A New Ajmaline-type Alkaloid from the Roots of Rauvolfia serpentina

A new ajmaline-type alkaloid, 21-Ο-methylisoajmaline (1), together with twenty-one known compounds, a mixture of β-sitosterol (2) and stigmasterol (3), reserpinine (4); tetrahydroalstonine (5), reserpine (6), venoterpine (7), yohimbine (8), 6'-O-(3,4,5-trimethoxybenzoyl)glomeratose A (9), isoajmaline (10), 3-epi-α-yohimbine (11), methyl 3,4,5-trimethoxy-trans-cinnamate (12), a mixture of β-sitosterol 3-Ο-β-D-glucopyranoside (13) and stigmasterol 3-Ο-β-D- glucopyranoside (14), rescidine (15), 7-deoxyloganic acid (16), ajmaline (17), suaveoline (18), (+)-tetraphyllicine (19), loganic acid (20), 3-hydroxysarpagine (21), and sarpagine (22), were isolated from the roots of Rauvolla serpentina. Their structures were elucidated by spectroscopic data analysis and comparison with literature data. Compounds 11, 12 and 15 were for the first time identified from the genus Rauvolfla and 5, 7, 11, 12, 15, 18 and 22 were found from R. sepentina for the first time. Compound 11 showed moderate anticholinesterase activity with IC₅₀ value of 15.58 μM, whereas 6 exhibited strong vasorelaxant activity with the EC₅₀ value of 0.05 μM.