In vivo antischistosomal efficacy of Porcelia ponderosa γ-lactones

Schistosomiasis, caused by the parasitic blood fluke Schistosoma mansoni, is a significant global health concern, particularly in tropical and subtropical regions. The available chemotherapeutic drug is restricted to praziquantel with present problems related to efficacy, toxicity and resistance, justifying the search for new drugs. Different natural products, including γ-lactones, have demonstrated anthelmintic activity. Thus, in this study, new γ-lactones from Porcelia ponderosa were investigated for their anti-S. mansoni effects in vitro and in vivo.

To evaluate the therapeutical potential against S. mansoni of the mixture of γ-lactones 1 + 2 obtained from Porcelia ponderosa seeds.

The precipitate formed during the concentration of CH₂Cl₂ extract from seeds of P. ponderosa showed to be composed by a mixture of the new γ-lactones 1 + 2 (in a ratio 77:23) which were chemically characterized using NMR and ESI-HRMS. This mixture was evaluated in vitro and in vivo against S. mansoni, using a murine model of schistosomiasis. Additionally, toxicity of the mixture of 1 + 2 (77:23) was determined using mammalian cell lines (in vitro) or the model organism Caenorhabditis elegans (in vivo).

Seeds of P. ponderosa afforded a mixture of two unreported γ-lactones, 3‑hydroxy-4-methylene-2-(tetracosa-17'Z,23'-diene-13',15'-diynyl)‑but-2-enolide (1) and 3‑hydroxy-4-methylene-2-(tetracos-17'Z-ene-13',15'-diynyl)‑but-2-enolide (2). Initially, the antischistosomal activity of the mixture of 1 + 2 (77:23) was investigated in vitro, and obtained results demonstrate reduced activity against Schistosoma mansoni worms (EC₅₀ of 83.3 μg/ml) in comparison to positive control praziquantel (EC₅₀ of 1.5 μg/ml). However, when tested in vivo using oral administration at 400 mg kg^-1, the standard dose used in the murine model of schistosomiasis, the mixture of 1 + 2 (77:23) revealed expressive reductions in both worm burden (65.7 %) and egg production (97.2 %), similar of those observed to praziquantel (89.7 % and 91.5 %, respectively). On the other hand, when treated using 200 and 100 mg kg^-1, reductions in worm burden (25.7 and 12.4 %) and egg production (33.6 and 13.3 %) were also observed. Importantly, the mixture of 1 + 2 (77:23) exhibited no toxicity using mammalian cell lines (in vitro) or C. elegans (in vivo).

Considering the promising in vivo activity of γ-lactones from P. ponderosa, the mixture of 1 + 2 (77:23) can be considered as promising candidate for the development of novel antischistosomal therapeutics, underscoring the importance of biodiversity exploration in the search for effective treatments against neglected tropical diseases.