Infectious bursal disease virus (IBDV) causes a highly contagious disease in young chicks and leads to significant economic losses in the poultry industry. To determine a suitable cell line for IBDV infection, replication, and growth kinetics of the virus, DF-1 cells and chicken embryo fibroblasts (CEF) were used. The population doubling per day (Pd/D) was found to be higher in DF-1 as compared to CEF cells. A suitable time of infection (TOI) was established for increased production of virus and greater infectivity titers. The DF-1 and CEF cells were found to be susceptible to infection by producing marked cytopathic effects (CPEs), and the growth curves of IBDV in DF-1 and CEF cells were evaluated by infectivity assay using tissue culture infectious dose (TCID50). The cytopathic effects of the virus in DF-1 and CEF cells were found to be similar, but higher viral titers were detected in the DF-1 cells as compared to CEF. Thus the DF-1 cell line had a higher growth potential and infectivity, which will be of advantage in vaccine production.

Phenolic contents, antioxidant and antimicrobial activities were determined by two samples from summer (June) and winter (December) seasons of Ligularia fischeri var. spiciformis Nakai. A total of 24 phenolic compounds were identified by ultra-performance liquid chromatography (UPLC) analysis. Myricetin (1964.35 and 1829.12 µg/g) was the most dominant flavonol compared to quercetin and kaempferol. Salicylic acid (222.80 and 215.25 µg/g) was the most important phenolic compound compared to pyrogallol, caffeic acid, gentisic acid, o-coumaric acid, gallic acid, protocatechuic acid and ferulic acid in summer (June) and winter (December) seasons. Phenolic contents and antioxidant capacities were estimated for the various solvent extracts (petroleum ether, butanol, ethyl acetate, methanol and water). Ethyl acetate extract exhibited the highest phenolic (332.64 and 299.44 mg/g gallic acid equivalent) and flavonoid contents (5.72 and 5.29 mg/g quercetin equivalent) and also the strongest antioxidant activity in summer and winter seasons. Due to these metabolic variations, the antioxidant and antimicrobial activities were increased with summer seasons compared to winter seasons. Our study shows that the samples collected in June had higher phenolic compounds, stronger antioxidative and antimicrobial activity than the samples of L. fischeri leaf extracts collected in December.