Antidiabetic Effects of Pterocarpus marsupium (Gammalu)

Herbal medicines are considered to offer gentle means of managing chronic diseases at a lower cost. Pterocarpus marsupium Roxb. (PM) (Gammalu in Sinhala) heartwood and bark have been used as antidiabetic remedies in many cultures for thousands of years. The aim of this review is to address the existing evidence on antidiabetic effects of the P. marsupium. The hypoglycaemic effects, antidyslipidaemic effects, antioxidative effects and the safety of the PM heartwood and the bark have been scientifically validated using a multitude of in vitro and in vivo studies. Multiple mechanisms responsible for hypoglycaemic effects of PM including b-cell regeneration, insulin release and insulin-like actions of some compounds isolated were identified. (-)-Epicatechin, a flavonoid isolated from the bark has shown insulin-like effects, effects on b-cell regeneration and insulin release. Several compounds including pterostilbene and marsupsin isolated from the PM heartwood were identified as compounds with hypoglycaemic effects. The latex (gum) of the tree is a popular remedy used in Sri Lanka for diabetes even though the literature on PM does not discuss about the antidiabetic effects of the latex. Few investigations focused on the antidiabetic effects of PM latex have demonstrated strong inhibitory effects of the latex on α-amylase and α-glucosidase activities and on protein glycation. Investigations focusing on the antidiabetic effects and possible toxicity of the PM latex are essential to validate its efficacy and safety.