Terpenoids of Boswellia neglecta oleo-gum resin

Abstract

ABSTRACT. Oleo-gum resin exudate from Boswellia neglecta afforded a new ursane-type triterpene characterized as 3α-acetoxy-28-hydroxy-11-oxours-12-en-24-ioc acid (1) together with twelve known compounds. Their structural elucidation was accomplished using physical, chemical and spectroscopic methods.

Chemical, molecular and structural studies of Boswellia species: β-Boswellic Aldehyde and 3-epi-11β-Dihydroxy BA as precursors in biosynthesis of boswellic acids

“…This proton was associated with a carbon signal at δ 81.8 in the HSQC spectrum and showed COSY correlation with a signal at δ H 1.81 (H-9) and 5.52 indicating the location of hydroxyl group at C-11. The configuration of H-11 in 1 was determined to be axial on the basis of coupling constants with H-9 and H-12 and further supported by NOESY correlation between H-11 and CH 3 -25which is in close agreement with the reported compounds 2 – 4 ( Fig 2 ) [ 51 ]. One known analogue 15 has also been isolated from the same species having 13 C-NMR at δ 70.6, and 1 H-NMR at δ 4.24 (dd, J = 9.6, 3.0 Hz) corresponded to the C-11 position.…”

“…Besides olefinic double bond, the 1 H NMR spectrum of 1 displayed a peak at δ H 4.53 previously observed in boswellic acid derivatives [ 51 ]. The three bond long range correlations from this signal to C-9 (δc 49.0), C-12 (δc 124.5), and C-13 (δc 146.3) in the HMBC spectrum allowed its assignment to H-11.…”

“…In the 1 H NMR spectrum (experimental) of compound 5 , the presence of vinylic proton at 5.12 (1H, t, J = 3.0 Hz, H-12), one oxymithine proton at 4.11 (1H, br s, H-3), five tertiary methyls at 1.10, 1.08, 1.02, 0.82, and 0.78 (all singlets), and two secondary methyls at 0.90, (3H, d, J = 6.0 Hz) and 0.77 (3H, d, J = 6.0 Hz) were observed, unambiguously confirming the presence of Δ 12 -ursane skeleton [ 51 ]. The 13 C NMR spectrum (experimental part) exhibited a total of 30 carbon signals which were sorted out into nine CH 2 , seven CH 3 , seven CH including one olefinic, and one oxygen-bearing carbon as well as seven quaternary carbons.…”

“…It analogue ( 15) was previously isolated for the first time from B . sacra [ 51 ]. Compound 1 was isolated as white amorphous powder having molecular formula of C 30 H 48 O 4 and evidenced by ESI-MS which exhibited molecular ion peaks at 495 [M + Na] + and 477 [M + –H 2 O + Na] (7˚ of unsaturation).…”

“…The OH group is introduced at C-11 of the β-boswellic acid 10 which led to the formation of diol 15 which has also been isolated from Boswellia sacra , as a new source, by our group and its ethoxy analogue was reported earlier from B . neglecta [ 51 ] which upon oxidation of the OH at C11 should lead to ß-KBA 16 . Acetylation of the OH at C-3 in β-boswellic acid 5 via Ac-CoA and an acetyl-transferase will give β-ABA 17 .…”