Antimicrobial activities of saponins from Melanthera elliptica and their synergistic effects with antibiotics against pathogenic phenotypes

Cyrille Ngoufack Tagousop; Jean-de-Dieu Tamokou; Irene Chinda Kengne; David Ngnokam; Laurence Voutquenne-Nazabadioko

doi:10.1186/s13065-018-0466-6

Antimicrobial activities of saponins from Melanthera elliptica and their synergistic effects with antibiotics against pathogenic phenotypes

Chem Cent J. 2018 Sep 20;12(1):97. doi: 10.1186/s13065-018-0466-6.

Authors

Cyrille Ngoufack Tagousop¹, Jean-de-Dieu Tamokou², Irene Chinda Kengne³, David Ngnokam⁴, Laurence Voutquenne-Nazabadioko⁵

Affiliations

¹ Research Unit of Environmental and Applied Chemistry, Department of Chemistry, Faculty of Science, University of Dschang, P.O. Box 67, Dschang, Cameroon.
² Research Unit of Microbiology and Antimicrobial Substances, Department of Biochemistry, Faculty of Science, University of Dschang, P.O. Box 67, Dschang, Cameroon. jtamokou@yahoo.fr.
³ Research Unit of Microbiology and Antimicrobial Substances, Department of Biochemistry, Faculty of Science, University of Dschang, P.O. Box 67, Dschang, Cameroon.
⁴ Research Unit of Environmental and Applied Chemistry, Department of Chemistry, Faculty of Science, University of Dschang, P.O. Box 67, Dschang, Cameroon. dngnokam@yahoo.fr.
⁵ Groupe Isolement et Structure, Institut de Chimie Moléculaire de Reims (ICMR), CNRS, UMR 7312, Bat. 18, BP.1039, 51687, Reims cedex 2, France.

Abstract

Background: Resistance of bacteria and fungi to antibiotics is one of the biggest problems that faces public health. The present work was designated to evaluate the antimicrobial activities of saponins from Melanthera elliptica and their synergistic effects with standard antibiotics against pathogenic phenotypes. The plant extract was prepared by maceration in methanol. The methanol extract was partitioned into ethyl acetate and n-butanol extracts. Column chromatography of the n-butanol extract followed by purification of different fractions led to the isolation of four saponins. Their structures were elucidated on the basis of spectra analysis, and by comparison with those from the literature. The antimicrobial activities of the extracts/compounds alone and their combinations with tetracycline and fluconazole were evaluated using the broth microdilution method through the determination of minimum inhibitory concentration (MIC) and minimum microbicidal concentration.

Results: Four compounds: 3-O-β-D-glucuronopyranosyl-oleanolic acid (1), 3-O-β-D-glucuronopyranosyloleanolic acid 28-O-β-D-glucopyranosyl ester (2), 3-O-β-D-glucopyranosyl(1 → 2)-β-D-glucuronopyranosyl oleanolic acid (3) and 3-O-β-D-glucopyranosyl(1 → 2)-β-D-glucuronopyranosyl oleanolic acid 28-O-β-D-glucopyranosyl ester (4) were isolated. Compounds 1, 2 and 3 showed the largest antibacterial activities (MIC = 8-128 μg/mL) whereas compound 4 displayed the highest antifungal activities (MIC = 8-16 μg/mL). The antibacterial activities of compounds 1 and 2 (MIC = 16-32 μg/mL) against multi-drug-resistant Escherichia coli S2 (1) and Shigella flexneri SDINT are equal to those of vancomycin (MIC = 16-32 μg/mL) used as reference antibiotic.

Conclusions: The present study showed significant antimicrobial activity of compounds 1, 2, 3 and 4 against the tested microorganisms. The saponins act in synergy with the tested standard antibiotics. This synergy could lead to new options for the treatment of infectious diseases and emerging drug resistance.

Keywords: Additive; Antibacterial; Antifungal; Asteraceae; Melanthera elliptica; Saponins; Synergy.