Antimicrobial and α-glucosidase inhibitory activities of chemical constituents from Gardenia aqualla (Rubiaceae)

An aliphatic alkene namely pentapentacontene (4) was isolated for the first time from a natural source, Gardenia aqualla, along with fourteen other compounds including nonacosanol (1), tetratriacontanol (2), octatriacontanol (3), beta-sitosterol (5) and stigmasterol (6), daucosanol (7), ursolic acid (8), uvaol (9), 3 beta,19 alpha,23 beta,24 alpha-tetrahydroxyurs-12-en-28-oic acid (10), lupenone (11), oleanolic acid (12), vanillin (13), vanillic acid (14) and D-mannitol (15). alpha-glucosidase inhibitory assay revealed that MeOH and EtOAc extracts of leaves had the best activity with IC50 of 9.65 and 20.03 mu g/ml respectively. All the tested compounds showed dose dependent inhibition of alpha-glucosidase and some of them were found to be comparable to acarbose. Compound 10 was the most potent with IC50 = 1.72 mu M. It also showed the most interesting antibacterial activity, against the isolate strain of S. typhi and P. aeruginosa and also exhibited the most significant antifungal activities against all the tested yeasts.