb. without excipients, increasing the EM/THSG ratio by over 2.6-fold compared to unprocessed herbs, aiming to control effects and reduce toxicity. Objective: This study aimed to evaluate the impact of the excipient-free processing method on the total phenolic content and in vitro antioxidant activity of Fallopia multiflora Thunb. Materials and Methods: Fallopia multiflora Thunb. materials, meeting the standards of the Vietnamese Pharmacopoeia V, were processed by soaking in water for 3 hours, followed by boiling in water for 90 minutes. Total phenolic content was evaluated using the Folin-Ciocalteu (FC) reagent. In vitro antioxidant activity was evaluated using the DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging assay. Results: After processing, total phenolic content, expressed as gallic acid equivalents (GAE), increased slightly by 1.04% (from 22.17 ± 0.05 mg GAE/g to 22.40 ± 0.07 mg GAE/g). Notably, antioxidant activity increased significantly, as evidenced by a 1.9-fold decrease in the extract concentration required to neutralize 50% of DPPH radicals (from 126.94 ± 0.77 µg/ml to 66.46 ± 0.31 µg/ml). Conclusion: The excipient-free processing method increased the total phenolic content and enhanced the antioxidant activity of Fallopia multiflora Thunb.