Phytochemicals with α-glucosidase inhibitory activity from cissus javana, dendrobium christyanum, gastrochilus bellinus and huberantha jenkinsii

Abstract

Phytochemical investigations of Cissus javana DC., Dendrobium christyanum Rchb. f., Gastrochilus bellinus Rchb. f. Kuntze and Huberantha jenkinsii (Hook. f. & Thomson) Chaowasku led to the isolation of twenty-seven compounds, six of which were new naturally occurring compounds. From Cissus javana, three known compounds were isolated, including bergenin, stigmast-4-en-3-one, and β-sitosterol. From Dendrobium christyanum, thirteen known compounds were identified, namely, n-eicosyl trans-ferulate, n-docosyl 4-hydroxy-trans-cinnamate, 4,5-dihydroxy-2-methoxy-9,10-dihydrophenanthrene, moscatilin, aloifol I, gigantol, batatasin III, dendrosinen B, coniferyl aldehyde, methyl haematommate, atraric acid, vanillin and diorcinolic acid. From Gastrochilus bellinus, four new compounds, comprising three phenanthropyrans and a phenanthrene derivative, were isolated and structurally characterized. From Huberantha jenkinsii, two new alkaloids of 8-oxoprotoberberine type were isolated along with five known compounds including mangiferin, allantoin, oxylopinine, N-trans-feruloyl tyramine and N-trans-p-coumaroyl tyramine. The structures of these compounds were determined by UV, IR, MS and NMR spectroscopic methods, and comparison of the data with literature values. Methyl haematommate (IC50 18.7 ± 2.1 µM), n-docosyl 4-hydroxy-trans-cinnamate (IC50 4.6 ± 0.2 µM), N-trans-feruloyl tyramine (IC50 30.6 ± 2.9 µM) and N-trans-p-coumaroyl tyramine (IC50 0.6 ± 0.1 µM) showed potent α-glucosidase inhibitory activity in comparison with the drug acarbose (IC50 724.7 ± 46 µM). N-Docosyl 4-hydroxy-trans-cinnamate at 0.212 mM also displayed 31.6 ± 4.4 %. enhancement of glucose uptake in L6 cells. Mangiferin showed moderate α-glucosidase inhibition (IC50 253.6 ± 14.2 µM) and recognizable cellular glucose uptake stimulatory activity (208.1 ± 10.7% enhancement at a concentration of 0.237 mM) as compared with insulin (146.6 ± 35.8 % at a concentration of 500 nM).