In Africa, vector-borne diseases are a major public health issue, especially in cities. Urban greening is increasingly considered to promote inhabitants’ well-being. However, the impact of urban green spaces on vector risk remains poorly investigated, particularly urban forests in poor hygienic conditions. Therefore, using larval sampling and human landing catches, this study investigated the mosquito diversity and the vector risk in a forest patch and its inhabited surroundings in Libreville, Gabon, central Africa. Among the 104 water containers explored, 94 (90.4%) were artificial (gutters, used tires, plastic bottles) and 10 (9.6%) were natural (puddles, streams, tree holes). In total, 770 mosquitoes belonging to 14 species were collected from such water containers (73.1% outside the forested area). The mosquito community was dominated by Aedes albopictus (33.5%), Culex quinquefasciatus (30.4%), and Lutzia tigripes (16.5%). Although mosquito diversity was almost double outside compared to inside the forest (Shannon diversity index: 1.3 vs. 0.7, respectively), the species relative abundance (Morisita–Horn index = 0.7) was similar. Ae. albopictus (86.1%) was the most aggressive species, putting people at risk of Aedes-borne viruses. This study highlights the importance of waste pollution in urban forested ecosystems as a potential driver of mosquito-borne diseases.

Objective: This study aimed to valorize two medicinal plants used against Loa loa filarial in Gabon. Material and Methods: Powders of leaves of Senna occidentalis and stems and leaves of Cissus quadrangularis were proposal to successive extractions by solvents with increasing polarities (cyclohexan, dichloromethan, methanol and demineralized water). Qualitative Phytochemistry screening was established using the standard color and/or precipitation reactions. Results: The results reveal the predominance of total sugar, alkaloids, and phenols in all extracts. Cathechic tannins, reducing sugar, and flavonoids on many extracts were tested. Gallic tannins and coumarins are found in some extracts. They are very few quinones, triterpenes or sterols in the two species. Conclusion: Some secondary metabolites have proved filaricide activities already. The abundance of chemical compounds present in these medicinal plants would justify their usage. However, the evaluation of biological activities on the Loa loa filarial along with toxicity remains unexplored.

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In Africa, vector-borne diseases (VBDs) are still a major public health issue especially in cities that gather an increasing human population. Market gardening practices, for example, can favor the transmission of urban malaria, while insufficient water supply and waste management favor the circulation of arboviroses related to Aedes mosquitoes. Urban planning is a major challenge to mitigate vector risks. As a planning strategy, greening is a concept that is increasingly considered as a major element impacting the well-being of inhabitants, but also for the restoration of biodiversity in cities. Nevertheless, the impact of urban green spaces on vector risk remains poorly investigated, as they may serve as refuge for vectors. This is why the diversity of mosquitoes in terms of species and larval habitat, through larval prospections in environmental water collections and human landing catches, is studied here at an intra-urban interface area between a forest and an urban ecosystem in order to assess the vector risk generated by preserving a forest patch in the heart of Libreville, capital of Gabon, central Africa. Out of 104 water containers explored, 94 (90.4%) were artificial, mainly comprising gutters, used tires, and plastic bottles, while 10 (9.6%) were natural, comprising a puddle, streams, and tree holes. The majority of the water collections recovered (73.1%) were found outside of the forested area, natural and artificial ones considered together. A total of 770 mosquitoes belonging to 14 species were collected from water collections. The mosquito community was largely dominated by anthropophilic species like Aedes albopictus (33.5%), Culex quinquefasciatus (30.4%), and Lutzia tigripes (16.5%). The Shannon index of diversity showed that mosquitoes were almost twice less diversified inside the forest (0.7) than outside (1.3). However, both communities were quite similar in terms of common species and relative abundance (Morisita-Horn index = 0.7). Regarding Human landing catches, Aedes albopictus (86.1%) was the most aggressive species, putting people at risk of Aedes-borne viruses. This study uncovered the importance of considering urban forested ecosystems as potential drivers of disease emergence and spread in urban areas, as they might locally boost urban mosquito densities due to poor environmental practices, mainly maintained by humans through poor environmental practices. In Gabon, this study should contribute to guide targeted vector control strategies, especially regarding the implementation of policies for a better environmental management and vector surveillance in urbanized areas.

The report focused on the extraction of oilseeds of Desbordesia glaucescens (Engl.) Tiegh. from Gabon as well as on the phytochemical study and evaluation of the anti-free radical activity of the extracts obtained. The extraction was carried out by cold maceration with solvents of increasing polarities: hexane, tricholroethylene, acetone, ethanol and distilled water. The anti-free radical activity was measured by scavenging the free radical cation of 2,2'-azinobis [3-ethylbenzothiazolin-6-sulfonic acid] (ABTS • +) with gallic acid as the standard antioxidant. Total extraction yields were in the order of 82.31%. Phytochemical tests demonstrated the presence of secondary metabolites of alkaloids, tannins, polyphenolstypes, reducing compounds, free anthracene derivatives, anthraquinones, total sugars, coumarins, free quinones, sterols and terpenes, carotenoids, flavonoids, cardiac glycosides, mucilages, saponins and leucoanthocyanins. The results of the anti-free radical activity showed that the polar extracts were much more anti-free of the free radicals than the non-polar extracts. The aqueous extract was the most active with an IC50 of 10 µg. mL -1 , followed by ethanolic extract with IC50 of 14 µg. mL -1 and acetone extract with IC50 of 150 µg. mL -1 . Cyclohexane and trichlorethylene extracts were more or less inactive. Gallic acid, the standard antioxidant, showed an IC50 of 0.37 µg. mL -1 .