Malaria is a vector borne disease responsible for high morbidity, mortality and poverty in many tropical and subtropical countries. The disease is transmitted through a bite from an infected female Anopheles mosquito, amongst which Anopheles gambiae s.s serves as the most prevalent vector. The control of An. gambiae s.s population can therefore lead to a reduction in malaria spreading. Previous studies have reported the crude extracts of Kotschya thymodora to be active against the larvae of An. gambiae s.s and Culex quinquefasciatus. In this report the phytochemical study on the crude aqueous ethanolic extract of K. thymodora leaves led to isolation of vanillic acid (1) and protocatechuic acid (2). The structures of these compounds and mosquitoes larvicidal activity against An. gambiae s.s were established by using spectroscopic techniques and WHO protocol of 1996 respectively. The two phenolic acids exhibited a moderate mosquito larvicidal activity with LC50 of 77.35 μg/mL (vanillic acid, 1) and 62.4 μg/mL (protocatechuic acid, 2) after 48 hrs exposure time. This is the first report on the isolation of the two phenolic acids from plants belonging to the genus Kotschya and their larvicidal potential against An. gambiae s.s. Keywords: larvicidal activity, vanillic acid, protocatechuic acid, Anopheles gambiae s.s and Kotschya thymodora
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.
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