Abstract
BackgroundAntimicrobial resistance is a serious threat against humankind and the search for new therapeutics is needed. This study aims to investigate the antimicrobial and antioxidant activities of ethanol extracts and compounds isolated from Dissotis senegambiensis and Amphiblemma monticola, two Cameroonian Melastomataceae species traditionally used for the treatment of fever, malaria and infectious diseases.MethodsThe plant extracts were prepared by maceration in ethanol. Standard chromatographic and spectroscopic methods were used to isolate and identify fourteen compounds from the two plant species [1–6 (from D. senegambiensis), 3, 4 and 7–14 (from A. monticola)]. A two-fold serial micro-dilution method was used to determine the minimum inhibitory concentration (MIC) against four bacterial strains including two resistant bacterial strains, methicillin resistant S. aureus (MRSA3) and methicillin resistant S. aureus (MRSA4) and three yeast strains.ResultsThe fractionation of EtOH extracts afforded fourteen compounds belonging to triterpenoid and phenolic derivatives. The ethanol extracts, compounds 3, 5–8, 10 and the mixture of 10 + 12 were active against all the tested bacterial and fungal species. Compound 7 (MIC = 16–32 μg/mL) and 10 (MIC = 8–16 μg/mL) displayed the largest antibacterial and antifungal activities, respectively. Compounds 7, 10 and the mixture of 10 + 12 showed prominent antibacterial activity against methicillin- resistant S. aureus (MRSA) which is in some cases equal to that of ciprofloxacin used as reference antibacterial drug. Compound 8 also showed high radical-scavenging activities and ferric reducing power when compared with vitamin C and butylated hydroxytoluene used as reference antioxidants. The tested samples were non-toxic to normal cells highlighting their good selectivity.ConclusionsThe result of this investigation reveals the potential of D. senegambiensis and A. monticola as well as the most active compounds in the search for new antimicrobial and antioxidant agents. So, further investigations are needed.
Highlights
Antimicrobial resistance is a serious threat against humankind and the search for new therapeutics is needed
The Ethyl acetate (EtOAc) and n-BuOH extracts from D. senegambiensis and EtOH extract from the roots of A. monticola were fractionated by silica gel column chromatography to afford fourteen compounds (1–14) (Fig. 1)
The results showed that the fractionation of EtOH extracts of D. senegambiensis and A. monticola reduced their antimicrobial activity in EtOAc and n-BuOH extracts
Summary
Antimicrobial resistance is a serious threat against humankind and the search for new therapeutics is needed. This study aims to investigate the antimicrobial and antioxidant activities of ethanol extracts and compounds isolated from Dissotis senegambiensis and Amphiblemma monticola, two Cameroonian Melastomataceae species traditionally used for the treatment of fever, malaria and infectious diseases. Increase in infections as a result of emergence of drug-resistant microorganisms and hitherto unknown pathogenic microbes pose enormous public health concerns [1] These necessitate continued search for compounds with antimicrobial activities. Fourteen compounds [β-amyrin palmitate (1), α-amyrin acetate (2), ursolic acid (3), sitosterol-3-O-β-D-glucopyranoside (4), vitexin (5) and trans-tiliroside (6) (from D. senegambiensis), ursolic acid (3), sitosterol3-O-β-D-glucopyranoside (4), 3,4′-di-O-methylellagic acid (7), dimethyl 4,4′,5,5′,6,6′-hexahydroxybiphenyl2,2′-dicarboxylate (8), lupeol (9), ellagic acid (10), 3hydroxy-4,5-dimethoxybenzoic acid (11), 3-O-methylellagic acid 4′-O-β-D-xylopyranoside (12), oleanolic acid (13) and amphiblemmone A (14) (from A. monticola) ] were isolated and characterized. Antimicrobial and antioxidant activities of ethanol extracts of D. senegambiensis and A. monticola and some compounds (3–10, a mixture of 3 and 13, and a mixture of 10 and 12) isolated in sufficient quantities are reported here for the first time
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