Antimicrobial activity of scent leaf (<em>Ocimum gratissimum</em>), turmeric (<em>Curcuma longa</em>) and negro-pepper (<em>Xylopia aethiopica</em>) on selected tomato (<em>Lycopersicon esculentum</em>)

In this study, three spices of plant extracts: scent leaf (Ocimum gratissimum), tumeric (Curcuma longa) and the fruit of Negro-pepper (Xylopia aethiopica) were studied for their antimicrobial activities. Standard methods were adopted for extraction of soluble components in them. Antimicrobial potentials of the three extracts were tested separately and in consortium against selected spoilage microorganisms. Results showed that Ocimum gratissimum, Curcuma longa and Xylopia aethiopica had antimicrobial effects on some of the microorganisms tested. However, none of the extracts were able to inhibit the growth of Proteus vulgaris. Results indicated that minimum inhibitory concentration of scent leaf at 400 mg/mL was able to inhibit the growth of Pseudomonas aeruginosa, Staphylococcus aureus and Citrobacter freundii, while 500 mg/mL was effective on Escherichia coli as well. Similarly, turmeric at 400 mg/mL inhibited the growth of Bacillus subtilis, Pseudomonas aeruginosa and Staphylococcus aureus, while 500 mg/mL of the same extract inhibited Citrobacter freundii as well. Negro pepper shows inhibition above 300 mg/mL. Combined effects of these extracts showed varying degrees of inhibitions.