Study Of Insecticidal Activity Of Secondary Metabolites From Solanum Rostratum Dunal

Solanum rostratum Dunal being to the Solanaceae Solanum family, is a kind of exotic poisonous weeds. Solanum rostratum Dunal with the strong reproductive ability is so easy to form dominant communities, and stop other plants from growing. The whole plant of Solanum rostratum Dunal is covered with thorns which are toxic. All in all, Solanum rostratum Dunal has constituted a serious threat to our farming and ecological safety. The previous studies of our laboratory have discovered that the extracts of Solanum rostratum Dunal have insecticidal activity. The in-depth research was carried on and a definite result of the extraction, isolation method and the character of insecticidal substance of the secondary metabolites from Solanum rostratum Dunal was got in this paper. The results of our study have been reported rarely. This research provides a very good material for enriching resources of botanic insecticide, as well provides a feasible way of the development and utilization of Solanum rostratum Dunal. The results of this research also provide a very good reference for the utilization of other invasive plants.The main results of this research are as follows:1. The powder of Solanum rostratum Dunal was extracted with 95% ethanol, acetone, ethyl acetate, petroleum ether and hydrochloric acid solution(pH=2) respectively. Among them, the extracted rate of the hydrochloric acid solution(pH=2) was the highest, about 0.061 g/g, and the second was 95% ethanol, about 0.051 g/g .The insecticidal activity of five kinds of extracts against Sitobion avenae F. and Plutella xylostella was determined, and the extracts were diluted into 500 mg/L. The result showed that 95% ethanol extract and hydrochloric acid solution (pH=2) extract displayed better insecticidal effects. The corrected mortality of 95% ethanol extract against Sitobion avenae F. was reached (75.02±1.07)% after 24h with LC50 343.3681mg/L, and the corrected mortality of 95% ethanol extract against Plutella xylostella. after 72h was reached (64.85±1.24) % .2. The powder of fruit, root,stem and leaf were separately extracted with 95% ethanol. The result showed that the extract from the fruit had best insecticidal activity with corrected mortality of (79.50±0.69) % after 24h, and the corrected mortality of stem and leaf, root was (52.21±1.02) % and (7.13±0.15) % after 24h, respectively. Solanum rostratum Dunal produced different insecticidal substance at different development stages. Among them, the extract of Solanum rostratum Dunal harvested at green fruit stage displayed best insecticidal effects, that of mature stage was reduced, and that of seedling stage had no effect.3. Extraction means were extraction, ultrasonic wave extraction and microwave extraction. The result showed that both the extracted rate and insecticidal activity were increased 20% more than extraction.4. The results of the analysis for 95% ethanol extract of Solanum rostratum Dunal by means of tube-test and thin layer chromatography showed that the extract mainly contained alkaloid. When the value of pH was reached 10.5, the extraction had best poisonous activity against Sitobion avenae F., with the 24h corrected mortality of (63.33±1.93)% under the concertration of 500mg/L. 95% ethanol extract was purified using lead salt precipitation method, liquid-liquid extraction and resin. The results showed that ADS-7 macroporous resin had better insecticidal activity with corrected mortality of (54.05±2.02)% after 24h, and the adsorption of the active substance was less.5. After purified with resin, the extract was isolated by HSCCC. The solvent system containing chloroform, methanol and hydrochloric acid solution (pH=1) (2:1:1, V/V/V) was run on a preparative scale, the upper phase and the lower phase separated from which provided mobile phase and stationary phase, respectively. The HSCCC separation of the active substance was carried out under the following conditions: the flow rate 2.0 mL/min, clockwise rotation speed 900 r/min and the temperature 25℃. The detection wavelength was 214 nm. Seven parts were separated by the method of high-speed counter-current chromatography (HSCCC), and the results showed that the fifth and seventh part had higher insecticidal activity. The further purification and the structure identification of the fifth and seventh part need further research.