Antioxidant and inhibitory properties of Dombeya burgessiae leaf extracts on enzymes linked to diabetes mellitus

Abstract

This study evaluated the in vitro antioxidant and antidiabetic potential of different extracts of Dombeya burgessiae leaf. Different concentrations (3.13–100 µg/ml) of aqueous, ethanol and hydro-ethanol extracts of D. burgessiae were subjected to standard in vitro antioxidant tests, namely 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl and superoxide radical scavenging abilities as well as iron chelating potential. The antidiabetic study was done by assessing the inhibitory effects of these extracts on the activities of diabetes-related enzymes (α-amylase, α-glucosidase, maltase and sucrase). Ethanol extract of D. burgessiae exhibited the best DPPH radical (EC₅₀: 68.45 µg/ml) scavenging ability while hydro-ethanol extract displayed the most potent hydroxyl (EC₅₀: 30.71 µg/ml) and superoxide (EC₅₀: 27.09 µg/ml) radical scavenging, as well as iron chelating (EC₅₀: 38.09 µg/ml) ability. Hydro-ethanol extract also exhibited the best inhibition of α-amylase (IC₅₀: 43.99), α-glucosidase (IC₅₀: 10.94 µg/ml) and sucrase (IC₅₀: 16.21 µg/ml) activities while maltase was most inhibited by aqueous extract (IC₅₀: 28.76 µg/ml) of D. burgessiae. A Lineweaver–Burk plot revealed that hydro-ethanol extract inhibited α-glucosidase and maltase in non-competitive and uncompetitive manners, respectively while both α-amylase and sucrase were inhibited mixed non-competitively. Hydro-ethanol extract of D. burgessiae possessed antioxidant as well as antidiabetic potential, and one of its mechanisms of antidiabetic action is the inhibition of diabetes-related enzymes.

Keywords:

• oxidative stress
• hyperglycaemia
• enzyme inhibition
• acarbose

DISCLOSURE STATEMENT

The authors declare no conflict of interest in the publication of this manuscript.

ORCID

Mutiu Idowu Kazeem http://orcid.org/0000-0002-8058-1938

Additional information

Funding

The authors hereby acknowledge the National Research Foundation (NRF), South Africa for the NRF Freestanding Postdoctoral Fellowship granted to Dr. M. I. Kazeem (grant no. 88342), tenable at the Phytomedicine and Phytopharmacology Research Unit of the Department of Plant Sciences, University of the Free State, Qwaqwa Campus, Phuthaditjhaba, South Africa. Our gratitude equally goes to the UFS-Qwaqwa Research Committee for the funding (211427604).