Exploration Of Environment - Friendly Plant - Derived Pesticides

Botanical pesticides show the characteristic of environmental harmony comparing with the synthetic organic pesticides, and become the future trend in the area of research and development of pesticides. Illicium micranthum Dunn is a kind of special palnt in China. It was toxicity, and was used as a native pesticide in folk. In order to finding the plants or active constituents with dramatically insecticidal activity, and utilizing the wild plant resources deeply and effectively,I. micranthum was chosen as the object of study and its chemical constituents were separated and extracted systematically. Using the Bradtsua idiruogaga Yang et Zhang as the test insects, we also explored the insecticidal activity of chemicals from I. micranthum preliminary.I. micranthum belonging to Illicium was the shrub or tree, and distributed in the southwest region of China. In the research, the ethyl acetate extract of the branches and leaves was purified by silica gel column chromatography (Silica gel CC), Sephadex LH-20 column chromatography (Sephadex LH-20 CC), and preparing thin-layer chromatography (PTLC) repeatedly. As a result,17 compounds were isolated from branches and leaves of I, micranthum. The structures of compounds were identified by spectroscopic techniques including UV, IR, EI-MS,1H-NMR,13C-NMR and 2D-NMR (1H-1H COSY, HMQC, HMBC, NOSEY), and comparison of their spectroscopic data with those reported in the references. The compounds include five cadinane sesquiterpenes:Illicmicrcadinane A(Q4), Illicmicrcadinane B(Q5), Illicmicrcadinane C(Q6),5α,10β-Dihydroxy-muurol-4(15)-ene(Q7), Illicmicrcadinane D(Q12); tow germacrane sesquiterpenes:leitneridanin B(Q2), eleganodiol(Q11); one guaiane sesquiterpene:(-)-4α,7β-aromadendraediol(Q8); one farnesane sesquiterpene:(7S)-10-oxo-4-ξ-methyl-7-isopropyl-5E-undecen-4-olide(Q1); five monoterpenes:(1R,2R,4R)-1-methyl-4-(1-methylethyl)-1,2,4-cyclohexanetriol(Q9),4-Hydroxy piperitone(Q10), Olibanumol C(Q13), a,a-dimethyl-4-hydroxyme-thylbenzyl alcohol(Q14), Illicmicrene A(Q15); three other chemicals:4-hydroxy-4,6-dimethyl-l-tetralone(Q3), isovanillic acid(Q16),2,4-dihydroxybenzoic acid(Q17). There are five new compounds which had not been reported in the literatures:Illicmicrcadinane A(Q4), Illicmicrcadinane B(Q5), Illicmicrcadinane C(Q6), Illicmicrcadinane D(Q12) and Illicmicrene A(Q15).According to the results of compounds ideification,7 compounds with representative structures and appropriate contents were chosen to do tests of insecticidal activity. Two compounds leitneridanin B(Q2) and (1R,2R,4R)-1-methyl-4-(1-methylethyl)-1,2,4-cyclohexanetriol(Q9) presented strongly toxic activity against the four leek larvaes of B. idiruogaga. The mortality of larvaes rose with the increasing of compound test concentration, when the concentration reached 100mg/L, eitneridanin B and (1R,2R,4R)-1-methyl-4-(1-methylethyl)-1,2,4-cyclohexanetrio showed dramatically toxic activity, with the 48 h corrected mortality 91.23%、70.18% and LD50 value 14.2 mg/L、30.4 mg/L respectively. The activity also enhanced when the time increasing, with the 72 h corrected mortality 92.85%、80.35% and LD50 value 9.4 mg/L、22.5 mg/L respectively.The studies of terpenoid in botanical pesticide were quite generally. A sesquiterpene compound leitneridanin B and a monoterpene (1R,2R,4R)-1-methyl-4-(1-methylethyl)-1,2,4-cyclohexanetriol isolated from the branches and leaves of Ⅰ. micranthum presented apparently insecticidal activity, and had simple structures which were easy to be synthesized. These tow compounds have the potential to develop botanical pesticides.