Abstract
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(-) 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.
Highlights
Cola Schott & Endl. (Sterculiaceae) is a genus of about 125 species of trees indigenous to the tropical rain-forest African region (Ratsch, 2005)
Cardenolides are present in C. acuminata, C. nitida and C. gigantea but absent in C. millenii
The results of the antimicrobial screening of the ethanol crude plant extracts of the species are presented in Table 3 while Table 4 shows the minimum inhibitory concentration (MIC) of each extract
Summary
Cola Schott & Endl. (Sterculiaceae) is a genus of about 125 species of trees indigenous to the tropical rain-forest African region (Ratsch, 2005). Cola is one of the largest in the family Sterculiaceae and is related to the South American genus Theobroma. It comprises of evergreen moderately sized trees often growing to a height of 20m with glossy ovoid leaves up to 30cm long. In an attempt to resolve this confusion, Chevalier and Perrot (1911) created the Subgenus Eucola containing five species of edible kolanuts – Cola nitida (important for trade), Cola acuminata (important for socio-cultural values), Cola ballayi, Cola verticillata and Cola sphaerocarpa. The latter three species are not known to be cultivated
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