Phenolics, antioxidant activity, and α-amylase inhibitory effect of Alpinia menghaiensis rhizome extracts

Abstract

Alpinia menghaiensis S.Q. Tong & Y.M. Xia, a member of the Zingiberaceae family, is often used in traditional medicine. Limited information regarding phenolics and bioactivities of this plant species is available in the literature. This study evaluates the phenolic composition, antioxidant activity, and α-amylase inhibitory effect of Alpinia menghaiensis rhizome extracts. The results revealed that the methanol/acetone extract contained the highest levels of catechin (9.22 ± 0.27 mg/g), p-coumaric acid (1.38 ± 0.02 mg/g), quercetin (1.74 ± 0.18 mg/g), and the highest total phenolic content (86.75 ± 5.89 mg/g). It also showed the most potent capacity to scavenge free DPPH and ABTS radicals, with IC50 values of 257.83 ± 13.02 and 497.20 ± 14.18 μg/mL, respectively. The extract obtained with ethyl acetate exhibited the strongest α-amylase inhibitory activity (IC50 = 394.03 ± 13.09 μg/mL). Correlation analysis demonstrated a strong positive correlation between total phenolic content and both DPPH (r = 0.958) and ABTS (r = 0.956) scavenging activities. These findings indicate that A. menghaiensis rhizomes are a rich source of phenolic compounds with significant antioxidant and enzyme inhibitory potential, making them a promising candidate for use in functional foods or pharmaceutical applications.