New lipoxygenase and cholinesterase inhibitory sphingolipids from Carthamus oxyacantha.

Two new sphingolipids: oxyacanthin A [(2S,3S,4R)-2-{[(2R,5E)-2-hydroxyoctadec-5-enoyl]amino}hexaeicosane-1,3,4-triol; 1] and B [(2S,3S,4R)-2-{[(2R,5E)-2-hydroxyoctadec-5-enoyl]amino}hexaeicosane-1,3,4-triol-1-O-ß-D-glucopyranoside; 2], together with 1-octacosanol, ß-sitosterol, ß-sitosterol 3-O-ß-D-glucopyranoside and luteolin 7-O-ß-glucopyranoside were isolated from the methanolic extract of the whole plant of Carthamus oxyacantha. Their structures were elucidated using (1)H and (13)C NMR spectra and 2D NMR analyses (HMQC, HMBC and COSY) in combination with mass spectrometry (EI-MS, HR-EI-MS, FAB-MS and HR-FAB-MS) experiments and in comparison with the literature data of the related compounds. Both the compounds 1 and 2 showed inhibitory potential against lipoxygenase (LOX) in a concentration-dependent manner with IC50 values 83.3 ± 1.3 and 245.7 ± 1.1 µM, whereas compound 2 showed inhibition against enzymes acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) with IC50 values 65.3 ± 0.1 and 93.6 ± 0.1 µM, respectively.

Isolation of natural compounds from Phlomis stewartii showing α-glucosidase inhibitory activity.

Stewartiiside (1), a phenylethanoid glycoside and three 28-nortriterpenoids: stewertiisins A-C [(17R)-19(18→17)-abeo-3α,18ß,23,24-tetrahydroxy-28-norolean-12-ene, 2; (17R)-19(18→17)-abeo-2α,16ß,18ß,23,24-pentahydroxy-28-norolean-12-en-3-one, 3; (17R)-19(18→17)-abeo-2α,3α,23,24-tetrahydroxy-28-noroleane-11,13-diene, 4] together with eight known compounds: lunariifolioside (5), notohamosin A (6), phlomispentanol (7), isorhamnetin 3-(6-p-coumaroyl)-ß-D-glucopyranoside (8), tiliroside (9), caffeic acid (10), p-hydrxybenzoic acid (11) and oleanolic acid (12) were isolated from the ethyl acetate soluble fraction of the methanolic extract of whole plant of Phlomis stewartii. The structures of these isolates (1-12) were elucidated by the combination of 1D ((1)H and (13)C NMR), 2D (HMQC, HMBC COSY, NOESY) NMR spectroscopy and mass spectrometry (EIMS, HREIMS, FABMS, HRFABMS) and in comparison with literature data of related compounds. All the isolates (1-12) showed α-glucosidase inhibitory activity with IC50 values ranging between 14.5 and 355.4 µM, whereas, compounds 1, 5, 9 and 10 showed promising α-glucosidase inhibitory activity with IC50 values below 30 µM.