Influence of extraction time on Flavonoid, Phenolic and DPPH Activity from Croton tonkinensis Gagnep. and Vitex negundo L.

Abstract

This study was conducted on ethanol extracts of Vitex negundo L. and Croton tonkinensis Gagnep. leaves which grown at the experimental farm of the Institute of Biotechnology, Tra Vinh University. The research objective was to evaluate the effect of sonication time on the content of flavonoids (TFC), phenolics (TPC), and antioxidant activities by DPPH method. The results showed that sonication time had a statistically significant effect on the content of TFC, TPC, and DPPH activity, and also showed clear differences between the two plant species. In Vitex negundo L., TFC (50 mgQE·g^-1), TPC (36.15 mgGAE·g^-1), and antioxidant activity (IC₅₀ = 1.33 mg·mL^-1) were highest at a sonication time of 5 minutes. Conversely, in Croton tonkinensis Gagnep, the TFC (25 mgQE·g^-1) and TPC (20.13 mgGAE·g^-1) content gradually increased with sonication time (15-30 minutes), then slightly decreased with increasing sonication time. The lowest antioxidant activity (IC₅₀ = 1.57 mg·mL^-1) was observed when the sonication time increased to 45 minutes. The study results show that polyphenol content and antioxidant activity depend on the stability and structural characteristics of the compounds under sonication. This research provides a scientific basis for optimizing the extraction process to improve the yield and biological activity of polyphenol compounds from plant sources.