Insecticidal Activities And Chemical Constituents Of The Stem Barks Of Croton Tiglium L. And Edgeworthia Chrysantha Lindl

Croton tiglium and Edgeworthia chrysantha had been long-time known as popular legend for their good insecticidal activities. Herein, the insecticidal activities and chemical constituents of the stem barks of C. tiglium and E. chrysantha were researched, based on biological screening.A D101 column chromatography（CC） was firstly carried out to separate the ethanol extract of the stem barks of C. tiglium into several fractions, of which fractions bd85 and bd75 were found to show potent molluscicidal activities against Pomacea canaliculata, insecticidal activities against Aedes albopictus, acaricidal activities against Tetranychus cinnabarinus, and growth inhibition activities against Tenebrio molitor, and fraction bd95 exhibited growth inhibition activities against T. molitor to some extent.Fractions bd85, bd75 and bd95 were then put into separation using column chromatography（CC） over silica gel, D301 R, MCI and Sephadex LH-20, as well as recrystallization. Twenty-five compounds were isolated from the above fractions as follows: the new ent-trachyloban-17-oic acid（1）, and the known ones such as β-rosasterol（2）, β-sitosterol（3）, tetracosanol palmitate（4）, stigmasterol（5）, ethyl montanate（6）, ursolic acid（7）, betulinic acid（8）, 3β-acetoxysitost-5-en-7-one（9）,（24S）-3β-hydroxy-5α-stigmastan-6-one（10）, 7β-hydroxy-4,22-stigmastadien-3-one（11）,（22E,24S）-3β-hydroxy-5α-stigmastan-22-en-6-one（12）, 28-hydroxyoctacosanoic acid（13）, 3,4-dihydro-4,4-di-methyl-2H-1-benzopyran（14）, stigmast-4-ene-3β,6β-diol（15）, 5α,6β-dihydroxy-sitosterol（17）, cerevisterol（18）, 6,9-epoxy-ergosta-7,22-dien-3-ol（19）,（R）-2’-hydroxy-N-[（2S,3S,4R）-1,3,4-trihy-droxypentacosan-2-yl] octadecanamide（20）, β-sito-steryl-3-O-β-glucopiranoside（21）, stigmast-22-en-3-O-β-D-glucopyranoside（22）, acetoxysitost-5-en-7-one-3-O-β-D-glucopyranoside（23）, stigmasterol glucoside（24）, β-sitosteryl-3’-gluco-pyranoside-6’-O-palmitate（25）. Compounds 2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 17, 18, 19, 20, 21, 22, 23, 24 and 25 were obtained from C. tiglium for the first time.The Et OAc-soluble fraction of the ethanol extract of the stem barks of E. chrysantha showed potent molluscicidal activity against P. canaliculata and insecticidal activity against the third instar larvae of A. albopictu, and the Et OAc-soluble fraction, CHCl₃-soluble fraction were toxic to T. cinnabarinus. Sixteen compounds were isolated from these two active fractions by means of silica CC, MCI CC, Sephadex LH-20 CC and solvent recrystallization as: β-sitosterol（26）, umbelliferone（27）, daphnoretin（28）, 7-hydroxy-3-[（2-oxo-2H-1-benzopyran-6-methoxyl-7-yl）oxy]-2H-1-benzopyran-2-one（29）, β-sitosterol-3-O-β-D-glucopyranoside（30）, limettin（31）, edgeworoside C（33）, tiliroside（34）, edgeworin（35）, edgeworthin（36）, 5,8-dihydroxycoumarin（37） 、 22,23-dihydro-spinasterol-3-O-β-D-glucoside（38）、edgeworoside A（39）、edgeworoside C（40） and 5, 6, 3"-trihydroxyl-edgeworoside A（41）. Compounds 29, 36, 37 and 41 were isolated from E. chrysantha for the first time.Bioassay results for compounds from C. tiglium: In the concentration of 0.05 mg/m L, 24 h, compounds 17 and 25 made a lethality rate of 71.11% and 70.00% against P. canaliculata, respectively; compounds 17, 18 and 19 exhibited potent insecticidal activities againstthe third instar larvae of A. albopictu; compounds 2 and 3 showed significant contact toxicities against T. cinnabarinus.Bioassay results for compounds from E. chrysantha: LC50 for compounds 28, 36 and 35 against P. canaliculata occurred between 0.005 mg/m L and 0.05 mg/m L, and compound 28 was the most potent one with a lethality rate of 89.76% for 0.05 mg/m L, while compound 36 showed a toxicity not significantly different from that of 28; compounds 27, 28, 35 and 36 were the active consituents of E. chrysantha against the third instar larvae of A. albopictu; in 1.50 mg/m L, compounds 28 and 36 could kill 100% of the tested female adults of T. cinnabarinus. Given their outstanding toxicities as above, compounds 27, 28 and 36 were further carried into electrophysiological experiments by patch clamp to study the effect of different concentrations of them in Drosophila central nervous system, especially to the electrical activity of projection neuron（PN）, showing that compounds 27, 28 and 36 affected not only membrane potential but also the electrical activity of projection neurons.This research showed that steroidal compounds abounding in the stem barks of C. tiglium and the abundant coumarins from the stem barks of E. chrysantha deserved in-depth study. Besides, the occurence of ent-trachylobane diterpene may be worthy of further attention for research in agriculture pest management.