Abstract:
Background: Scientific investigations of biological activities of plant extracts are important to
develop formulations for diabetes mellitus as it is a major health concern in the world.
Therefore, it is beneficial to investigate the antioxidant and anti-diabetic activities of medicinal
plants which were less evaluated for their anti-diabetic activities.
Objectives: To evaluate in-vitro antioxidant activities, Total Phenolic Content (TPC) and anti diabetic activities of the fruits of Garcinia sp. and Bunchosia armeniaca, leaves of Plectranthus
zatarhendi, roots of Hibiscus furcatus and seeds of Gossypium sp.
Methods: Plant parts which were collected from the field or from grown pots in Sri Lanka were
forwarded for plant authentication at the National Herbarium, Peradeniya Botanical Gardens,
Sri Lanka. Series of different concentrations of aqueous (AE) and 1:1 dichloromethane:
methanol [organic (OE)] extracts of plants were subjected to estimation of TPC using Folin Ciocalteu reagent method, antioxidant activity by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay,
carbohydrate digesting enzyme inhibitory activity assays. Data were analysed using GraphPad
prism 8.4.2. (679) version software and results were expressed as simple descriptive statistics.
Results: Garcinia sp. OE showed the highest DPPH inhibition (IC50, 0.12±0.0 mg/mL)
followed by AE of P. zatarhendi and OE of P. zatarhendi. The highest TPC was found in the
AE of P. zatarhendi (2.43 mg GAE/g) followed by OE of P. zatarhendi and OE of Garcinia sp.
OE of Garcinia sp. showed the highest α-amylase and α-glucosidase enzymes inhibitory
activities with IC50, 1.99±0.0 mg/mL and, 1.76±0.0 mg/mL, respectively. All other selected plant
extracts showed less carbohydrate digesting enzyme inhibitory activities (IC50˃5 mg/mL). The
acarbose showed IC50, 0.19±0.0 mg/mL and 0.01±0.0 g/mL against α-amylase and α glucosidase enzymes, respectively.
Conclusions: It is concluded that the OE extracts of Garcinia sp. showed the highest in-vitro
antioxidant and anti-diabetic activities. However, the highest TPC was observed with the AE of
P. zatarhendi.
