Glucose Uptake Activity and Cytotoxicity of Abietane Diterpenes and Triterpenes Isolated from Lamiaceae Plant Species

The prevalence of diabetes mellitus (DM), considered one of the most common metabolic disorders, has dramatically increased and resulted in higher rate of morbidity and mortality around the world, in the past decade. It is well known that insulin resistance in target tissues and a deficiency in insulin secretion from pancreatic β-cells are the main characteristic of type 2 diabetes. The aim of this study was the bio-evaluation of compounds isolated from three selected plant species; namely, Salvia africana-lutea, Leonotis ocymifolia and Plectranthus madagascariensis, for their glucose uptake ability. Methanolic extracts were produced from the arterial part of each plant. Compounds were identified using different spectroscopic techniques. The glucose uptake ability of each compound was then evaluated in mammalian cells using 2-deoxyglucose-6-phosphate. The cytotoxicity of each compound was established via the MTT assay. Chromatographic purification of the three plant species yielded fifteen pure terpenoids. Compounds 1 (p = 0.0031), 8 (p = 0.0053), and 6 (p = 0.0086), showed a marked increase in glucose uptake, with p values of p=0.0031, p=0.0053 and p=0.0086, respectively. Additionally, 1, 4 and 6 exhibited cytotoxicity toward mammalian tissue with a decrease in cell viability of ~70%, ~68% and ~67%, respectively. The results suggested that several compounds demonstrated a marked increase in glucose uptake while two of the compounds exhibited signs of cytotoxicity. It may, therefore, be suggested that these compounds be considered as potential candidates for novel plant-derived alternative therapies in the treatment of type 2 diabetes.