Botanical description, bioactivity guided isolation and in silico mode of action of anti-diabetic constituents of Pterocarpus dalbergioides flowers

Diabetes mellitus, a serious disorder with associated life-threatening complications, needs effective preventive and therapeutic interventions. There is an utmost need for an effective, safe and economical anti-diabetic drug, thereby medicinal plants can be considered as a useful intervention. Pterocarpus dalbergioides, an evergreen tree native to the Andaman Island, has been employed as a folk remedy for diabetes. Botanical features of the flowers of P. dalbergioides were described by macroscopic and microscopic analysis of both the fresh flowers and their fine powder. Bioactivity-guided isolation focusing on the assessment of anti-diabetic activity of the flowers of the plant in alloxan-induced diabetic rats was performed. The molecular activity of three isolated compounds against six important targets having a prominent role in diabetes pathophysiology was also done. The results revealed that the n-butanol fraction prevented the diabetogenic effect of alloxan and decreased significantly the blood glucose level (p < 0.01) in treated rats. Three flavones, luteolin (F1), luteolin-7-O-glucoside (F2), and luteolin-7-O-rutinoside (F3) were isolated from the flower of the studied plant for the first time. A high-performance liquid chromatography technique (HPLC) was used to quantify luteolin as a major isolated phenolic compound. Docking-based mode of action prediction of isolated compounds revealed that all three compounds can act as an inhibitor of PTP1B, DPP4, α-amylase, and also an activator of PPAR-γ and FFAR1. Consequently, the current research includes botanical characteristics of the flowers of the plant which facilitate its authentication and indicates that P. dalbergioides flower could be of therapeutic benefit for the management of diabetes mellitus.