Process optimization and insecticidal activity of alkaloids from the root bark of Catalpa ovata G. Don by response surface methodology
Purpose: To optimize the extraction of total alkaloids from the root bark of Catalpa ovata using response surface methodology, and to determine the insecticidal activity of the total alkaloids extracted.
Methods: A combination of Box-Behnken design and response surface methodology (RSM) was used to optimize the acid water extraction of total alkaloids from the root bark of Catalpa ovata, with extraction rate of total alkaloids as index and the single factor experiment as basis, and the extraction time, material: liquid ratio and pH as 3 factors. The insecticidal activity of total alkaloids was determined against the three instar armyworm Mythimna separata (Lepidoptera: Noctuidae) and diamondback moth Plutella xylostella (Lepidoptera: Plutellidae).
Results: The optimum extraction conditions for total alkaloids were: material: liquid ratio of 1:10; extraction time of 3 h, pH of 1.0, and simmering. Under these conditions, total alkaloid extraction was 8.62 %, which was very close to the experimental value. The results were accurate and reliable, with reference value. The insecticidal activity of the total alkaloids indicate that when the concentration of the total alkaloids was 10 mg/L, the fatality rate of Plutella xyllostella and oriental armyworm was over 89 %, but the insecticidal activity of the total alkaloids was lower than that of avermectin which was employed as a reference.
Conclusion: The alkaloids from the root bark of Catalpa ovata are potential botanical insecticides.
Keywords: Catalpa ovata, Root bark, Total alkaloids, Response surface methodology, Insecticidal activity