Antibacterial activities of the methanol extract, fractions and compounds from Elaeophorbia drupifera (Thonn.) Stapf. (Euphorbiaceae)

Abstract

Background Elaeophorbia drupifera (Thonn.) Stapf. (Euphorbiaceae) is used in Cameroonian folk medicine to treat several ailments including bacterial-related diseases such as skin infections. In this study, the methanol extract from the leaves (EDL), fractions (EDLa-d), sub-fractions EDLc1-7 and EDLc31-35 as well as isolated compounds were tested for their antimicrobial activities against a panel of Gram-negative and Gram-positive bacteria including multidrug resistant (MDR) phenotypes.MethodsThe broth microdilution method was used to determine the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of the above samples; column chromatography was used for the fractionation and purification of the leaves extract whilst the chemical structures of compounds were determined using spectroscopic techniques.ResultsPhytochemical investigation lead to the isolation of a mixture (1:3) of stigmasterol and β-sitosterol (1 + 2), euphol (3), sitosterol-O-β- D -xylopyranoside (4), 3,3′,4′-tri-O-methylellagic acid (5), a mixture (1:1) of afzelin and quercetin-3-O-β-D-xylopyranoside (6 + 7), 3,3′,4′-tri-O-methylellagic acid 4-O-β-D-glucopyranoside (8), ellagic acid-4-O-β-xylopyranoside-3,3′,4′-trimethyl ether (9) from EDLc. Crude extract and fractions displayed selective activities with MIC values ranged from 32 to 1024 μg/mL for EDL against 84.9% of the 33 tested bacteria, 93.9% for EDLc, 69.7% for EDLb, 33.4% for EDLa and 0.03% for EDLd. MIC values ranged from 16 to 1024 μg/mL were obtained with EDLc3 and EDLc4 on all tested bacteria meanwhile other sub-fractions displayed selective activities. MIC value of 32 μg/mL was obtained with fractions EDLa against Escherichia coli AG100, EDLc against Enterobacer aerogenes ATCC13048 and EA298. For sub-fractions obtained from EDLc, the lowest MIC value of 16 μg/mL was recorded with EDLc3 against Staphylococcus aureus MRSA11. A corresponding value of 8 μg/mL against Providencia stuartii NAE16 was recorded with EDLc33 obtained from further fractionation of EDLc3. EDLc3 had MIC values below 100 μg/mL against all tested bacteria. Compound 5 as well as the mixture (1:1) of 6 and 7 inhibited the growth of all the tested bacteria with MICs ranged from 64 to 256 μg/mL.Conclusion Elaeophorbia drupifera is a potential source of phytomedicine to tackle MDR bacteria. Sub-fraction EDLc3 was more active than all isolated compounds and deserves further investigations to develop natural drug to combat Gram-negative, Gram-positive bacteria and otherwise MDR phenotypes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12906-016-1509-y) contains supplementary material, which is available to authorized users.

Effect of Fractioning on Antibacterial Activity of Enantia chlorantha Oliver (Annonaceae) Methanol Extract and Mode of Action

“…In addition, this result reflects the role of fractionation in the search for antimicrobial from plants. Indeed, several alternatives have been mentioned including the exploration of crude extracts, the search for active fractions derived from crude extracts, and the research of active molecules from plants [ 8 ].…”

“…Many approaches have so far been used to demonstrate the antibacterial activity of plants. They include crude extract preparation using variety of solvents [ 7 ], purification of active compounds from extracts [ 8 – 11 ], successive extraction with solvents with increasing polarity [ 12 ], and distillation. Solvent extraction has been the most used method but recent studies established increased activity with fractionation of crude extract [ 13 , 14 ].…”

In vitro antibacterial and antibiotic modifying activity of crude extract, fractions and 3′,4′,7-trihydroxyflavone from Myristica fragrans Houtt against MDR Gram-negative enteric bacteria

“…For compound characterization, ElectroSpray ionization mass spectrometry (ESI-MS), nuclear magnetic resonance (NMR) spectra, column chromatography (CC) and thin layer chromatography (TLC) were performed according to previously described protocols [ 17 – 19 ].…”

Evaluation of in-vitro antibacterial and antifungal activities of crude extracts and solvent fractions of methanol extract of leaves of Ricinus communis Linn (Euphorbiaceae) against selected pathogens

“…The crude methanol extract was subjected to further solvent fractionation by increasing polarity including n-hexane, chloroform, ethyl acetate, and aqueous. Voukeng et al [19] method was used for solvent fractionation with modi cation on the concentration of extract residue between fractionation intervals.…”