Estudo químico de Croton Limae A. P. S. Gomes, M. F. Sales & P. E. Berry (Euphorbiaceae)

Abstract

The present work reports the chemical study related to the stem and the roots of Croton limae, collected in Andaraí/BA. The phytochemical investigation of ethanol extract from the stem lead to the isolation of two kaurane-type diterpenes, ent-kaur-16-en-18-oic acid and ent-kaur-16-en-15-oxo-18-oic acid, two clerodane-type diterpenes, 3,12-dioxo-15,16-epoxy-4α-hydroxycleroda-13(16),14-diene and 3-oxo-4α-hydroxy-13,14,15,16-tetranorclerodan-12-oic acid, and the flavonoid quercetin 3-O-β-D-glucopyranoside. The investigation of the hexane extract from the roots lead to the isolation of one triterpene, acetyl aleuritolic acid, the new dimer ent-17(α-pinen-10’-yl)-15-oxokauran-18-oic acid, two news clerodane diterpenes, 3-oxo-15,16-epoxy-4α,12-dihydroxycleroda-13(16),14-diene and 15,16-epoxy-3α,4α,12-trihydroxycleroda-13(16),14-diene, one halimane-type diterpene, 15,16-epoxy-3α,12-dihydroxyhalima-5(10),13(16),14-triene and the mixture of steroids β-sitosterol and stigmasterol. From the ethanol extract of the roots, it was possible to isolate the flavonoids kaempferol 3-O-β-glucopyranoside and ombuine 3-O-β-rutinoside and the three new clerodane diterpenes 3α,4α,15,16-tetrahydroxyclerod-13-ene, 6-(β-D-glucopyranosyl)-3,12-dioxo-15,16-epoxi-4α-hydroxycleroda-13(16),14-dieno and 3-oxo-4α,12-dihydroxy-14,15,16-trinorclerodan-13-oic acid. Four aromatic derivatives amides from ent-kaur-16-en-18-oic acid were prepared through nucleophilic substitutive reactions. The corresponding methyl esters from the ent-kaur-16-en-18-oic acid and ent-kaur-16-en-15-oxo-18-oic acid were also obtained. Two new derivatives from 3,12-dioxo-15,16-epoxi-4α-hidroxicleroda-13(16),14-dieno were prepared through reduction reaction and another one by the biotransformation of diterpene, made by the fungus Rhizopus stolonifer. Some isolated compounds and derivatives were submited to cytotoxic activity using ovarian (OVCAR-8), glioblastoma (SF-295) and colon (HCT-116) cell lines, and the compounds ent-kaur-16-en-15-oxo-18-oic acid and ent-17(α-pinen-10’-yl)-15-oxokauran-18-oic acid registered activity during preliminaries assays. The secondary metabolites were isolated through usual chromatography techniques, using thin layer chromatography, column chromatography, size exclusion chromatography and high performance liquid chromatography. The determination of the structure of the isolated compounds was performed through physical (melting point and optical rotation) and spectrometric techniques, such infrared (IR), high resolution mass spectrometry and nuclear magnetic resonance (NMR), including bidimensional experiments, and comparison with literature data.