Objective: To investigate the chemical constituents of tuber of Gymnadenia conopsea.
Method: The constituents were isolated by using a combination of various chromatographic techniques including column chromatography over silica gel, Sephadex LH-20, and C-18, as well as reversed-phase HPLC. Structures of the isolates were identified by spectroscopic data analysis.
Result: Thirty-four compounds were isolated. Their structures were identified as six 2-isobutyltartrate benzyl ester glucosides: coelovirin A (1), coelovirin B (2), coelovirin E (3), coelovirin D (4), dactylorhin B (5) and loroglossin (6). Three 2-isobutylmalate benzyl ester glucosides: dactylorhin A (7), dactylorhin E (8) and militarine (9). Three lignans: arctigenin (10), lappaol A (11) and lappaol F (12). Six aromatic acid (alhyde or alcohol) derivatives: 4-beta-D-glucopyranosyloxyl-trans-phenylpropenoic acid (13), 4-beta-D-glucopyranosyloxyl-cis-phenylpropenoic acid (14), gastrodin (15), 4-beta-D-glucopyranosyloxylphenylaldehyde (16), 4-beta-D-glucopyranosyloxylbenzyl methyl ether (17), 4-beta-D-glucopyranosyloxyloxylbenzyl ethyl ether (18), and bis(4-hydroxybenzyl) ether mono 4-O-beta-D-glucopyranoside (19). Four cyclodipeptides: cyclo(L-Leu-L-Tyr) (20), cyclo(L-Leu-L-Pro) (21), cyclo(L-Val-L-Tyr) (22), and cyclo(L-Ala-D-Phe) (23). One N6-substituted andenosine: N6-(4-hydroxybenzyl)-adenine riboside (24). An aromatic amide: N-trans-feruloyltyramine (25). Nine aromatic acids (or aldehyde or alcohol): 3-hydroxybenzoic acid (26), 4-hydroxyisophthalic acid (27), 4-hydroxybenzyl alcohol (28), 4-hydroxybenzyl methyl ether (29), 4-hydroxybenzylaldehyde (30), 4-hydroxybenzoic acic (31), 4-hydroxy-3-methoxybenzoic acid (32), trans-p-hydroxyphenylpropenoic acid (33), and cis-p-hydroxyphenylpropenoic acid (34). At a concentration of 1.0 x 10(-6) mol x L(-1), compounds 10-12 showed antioxidative activity inhibiting Fe(+2) -cystine induced rat liver microsomal lipid peroxidation with inhibitory rates of 53%, 59%, and 52%, respectively(positive control VE with 35% inhibition).
Conclusion: These compounds were obtained from the genus Gymnadenia for the first time except for 5-7, 9, 15, 28-34. Compounds 10-12 possess antioxidant activity.