Estudo Químico e Atividade Antioxidante de Bauhinia Pentandra (Bong.) Vog. Ex Steud e Avaliação da Atividade Inibitória da Enzima Dna Topoisomerase II-a Humana de Substâncias Naturais e Semi-Sintéticas.

Abstract

The species Bauhinia pentandra (Bong.) Vog. ex Steud (Leguminosae), known as mororó com espinho , is common in Northeast of Brazil. The enzyme DNA topoisomerase II-α (topo II) is responsible for the relaxation of the DNA during the processes of cellular division and is involved in diverse types of cancer, being considered a potential target in the treatment of the cancer. This work aimed to study the chemical composition and antioxidant activity of the bark roots of B. pentandra and the inhibition activity of topo II in natural and semi-synthetic compounds. In the chemical study of the vegetal species was isolated of the cyanogenic glycoside lithospermoside and a mixture of β-sitosterol and stigmasterol. The lithospermoside was acetylated and the structures had been identified through spectral data as IV and RMN1H and 13C including 2D. The Ethanolic extract and the fractions in hexane, AcOEt, MeOH and the substance lihtospermoside were submitted to antioxidant tests (DPPH, ABTS, quelatogenic activity of Fe2+ ion). The determination of total phenolic also was performed with the extract and fractions. All the samples showed antioxidant activity, being the AcOEt with highest activity and higher content of phenolic compounds, then this fraction was analyzed by HPLC-DAD having confirming the presence of phenolic. The inhibition of topoisomerase II-α was analyzed with natural compounds lithospermoside and γ-hydroxyferruginin A, isolated from Vismia guianensis and the EtOH extract of the latex of this species, and with semi-syntetic compounds: peracetyl lithospermoside and ten flavonoids derivated of retusin, isolated from Solanum paludosum. At 220 μM concentration all samples tested were actives, except lithospermoside and its acetylated derivative. In the concentration of 110 μM only two flavonoids did not inhibit the action of topo II. The γ-hydroxyferruginin inhibited the activity of topo II in a minimum concentration of 0,1 μM, being this anthranoid prenilated a promising candidate for posterior therapeutical studies for the treatment of the cancer.