Chemical composition by PTP 1B inhibitory activity guided analysis of a plant- based antidiabetic polyherbal drug used in ethnomedical systems

Abstract Background Due to growing resistance and continued depletion of drugs that can be used as replacements, people turn to herbal antidiabetic medicines. A polyherbal drug consisting of a mixture of two herbal plants, Zanthoxylum chalybeum and Xeroderris stuhlmannii root powder mixed in equal amounts using a tea cup, was studied to investigate its chemical composition and possible mode of action. Methods Phytochemicals were isolated using Column and Thin Layer Chromatography, and antidiabetic activity was ascertained using an enzyme inhibition model. Active compounds identity was established using 1 HNMR, 13 CNMR, HSQC-NMR, UV, FT-IR and MS spectroscopy. Results Results showed that the polyherbal drug consisted of two alkaloids and three anthocyanins as the major active components. PTP 1B inhibition of alkaloids was not significantly different from that of metformin with percentage inhibition of 78.6 ± 3.2 and 79.6 ± 2.3%. The anthocyanins inhibited PTP 1B enzyme significantly better than metformin with percentage inhibition of 88.2 ± 3.2, 90.3 ± 2.3 and 93.6 ± 2.9%. One new compound, an alkaloid, 1, 2-dimethoxy-12-methyl-7-(3-methylbut-2-en-1-yl)-12, 13-dihydro [1,3] benzodioxolo [5,6-c] phenanthridin-13-ol, one previously reported alkaloid berberine, IUPAC name, 9,10-dimethoxy-5,6-dihydro[1,3] dioxolo [4',5':6,7] isoquinolino [2,1-b][2] benzazin-7-ium and three anthocyanins,, malvidin 3-o-glucoside, pelargonidin-3-O-gucoside and malvidin 3, 5-O-diglucoside were identified as the active compounds in the polyherbal drug extract. Conclusion Presence of alkaloids and anthocyanins that have PTP 1B inhibitory activity showed that the polyherbal drug is a potential medicine for managing diabetes.