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United States Department of Agriculture

Agricultural Research Service

Research Project: Integrated Aquatic Animal Health Strategies

Location: Aquatic Animal Health Research

Title: Antiparasitic effect of cynatratoside-C from Cynanchum atratum against Ichthyophthirius multifiliis on grass carp

Authors
item Fu, Yao-Wu -
item Zhang, Qi-Zhong -
item Xu, Dehai
item Liang, Jing-Han -
item Wang, Bin -

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 1, 2014
Publication Date: July 1, 2014
Citation: Fu, Y., Zhang, Q., Xu, D., Liang, J., Wang, B. 2014. Antiparasitic effect of cynatratoside-C from Cynanchum atratum against Ichthyophthirius multifiliis on grass carp. Journal of Agricultural and Food Chemistry. 62:7183-7189.

Interpretive Summary: The protozoa Ichthyophthirius multifiliis (Ich) is a severe parasite that infects most fresh water fish worldwide. Ich leads to high fish mortality and causes heavy economic loss in aquaculture. Chemotherapeutants that are permissible in fish to treat parasites are limited in the United States of America so there is an urgent need to find new parasiticides to treat Ich infections. In this study, cynatratoside-C was used to treat Ich infection after isolation from Cynanchum atratum roots by bioassay-guided fractionation. The cynatratoside-C killed 100% of the infective stage of Ich in vitro at 0.25 mg/L after 5 h of exposure. It completely terminated the Ich reproduction at 0.125 mg/L and treated infected grass carp at 2 mg/L within 48 h. The mechanism of cynatratoside-C for killing Ich is to destroy the plasma membrane of the parasite. Based on the results, cynatratoside-C could be used as a natural anti-Ich agent. The study results are important to aquaculture and will help develop effective parasiticides against I. multifiliis.

Technical Abstract: Ichthyophthirius multifiliis (Ich), a fish ectoparasite, results in a significant economic loss in the aquaculture industry. In this study, cynatratoside-C isolated from Cynanchum atratum roots by bioassay-guided fractionation was used to treat I. multifiliis. The cynatratoside-C at 0.25 mg/L demonstrated a 100% mortality of I. multifiliis in vitro after 5 h exposure. The 5 h median effective concentration (EC50) of cynatratoside-C to non-encysted tomonts was 0.083 mg/L. In addition, cynatratoside-C at concentrations of 0.125 and 0.06 mg/L could completely terminate the reproduction of encysted tomonts. The cynatratoside-C at 2 mg/L could cure the infected grass carp within 48 h. The mechanism of cynatratoside-C for killing I. multifiliis is to destroy the plasma membrane of tomonts and induce encysted tomonts releasing immature theronts which are weak in infection and finally died before infecting fish. Based on the results, cynatratoside-C could be used as a natural anti-I. multifiliis agent.

Last Modified: 11/22/2014
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