Impact of extraction methods on bioactive compounds and antioxidant activities of Thai jasmine rice leaf extracts

Studies have recently highlighted potential health benefits of young rice leaves; however, optimization of extraction process was often overlooked. The present study aimed to assess impacts of extraction methods, namely, maceration and decoction, on total phenolics content and antioxidant activities based on FRAP, DPPH, and ABTS assays of extracts from Thai cultivar of Jasmine rice leaves. The study examined influences of ethanol concentration (0–100% (v/v) for maceration), boiling time (10–30 min for decoction) and solvent-to-solid ratio (20–40 mL g−1 for both maceration and decoction). Results showed that under its optimal condition (50% (v/v) ethanol concentration and solvent-to-solid ratio of 30 mL g−1), maceration yielded significantly higher total phenolic content, 12.54 ± 0.94 mg GAE/g DW. Furthermore, mechanisms of single electron transfer responsible for antioxidant activities were explored, identifying flavonoids as potential chemical markers in rice leaf extracts. Flavonoid derivatives, specifically isoorientin (3.33 ± 0.10 mg/g DW) and isovitexin (0.98 ± 0.03 mg/g DW), were subsequently quantified. This research contributed to improved understanding of relations between bioactive compounds and their antioxidant activities. The findings also underscore potential of Thai Jasmine rice leaves as natural additives in future functional foods production.