Abstract
The aqueous leaves extracts of Psidium guajava, Vernonia amygdalina and Azadiracta indica were evaluated for phytochemical compositions, antibacterial and anti-fungi activities against microbial isolates. Ampicillin and vastatin were used as standards for antibacterial and antifungal assays respectively. All phytochemicals tested were present in the aqueous extract of the plants. Glycoside and anthraquinone were absent in methanol extract of P. guajava and A. indica respectively. Psidium guajava recorded the highest alkaloids (6.40±0.35 mg/g) and phenol (18.63±0.29 mg/g) while Azadirachta indica recoded the least. Vernonia amygdalina had the highest saponins (6.63±0.34 mg/g) while Azadirachta indica recoded the least (2.40±0.34 mg/g). However, Azadirachta indica had the highest tannin contents of (23.52±0.25 mg/100g). Aqueous extract of Azadirachta indica had a greater zone of inhibition range between 10.00±0.10 to 14.00±0.05 mm and 13.00±0.05 to 14.00±0.05 mm against bacteria and fungi respectively. Psidium guajava show a lower activity against bacteria (12.00±0.05 mm) and higher antifungal activities (11.00±0.05 mm and 19.00±0.05 mm). Vernonia amygdalina on the other hand had 13.00±1.45 mm zone of inhibition against Streptococcus faecalis and Pseudomonas aeruginosa, and antifungal activities range between 9.00±0.35mm and 15.00±0.45 mm. In conclusion Azadiracta indica extract exhibited more antibacterial activities while Psidium guajava exhibited more antifungal activities than the other plant extracts. Therefore, more research should be carried out to enable the purification of the specific biopotential chemicals from these plants and their subsequent processing into antimicrobial agents in food industries.
Highlights
Food safety is a global issue with significant implications to human health
Glycoside and anthraquinone were absent in methanol extract of P. guajava and A. indica respectively
The results of the present study shows similarities to the findings of Nwanneka et al [41]which investigated the antimicrobial activity of Psidium guajava leaf extract, the results showed that both aqueous and ethanol extracts of guava leaf inhibited the growth of the bacteria and fungi tested but the ethanolic extract showed stronger inhibition than the aqueous extract against the organisms
Summary
Food safety is a global issue with significant implications to human health. The world health organization reports that, annually, unsafe food results in the illnesses of at least 2 billion people worldwide [1]. Some countries have made progress in controlling foodborne disease but the number of those affected by foodborne diseases is growing globally [2]. Fruits and vegetables are prone to several post-harvest losses due to diseases like bacterial rot, smut etc which in turn reduces the shelf-life of the fruits. Estimated post-harvest losses are about 25-30 % due to microbial spoilage [3]. Wastage of spoilt fruits and vegetables can lead to scarcity and famine
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