Abstract:
The antimicrobial activity of S. guineense on microorganisms isolated from tomato fruits and preservative efficacy of S. guineense extract on tomato samples and its biosafety was investigated. Bacteria isolated from tomato samples undergoing spoilage were Bacillus cereus, Micrococcus luteus, Erwinia carotovora, Escherichia coli, Xanthomonas campestris, Lactobacillus plantarum and the fungi include Aspergillus niger, Aspergillus flavus, Fusarium oxysporium, Rhizopus stolonifer and Saccharomyces cerevisiae. The antimicrobial activity revealed that there was variation in inhibitory potency of aqueous and ethanol extracts of S. guineense. All the isolated Gram negative bacteria were resistant to Augmentin, Cloxacillin and Cefurcxime, while Ofloxacillin had a highest zone of inhibition of 21±0.60mm on E. coli. Among the fungal test organisms, maximum growth suppression to the aqueous extract was observed in R. stolonifer and S. cerevisiae when compared with F. oxysporium which showed highest zone of inhibition of 18±0.00mm and 5±0.60mm for ethanolic and aqueous extracts respectively. Phytochemical screening of S. guineense leaf extracts revealed the presence of tannin, saponin, steroid, flavonoid and cardiac glycosides. Preservative study revealed that ethanolic extract of S. guineense extends the shelf of tomato at 28±2oC and 4oC beyond 14 and 21days respectively while the control samples showed a rapid deterioration in texture, colour and weight within 7 and 16days respectively. There was significant difference in both the proximate and mineral composition of the treated and control tomato samples. Heamatological and histopathological analyses revealed that there were significant differences for some of the indices in the control and treated rats. The crude or fractionated components of S. guineense extracts may serve as alternative preservative agents to synthetic preservatives in extending the shelf life of tomato fruits.
