Abstract:

In this study, flavonoids were extracted from the leaves of Aquilaria sinensis (Lour.) Gilg by solvent extraction
method and assessed for their antioxidant activities by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging,
2,2’-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) radical scavenging, and potassium ferricyanide reduction assays.
Ethanol concentration, extraction temperature and liquid-to-solid ratio were identified by single factor method as main
variables that affect the extraction yield of flavonoids. The levels of the three variables were optimized by response surface
methodology. The optimum extraction conditions were found to be extraction at 60 ℃ for 3 h using 60% aqueous ethanol
with a liquid-to-solid ratio of 20:1 (mL/g), leading to an extraction yield of 2.88% (m/m). The antioxidant assays showed that
the extracted flavonoids presented a strong antioxidant activity to scavenge DPPH and ABTS radicals with median effective
concentrations (EC50) of (1.14 ± 0.08) mg/mL and (0.23 ± 0.01) mg/mL, respectively.

Key words: Aquilaria sinensis (Lour.) Gilg leaves, flavonoids, extraction, antioxidant activity