Victor N'GOka

It is important to know the intraspecific variability of the biological properties and chemical composition of plants in order to promote their better use. Thus, referring to the use of Pentaclethra eetveldeana (De Wild & T. Durand) leaves in a dementia traditional treatment, this study aims to highlight the antioxidant capacity and the chemical composition of the ethanolic extracts of Pentaclethra eetveldeana leaves from four localities of Congo-Brazzaville. The β-carotene bleaching, diphenyl-picryl-hydrazyl (DPPH) radical-scavenging and molybdenum reduction methods were used to determine the antioxidant potency. Subsequently, the yields of the extractions, the phytochemical screening and the quantification of the phenolic compounds were carried out. The results revealed that the extracts of the four localities presented an antiradical and an antilipid peroxidation superior to those of ascorbic acid in DPPH and β-carotene bleaching methods. Moreover, among the extracts, those of the leaves from Boundji and Brazzaville presented the best antilipid peroxidation, antiradical and reducing activities as well as the greatest extraction yields, the greatest quantities of total polyphenols and proanthocyanidins against low levels of flavonoids. Furthermore, saponins, polyphenols, alkaloids, reducing sugars and cardiotonic glycosides were identified in all ethanolic extracts except sterols and triterpenes which were only identified in the extracts of leaves collected in Brazzaville. In addition, flavones were identified in the leaves from Owando and Makoua; flavonols in the leaves from Boundji and Brazzaville. This study showed that Pentaclethra eetveldeana leaf ethanolic extracts exhibit antilipid peroxidation, antiradical properties and phytochemical that varied according to the region.

Oxidative stress and inflammation play a key role in the occurrence of neurodegenerative diseases. Traditionally, Pentaclethra eetveldeana leaves are used in dementia treatment. Therefore, this study aimed to evaluate the antioxidant and anti-inflammatory activities as well as the phytochemical composition of Pentaclethra eetveldeana leaves from four Congo-Brazzaville regions. The 1.2-diphenyl-1-picrylhydrazyl radical-scavenging, β-carotene bleaching and molybdenum reduction assays were used to assess the antioxidant activity. The protein denaturation and erythrocyte membrane stabilization tests were used to analyze the anti-inflammatory activity. Phytochemical screening, the quantification of polyphenols by spectrophotometry, as well as the determination of extraction yields were carried out. It was found that the extracts reduced molybdenum; furthermore, compared to ascorbic acid, they showed better antiradical activity and inhibited lipid peroxidation. Moreover, globally, the membrane-stabilizing power of the aqueous extracts was superior or comparable to diclofenac, while the same extracts were less effective for the inhibition of denaturation. All of the aqueous extracts contained polyphenols, saponins, alkaloids, anthraquinones, reducing sugar and cardiotonic glycosides. The total polyphenols, tannins and proanthocyanidins are produced proportionally from one region to another. Finally, the leaves from Brazzaville and Boundji contain flavonols, while those from Makoua and Owando contain flavones. Thus, Pentaclethra eetveldeana leaves contribute to traditional dementia treatment through their antioxidant and anti-inflammatory properties.

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