AIMS : To isolate the antibacterial compounds and to investigate the activity of extracts of,
and the antibacterial flavonoids isolated from leaves of Combretum apiculatum against four
important community-acquired and nosocomial bacterial pathogens viz. Staphylococcus
aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa.
METHODS AND RESULTS : Ten organic and aqueous extracts of the leaf powder of Combretum
apiculatum Sond subsp. apiculatum Exell were initially tested against S. aureus, E. faecalis, E.
coli and P. aeruginosa using a serial dilution microtitre plate and bioautography assays using
p-iodonitrotetrazolium violet (INT) as indicator of growth. The acetone extract was the most
potent and selected for further bioassay-guided fractionation of antibacterial compounds
which resulted in the isolation of three known flavonoids viz. flavokawain, alpinetin and
pinocembrin.
CONCLUSIONS : The flavonoids which were isolated from C. apiculatum for the first time were
moderately active against S. aureus and E. faecalis with MICs of 40 μg/ml. Ethyl ether and
ethyl acetate extracts were equally active against E. faecalis pointing to synergistic effects of
phytochemical constituents in exerting antibacterial activity.
SIGNIFICANCE AND IMPACT OF THE RESEARCH : The Combretaceae taxa are important materia
medica in Africa and Asia. The results confirm the validity of using C. apiculatum crude
extracts against bacterial infections and the superiority of extracts over isolated individual
compounds.
DOEL : Om antibakteriese verbindings te isoleer en die aktiwiteit van ekstrakte, fraksies
en antibakteriese verbindings uit Combretum apiculatum subsp. apiculatum blare teen vier
belangrike bakteriese patogene Staphylococcus aureus, Enterococcus faecalis, Escherichia
coli en Pseudomonas aeruginosa te bepaal.
METODES EN RESULTATE : Die aktiwiteit van tien organiese en watererige ekstrakte van blare
teen Staphylococcus aureus, Enterococcus faecalis, Escherichia coli en Pseudomonas aeruginosa is
bepaal deur ’n reeksverdunnings in mikroplate en bio-outografie met p-jodonitrotetrazolium
pers (INT) as aanduider van groei. Die asetoonekstrak het die hoogste aktiwiteit gehad en
is gebruik om die antibakteriese verbindings te isoleer en te karakteriseer. Drie bekende
flavonoiede- flavokawein, alpinetien en pinesembrien was verantwoordelik vir die aktiwiteit.
GEVOLGTREKKINGS : Die flavonoiede wat vir die eerste keer uit hierdie spesie geïsoleer is, was
redelik aktief teen die twee Gram-positiewe bakterieë Staphylococcus aureus en Enterococcus
faecalis met minimum inhiberende konsentrasies (MIK) van 40 μg/ml. Die etieleter en
etielasetaat ru-ekstrakte het dieselfde aktiwiteit teen E. faecalis gehad as die geïsoleerde
verbindings wat daarop dui dat daar sinergistiese interaksies tussen verbindings in die
ekstrak was.
IMPAK VAN DIE NAVORSING : Lede van die Combretaceae word wyd in Afrika en Asië gebruik
vir medisinale doeleindes. Die navorsing ondersteun die tradisionele gebruik teen infeksies
en dui ook daarop dat dit meer voordelig is om ekstrakte te gebruik as die geïsoleerde
antibakteriese verbindings.
