Phytochemical screening for identification of bioactive compound and antiprotozoan activity of fresh garlic bulb over trichodinid ciliates affecting ornamental goldfish

Ornamental fish culture is an economically important business of our country and contribute in the socioeconomic upliftment of the backward community with a little investment. However, parasitic outbreaks cause increased mortality, which in turn results in high economic loss in this industry. Trichodinids are known to be a major problem in fish farms causing serious damage, particularly under cultured condition of gold fish. The wide variety of chemicals used for treating trichodiniasis not only make the environment unfavorable for aquaculture but the pathogen also becomes resistant towards them over time. So, the chemicals should be used more rationally to prevent the protozoa from becoming resistant towards them and moreover there is an urgent requirement of alternative therapeutic strategies to control this protozoon mediated damage of the ornamental fishes. Hence, the present study has been designed to identify a non-chemotherapeutic agent for disease treatment in aquaculture which might be beneficial for the industry. Garlic is popularly known to be rich in a variety of secondary metabolites owing the ability to synthesize many different substances that has been widely exploited by the local community for its medicinal value, which led us to test it as a therapeutic agent for trichodiniasis in goldfish. After determining its toxicity level (LC50 value-29.79 mg/L) 15 mg/L ethanolic extract of garlic was found to reduce the trichodinids burden of goldfish significantly (P < 0.01) within 4 days only which clearly demonstrates the antiprotozoan activity of fresh garlic bulb. Further the bioactive components of garlic responsible for its antitrichodinid activity were identified using GC-MS.