Further Oleanane Triterpenoids from Vicoa indica

Abstract

i%BsTRACT.-vicosigenin El], a new 28-nortriterpenoid, and vicoside B 141, a new triterpenoid glucoside, were isolated from V i m indica. Their structures were elucidated by spectral methods. Previous investigations on Vicoa indica DC. (Asteraceae), a tribal female antifertility drug in India, led to the isolation of four sesquiterpenoid lactones ( 1,2), a monoterpene diol (3), and a 28-noroleanane glucoside, vicoside A E21 (4). The present work describes the isolation and characterization of a new 28-nortriterpenoid, vicosigenin (11, and a new triterpenoid glucoside, vicoside B (41, from the same plant.Chromatography of the CHCI, extract of the aerial parts of V. indica afforded vicosigenin El]. Compound 1 was assumed to have molecular formula C30H4806 from its DEPT spectrum. Its ir spectrum showed hydroxyl and ester bands at 3425 and 1735 cm-', respectively. The 'H-and l3C-nmr spectra of 1 exhibited signals for six tertiary methyl groups, a trisubstituted double bond, three secondary and one primary hydroxyl groups, and a formate group (see Experimental). The mass spectrum of 1 did not exhibit the molecular ion peak and gave the highest mass peak at m h 458 {M -HCOZH}+. The facile loss of formic acid from the molecule suggested that the formate group in 1 must be at C-17, as it is well known that substituents at C-17 are readily lost (5). Furthermore, fragment peaks at mlz 239 and 218 (base peak) were due to retro-'CSMDRIA Communication NO. 304. 'Present address: Regional Research Institute (Ayurveda) (CCRAS) 14, Jagannath Dutta Lane, Calcutta 7oooO9.Diels-Alder cleavage from m/z 458. This indicated that three hydroxyl groups were in the rings NB and one hydroxyl group was in the DIE portion of a 28-norolean-12-ene skeleton (4). The presenceofasingletat673.5 (C-17)coupled with the absence of a singlet at 6 28.0 for the Me-28 agreed with mass spectral data and confirmed placement of the -OCHO at C-17. With the exception of the glucose residue, the 'H-and 13C-nmr spectra of 1 exhibited resonances closely similar to vicoside A (21 previously isolated from the same plant (4). 'H-nmr signals for H-23, H-2, and H-16 observed at 6 3.32, 4.25 (m), and 4.00 (dd,J= 11.5 and 5 Hz), respectively, were in conformity with those of the aglycone part of the saponified product of vicoside A hexacetate (37 (4). The 13C-nmr data also confirmed the above assignments. Thus, the structure ofvico-1 R,=R2=R3=H, R,=OCHO 2 R,=P-D-GIc, R2=R3=H, R,=OCHO 3 R, = P-D-GIC(AC),, R,= R, = Ac, R,=OCHO 4 R,=P-D-GIc, R,=R,=H, R,=CHO 5 R,=P-D-GIc(Ac)~, R~= R~= A c , R,=CHO