[Molluscicidal activity of the secondary metabolites from XD 2-7 against and its preliminary mechanisms of molluscicidal actions].

OBJECTIVE

To evaluate the storage stability of metabolites from actinomycetes XD 2-7 and the mollcuscicidal activity against in the laboratory, and to preliminarily explore the mechanisms of the molluscicidal activity.

METHODS

The fermentation supernatant of XD 2-7 was prepared and stored at -20, 4 °C and 28 °C without light for 10 d; then, the molluscicidal effect was tested against following immersion for 72 h. The fermentation supernatant was boiled in a 100 °C water bath for 30 min and recovered to room temperature, and then the molluscicidal effect was tested against following immersion for 72 h. The pH values of the fermentation supernatant were adjusted to 4.0, 6.0 and 9.0 with concentrated hydrochloric acid and sodium hydroxide, and the fermentation supernatant was stilled at room temperature for 12 h, with its pH adjusted to 7.0; then, the molluscicidal effect was tested against following immersion for 72 h. The fermentation product of XD 2-7was isolated and purified four times with macroporous resin, silica gel and octadecylsilane bonded silica gel. The final products were prepared into solutions at concentrations of 10.00, 5.00, 2.50, 1.25 mg/L and 0.63 mg/L, and the molluscicidal effect of the final productswas tested against following immersion for 72 h, while dechlorination water served as blank controls, and 0.10 mg/L niclosamide served as positive control. The adenosine triphosphate (ATP) and adenosine diphosphate (ADP) levels were measured in in soft tissues using high performance liquid chromatography (HPLC) following exposure to the final purified fermentation products of XD 2-7.

RESULTS

After the fermentation supernatant of XD 2-7 was placed at -20, 4 °C and 28 °C without light for 10 d, immersion in the stock solution and solutions at 10- and 50-fold dilutions for 72 h resulted in a 100% (30/30) mortality. Following boiling at 100 °C for 30 min, immersion in the stock solution and solutions at 10- and 50-fold dilutions for 72 h resulted in a 100.00% (30/30) mortality. Following storage at pH values of 4.0 and 6.0 for 12 h, immersion in the fermentation supernatant of XD 2-7 for 72 h resulted in a 100.00% (30/30) mortality, and following storage at a pH value of 9.0 for 12 h, immersion in the fermentation supernatant of XD 2-7 for 72 h resulted in a 33.33% (10/30) mortality ( = 30.000, < 0.05). The minimum concentration of the final purified fermentation products of XD 2-7 was 1.25 mg/L for achieving a 100% (30/30) mortality. The ATP level was significantly lower in soft tissues exposed to 0.10 mg/L and 1.00 mg/L of the final purified fermentation products of XD 2-7 than in controls ( = 7.274, < 0.05), while no significant difference was detected in the ADP level between the treatment group and controls ( = 2.485, > 0.05).

CONCLUSIONS

The active mollcuscicidal ingredients of the XD 2-7 metabolites are maintained stably at -20, 4 °C and 28 °C for 10 d, and are heat and acid resistant but not alkali resistant. The metabolites from XD 2-7 may cause energy metabolism disorders in , leading to death.