Immunostimulatory effects of N -Oxide-Quaternary alkaloid fraction of a marine Chlorophycean macroalga in the striped murrel, Channa striata (Bloch)

N-Oxide–Quaternary Alkaloid Fraction (NOQAF) of a Chlorophycean macroalga, Caulerpa scalpelliformis (R.Br.) C. Ag f. denticulata (Deaisne) Weber van Bosse (Patent filed) was intraperitoneally administered at different doses (0, 2, 20 or 200 mg kg−1 body weight) in different groups of Channa striata to assess its effect on the non-specific immune responses and disease resistance against live virulent Aeromonas hydrophila. A reference positive control [MacroGard (Biotec Pharmacon ASA, Norway) 20 mg kg−1 body weight] was simultaneously maintained to compare its efficacy. The fraction (NOQAF) has been found to enhance the serum lysozyme, peroxidase, antiprotease and alternate complement activities and the reactive oxygen and nitrogen species production and peroxidase activity by the peripheral blood leucocytes than the control group during the study period. On experimental challenge with live virulent A. hydrophila, maximum RPS values of 88.8 and 87.4 were noted in the groups treated with single dose of 20 mg kg−1 and double dose of 2 mg kg−1 of NOQAF respectively. In conclusion, the intraperitoneal administration of the N-Oxide–Quaternary Alkaloid Fraction (NOQAF) of C. calpelliformis has been found to significantly enhance the non-specific immune responses and disease resistance against A. hydrophila in Channa striata.