Chemical profiling, antioxidant and carbohydrate-metabolising enzymes inhibitory potential of fractions from the leaves of Macaranga bateri Mull-Arg

Abstract

Macaranga barteri Mull-Arg is a popular medicinal plant used in different parts of West Africa for the treatment of various ailments including diabetes mellitus. The current study investigates in vitro antidiabetic potentials of ethanol extract fractions from Macaranga barteri. Their antioxidant properties and bioactive chemical constituents were also examined.

The antioxidant activity was determined using iron chelation, 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl, 2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS), superoxide anion and nitric oxide (NO) radical scavenging abilities of fractions from M. bateri while the antidiabetic potential was assessed by evaluating the inhibitory effects of the extracts on the activities of α-amylase and α-glucosidase. Bioactive constituent investigations were carried out using standard methods and GC-MS analysis.

The methanol fraction displayed significantly higher (p < 0.05) DPPH (0.47 mg/mL) and NO (1.68 mg/mL) scavenging activities while ethylacetate (0.61 mg/mL) and hexane (0.49 mg/mL) exhibited strong metal chelating and ABTS radical scavenging activity, respectively. The methanol fraction displayed significantly higher (p < 0.05) inhibition against α-amylase (1.14 mg/mL) and α-glucosidase (0.46 mg/mL). The hexane fraction inhibited α-amylase and α-glucosidase in mixed non-competitive and uncompetitive modes, respectively. Total phenol and flavonoid for the methanol fraction were 40.35 mg gallic acid g^-1 and 286.02 mg quercetin g^-1, respectively while the total proanthocyanindins of the ethylacetate fraction was 74.29 mg catechin g^-1.

The GC-MS chromatogram revealed neophytadine (6.01%), trans-caryophyllene (5.03%), methyl hexadecanoate (4.00%) and phytol (2.32%) as major constituents of the methanol fraction.

The results indicate M. bateri leaves as a source of bioactive constituents with therapeutic potentials in the management of diabetes.

Keywords:

• Macaranga barteri
• antioxidant
• α-glucosidase
• α-amylase
• phytochemical