Bioactivity Of Citrulus Colocynthis Extracts Against The Two Vegetable Insect Pests And Effects On Detoxification Metabolizing Enzymes

Plutella xylostella and Brevicoryne brassicae are two common pests in cruciferous vegetable planting,which seriously affect the yield as well as the quality of vegetables.At the same time,the extensive using of chemical insecticides is seriously restricted by the food and environmental safety.It is significant to find new biological pesticides which are suitable for vegetable pests.In this paper,five kinds of organic solvents and three kinds of extraction are used to extract the Citrulus colocynthis fruit,the economic,simple and efficient extraction method as well as the best extraction solvent were screened out.The bioactivity of the extracts of C.colocynthis on P.xylostella and B.brassicae was studied.The insecticidal activity of the extracts of C.colocynthis against vegetable pests was also investigated.The effects of n-butanol extract from C.colocynthis on detoxification enzymes of P.xylostella and B.brassicae were studied.This study provides reference for the development and utilization of botanical insecticides for vegetable pests.The main results are as follows:1.The extraction of C.colocynthis shows that: Methanol,ethanol,n-butanol,ethyl acetate,petroleum ether these five kinds of organic solvents with different polarity were selected.Three extraction methods: cold soak extraction,ultrasonic extraction and Soxhlet extraction,are used to extract the active substances in C.colocynthis.From the comprehensive consideration of extraction rate and actual production,it is concluded that ultrasonic extraction is the most economical and practical extraction method in the laboratory.2.Biological activity of the extracts for C.colocynthis against vegetable pests: The research object is P.xylostella and B.brassicae.The insecticidal effects of the five kinds of organic solvent extracts of C.colocynthis extracted by ultrasonic extraction on the different modes of action of the tested insects were studied.The results are:?1?Among the five organic solvent extracts of C.colocynthis,n-butanol extract of C.colocynthis had the highest contact activity to P.xylostella and B.brassicae.The median lethal concentration of LC₅₀ after contact treatment for 72 h were 5.59 mg/mL and 1.37 mg/mL,respectively.The contact effect extract of C.colocynthis on B.brassicae was significantly greater than that on P.xylostella.?2?Among the five organic solvent extracts of C.colocynthis,n-butanol extract have the best effect on the stomach toxicity of P.xylostella.The average correctio mortality of P.xylostella is 47.78 % after 72 hours treatment with the highest concentration of 100 mg/ml.?3?Among the five organic solvent extracts of C.colocynthis,the nonselective antifeeding rate of ethyl acetate extract was the most obvious.At the highest concentration of 100 mg/ml,the nonselective antifeeding rate of P.xylostella was 61.61 % and 54.02 % for 24 hours and 48 hours,respectively.?4?For the deterrent effects of five organic solvent extracts of C colocynthis on B.brassicaes,the extracts of C.colocynthis have different degrees of repellency to B.brassicae.With the extension of the treatment time,the repellent effect of the extract on B.brassicae decreased.Under the condition of the highest concentration of 100 mg/ml,n-butanol extract of C.colocynthis has the highest repellence rate among the five organic solvent extracts the average deterrent rate was 93.22 %.Among the five organic solvent extracts,the average deterrent rate of the ethanol extract of C.colocynthis was the lowest,only 71.41 %.3.The activities of AChE,GST and CarE were measured after contact treatment.The aim of this study was to explore the functional targets and the activity of detoxifying enzymes the extract of C.colocynthis on two vegetable pests.The results are:?1?The n-butanol extract of C.colocynthis had a certain effect for on AChE on P.xylostella and B.brassicae.The AChE activity of P.xylostella treated with LC10 at 0.96 mg/ml for 24 hours was almost the same as that of the contro.The AChE activity of B.brassicae was significantly lower than that of the control.With the increasing of the treatment concentration,the inhibitory effect of the extract on AChE in P.xylostella and B.brassicae increases gradually.With the extension of the treatment time,the AChE activity of P.xylostella begin to be inhibited and then activated.At 24 hours,the AChE activity of B.brassicae reached the maximum inhibition.?2?The n-butanol extract of C.colocynthis exhibits different effects on GST activity on P.xylostella and B.brassicae.The activity of GST at low concentrations of 0.96 mg/mL were activated and at high concentrations inhibited in P.xylostella.With the extension of the treatment time,the GST activity of P.xylostella was significantly lower than that in the control,and the inhibition of GST activity reached the maximum at 36 h.The activity of GST on B.brassicae was inhibited to a certain extent,and the inhibition of GST activity is most obvious at 36 h after treatment.?3?The activity of CarE on P.xylostella was inhibited by n-butanol extract of C.colocynthis at different concentrations.With the increasing of the concentration,the inhibition was more obvious.The n-butanol extract of C.colocynthis generally showed an inhibitory effect of CarE on B.brassicaes.When the B.brassicae was treated with low concentration of 0.30 mg/ml,the activity of CarE was induced.With the increase of concentration,the activity of CarE decreased,and the inhibitory effect was more obvious.With the prolongation of the treatment time,the activity of CarE on P.xylostella began to increase in a large arc after 12-36 h treatment,which showed an active state.After treatment,the activity of CarE on B.brassicae fluctuated greatly while the radian was unobvious and it was still inhibited.