European Journal of Biomedical and Pharmaceutical Sciences

IN VITRO ANTIBACTERIAL AND ANTIFUNGAL ACTIVITIES OF AQUEOUS EXTRACT FROM MORINDA MORINDOIDES (BAKER) MILNE-REDHEAD (RUBIACEAE) LEAVES USED AS ANTIDIARRHOEAL REMEDY IN TRADITIONAL MEDICINE IN DEMOCRATIC REPUBLIC OF CONGO AND ITS ISOLATED CONSTITUENTS

Mbamu Maya B., Cimanga Kanyanga, R.*, Kambu Kabangu, O., Vlietinck, A. J. and Pieters, L.

ABSTRACT

The study reports the antibacterial and antifungal activities in vitro of aqueous extract (decoction) from Morinda morindoides leaves and of its soluble fractions, and isolated flavonoids and iridoids. Results revealed that aqueous extract and its soluble fractions were devoid with antibacterial activity against all selected standard ATCC bacteria strains with minimal inhibitory (MIC) and bactericidal concentrations (MBC) > 500 μg/ml). Against clinical isolates mainly implicated in diarrhea, aqueous extract and its some fractions exhibited good antibacterial and bactericidal activities with MIC and MBC values < 100 μg/ml against a large game of selected bacteria. In some cases, they exhibited moderate or weak activity with MIC and MBC values of 125, 250 or 500 μg/ml according to the case. Among flavonoids, chrysoeriol exhibited antibacterial activity against Bacillus cereus ATCC 4579, Candida albicans ATCC 102301, Escherichia coli ATCC 8739, Mycobacterium fortuitum ATCC 6841, Streptococcus pyogenes ATCC and Staphylococcus aureus ATCC 6538 with MIC and MBC ranging from 62.5 to 500 μg/ml. Quercetin, luteolin showed moderate or weak activity against Bacillus cereus ATCC 4579, Streptococcus pyogenes ATCC 12344, E. colis ATCC 8739 and Pseudomonas aeruginosa ATCC 154452 respectively (MIC and MBC = 250 and 500 μg/ml) while luteolin-7-O-glucoside exhibited moderate activity against Bacillus cereus ATCC4579, C. albicans ATCC 102301, Klebsiella pneumonia ATCC 883 and S. pyogenes ATCC12344 (MIC and MB = 125 or 250 μg/ml), low activity against Proteus vulgaris ATCC1335 and P. aeruginosa ATCC 15445 (MIC and MBC = 500 μg/ml). Iridoids exhibited antibacterial activity with MIC ranging from 7.81 to 250 μg/ml and bactericidal activity with MBC from 15.63 to 500 μg/ml against all selected standard ATCC bacteria. Against clinical isolates, flavonoids chrysoeriol, luteolin, luteolin-7-O-glucoside, kaempferol, kaempferol-3-O-glucoside and quercetin, and iridoids gaertneric acid, acetylgaertneroside, dihydroxygaertneroside, dihydroxymethoxygaertneroside, gartneroside, epoxygaertneroside, epoxymethoxygartneroside, and methoxygaertneroside showed good antibacterial and bactericidal activity (MIC and MBC < 100 μg/ml) or moderate and weak (MIC and MBC = 125, 250 or 500 μg/ml) activity or were inactive (MIC and MBC > 500 μg/ml). All tested samples were devoid with cytotoxic effect against Vero cell lines (CC50 > 100 μg/ml). These results partly indicated that aqueous extract of M morindoides can act as antidiarrhoeal remedy partly by its antibacterial property and this activity is due to the presence of flavonoids and iridoids. Aqueous extract showed good antifungal activity by diffusion method while all isolated constituents were devoid with this biological activity.

Keywords: Morinda morindoides, Rubiaceae, leaf, flavonoids, iridoids, antibacterial activity, cytotoxicity.