Bioactive compounds from Tetradenia riparia and Tetracera poggei: antioxidant activity, UPLC-QTOF-MS phytochemical profiling, and in silico targeting of the RNA-binding protein DRBD18 of Trypanosoma brucei

Résumé

Oxidative stress has been implicated in the pathogenesis of African trypanosomiasis. Therefore, plant-derived antioxidants have been investigated as potential therapeutic agents, as they may not only reduce oxidative damage by scavenging reactive oxygen species but also impair parasite survival. The present study investigates the antioxidant activity and phytochemical composition of two Central African medicinal plants, Tetradenia riparia (Hochst.) Codd and Tetracera poggei (Gilg.), and evaluates the potential binding of their major constituents to the mRNA-binding protein DRBD18 of Trypanosoma brucei through in silico molecular docking. Aqueous and methanolic extracts were prepared by decoction and percolation. Qualitative phytochemical screening and quantitative spectrophotometry (Folin–Ciocalteu, AlCl 3 ) revealed rich profiles of polyphenols, flavonoids, tannins, anthocyanins, and alkaloids in both species. UPLC-QTOF-MS in negative ESI mode identified eleven compounds in T. riparia , including rosmarinic acid, luteolin, acacetin, and diterpenoid SP-II and thirteen compounds in T. poggei , dominated by galloylated catechin derivatives (epi-gallocatechin 3-O-gallate, catechin 3-O-gallate (−)-epicatechin-3-(3-O-methyl)-gallate). Antioxidant activity by DPPH and ABTS radical scavenging assays showed that percolated extracts consistently outperformed decocted extracts; T. poggei percolated extract showed the strongest DPPH activity (IC 50 = 4.141 ± 0.175 μg/mL). Molecular docking against the RRM1 and RRM2 domains of DRBD18 (AlphaFold model AF-Q57XR9-F1) revealed that diterpenoid SP-II and (−)-epicatechin-3-(3-O-methyl)-gallate displayed the highest binding affinities (RRM1: −7.3 kcal/mol). The strong antioxidant capacity of the identified compounds, particularly galloylated catechins and rosmarinic acid, is routinely linked to their structural features that also favor RRM domain binding, highlighting their potential as antioxidant compounds and candidate DRBD18 ligands warranting further biological investigation. These findings provide a rational basis for the further development of plant-derived agents targeting oxidative stress and RNA-binding mechanisms in T. brucei .

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