Free radical scavenging potential and antibacterial activity of Cola nitida and Garcinia kola extracts against bacterial strains isolated from patients with urinary tract infections

Cola nitida and Garcinia kola are found and widely consumed in West Africa. The seeds of these plants have various traditional uses and are reported to exhibit several bioactivities. Their phytochemical, antioxidant and antibacterial properties of methanol, ethanol and aqueous extracts were investigated in the present study. Phytochemical screening and quantification of total phenolic contents analysis were carried out for phytochemical investigation. Preliminary phytochemical screening revealed the presence of flavonoids, alkaloids, tannins, saponins, protein and glycosides in the seed extracts. Quantitative phytochemical constituents revealed 0.818 ± 0.021and 0.700 ± 0.017mg of phenolic compounds and total flavonoid content of 25.63 ± 1.60 and 25.10 ± 1.85mg in G. kola and C. nitida respectively. The extracts showed potent antioxidant activities compared to standard antioxidants by significantly inhibiting 2, 2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl radical (∙OH), and superoxide anion radicals (O₂∙) dose dependently. The methanol extracts of G. kola and C. nitida showed significant inhibitory action (p<0.05) against the bacterial isolates. The minimum inhibitory concentration obtained for methanol extract of the plants and both the mixture was 12mm at 31.25mg/ml for Klebsiella pneumoniae while the ethanol and aqueous extract of the plants and both the mixture was 13mm and 12.33mm at 31.25mg/ml and 125mg/ml respectively for E. coli. A direct correlation was observed between total phenolic content of extracts and radical scavenging potential, thus linking the observed bioactivities of these extracts to the presence of the phytochemical. The mixture of these seed extracts showed greater effect against the bacterial isolates, therefore providing a platform for advance studies in the development of drugs against infectious diseases.