Effect of Chrysosporium keratinophilum metabolites against Culex quinquefasciatus after chromatographic purification

Chrysosporium keratinophilum is known to be a keratinophilic fungus and an effective mosquito control agent. This fungus was grown on Sabauraud dextrose broth in the laboratory at 25°C, while the relative humidity was maintained at 75 ± 5% for 15 days. Filtration process of metabolites was done using whatman-1 filter paper, column chromatography and flash, chromatography. Larvicidal efficacy was performed against all instars of Culex quinquefasciatus. Larvicidal efficacy was performed at six different concentrations with different effective ratios (ethanol/metabolites: 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, and 1:9). The mortality values were then subjected by the probit analysis. The larval mortalities were observed for a period of 24, 48, and 72 h, respectively. The first and second instars were highly susceptible to 2:8 ratio. In the first instar after column chromatography, LC₅₀ = 26.66 ppm, LC₉₀ = 121.96 ppm, LC₉₉ = 231.86 ppm were observed after 72 h, while after flash chromatography the LC₅₀ = 20 ppm, LC₉₀ = 123.02 ppm, LC₉₉ = 281.83 ppm were observed after 48 h. In the second instar after column chromatography, LC₅₀ = 18.19 ppm, LC₉₀ = 102.32 ppm, LC₉₉ = 162.18 ppm were observed after 72 h, while doing flash chromatography 100% mortality could be recorded after 24 h. In the third instar after column chromatography, the LC₅₀ = 38.01 ppm, LC₉₀ = 131.82 ppm, LC₉₉ = 245.47 ppm were observed after 72 h, while after flash chromatography the LC₅₀ = 17.78 ppm, LC₉₀ = 100 ppm, LC₉₉ = 151.35 ppm. In the fourth instar, LC₅₀ = 61.65 ppm, LC₉₀ = 181.97 ppm, LC₉₉ = 436.51 ppm, while after flash chromatography LC₅₀ = 40 ppm, LC₉₀ = 120 ppm, and LC₉₉ = 223.87 ppm were observed after 72 h. The extracellular metabolites of C. keratinophilum could be a fungal based larvicides resource for the control of C. quinquefasciatus larvae. This could be another agent for biotechnological exploitation, if found suitable in field trials.