Chemical composition and biological properties of Piper cabralanum C. DC. (Piperaceae)

Several species of Piperaceae have been used worldwide for the treatment of many conditions, especially inflammatory, parasitic and tumour. Piper cabralanum C.DC. is endemic from Brazilian Atlantic Forest and occurs in humid and shadows areas. Leaves of this species were collected in the city of Teresópolis, dried and then subjected to extraction with methanol. The obtained methanol extract (PCa-MeOH) was then submitted to liquid-liquid partition with different solvents, yielding fractions soluble in n-hexane (PCa-Hex), dichloromethane, ethyl acetate and n-butanol. The crude methanol extract and its partitions were tested against promastigotes of Leishmania amazonensis as well as against strains of leukemic tumour cells K562 and multidrug resistant cell line K562-Lucena-1. Only PCa-MeOH and PCa-Hex showed high activity against L. amazonensis promastigotes (IC₅₀= 30 µg/ml and 25 µg/ml, respectively). These two sample materials were also active against tumour cells K562 and K562-Lucena-1 (MIC = PCa-MeOH: 400 µg/ml; PCa-Hex: 500 µg/ml). These results led us to investigate the chemical composition of the n-hexane fraction. Purifications were done by column chromatography with silica gel, and the resulting non-polar fractions and pure compounds were analyzed by gas chromatography coupled to mass spectrometry and by nuclear magnetic resonance, which allowed the characterization of hydrocarbons, sesquiterpenes, squalene, a mixture of steroids (campesterol, stigmasterol and β-sitosterol), two C6-C3 derivatives (3,4-dimethoxy-hydrocinnamic acid and methyl 3,4-dimethoxydihydrocinnamate) and a mixture of 3-O-β-D-glucosyl-β-sitosterol e 3-O-β-D-glucosyl-β-stigmasterol. These are the first chemical and biological findings for P. cabralanum.

Keywords: Piper, Brazilian Atlantic Forest, antiparasitic, antitumour, hydrocinnamic derivatives