New Enzyme Inhibitory Constituents from Tribulus longipetalus

Normal and reversed phase chromatographic purification of the chloroform soluble fraction of the methanolic extract of Tribulus longipetalus led to the isolation of a new tyramine amide, longipetalamide (1), two new benzocoumarins, longipetalasin A (8-n-propyl-threo-1S,2S-dihydroxy-5-methoxy-5a,9abenzocoumarin; 2) and B (8-n-propyl-threo-1S,2S-dihydroxy-5,10-dimethoxy-5a,9a-benzocoumarin; 3) together with 1,2,3-propantriyl trioleate (4), crotamide A (5), stigmasterol (6), (25S)-5α-furustan-22-methoxy3β,26-diol (7), neotigogenin (8), tigogenin (9), methyl 4-hydroxyphenyl acetate (10) and 2-O-methylinositol (11). All the isolates (1-11) were characterized by using UV, IR, 1D( 1 H and 13 C), 2D-NMR (HSQC, HMBC, COSY) spectroscopy, mass spectrometry (EI-MS, HR-EI-MS, FAB-MS, HR-FAB-MS) and in comparison with the data reported in literature. The compounds 1-11 were evaluated for their enzyme inhibition studies against αglucosidase, lipoxygenase (LOX), acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes and found that 2 and 3 were the significant inhibitors of enzyme α-glucosidase with IC50 values 94.17 ± 0.09 and 85.65 ± 0.08 μM, respectively.