Background: Traditional Indian and Australian medicinal plant extracts were investigated to determine their therapeutic potential to inhibit key enzymes in carbohydrate metabolism, which has relevance to the management of hyperglycemia and type 2 diabetes. The antioxidant activities were also assessed.Methods: The evaluation of enzyme inhibitory activity of seven Australian aboriginal medicinal plants and five Indian Ayurvedic plants was carried out against α-amylase and α-glucosidase. Antioxidant activity was determined by measuring (i) the scavenging effect of plant extracts against 2, 2-diphenyl-1-picryl hydrazyl (DPPH) and 2, 2′-azinobis-3-ethylbenzothiazoline-6-sulfonate (ABTS) and (ii) ferric reducing power. Total phenolic and total flavonoid contents were also determined.Results: Of the twelve plant extracts evaluated, the highest inhibitory activity against both α-amylase and α-glucosidase enzymes was exerted bySantalum spicatumandPterocarpus marsupiumwith IC₅₀values of 5.43 μg/ml and 0.9 μg/ml, respectively, and 5.16 μg/ml and 1.06 μg/ml, respectively. However, the extracts ofAcacia ligulata(IC₅₀ = 1.01 μg/ml),Beyeria leshnaultii(0.39 μg/ml),Mucuna pruriens(0.8 μg/ml) andBoerhaavia diffusa(1.72 μg/ml) exhibited considerable activity against α-glucosidase enzyme only. The free radical scavenging activity was found to be prominent in extracts ofAcacia kempeana,Acacia ligulatafollowed byEuphorbia drummondiiagainst both DPPH and ABTS. The reducing power was more pronounced inEuphorbia drummondiiandPterocarpus marsupiumextracts. The phenolic and flavonoid contents ranged from 0.42 to 30.27 μg/mg equivalent of gallic acid and 0.51 to 32.94 μg/mg equivalent of quercetin, respectively, in all plant extracts. Pearson’s correlation coefficient between total flavonoids and total phenolics was 0.796.Conclusion: The results obtained in this study showed that most of the plant extracts have good potential for the management of hyperglycemia, diabetes and the related condition of oxidative stress.

Plant-derived compounds have been used clinically to treat type 2 diabetes for many years as they also exert additional beneficial effects on various other disorders. The aim of the present study was to investigate the possible mechanism of anti-diabetic activity of twelve (seven Australian Aboriginal and five Indian Ayurvedic) plant extracts. The ethanolic plant extracts were investigated for glucose uptake and adipogenesis in murine 3T3-L1 adipocytes. Cytotoxicity studies were also carried out against two cancerous cell lines, HeLa and A549, to investigate the potential anti-cancer activities of the extracts. Of the seven Australian Aboriginal plant extracts tested, only Acacia kempeana and Santalum spicatum stimulated glucose uptake in adipocytes. Among the five Indian Ayurvedic plant extracts, only Curculigo orchioides enhanced glucose uptake. With respect to adipogenesis, the Australian plants Acacia tetragonophylla, Beyeria leshnaultii and Euphorbia drumondii and the Indian plants Pterocarpus marsupium, Andrographis paniculata and Curculigo orchioides reduced lipid accumulation in differentiated adipocytes. Extracts of Acacia kempeana and Acacia tetragonophylla showed potent and specific activity against HeLa cells. The findings suggest that the plant extracts exert their anti-diabetic properties by different mechanisms, including the stimulation of glucose uptake in adipocytes, inhibition of adipogenesis or both. Apart from their anti-diabetic activities, some of the extracts have potential for the development of chemotherapeutic agents for the treatment of cervical cancer.