Antimicrobial activity and cytotoxicity of the ethanol extract, fractions and eight compounds isolated from Eriosema robustum (Fabaceae)

BACKGROUND: The aim of this study was to evaluate the antimicrobial activity and the cytotoxicity of the ethanol crude extract, fractions and isolated compounds from the twigs of Eriosema robustum, a plant used for the treatment of coughs and skin diseases. METHODS: Column chromatographic and spectroscopic techniques were used to isolate and identify eight compounds, robusflavones A (1) and B (2), orostachyscerebroside A (3), stigmasterol (4), 1-O-heptatriacontanoyl glycerol (5), eicosanoic acid (6), 3-O-β-D-glucopyranoside of sitosterol (7) and 6-prenylpinocembrin (8), from E. robustum. A two-fold serial microdilution method was used to determine the minimum inhibitory concentration (MIC) against fungi and bacteria, and the 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide reduction assay was used to evaluate the cytotoxicity. RESULTS: Fraction B had significant antimicrobial activity against Aspergillus fumigatus and Cryptoccocus neoformans (MIC 0.08 mg/ml), whilst the crude extract and fraction A had moderate activity against A. fumigatus and Candida albicans (MIC 0.16 mg/ml). Fraction A however had excellent activity against Staphylococcus aureus (MIC 0.02 mg/ml), Enterococcus faecalis and Escherichia coli (MIC 0.04 mg/ml). The crude extract had significant activity against S. aureus, E. faecalis and E. coli. Fraction B had good activity against E. faecalis and E. coli (MIC 0.08 mg/ml). All the isolated compounds had a relatively weak antimicrobial activity. An MIC of 65 μg/ml was obtained with robusflavones A (1) and B (2) against C. albicans and A. fumigatus, orostachyscerebroside A (3) against A. fumigatus, and robusflavone B (2) against C. neoformans. Compound 8 had the best activity against bacteria (average MIC 55 μg/ml). The 3 fractions and isolated compounds had LC50 values between 13.20 to > 100 μg/ml against Vero cells yielding selectivity indices between 0.01 and 1.58. CONCLUSION: The isolated compounds generally had a much lower activity than expected based on the activity of the fractions from which they were isolated. This may be the result of synergism between different compounds in the complex extracts or fractions. The results support the traditional use of E. robustum to treat infections. The crude extract had a good activity and low preparation cost, and may be useful in topical applications to combat microbial infections.The authors are grateful to the University of Pretoria for the Post-doctoral Fellowship awarded to MD Awouafack to work at the Faculty of Veterinary Science, Department of Paraclinical Sciences, Phytomedicine Programme, and the National Research Foundation and Medical Research Council for research funding.http://www.biomedcentral.com/1472-6882/13/289am2014mn201

Alkenylbenzoquinones and other compounds from the fruit of Maesa lanceolata exhibited potent cytotoxic, antibacterial, and antiradical scavenging activities

Seumo AS, Nanfack ARD, Ndontsa BL, et al. Alkenylbenzoquinones and other compounds from the fruit of Maesa lanceolata exhibited potent cytotoxic, antibacterial, and antiradical scavenging activities. Natural Product Research . 2021.A phytochemical study of the methanol extract of the fruit of Maesa lanceolata resulted in the isolation of a new alkenylbenzoquinone (1), alongside the known compounds (Z)-2,5-dihydroxy-6-methyl-3-(pentadec-10'-enyl)-1,4-benzoquinone (2), 2,5-dihydroxy-6-methyl-3-(nonadec-14'-enyl)-1,4-benzoquinone (3), 2,5-dihydroxy-6-methyl-3-(tridecyl)-1,4-benzoquinone (4), (2S,3S,4R,2'R,9E)-[2'-hydroxytetraeicosanoyl]-2-aminooctadec-9-ene-1,3,4-triol (5), monopalmitin (glyceryl palmitate) (6), lupeol (7), and 3-O-(beta-D-glucopyranoside)-beta-sitosterol (8). The structures of the compounds were established by the means of spectroscopic (1D- and 2D-NMR) and spectrometric techniques (MS). The isolated compounds were assessed for their antibacterial, cytotoxic, and antiradical activities. Compound 2 showed moderate activity against Staphylococcus warneri (DSMZ 20036), while the other compounds were inactive. The two quinones 1 and 2 were significantly cytotoxic, with IC50 values of 0.005M and 12.5M respectively, and were weakly active towards DPPH radical (IC50 >250g/mL)

A new alkylbenzoquinone from <i>Embelia rowlandii</i> Gilg. (Myrsinaceae)

<p>A new alkylbenzoquinone named embeliquinone (<b>1</b>) together with five known compounds, lupeol (<b>2</b>), 3-<i>O</i>-[6′-<i>O</i>-palmitoyl-<i>β</i>-d-glucosyl]-spinasta-7,22(23)-diene (<b>3</b>), quercetin (<b>4</b>), (2<i>S</i>,3<i>S</i>,4<i>R</i>,8<i>E</i>)-2-[(2′<i>R</i>)-2′-hydroxy-heneicosanoylamino]-heneicosane-1,3,4-triol-8-ene (<b>5</b>), and <i>β</i>-sitosterol-3-<i>O</i>-<i>β</i>-d-glucopyranoside (<b>6</b>) were isolated from the MeOH leaf extract of <i>Embelia rowlandii</i> by using repeated open column chromatography techniques. The structure of the new compound was characterized by analyses of 1D- and 2D-NMR, and MS data. Embeliquinone (<b>1</b>) had moderate anti-cell proliferation activity against A549 cell line with the IC₅₀ value of 21.8 μM. In addition, <b>1</b> exhibited weak antibacterial activities against <i>Klebsiella pneumoniae</i> and <i>Staphylococcus aureus</i> with an MIC value of 206.0 μM in both cases.</p

Chemical constituents of Mussaenda erythrophylla Schumach. & Thonn. (Rubiaceae) and their chemophenetic significance

Bouzeko ILT, Dongmo FLM, Ndontsa BL, et al. Chemical constituents of Mussaenda erythrophylla Schumach. &amp; Thonn. (Rubiaceae) and their chemophenetic significance. Biochemical Systematics and Ecology. 2021;98: 104329.The chemical investigation of the CH2Cl2/MeOH (1:1) extract from the aerial part of Mussaenda erythrophylla Schumach. & Thonn. (Rubiaceae) resulted in the isolation of sixteen known compounds (1-16) distributed in coumarins, flavonoid glucosides, quinic acid derivatives, triterpenoids, monoglycerid, steroids, tetraterpenoid and polyol. The structures of the compounds were determined by spectrometric and spectroscopic analysis including MS and NMR data followed by their comparison with reported ones in the literature. The chemophenetic significance of the isolated compounds was discussed. The crude extract and some of the isolated compounds were assessed in vitro for their antileishmanial, cytotoxic and antiplasmodial activities. The crude extract of M. erythrophylla showed moderate antileishmanial activity (IC50 = 61.6 mu g/mL) while the hexane soluble fraction showed good antileishmanial activity (IC50 = 31.06 mu g/mL) compared to the reference drug amphotericin B (IC50 = 0.11 mu M). Compounds 11 and 9 also exhibited potent antileishmanial activity (IC50 = 53.7-52.0 mu M). The crude extract as well as the ethyl acetate soluble fraction also exhibited good antiplasmodial activity (IC50 = 7.43 +/- 0.00 mu g/mL and 14.49 +/- 2.96 mu g/mL respectively), while compounds 11, 15 and 16 showed weak activity with IC50 > 20 mu M compared to the reference drug artemisinin (IC50 = 0.014 +/- 0.001 mu M)