Abstract
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
Highlights
Solutions of various pH, extraction time and solid: liquid ratio were considered as single factors and their effects on the extraction of alkaloids of the root bark of catalpa ovata were studied on the basis of single factor experiments
According to the optimized process conditions of response surface methodology (RSM), 30 g of root bark powder Catalpa ovata was extracted with distilled water using known solid-liquid ratio, and the pH of the extracting medium was adjusted with 0.5 % HCl
The possible reason was that the concentration differences between the inside and the outside of cells gave rise to the changes in the extraction rate of the total alkaloids in the root bark of Catalpa ovate
Summary
Solutions of various pH, extraction time and solid: liquid ratio were considered as single factors and their effects on the extraction of alkaloids of the root bark of catalpa ovata were studied on the basis of single factor experiments. According to the optimized process conditions of RSM, 30 g of root bark powder Catalpa ovata was extracted with distilled water using known solid-liquid ratio, and the pH of the extracting medium was adjusted with 0.5 % HCl. extraction was continued for some time under simmering, and the mixture was filtered to remove residues. Three different concentrations of the total alkaloids of the root bark of Catalpa ovata (600mg/L, 100mg/L and 10 mg/L) were prepared in acetone for use in the determination of insecticidal activity against Plutella xyllostella (Linnaeus) and oriental armyworm, using Airbrush [19]. With increase in extraction time, the extraction rate of the total alkaloids increased gradually, reached a peak at 3 h, and decreased gradually
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