Pentaclethra eetveldeana Leaves from Four Congo-Brazzaville Regions: Antioxidant Capacity, Anti-Inflammatory Activity and Proportional Accumulation of Phytochemicals

Abstract

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.

Keywords: Pentaclethra eetveldeana; antidenaturation; antioxidant; flavones; flavonols; leaf aqueous extract; membrane stabilization; secondary metabolites.

Figure 1

Total polyphenols, proanthocyanidins, tannins and flavonoids of Pentaclethra eetveldeana leaf extracts from Boundji, Brazzaville, Owando and Makoua, in units of µg of gallic acid equivalent (µg GAE), µg of apple proanthocyanidin equivalent (µg APE), µg of tannic acid equivalent (µg TAE), µg of quercetin equivalent (µg QE), respectively. For each compound, the same letter means a significant difference (p < 0.01) between the two.

Figure 2

Relative antioxidant activities (%) of Pentaclethra eetveldeana leaf extracts. The same letter means significant difference (p ≤ 0.05).

Figure 3

Positive correlations between relative antioxidant activities (%) and flavonoids (µg QE/g).

Figure 4

(a) Positive correlations between total antioxidant capacity (µg AAE/g), extraction yields (%), total polyphenols (µg GAE/g), proanthocyanidins (µg APE/g) and tannins (µg TAE/g). (b) Negative correlations between DPPH radical scavenging activity (µg/mL), extraction yields (%), total polyphenols (µg GAE/g), proanthocyanidins (µg APE/g) and tannins (µg TAE/g). IC₅₀ and extraction yields were multiplied by 100 for better visibility in the figure.

Figure 5

Antidenaturation activity of Pentaclethra eetveldeana leaf aqueous extracts. For the same concentration, the same letter means no significant difference; no letter in common or no letter means a significant difference (p < 0.05).

Figure 6

Inhibition (%) of heat-induced hemolysis by Pentaclethra eetveldeana leaf extracts. For the same concentration, the same letter means no significant difference; no letter in common or no letter means a significant difference (p < 0.05).

Figure 7

Inhibition (%) results of hypotonicity-induced hemolysis by Pentaclethra eetveldeana leaf extracts. For the same concentration, the same letter means no significant difference; no letter in common or no letter means a significant difference (p < 0.05).

Figure 8

Leaves of Pentaclethra eetveldeana. (a) Pentaclethra eetveldeana leaves seen from behind; (b) Pentaclethra eetveldeana leaves seen from the front; (c) Close-up view of the sides of Pentaclethra eetveldeana leaves.