Bioassay-guided isolation and identification of active compounds from Semen pharbitidis against Dactylogyrus intermedius (Monogenea) in goldfish (Carassius auratus).

The present study was undertaken to isolate the active compounds responsible for the anthelmintic activity of methanol extract of Semen pharbitidis against Dactylogyrus intermedius in goldfish (Carassius auratus). The active methanol extract was fractionated on silica gel column chromatography in a bioassay-guided fractionation, eventually yielding two bioactive compounds: palmitic acid and pharnilatin A by comparing spectral data (NMR and ESI-MS) with literature values. According to in vivo anthelmintic assays, they were found to be 50% effective at the concentrations (EC(50)) of 5.3 and 1.4 mg L(-1), respectively. The promising palmitic acid and pharnilatin A from S. pharbitidis were also subjected to acute toxicity tests for the evaluation of their safety to the host (goldfish). After 48h exposure, the mortalities of goldfish were recorded, and the established LC(50) values were 2.45- and 5.29-fold higher than the corresponding EC(50), demonstrating that pharnilatins A may have better application potential than palmitic acid. The present results provide evidence that pharnilatins A might be potential source of new anti-parasitic drug for the control of Dactylogyrus.