[Development of a new hydrocarbon extract from the medicinal raw material of Circassian walnut (Juglans regia) and study of its antiparasitic activity].

The authors developed a technology for preparing a hydrocarbon extract from the medicinal raw material of Circassian walnut (Juglans regia), including its green fruits, green leaves, and fresh roots. To prepare the preparation, they obtained for the first time a new extragent called petroleum Russia that was found to contain more than hundred chemical compounds by chromatography mass spectrometry. The new agent was named irillen. Experiments on albino mice and albino rats established that the new agent was low toxic. The lethal doses of irillen were calculated: LD50 was 16377 +/- 457.5 mg/kg; LD16 = 12986.4 mg/kg; LD84 was 18976.6 mg/kg for albino mice; LD50 was 16998.0 +/- 535.4 mg/kg; LD16 = 12875.3 mg/ kg; LD84 = 18583.4 mg/kg for albino rats. The irillen prepared by the authors should be referred to as a low toxic and practically nontoxic agent (Toxicity Class IV and V). Irillen has a broad spectrum of antiparasitic activity. It is effective in treating toxocariasis in dogs, larval alveolar echinococcosis, ascaridiasis, and eimeriasis in chickens, and siphachiasis.

Anticoccidial kinase inhibitors: identification of protein kinase targets secondary to cGMP-dependent protein kinase.

Trisubstituted pyrrole inhibitors of the essential coccidian parasite cGMP dependent protein kinase (PKG) block parasite invasion and show in vivo efficacy against Eimeria in chickens and Toxoplasma in mice. An imidazopyridine inhibitor of PKG activity with greater potency in both parasite invasion assays and in vivo activity has recently been identified. Susceptibility experiments with a Toxoplasma knock-out strain expressing a complementing compound-refractory PKG allele ('T761Q-KO'), suggest a role for additional secondary protein kinase targets. Using extracts from this engineered T. gondii strain and a radiolabeled imidazopyridine ligand, a single peak of binding activity associated with calmodulin-like domain protein kinase (CDPK1) has been identified. Like PKG, CDPK1 has been implicated in host cell invasion and exhibits sub-nanomolar sensitivity to the compound. Amino acid sequence comparisons of coccidian CDPKs and a mutational analysis reveal that the binding of the ligand to PKG and CDPK1 (but not other CDPK isoforms) is mediated by similar contacts in a catalytic site hydrophobic binding pocket, and can be blocked by analogous amino acid substitutions. Transgenic strains over-expressing a biochemically active but compound-refractory CDPK1 mutant ('G128Q') fail to show reduced susceptibility to the compound in vivo, suggesting that selective inhibition of this enzyme is not responsible for the enhanced anti-parasitic potency of the imidazopyridine analog. An alternative secondary target candidate, the alpha-isoform of casein kinase 1 (CK1alpha), shows sensitivity to the compound in the low nanomolar range. These results provide an example of the utility of the Toxoplasma model system for investigating the mechanism of action of novel anticoccidial agents.