BACKGROUND: Some 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.
METHODS: Dried acetone leaf extracts were reconstituted with appropriate solvents and used to determine total
polyphenolic content antioxidant activity, α-amylase and α-glucosidase inhibitory activity.
RESULTS: The 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.
CONCLUSION: Antidiabetic 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.