Potential anti-plasmodial constituents of Terminalia pennyana stem bark

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Purpose: To evaluate the in vivo antiplasmodial activity of Terminalia pennyana stem bark and employ vacuum liquid chromatography (VLC) and high-performance liquid chromatography-mass spectrometry (HPLC-MS) to fractionate the extract and dereplicate its bioactive constituents. Methods: Terminalia pennyana stem bark was macerated in 96% methanol (3 L) for 48 h to obtain crude extract. The extract was separated using liquid-liquid partitioning and further fractionated on silica gel using vacuum liquid chromatography with a dichloromethane-methanol gradient to yield six subfractions (TPMEv1-TPMEv6). Based on bioactivity, selected fractions were dereplicated by C18-HPLC-MS technique. A four-day Rane's curative model in P. berghei-infected mice was used to evaluate in vivo antiplasmodial activity. Results: Cold maceration yielded 3.89 %w/w methanol extract (TPM). Partitioning of TPM afforded 6.65 g (2.16 %) ethyl acetate (TPME), while the VLC of TPME generated six subfractions, including the most active TPMEv2 (0.21 %) and TPMEv3 (0.16 %). The dereplication of TPMEv2 and TPMEv3 using the HPLC-MS technique detected two flavan-3-ols: catechin/epicatechin (C15H14O6) at m/z 291.0865 and a lignan, pinoresinol (C20H22O6) at m/z 359.1024. In an in vivo bioassay study, TPM, TPME, TPMEv2 and TPMEv3 at a dose of 200 mg/kg inhibited parasitaemia by 45.3, 58.6, 63.2, and 79.4%, respectively, with mean survival times of 21.4, 25.2, > 28, and > 28 days (p < 0.01), when compared with the effect of artesunate (83.4 % inhibition, > 28 days). Conclusion: Terminalia pennyana extract and TPMEv2 and TPMEv3, which are rich in catechins and pinoresinol, exhibit strong, dose-dependent antiplasmodial effects.

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