Abstract

In realization of the widespread use of herbal medicines across the globe, World Health Organization (WHO) in 1985 estimated that perhaps more than 80% of the world’s population relies on plant-based herbal medicine for their primary health care needs. The present study was carried out to evaluate the antimicrobial, antioxidant, and toxic potentials of the ethanolic extract of the leaves of Ocimum gratissimum, Gongronema latifolium and rhizomes of Zingiber officinale. The plant materials were extracted using standard methods. The qualitative and quantitative phytochemical analyses were carried out using standard methods. The antimicrobial activity of the extracts was evaluated by determination of the diameter zone of inhibition on five different organisms namely; Bacillus subtilis, Candida albicans, Escherichia coli, Salmonella typhi and Staphylococcus aureus using agar well diffusion method. Gentamycin and Fluconazole were used as positive control while 70% ethanol was used as negative control. The minimum inhibitory concentration and the minimum bactericidal/fungicidal concentration were determined using standard methods. The extracts were screened for antioxidant activity using 2, 2-Di Phenyl – 1- Picryl- Hydroxyl (DPPH). Standard vitamin C was used as a reference antioxidant. The toxicity potential of the plant extracts was evaluated on albino rats using the LD_50. The phytochemical analyses of the three plant species revealed the presence of alkaloids, tannins, saponins, flavonoids, carbohydrates, steroids, terpenes and cardiac glycoside. Ocimum gratissimum exhibited high zones of inhibition on Candida albicans (27.5± 1.44 mm) at the concentration of 400 mg/ml, Salmonella typhi (23.67 ± 6.7 mm) at the concentration of 400 mg/ml. The zones of inhibition of Gongronema latifolium were higher on Staphylococcus aureus (28.33 ± 2, 47 mm) and Candida albicans (26.1.7± 1.26 mm) at the concentration of 400mg/ml. The ethanolic extracts of Ocimum gratissimum, Gongronema latifolium and Zingiber officinale were bactericidal and fungicidal at different concentrations. The antibiotic drug exhibited higher antimicrobial activity than the plant extracts. The plant extracts exhibited antioxidant potential at various concentrations. Ocimum gratissimum exhibited the highest antioxidant activity (96%) followed by Zingiber officinale (92%) while G. latifolium has the least antioxidant activity (46%). The LD₅₀ of the plant extracts revealed that the extracts were toxic to the laboratory animals at high dose. The findings of the present study justify that  O. gratissium, G. Latifolium and Z. officinale possess significant antimicrobial, antioxidant and safety potentials which make them potential candidates for chemotherapy.