Abstract
BackgroundSome Ficus species have been used in traditional African medicine in the treatment of diabetes. The antidiabetic potential of certain species has been confirmed in vivo but the mechanism of activity remains uncertain. The aim of this study was to determine the activity and to investigate the mechanism of antidiabetic activity of ten selected Ficus species through inhibition of α-amylase and α-glucosidase activity, and the possible relationship between these activities, the total polyphenolic content and the antioxidant activity.MethodsDried acetone leaf extracts were reconstituted with appropriate solvents and used to determine total polyphenolic content antioxidant activity, α-amylase and α-glucosidase inhibitory activity.ResultsThe crude acetone extract of F. lutea had the highest polyphenolic content (56.85 ± 1.82 mg GAE/g of dry material) and the strongest antioxidant activity with a TEAC value of 4.80 ± 0.90. The antioxidant activity of the acetone extracts of the Ficus species may not be ascribed to total polyphenolic content alone. The crude extract at a concentration of 0.5 mg/ml of F. lutea (64.3 ± 3.6%) had the best α-glucosidase (sucrase) inhibitory activity. The EC50 of F. lutea (290 ± 111 μg/ml) was not significantly different from that of F. sycomorus (217 ± 69 μg/ml). The α-amylase inhibitory activity of F. lutea (95.4 ± 1.2%) at a concentration of 1 mg/ml was the highest among the Ficus species screened. The EC50 for F. lutea (9.42 ± 2.01 μ g/ml), though the highest, was not significantly different (p < 0.05) from that of F. craterostoma and F. natalensis. It was apparent that the crude acetone extract of F. lutea is a partially non-competitive inhibitor of α-amylase and α-glucosidase. Based on correlation coefficients polyphenolics may be responsible for α-glucosidase activity but probably not for α-amylase activity.ConclusionAntidiabetic activity potential via inhibition of α-amylase and α-glucosidase was discovered in Ficus lutea which has not been previously reported. The acetone extract of the leaves was high in total polyphenolic content and antioxidant activity, and was a potent inhibitor of α-amylase activity. Research is underway to isolate the active compound(s) responsible for the antidiabetic activity and to confirm the in vitro antidiabetic activity and to investigate in vitro toxicity.
Highlights
Some Ficus species have been used in traditional African medicine in the treatment of diabetes
Diabetes mellitus is an endocrine disease characterised by chronic hyperglycaemia with the disturbance of carbohydrate, fat and protein metabolism resulting from defects in insulin secretion, insulin action or both [1], and is typically associated with the failure of pancreatic β-cells
It is possible that the extracts of the Ficus species used in this study demonstrated potent α-amylase inhibitory activity because they contain more of the flavonoid groups with the extract of F. lutea being the most potent
Summary
Some Ficus species have been used in traditional African medicine in the treatment of diabetes. In type 1 diabetes, or insulin dependent diabetes mellitus, the body has little or no insulin secretory capacity and depends on exogenous insulin to prevent metabolic disorders and death. In sub-Saharan Africa the disease is considered to be an important emerging disease partly due to changes in diet and lifestyle of the people (a highly refined diet coupled to reduced physical activity). This is brought about by westernization, urbanization and mechanization, i.e. the disease which was once associated with only the affluent has increased in prevalence from 1% to 20% while in South Africa it is 4% to 6% [3,6,7]
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