In Vitro Antidiabetic and In Vivo Hypoglycaemic Activities and Toxicity of Canarium zeylanicum Bark Extracts

Abstract Aqueous bark extract of Canarium zeylanicum (Retz.) Blume (Burseraceae) is an antidiabetic remedy in indigenous medicine. Its antidiabetic potential has not been scientifically evaluated. In this study, antidiabetic activity and toxicity of the bark of C. zeylanicum were evaluated using a selected in vitro and in vivo set of experiments. A hot water extract (HWE) and an organic solvent extract (OSE) of the bark and respective negative and positive controls were subjected to in vitro α-amylase- and α-glucosidase-inhibitory and brine shrimp lethality assays. In vivo hypoglycaemic activity and hepato- and nephro-toxicities were evaluated by twice daily administration of each extract and the controls to 8 groups (n=10) of normoglycaemic Wistar rats for 14 days. Data of in vivo studies were statistically analysed using Minitab 16 with P- <0.05. IC50 values of HWE, OSE and the positive control in the α-amylase-inhibitory assay were 65.3 ± 18.5, 8.4 ± 4.1 and 0.04 ± 0.1 µg/ml, respectively; corresponding IC50 values in the α-glucosidase-inhibitory assay were 2.9 ± 0.1, 21.6 ± 0.5 and 0.01 ± 0.0 µg/ml. Brine shrimp lethality assay revealed that the extracts were non-toxic. In vivo studies revealed that extracts possess hypoglycaemic activity with higher percentage reduction (38.2 ± 12.9) of fasting blood sugar by OSE, high glucose tolerance, and the extracts were neither hepatotoxic nor nephrotoxic. Lupeol is one of the counterparts for the antidiabetic actions while some active compounds could not be resolved further. Results indicate that C. zeylanicum is a potential source for developing effective non-toxic antidiabetic drugs.