Protective effects of selected solvent extracts of Terminalia arjuna against environment mediated parasitic infection in Labeo rohita

Abstract

The present study was an attempt to perform functional screening and evaluating the effects of solvent extracts of Terminalia arjuna against Argulus bengalensis. Solvent extracts were used at 10, 20, 30, 40, and 50 mg/L, at 1, 2, 3, 4 and 5 hours and 12, 24, 36,48 and 60 hours under in-vitro and invivo conditions, respectively in moderately parasitically challenged (25-30, A. bengalensis/fish) Labeo rohita juveniles of 30±1.5 g. The 5% dimethyl sulphoxide was used as negative control (DMSO). The LC50 values of solvent extracts for L. rohita were 67.67±12.59, 78.13±14.17, 79.12±17.68, 56.47±12.67 and 256.43±8.93 mg/L for Terminalia arjuna ethanolic bark extract, Terminalia arjuna methanolic bark extract and Terminalia arjuna acetone bark extract, respectively, at 60 hours interval. Under invitro condition, 100% anti-parasitic efficacy (AE) and minimum therapeutic index (TI) value (1.2) was ascertained by Terminalia arjuna ethanolic bark extract at 50 mg/L in 2 hour, and minimum LC50 was reported by Terminalia arjuna ethanolic bark extract under in-vitro condition (13.14±3.79 mg/L) and maximum by Terminalia arjuna acetone bark extract under in-vitro condition (75.8±12.69 mg/L) at 5 hour interval. While, under in-vivo conditions, minimum LC50 for immersion and bath treatments was observed with Terminalia arjuna ethanolic bark extract (27.92±9.56 mg/L) and TAEBIM (33.6±7.58 mg/L), correspondingly, at 60 hours. The minimum TI was reported in bath treatment of Terminalia arjuna ethanolic bark extract (1.1). The RPS was also improved in bath treatment as compare to the immersion treatment. The 100% anti-parasitic activity was observed in bath treatment of Terminalia arjuna ethanolic bark extract at 24 hours. The PCA bi-plot explains 79.34% and 14.32% variations for component 1 & 2, respectively. The efficacy of solvent extracts varied significantly in response to concentrations of the extracts and exposure times and toxicity of the extracts (Exposure time*extract *treatment: F=16.12, P= 0.04). The study provides, the evidences for safe and effective application of prospective solvent extracts of T. arjuna against A. bengalensis in L. rohita juveniles, and yield first-hand information on acute toxicity of solvent extract in L. rohita.