Avaliação in vitro da atividade antineoplásica do ácido lecanórico e de seus produtos de modificação estrutural

Abstract

Lichens are a symbiotic association of a fungus and one or more photosynthetic partners. Phenolic substances from lichens exhibit a wide range of biological actions, including antimicrobial, antineoplasic, and cytotoxic activities. The purpose of this study was evaluate in vitro the antineoplasic activity of orsellinates obtained from estructural modifications of lecanoric acid, a depside isolated from the lichen Parmotrema tinctorum. A cytotoxicity assay was carried out in vitro with sulforhodamine B (SRB) using the following cell lines: larynx (Hep2), breast (MCF-7), lung (786-0), melanoma (B16-F10) and a normal cell line of kidney of monkey (VERO). Among all the compounds tested, n-butyl orsellinate was the most active, followed by sec-btyil orsellinate and terc-butyl orsellinate (IC50: 7,2, 8,9 e 10,2 μg mL-1). The last one showed the higher selective index (2,6). Ethyl orsellinate, n-propyl and n-butyl were more active against Hep2 than against MCF7, 786-0, or B16-F10. Iso-propyl and npentyl orsellinates showed greater activity against 786-0. The inicial compound lecanoric acid and methyl-orsellinate were inactive against the four cell lines evaluated. These results corroborate previous information that structural modifications of lecanoric acid and chain elongation of orsellinates (from methyl to butyl) increase the potency of antineoplasic activity, probably owing to an increase in lipophilicity.