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.
