Investigação de metabólitos secundários de Tabernaemontana catharinensis A. DC. – (Apocynaceae) e suas potenciais atividades antimicrobianas

Abstract

The phytochemical investigation of hexane and methanolic crude extracts and their fractions from the bark of the stem of Tabernaemontana catharinensis (Apocynaceae, commonly known as cobrina) led to the isolation of nine monoterpene indole alkaloids, voachalotin, affinisine, 16-epiaffinisin, voacangin, voacristin, vinpocetine, voacangine hydroxylindolenine, 12-methoxy-N4-methyl voachalotine and 12-methoxy-N4-methyl-5-epiquachalotine. The alkaloid vinpocetine and 12- methoxy-N4-methyl-5-epi voachalotin are isolated for the first time in the family Apocynaceae. A Nmethyl affinisine derivative was obtained through an affinisin methylation reaction. The extracts, fractions and isolated compounds showed antibacterial activity (Gram-positive and Gram-negative) and effective antifungal, against the tested strains. The inhibitory potential of the pairs of diastereoisomers, corinantean skeleton, affinisine, 16-epiaffinisina and 12-methoxy-N4-methyl-5- epivoachalotine, 12-methoxy-N4-methyl voachalotine presented MIC values (1.56 μg.mL -1) lower than the fluconazole standard (MIC 3.12 μg.mL-1) compared to fungal strains. The methylation of the affinisine compound potentiated the inhibition against some microorganisms. The ibogan skeletal alkaloids, Voacangina, and Voacristina presented better inhibitory potentials against bacteria, presenting MIC of 3.12; 12.5 and 25 μg.mL -1 against the microorganisms Pseudomonas aeroginosa, Bacillus cereus and Salmonella typhimurium, respectively, being equal to or close to the chloramphenicol standard. The importance of stereochemistry in relation to the effectiveness of the MIC, which is visible in the activities presented in this paper. Thus, the phytochemical study and the pharmacological activities of the identified compounds of the stem bark of T.catharinensis broaden the knowledge alluding to chemotaxonomy, as well as justifying its antifungal use in folk medicine.