When considering all trees irrespective of their species, natural tropical rain forests typically exhibit spatial patterns that range from random to regular. The regularity is often interpreted as a footprint of tree competition. Using 23 permanent sample plots totalling 61 ha in the rain forests of central Africa, we characterized their spatial patterns and modelled those that exhibited regularity by a Strauss point process. This Strauss process is obtained as a Markov point process whose interaction function is an exponential function of a competition index commonly used in forestry. The parameter of this Strauss process characterizes the strength of competition. The 23 plots in central Africa differed in tree density and basal area, and could be discriminated depending on the type of spatial patterns: plots having a large basal area with respect to their density had a non regular pattern, whereas those having a small basal area with respect to their density had a regular pattern. For those plots that exhibited regularity, average tree size could be used to predict the strength of competition. The parameter of the Strauss process was significantly related to the average size by a linear relationship, such that competition decreases as average tree size increases. This relationship extrapolated to a null value of the Strauss parameter when average tree size reaches 32 cm in diameter. This relationship between average tree size and spatial pattern is a testable feature for future studies on the relationship between competition and spatial pattern in natural forests. (Résumé d'auteur

In traditional medicine, Annnickia chlorantha (Annonaceae)is used in many parts of Africa to treat several pathologies. It is used for the management of stomach problems, for the treatment of jaundice, tuberculosis, urinary tract infections, malaria, hepatitis and ulcers forms, for gallstones or even diarrhea. The phytochemical analysis and determination of the antiradical activity of the methanolic extract of the trunk bark from Annickia chlorantha from Gabon was the subject of this study. Phytochemical screening revealed the abundance of alkaloids, polyphenols and catechics tannins.The total polyphenol content released by the Folin-Ciocalteu method was 309.17 ± 38.05 g of gallic acid equivalent per 100 mg of dry matterand the total flavonoids content performed with AlCl3 was 155.16 ± 21.06 g of quercetin equivalent per 100 mg of dry matter. The antiradical activity was limited to 81.58% ± 1.25 without disappearance of the ABTS•+ radical after 6 minutes of incubation. These results confirm the correlation between the polyphenol content and the antiradical activity.

Abstract. Mengome, Mewono L, Mboma R, Engohang-Ndong J, Angone SA. 2021. Ethnobotanical survey and phytochemical screening of anti-snakebite plants used in Bissok District of Gabon. Biodiversitas 22: 3264-3275. Snakebites remain a major health issue in tropical and subtropical regions in the world. The limited access of antivenom sera in remote areas of many countries forces populations to rely on plant-based remedies to manage snakebite-induced injury. In this study, we conducted an ethnobotanical survey of medicinal plants used for the management of snakebites in the district of Bissok (Northern Gabon). After collecting and verifying the authenticity of the plants, we further performed their phytochemical analysis. The procedure used in this study involved a structured questionnaire and direct interviews of local populations. Overall, data collected on-site included local names, the part of the plant used, the preparation, and the route of administration. The presence of some phytochemical compounds was determined according to standard methods. Overall, a total of 29 species of plants belonging to 20 different families were reported to be used to treat snakebites. The plants used were herbs (44.80%), trees (24.10%), shrubs (20.70%), liana (10.30%), and rhizomes (6.90%). They were mainly used as poultice or crush, and to a lesser extent as decoction and maceration. Regarding the route of administration, interviewees reported mainly external use on the site of the bite. Concerning the chemical composition, we found that the antivenom plants were rich in chemical compounds known to have antivenom, antipyretic and antimicrobial properties, e.g. alkaloids, terpenoids, flavonoids, steroids, coumarins, phenols, tannins gallic Our results open avenues to develop venom enzyme inhibitory assays.

An ethnobotanical study of medicinal plants was carried out among the Mitsogho people of thefour (4) villages located from Oyane 4 to Four-Place (Estuaire-Gabon). The objective of this study was firsttodraw up an inventory of plants used in their traditional medicine against infant diarrhea and then to describe the recipes applied by the local population. Sixteen (16) plants species belonging to sixteen (16) genus and eleven (11) families were identified. The most species cited were Sida rhombifolia (18%), Cyathula prostrata (12%), Desmodium adscendens (12%), andPsidium guineense (12%). Those with the lowest frequencies were among others Picralima nitida (6%) and Santiria trimera (6%). The most represented families are Malvaceae (25%), Apocynaceae (12.5%) and Fabaceae (12.5%). The plants inventoried are mainly woody (81%) trunk bark (56%) and leaves (37%) are the most used plant parts. Twenty-two (22) recipes have been described, of which 77% contain a single plant and 23% are mixture.

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