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.Electronic supplementary materialThe online version of this article (10.1186/s12906-018-2229-2) contains supplementary material, which is available to authorized users.

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The phytochemical study of the EtOH extract of the roots of Amphiblemma monticola Jacq.-Fél. led to the isolation of a new C-methyl isoflavone, amphiblemmone A (1), along with ten known compounds, including 3,4'-di-O-methylellagic acid (2), dimethyl 4,4',5,5',6,6'-hexahydroxybiphenyl-2,2'dicarboxylate (3), lupeol (4), ellagic acid (5), β-sitosterol (6), sitosterol 3-O-β-D-glucopyranoside (7), 3-hydroxy-4,5-dimethoxybenzoic acid (8), 3-Omethylellagic acid 4′-O-β-D-xylopyranoside (9), and a mixture of oleanolic acid (10) and ursolic acid (11). The structures were elucidated using spectroscopic analyses (IR, UV, NMR and MS) and comparison with literature data. Compounds 2-11 were isolated for the first time from the genus Amphiblemma. This is the first report of compounds 2-4, 8 and 9 from the Melastomataceae family.