No abstract

Background Fish constitutes a nutritious food that deteriorates quickly when poorly preserved. Several biochemicals, including formaldehyde, naturally accumulate in the fish post-mortem. Apart from this natural formaldehyde, reports indicate the unlawful addition of formalin (37% formaldehyde solution) to the stored fish to prolong freshness. This is risky since formaldehyde is carcinogenic, genotoxic, and a potentiator of other carcinogens. Aim This study aimed to investigate both the freshness and the extent of contamination with formaldehyde of mackerel sold in Dar es Salaam. Methods A total of 60 mackerel samples were conveniently and equally obtained from the local markets, street vendors, and supermarkets in five districts of the Dar es Salaam region. Freshness was evaluated based on organoleptic characteristics. Formaldehyde analysis was done by High-Performance Liquid Chromatography (HPLC). Analysis of variance of formaldehyde concentration in fish flesh by source outlet and district was subsequently run. Results The analyzed mackerel samples had acceptable levels of freshness (2.46 ± 0.50) and a mean formaldehyde concentration of 10.89 ± 2.44 mg/kg. On average, the samples from supermarkets were the freshest (2.20 ± 0.21) however the most contaminated with formaldehyde (16.07 ± 4.68 mg/kg), while those from local markets were the least contaminated (3.91 ± 1.86 mg/kg) (p=0.000). Moreover, 0% (n=0), 20% (n=4), and 35% (n=7) of samples from local markets, street vendors, and supermarkets respectively, had formaldehyde concentrations above 20 mg/kg, the previously estimated highest concentration for natural formaldehyde in fish. Conclusion Mackerels found in Dar es Salaam have acceptable freshness but are substantially contaminated with formaldehyde. Whether this formaldehyde is natural or artificially added, our findings are inconclusive, given the conflicting global cut-off values for natural formaldehyde in fish. We, therefore, recommend a contextualized study to establish the time dynamics of formaldehyde formation in the stored fish. In the meantime, we advise the public to dwell on the local markets for fish rather than the supermarkets and street vendors.

Background: Research and development of the new antibacterial agents are among the strategized measures to combat antimicrobial resistance (AMR). In the recent decades, biotransformation has been demonstrated as an alternative and effective approach for scavenging the new molecules. There is a high probability of obtaining active metabolites through biotransformation of known compounds possessing antibacterial activities. This study intended to search for new compounds by biotransformation of ceftriaxone and ciprofloxacin antibiotics using Pleurotus ostreatus mushroom.Method: Pleurotus ostreatus mushroom culture was incorporated with antibiotics and incubated for 12 days. The mixture was extracted and analysed by using Thin layer Chromatography (TLC) method to identify newly formed compounds. The TLC chromatograms were then subjected to agar overly bioautography to determine antibacterial activity of the new compounds. Results: Ceftriaxone and Ciprofloxacin antibiotics were metabolized by P. ostreatus to possibly new metabolites. The TLC analysis indicated that ceftriaxone was metabolized to give three new spots and ciprofloxacin gave only one new spot which infer the formation of new compounds from biotransformation by P. ostreatus mushroom. Bioautography showed the new spots from biotransformation of ceftriaxone to be active against S. aureus both standard and clinical isolates as well as active against methicillin resistant Staphylococcus aureus strains. The new spot from biotransformation of ciprofloxacin was only active to standard of E. coli.Conclusion: P. ostreatus mushroom has the potential to bio transform ceftriaxone and ciprofloxacin giving antibacterial active metabolites. This shows biotransformation can be considered an alternative tool for searching of new drugs.