The in-vitro antimicrobial evaluation of ethanol extracts of four
species of Cola Schott & Endl. was done using human isolated
strains of Staphylococcus aureus , Staphylococcus albus , Bacillus
subtilis , Klebsiella pneumonia , Pseudomonas aeruginosa , Candida
albicans , Aspergillus niger as test organisms. The assays were
carried out by agar well diffusion, erythromycin and ketoconazole
served as the control drugs. The leaf ethanol extracts of the plants
were found to be more effective against the tested fungi than the
bacteria at high concentrations. None of the extracts was active
against Staphylococcus aureus. Plant extract of C. acuminata (P.
Beauv.) Schott & Endl. and C. nitida (Vent) Schott & Endl.
showed activity on S. albus at concentrations ranging from 10-150
mgml-1 having comparable diameters of zone of inhibition of
7.3±0.03-16.0±0.0 for C. acuminata and
10.0±0.0-19.0±0.0 for C. nitida. Also, these two species of
Cola demonstrated activities on C. albicans and A. niger at
concentrations ranging from 90-150mgml-1 with relatively close
diameters of zone of inhibition. Only C. acuminata inhibited the growth
of K. pneumoniae at the MIC of 90mgml-1 whereas, C. albicans was
inhibited by C. acuminata, C. millenii K. Schum and C. gigantea A.Chev.
at the MIC of 120mgml-1. Phytochemical screening of the four species of
Cola showed the presence of alkaloids, saponins, tannins and
cardenolides in all the plants which apart from showing the probable
closeness of the species could also be responsible for the observed
activities. The antimicrobial property shown by the plant extracts is
an evidence of the ethnomedicinal uses of the plants. The similarity
observed in the phytochemical constituents and antimicrobial activities
demonstrated by C nitida (Vent.) Schott & Endl., C. millenii and
C.gigantea A. Chev. and C. acuminata suggest a probable closeness among
these species. The results obtained in this study provide preliminary
evidence of the chemotaxonomic significance of secondary metabolites
and antimicrobial activities in infra-generic taxonomy of species of
Cola