New 3,4-Seco Ent-Kaurenes from Croton Caracasana Flowers

Abstract

Two new 3,4-seco-ent-kaurenes, caracasine (1) and caracasine acid (2), were isolated from non-polar extracts of the flowers of Croton caracasana (Euphorbiaceae), together with six known terpenes, stigmasterol (4), stigmastenone (5), 2,6-dimethylocta-3,7-diene-2, 6-diol (6), spathulenol (7), caryophyllene oxide (8), and aromadendrene (9), and the flavonoid tribuloside (10). The chemical structures were determined by spectroscopic means and chemical correlations. All isolated compounds are being described for the first time for this species.

Crotofolane Diterpenoids from Croton caracasanus

“…An olefin between these two carbons, confirmed by the strong correlations observed in the HMBC experiment [δ H 5.97 (H-10) with δ C 148.8 (C-9), δ C 141.6 (C-8) and δ C 39.0 (C-11)] agrees with the proposed structure of 2, which could be obtained biogenetically by dehydration of crotofolin E (5), and is named by us as crotocarasin B. 13 C NMR (Tables 1 and 2) with those of 5, suggested a similar structure, but with additional signals. The presence of a multiplet at δ H 3.80 (m, H-21), integrating for two protons, and a new methyl signal at δ H 1.19 (t, J = 7.2 Hz, H-22), showed the presence of an ethoxy group in this compound.…”

“…More recently, new crotofolanes were reported from C. cascarilloides [11]. As part of our continuing interest in the chemistry of Croton species occurring in Venezuela [12][13][14][15], we now report the isolation and structural elucidation of four new diterpenoids with a crotofolane skeleton, isolated from stems of C. caracasanus Pittier, a species closely related to C. corylifolius. The in vitro cytotoxicity of the isolated metabolites against PC-3, HeLa, and MCF-7 tumor cell lines was also assessed.…”

“…A terminal olefinic methylene group at δ H 4.46 and 4.94 (s, H-18), and one allylic proton at δ H 3.14 (s, H-5) were also evident. 13 C NMR and DEPT data (Table 2) indicated the presence of three methyl, four methylene and five methine carbons, one of them oxygenated, at δ C 82.3 ppm (C-9). The crotofolane skeleton was proposed on the basis of the mentioned features and the COSY, HMQC, and HMBC ( Figure 2) correlations, and also by comparison of spectroscopic data of compound 1 with those of crotofolin E (5), isolated many years ago from C. corylifolius and also isolated in this work (Figure 1).…”

“…The presence of a multiplet at δ H 3.80 (m, H-21), integrating for two protons, and a new methyl signal at δ H 1.19 (t, J = 7.2 Hz, H-22), showed the presence of an ethoxy group in this compound. 13 C NMR and DEPT spectra showed 22 carbon atoms with 26 attached protons. The signals that identify the principal subunits found in 1 and 5 were also visualized.…”

Cytotoxic Activity of seco-Entkaurenes from Croton caracasana on Human Cancer Cell Lines

“…The cytotoxic effects against the Jurkat cells of caracasine acid (2) are noteworthy. When a primary culture of human dermis fibroblasts was treated with 1 and 2, these Tested compounds: The 3,4-seco-entkaurenes caracasine (1) and caracasine acid (2) were isolated from flowers of Croton caracasana by a procedure described by Suárez et al [11].…”