Antioxidant, antimicrobial activity and inhibition of α-glucosidase activity by Betula alnoides Buch. bark extract and their relationship with polyphenolic compounds concentration

Abstract

Betula alnoides has been widely used in local traditional medicinal treatment for a variety of diseases, wounds and to cure diabetes. The air-dried, powdered (200 g) bark was extracted with 80% methanol at room temperature. The combined 80% methanolic extract was partitioned with organic solvents to yield n-hexane, ethyl acetate (EtOAc), n-butanol (BuOH; water saturated), and aqueous fractions for the investigation of antioxidant and antimicrobiology and α-glucosidase activity effects (GAE) of B. alnoides. Antioxidant activity was studied by using antioxidant tests, including electron donation ability test, reducing power, and metal-chelating activity assay. Antioxidant, antimicrobial activity and α-glucosidase inhibitory effect of 80% methanolic extracts and fractions derived from the bark of B. alnoides were evaluated and determined. The results showed that 80% methanolic extracts exhibited high 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity (80.68%). In addition, both the 80% methanolic extract and EtOAc fraction exhibited more potent reducing activity than did butylated hydroxyanisole (BHA) and trolox. The aqueous fraction had higher metal-chelating activity than other fractions. The EtOAc fraction had the highest phenolic and flavonoid content (217.73 ± 1.02 mg GAE/g extract, and 38.42 ± 1.87 mg QE/g extract, respectively). The 80% methanolic extract and EtOAc fraction showed higher levels of antimicrobial activity than did other fractions. The 80% methanolic extract had the most powerful α-glucosidase inhibitory effect (98.46%) at a concentration of 40 µg/mL. The results suggest that bark extracts of B. alnoides could be a potential source of natural antioxidants and for treating pathogenic diseases.

Keywords::

• Betula alnoides
• flavonoid
• methanolic extracts
• antioxidant activity
• antimicrobial activity
• α-glucosidase inhibitory effect

Acknowledgments

This research was conducted by the financial support of Bioherb Research Institute, Kangwon National University (Korea). Also, authors express their gratitude to the Brian Pool (Konkuk University, Korea) for supporting this project.

Declaration of interest

The authors declare no conflict of interest.