Inhibition of dehydrogenase activity in S. typhimurium by ethanolic and methanolic extracts of Carica papaya and Ocimum gratissimum

Dehydrogenase and inhibitions of dehydrogenase activities in Salmonella typhimurium by ethanolic and methanolic leaf extracts of Ocimum gratissimum and Carica papaya were investigated. Dehydrogenase activity assay was carried out using 2, 3, 5-triphenyl tetrazolium chloride (TTC) as the electron acceptor. Pure culture of S. typhimurium was exposed to varied concentrations of ethanolic and methanolic extracts of Ocimum gratissimum and Carica papaya [0-4000 μg/ml]. The ethanolic and methanolic extracts exhibited a concentration dependent response  against the tested organism. Results obtained revealed that  the ethanolic extracts showed a higher bactericidal effect on the test organism than the methanolic extracts at the threshold and total inhibitory concentrations. The IC50 were 45.349 and 15.697; IC100 were 43.732 and 35.526 for ethanolic extracts of Carica papaya and Ocimum gratissimum respectively while the IC50 were 7.108 and 13.696; IC100 were 40.815 and 31.104 for methanolic extracts of Carica papaya and Ocimum gratissimum respectively. This in-vitro study further revealed that the leaf of Carica papaya was more potent on Salmonella typhimurium than the leaf of Ocimum gratissimum. The findings from this study seem to provide the in-vitro evidence that justifies Carica papaya and Ocimum gratissimum as good candidate medicinal plants for the potential treatment of Salmonella typhimurium infections