Abstract
BackgroundCandida albicans is one of the organisms living on the human body symbiotically, but, in hosts with low immunity it becomes one of the most pathogenic fungal organisms. Combretum zeyheri has been reported to have antifungal, antibacterial and antioxidant activities. Medicinal plants are believed to be non-toxic by the general public. Toxicity studies, however, have indicated that they are capable of causing numerous side effects, therefore, evaluation of safety is required. The objective of this study was to determine the toxicity of the antifungal constituents of Combretum zeyheri on mammalian cells.MethodsAlkaloids, saponins, flavonoids-enriched extracts and crude ethanol extracts were prepared from the leaves of Combretum zeyheri. The broth microdilution method was used to investigate for antifungal activity, with miconazole used as the positive control. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was used to determine cell viability of the Candida albicans cells. The most potent extracts; the ethanol extract, alkaloids and saponins respectively, were further tested for their toxicity on sheep erythrocytes, mouse peritoneal macrophages and Jurkat T cells.ResultsAll Combretum zeyheri extracts displayed a dose-dependent antifungal activity and had IC50 values ranging from 16 μg/ml to 159 μg/ml for Candida albicans. The alkaloids, saponins and ethanol extracts were found to be non-toxic towards mouse peritoneal cells and Jurkat T cells. In the haemolysis assay, all extracts were haemolytic at varying degrees and showed their greatest haemolytic activity at the highest concentration of 5 mg/ml. The saponins were the least haemolytic, followed by the ethanol extracts and the alkaloids respectively. Although these extracts were haemolytic to some extent, they may considered safe at therapeutic concentrations since there was a large difference between the antifungal IC50 and haemolysis EC50 values, hence a large therapeutic window.ConclusionsCombretum zeyheri antifungal constituents are, therefore, a potential source of lead compounds which can be developed into antifungal drugs of natural origin owing to Combretum zeyheri’s effective antifungal activity and low toxicity to mammalian cells.
Highlights
Candida albicans is one of the organisms living on the human body symbiotically, but, in hosts with low immunity it becomes one of the most pathogenic fungal organisms
These included: diethyl ether, ethanol, n-butanol, sodium chloride, starch, Hank’s Balanced Salt Solution (HBSS), foetal bovine serum (FBS), penicillin, streptomycin, RPMI 1640 powder, sodium bicarbonate, trypan blue, acetic acid, ammonium hydroxide, methanol, 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyltetrazolium bromide (MTT), miconazole, ketoconazole, dimethyl sulfoxide, Sabouraud dextrose agar, Sabouraud dextrose broth, citric acid, sodium citrate dihydrate, D- glucose, peptone from vegetables, sulphuric acid, barium chloride, disodium hydrogen phosphate, potassium dihydrogen phosphate, potassium ferricyanide, potassium chloride, potassium cyanide, sodium bicarbonate and triple distilled grade water was used for all experiments
Antifungal activity The antifungal activity of C. zeyheri ethanol extract, alkaloids, flavonoids and saponins was determined by the broth microdilution method
Summary
Candida albicans is one of the organisms living on the human body symbiotically, but, in hosts with low immunity it becomes one of the most pathogenic fungal organisms. Medicinal plants are believed to be non-toxic by the general public. The objective of this study was to determine the toxicity of the antifungal constituents of Combretum zeyheri on mammalian cells. Candida albicans is one of the organisms living on the human body symbiotically, The emergence of mutant pathogenic strains that are resistant to current drugs, necessitates the need to find new, safe and effective drug compounds with minimum or acceptable side effects [4]. The prevalence of fungal infections is increased by antibiotic resistance and antifungal drug toxicity especially after prolonged treatment, there is need for new, safe and non-toxic drugs [1]. These bioactive compounds include alkaloids, flavonoids, glycosides, saponins, terpenoids, tannins, carbohydrates and sterols [1]
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