Due to the development of praziquantel (PZQ) schistosomes resistant strains, the discovery of new antischistosomal agents is of high priority in research. This work reported the in vitro and in vivo effects of the edible and ornamental pomegranate extracts against Schistosoma mansoni. Leaves and stem bark ethanolic extracts of both dried pomegranates were prepared at 100, 300, and 500 μg/mL for in vitro and 600 and 800 mg/kg for in vivo. Adult worms Schistosoma mansoni in RPMI-1640 medium for in vitro and S. mansoni infected mice for in vivo tests were obtained from Theodor Bilharz Research Institute, Cairo, Egypt. In vitro activity was manifested by significant coupled worms separation, reduction of motor activity, lethality, and ultrastructural tegumental alterations in adult worms. In vivo activity was manifested revealed by significant reduction of hepatic granulomas number and diameter, decreased number of bilharzial eggs in liver tissues, lowered liver inflammatory infiltration, decreased hepatic fibrosis, and inducible nitric oxide synthase (iNOS) expression. Ethanolic stem bark extract of edible pomegranate exhibited highest antischistosomal activities both in vitro and in vivo. Therefore, pomegranate showed a good potential to be used as a promising new candidate for the development of new schistosomicidal agents.

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Polyprenylated xanthones are natural products with a multitude of biological and pharmacological activities. However, their biosynthetic pathway is not completely understood. In this study, metabolic profiling revealed the presence of 4-prenylated 1,3,5,6-tetrahydroxyxanthone derivatives in St. John’s wort (Hypericum perforatum) root extracts. Transcriptomic data mining led to the detection of five variants of xanthone 4-prenyltransferase (HpPT4px) comprising four long variants (HpPT4px-v1 to HpPT4px-v4) and one short variant (HpPT4px-sh). The full-length sequences of all five variants were cloned and heterologously expressed in yeast (Saccharomyces cerevisiae). Microsomes containing HpPT4px-v2, HpPT4px-v4, and HpPT4px-sh catalyzed the addition of a prenyl group at the C-4 position of 1,3,5,6-tetrahydroxyxanthone, 1,3,5-trihydroxyxanthone, and 1,3,7-trihydroxyxanthone, whereas microsomes harboring HpPT4px-v1 and HpPT4px-v3 additionally accepted 1,3,6,7-tetrahydroxyxanthone. HpPT4px-v1 produced in Nicotiana benthamiana displayed the same activity as in yeast, while HpPT4px-sh was inactive. The kinetic parameters of HpPT4px-v1 and HpPT4px-sh chosen as representative variants indicated 1,3,5,6-tetrahydroxyxanthone as the preferred acceptor substrate, rationalizing that HpPT4px catalyzes the first prenylation step in the biosynthesis of polyprenylated xanthones in H. perforatum. Dimethylallyl pyrophosphate was the exclusive prenyl donor. Expression of the HpPT4px transcripts was highest in roots and leaves, raising the question of product translocation. C-terminal yellow fluorescent protein fusion of HpPT4px-v1 localized to the envelope of chloroplasts in N. benthamiana leaves, whereas short, truncated, and masked signal peptides led to the disruption of plastidial localization. These findings pave the way for a better understanding of the prenylation of xanthones in plants and the identification of additional xanthone-specific prenyltransferases.