Phytochemical study guided by the myorelaxant activity of the crude extract, fractions and constituent from stem bark of Hymenaea courbaril L

Abstract

Ethnopharmacological relevance: Hymenaea courbaril L. (Caesalpinoideae) is used in Brazilian folk medicine to treat anemia, kidney problems, sore throat and other dysfunctions of the respiratory system, such as bronchitis and asthma, although such properties are yet to be scientifically validated.

Aim of the study: In order to give a scientific basis to support the traditional use of Hymenaea courbaril, this study was designed to evaluate antioxidant, myorelaxant and anti-inflammatory properties of the ethanol extract from stem bark and its fractions. The myorelaxant effect of astilbin, a flavonoid isolated from the bioactive ethyl acetate fraction (EAF), has also been evaluated.

Material and methods: In the present study ethanol extract from stem bark (EEHC) and fractions were analyzed using bioassay-guided fractionation. The following activities were investigated: antioxidant by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, myorelaxant on rat tracheal smooth muscle, and anti-inflammatory using ovalbumin-induced leukocytosis and airway hyperresponsiveness in rats.

Results: The results of the present investigation show that the whole extract of Hymenaea courbaril and some of its fractions strongly scavenged DPPH radical. The extract showed myorelaxant activity on rat trachea, being EAF its highest efficient fraction. Bio-guided study allowed the isolation of astilbin, a well-known flavonoid. The activity induced by this compound indicates that it may be partly responsible for the myorelaxant effect of EAF. EAF reduced contractions that depended on divalent cation inflow through voltage-operated Ca(2+) channels (VOCCs) or receptor-operated Ca(2+) channels (ROCCs), but it was more potent to inhibit VOCC- than ROCC-dependent contraction induced by Ca(2+) addition in ACh-enriched Ca(2+)-free medium. Oral pretreatment of antigen-challenged animals with EAF prevented airway hyperresponsiveness on KCl-induced contraction and reduced the number of total white cells, particularly eosinophils and neutrophils in bronchoalveolar lavage.

Conclusions: This study provided scientific basis that Hymenaea courbaril presents potential antioxidant, myorelaxant and anti-inflammatory actions, which support its use in folk medicine to treat inflammatory airway diseases.

Keywords: 1,1-diphenyl-1-picrylhydrazyl; ACh; AcOEt; Anti-inflammatory activity; Antioxidant activity; BALF; CCh; CH(2)Cl(2); DEAF; DF; DPPH; EAF; EEHC; HDF; HF; Hex; Hymenaea courbaril L.; Hymenaea courbaril stem bark ethanol extract; MF; MeOH; Myorelaxant activity; NMR; OVA; ROCCs; TLC; VOCCs; acetylcholine; bronchoalveolar lavage fluid; carbachol; dichloromethane; dichloromethane fraction; dichloromethane:ethyl acetate fraction; ethyl acetate; ethyl acetate fraction; hexane; hexane fraction; hexane:dichloromethane fraction; methanol; methanol fraction; nuclear magnetic resonance; ovalbumin; receptor-operated Ca(2+) channels; thin layer chromatography; voltage-operated Ca(2+) channels.