Fu Yao-Wu, Zhang Qi-Zhong, Xu De-Hai, Liang Jing-Han, Wang Bin
Key Laboratory of Eutrophication and Red Tide Prevention of Guangdong Higher Education Institutes, Engineering Research Center of Tropical and Subtropical Aquatic Ecological Engineering Ministry of Education, Institute of Hydrobiology, Jinan University , Guangzhou 510632, People's Republic of China.
J Agric Food Chem. 2014 Jul 23;62(29):7183-9. doi: 10.1021/jf5018675. Epub 2014 Jul 11.
Ichthyophthirius multifiliis (Ich), a fish ectoparasite, comprises an important challenge in the aquaculture industry. In this study, a steroidal glycoside, 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 nonencysted 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 exact mechanism of cynatratoside-C for killing I. multifiliis is unknown, but it manifests itself microscopically through loss of membrane integrity of nonencysted tomonts or through releasing immature theronts from encysted tomonts. The immature theronts finally died before infecting fish. On the basis of these results, cynatratoside-C could be used as a natural anti-I. multifiliis agent.
多子小瓜虫（Ichthyophthirius multifiliis，Ich）是一种鱼类体外寄生虫，给水产养殖业带来了重大挑战。在本研究中，通过生物活性导向分离从白薇（Cynanchum atratum）根中分离得到的甾体糖苷——白薇苷-C，被用于治疗多子小瓜虫。0.25mg/L的白薇苷-C在体外暴露5小时后可使多子小瓜虫的死亡率达到100%。白薇苷-C对未包囊的滋养体的5小时半数有效浓度（EC50）为0.083mg/L。此外，浓度为0.125mg/L和0.06mg/L的白薇苷-C可完全终止包囊滋养体的繁殖。2mg/L的白薇苷-C可在48小时内治愈感染的草鱼。白薇苷-C杀灭多子小瓜虫的确切机制尚不清楚，但在显微镜下表现为未包囊的滋养体膜完整性丧失，或从包囊滋养体中释放出未成熟的幼虫。未成熟的幼虫最终在感染鱼类之前死亡。基于这些结果，白薇苷-C可作为一种天然的抗多子小瓜虫药物。
