New Bioactive Flavonoid Derivative from the Leaves of <i>Caloncoba echinata</i>

Abstract

Background: <i>Caloncoba echinata</i> is used in traditional medicine as vomiting, against lice and mange as well as in the treatment of dermal infection, leprosy, pustular eruption (small-pox) [1, 4]. It has been reported that the non-edible vegetable oil from <i>Caloncoba</i> <i>echinata</i> seeds possess potent antibacterial activity on <i>Escherichia coli</i> and <i>Staphylococcus aureus </i>[5]. Objective: This work addressed the phytochemical investigation of the methanolic extract of leaves of <i>Caloncoba echinate</i>. Both extracts and all the isolates were screened for the antibacterial activities. Method: All the compounds were characterized by spectroscopic and mass spectrometric methods, and by comparison with literature data. The antibacterial activity of both extract and some isolated compounds against bacteria was determined using broth microdilution method in 96-well microtitre sterile plates as previously described [11]. Results: From the methanolic crude extract of the leaves of <i>Caloncoba echinate</i>, a new derivative flavonol named Kaempferol-4',7-dimethoxy-3-<I>O</I>-(6"-<I>O</I>-acetyl)-<i>β</i>-<I>NULL</I>-glucopyranoside (<i>1</i>) together with nine known compounds namely ermanin-3-<I>O</I>-<i>β</i>-<I>D</I> glucopyranoside (<i>2</i>), Kaempferol-4′,7-dimethoxy-3-<I>O</I>-(3",4",6"-<I>O</I>-triacetyl)-<i>β</i>-<I>NULL</I> glucopyranoside (3), friedelan-3-one (4), 29-hydroxyfriedelan-3-one (<i>5</i>), mixture of <i>β</i>-sitosterol and stigmasterol (<i>6-7</i>), mixture of <i>β</i>-sitosterol and stigmasterol glucoside (<i>8-9</i>), Lupeol (10) were isolated. Furthermore, compounds (<i>2</i>) and (<i>5</i>) were reported here for the first time from the <i>Caloncoba</i> genus. Crude extract exhibited a significant activity against the five bacteria with the MIC = 62.5µg/mL for <i>Salmonella typhi</i>,<i> Escherishia coli</i>,<i> Shigella flexineri</i> and the MIC = 32.25µg/mL for <i>Salmonella typhimurium</i>,<i> S. enteritidis</i>. For the isolated compounds, the best activities were recorded by compound (<i>1</i>) showing a moderate activity against <i>Salmonella typhi</i> (MIC = 32.25µg/mL; MBC/MIC = 8), <i>Salmonella typhimurium</i> (62.5µg/mL; MBC/MIC = 4), <i>Salmonella enteritidis</i> (62.25 µg/mL; MBC/MIC = 2). Conclusion: These results showed that the antimicrobial activities could be mainly attributed to the constituents of flavonol glycoside <i>(1)</i>. In addition, the antibacterial bioactivities and determined constituents support the use of this specie by traditional healers to treat a certain number of bacterial diseases.