Antidiabetic and antioxidant properties of Ficus deltoidea fruit extracts and fractions

Diabetes is a serious metabolic disorder affecting the metabolism of carbohydrate, protein and fat. A number of studies have shown that diabetes mellitus is associated with oxidative stress, leading to an increased production of reactive oxygen species. Ficus deltoidea is traditionally used in Malaysia for regulating blood sugar, blood pressure and cholesterol levels. The use of F. deltoidea as an alternative medicinal herb is increasingly gaining popularity with the sale of F. deltoidea tea bags and capsules in the local market. The present study was undertaken to investigate the antidiabetic and antioxidant activities of the fruits from different varieties of F. deltoidea, employing in vitro methods.

Two fruit varieties of F. deltoidea (var. angustifolia (SF) and var. kunstleri (BF)) were extracted separately using double-distilled water. The resulting aqueous extracts were partitioned using ethyl acetate to obtain the ethyl acetate and water fractions. The crude aqueous extracts and the corresponding fractions were evaluated for their phenolic, flavonoid, sugar and protein contents. Protein profiling of the extracts and fractions were also carried out by means of SDS-PAGE and SELDI-TOF MS. Antidiabetic activities were assessed based on the ability of the samples to inhibit yeast and mammalian α-glucosidase as well as α-amylase. Antioxidant capacities were examined by measuring the ability of the samples to reduce ferric ions and to scavenge DPPH, superoxide anion, ABTS and nitric oxide radicals.

The crude extracts and fractions of SF and BF inhibited both yeast and rat intestinal α-glucosidases in a dose-dependent manner, but did not inhibit porcine pancreatic α-amylase. The water fraction of BF showed the highest percentage of α-glucosidase inhibition while having the highest amount of protein (73.33 ± 4.99 μg/mg fraction). All the extracts and fractions exhibited antioxidant activities, with SF crude extract showing the highest antioxidant activity and phenolic content (121.62 ± 4.86 mg/g extract). Fractionation of the crude extracts resulted in loss of antioxidant activities. There was no positive correlation between phenolic and flavonoid content with α-glucosidase inhibitory activities. However, phenolic content correlated well with antioxidant activities of the crude extracts but not with the fractions.

The antioxidant activities of the fruits of F. deltoidea might be asserted by the phenolic content but other polar plant components were possibly involved in the antidiabetic properties. The study of these compounds having both antihyperglycemic and antioxidant activities may provide a new approach in the treatment of diabetes mellitus.