Quick identification of piperidine alkaloid from roots of Grewia nervosa and their glucosidase inhibitory activity

Abstract

Grewia nervosa is herbal plant used as traditional medicine for different purposes. Bioassay-guided chemical fractionation of G. nervosa roots resulted in an identification of two known and one new compound, named Microgrewiapine A, Homomicrogrewiapine and N-methyl-microcosamine respectively. Their structures were determined using combination of LC-HRMS, 1H NMR and IR spectra analyses followed by comparison with those reported in the literature. The problematic separation of these alkaloids on traditional column chromatography (Silica gel, Octadecyl silane (ODS), Sephadex) was resolved by using HPLC method. Structurally identical compounds from the piperidine family have been characterized by using HRMS analysis in combination with NMR data of crude sample. The major constituent i.e. N-methyl-microcosamine in n-butanol fraction of methanol root extract (MRE) was found to possess the dose dependent α-glucosidase inhibition activity with an IC50 value of 53.40 mu M. Furthermore, N-Methyl-microcosamine showed maximum α-glucosidase inhibition was 97.48 plus or minus 0.7 percent at 107.5 mu M, which is approximately 1.3 x 10 sup(3) fold higher than the activity shown by acarbose (97.72 percent inhibition at 61.95 mM), a standard anti-diabetic drug available commercially. This work also reports the in vitro α-glucosidase inhibitory activity of the major alkaloids isolated from G. nervosa for the first time.