The anthelmintic potentials of medicinal plant extracts and an isolated compound (rutin, C27H30O16) from Terminalia catappa L. against Gastrothylax crumenifer.

Paramphistomosis is a pathogenic disease that occurs frequently in tropical and subtropical countries including Thailand. This disease is affected in the parasites causing severe gastrointestinal disorders and death in infected animals. In the present study, we examined the anthelmintic efficacy of albendazole (ABZ) and crude plant extracts from barks of Bombax ceiba L., Diospyros rhodocalyx Kurz. and Vitex glabrata R.Br., and leaves of Terminalia catappa L. and Cassia alata L. against Gastrothylax crumenifer. The hightest anthelmintic activity on the parasites after 24 h incubation was observed in the n-butanol extract of T. catappa leaf. In this study, fractionation bioassay of n-butanol extract of T. catappa leaf was conducted to both separation and discrimination of rutin served as a new efficient compound (LC50 = 28.96; LC90 = 88.75 μg/mL) against G. crumenifer. This compound was confirmed by 1H nuclear magnetic resonance (1H NMR), 13C NMR, infrared (IR) and ultraviolet (UV) spectra as well as mass spectra data. The rutin-treated parasites with all dosages showed swift decrease of the motility and the relative motility (RM) and survival index (SI) were decreased obviously from 3 h until flukes were killed after 12 h of incubation. When observed with light microscopy, the parasites showed the earliest change in a limited region of the tegument. When observed by scanning electron microscopy, the parasites' tegument exhibited similar sequences of surface changes after treatments with rutin and ABZ, but less severity in ABZ treatment. The sequences of changes comprised swelling of folds and ridges, formation of blebbing, rupturing of blebs, erosions, lesions and the tegument demolition. Hence, rutin could be considered as the potential anthelmintic agent for treatment of paramphistomosis.