Activity Research On Extracts From Five Plants And Preliminary Track Of Acricidal Substance In Phytolacca Americana L. Against Tetranychus Cinnabarinus (Acari: Tetranychidae)

Phytolacca americana L., Veratrum nigrum L., Kochia scoparia (L.) Schrad, Pseudolarix kaempferi Gord and Nicotiana tabacum are five traditional medicine plants in China. With some insecticidal and antibacterial bioactivity, they have enormous potential application value in agriculture. Tetranychus cinnabarinus is a kind of recognized phytophagous mite which is difficult to prevent. There are 113 species in 32 families of plants and 18 species of vegetables which are vulnerable to Tetranychus cinnabarinus, such as tomato, pepper, watermelon, legume, onion and amaranth. For a long time, the irrational usage of numerous chemical acaricides has brought about corresponding side effects and caused widespread concern, so the development of acaricides from natural plants which are green, safe and environmentally friendly is very important.This paper systematically studied the activity of extracts from Phytolacca americana L., Veratrum nigrum L., Kochia scoparia (L.) Schrad, Pseudolarix kaempferi Gord and Nicotiana tabacum against Tetranychus cinnabarinus, and traced the bioactivity of the active ingredient that is extracted from selected Phytolacca americana L.. The main achievement was as follows:1. In this study, five different polar solvents including water, acetone, ethanol, ethyl acetate and petroleum ether were separately adopted to conduct parallel extraction from Phytolacca americana L., Veratrum nigrum L., Kochia scoparia (L.) Schrad, Pseudolarix kaempferi Gord and Nicotiana tabacum. The plant parts used in this study were the root of P. americana, the rhizome of V. nigrum, the seed of K. scoparia, the root bark of P. kaempferi and the leave of N. tabacum.25 kinds of crude extracts were obtained and were used to determine laboratory contact toxicity against Tetranychus cinnabarinus. Among which,8 kinds of extracts that resulted in the corrected mortality against Tetranychus cinnabarinus was larger than 50% at 48h were selected as the effective extracts. Then laboratory toxicity against different states of Tetranychus cinnabarinus was tested using these effective extracts. The results were:acetone extract of P. americana root (LCso against adult and nymph Tetranychus cinnabarinus were 2.2839mg/mL and 0.3528mg/mL respectively at 48h, LCso against egg Tetranychus cinnabarinus was 7.0542mg/mL at 6d), ethyl acetate extract of V. nigrum rhizome (LCso against adult and nymph Tetranychus cinnabarinus were 2.4006mg/mL and 0.5008mg/mL respectively at 48h, LCso against egg Tetranychus cinnabarinus was 12.4556mg/mL at 6d), petroleum ether extract of P. kaempferi root bark (LC50 against adult and nymph Tetranychus cinnabarinus were 2.4908mg/mL and 0.7231mg/mL respectively at 48h, LCso against egg Tetranychus cinnabarinus was 14.8403mg/mL at 6d), acetone extract of N. tabacum leave (LCso against adult and nymph Tetranychus cinnabarinus were 2.4716mg/mL and 0.6366mg/mL respectively at 48h, LCso against egg Tetranychus cinnabarinus was 13.4865mg/mL at 6d) and acetone, ethanol, ethyl acetate and petroleum ether extracts of K. scoparia seed (LCso against adult and nymph Tetranychus cinnabarinus were 2.6743mg/mL, 2.4783mg/mL,2.0332mg/mL,3.1216mg/mL and 0.8435mg/mL,0.6022mg/mL,0.3357mg/mL, 1.2026mg/mL respectively at 48h, LCso against egg Tetranychus cinnabarinus were 16.3383mg/mL, 12.5156mg/mL,8.9202mg/mL and 18.3846mg/mL respectively at 6d). It has showed that there exists some secondary metabolites which have good bioactivity against Tetranychus cinnabarinus in the five species of plants, and the extracts from P. americana root and K. scoparia seed have the highest toxicity against Tetranychus cinnabarinus. According to the economic, environmental, practical and innovative factors, this paper selected acetone extract of P. americana root as the object for further study and carried out the bioactivity trace against Tetranychus cinnabarinus.2. Based on silica gel column chromatography separation and examination of thin-layer chromatography (TLC), this study carried out the acaricidal activity trace against Tetranychus cinnabarinus of the acetone extract from P. americana root. The result showed that group 8 had the best acaricidal activity and its LCso against adult and nymph Tetranychus cinnabarinus were 0.2663mg/mL and 0.1511mg/mL respectively at 24h. After the process of recrystallization, some white strip crystals was got and its melting point is 250.5℃～252.2℃. The bioactivity of re-crystals against Tetranychus cinnabarinus was demonstrated and its LCso against adult and nymph Tetranychus cinnabarinus were 0.1260mg/mL and 0.0956mg/mL respectively at 24h. It showed that there are some substances which have obvious acaricidal activity against Tetranychus cinnabarinus in P. americana root.