Antioxidant Activity and a-Glucosidase Inhibitory Activity of Mesona chinensis Aqueous Extract

Mesona chinensis is raw material for the production of a black grass jelly in Thailand. Mesona chinensis aqueous extract (MCAE) has been reported as a promising anti-hyperglycemia agent. The better understanding of MCAE on its production and biological activities would facilitate the development of a new functional ingredient and beverage. Thus, the effects of botanical source on bioactive compounds, antioxidant activity and hypoglycemic activity of MCAE were investigated. In this present study, we prepared four MCAEs from M. chinensis plants imported from China (2 sources), Vietnam, and Indonesia. Based on data analysis, botanical source of M. chinensis significantly governed total phenolic content, total flavonoids content, DPPH radical scavenging activity and a-glucosidase inhibition activity of MCAE ( p<0. 05) . The results showed that MCAEs possessed considerable amount of total phenolics (68.63-133.27 mg GAE/g) and trace amount of total flavonoids (3.49-5.83 mg QE/g). MCAEs exhibited potent antioxidant (IC₅₀=17.54-37.98 mg/mL) and efficient inhibitor against alpha-glucosidase (IC₅₀=4.77-26.86 mg/mL). The enzyme kinetics data revealed that MCAE inhibited a-glucosidase activity in a concentration-dependent manner. Moreover, the Lineweaver-Burk plot elucidated that the inhibition type of a-glucosidase activity by MCAE was a noncompetitive manner with the inhibitory constant (K_i) of 2.67 mg/mL.