Acute Toxicity,Bioactivity, and Enantioselective Behavior with Tissue Distribution in Rabbits of Myclobutanil Enantiomers

The enantioselective bioactivity against pathogens (Cercospora arachidicola, Fulvia fulva, and Phytophthora infestans) and acute toxicity to Daphnia magna of the fungicide myclobutanil enantiomers were studied. The (+)‐enantiomer in an antimicrobial activity test was about 1.79–1.96 times more active than the (–)‐enantiomer. In the toxicity assay, the calculated 24‐h LC₅₀ values of the (–)‐form, rac‐form and (+)‐form were 16.88, 13.17, and 11.91 mg/L, and the 48‐h LC₅₀ values were 10.15, 9.24, and 5.48 mg/L, respectively, showing that (+)‐myclobutanil was more toxic. Meanwhile, the enantioselective metabolism of myclobutanil enantiomers following a single intravenous (i.v.) administration was investigated in rabbits. Total plasma clearance value (CL) of the (+)‐enantiomer was 1.68‐fold higher than its antipode. Significant differences in pharmacokinetics parameters between the two enantiomers indicated that the high bioactive (+)‐enantiomer was preferentially metabolized and eliminated in plasma. Consistent consequences were found in the tissues (liver, brain, heart, kidney, fat, and muscle), resulting in a relative enrichment of the low‐activity (–)‐myclobutanil. These systemic assessments of the stereoisomers of myclobutanil cannot be used only to investigate environmental and biological behavior, but also have human health implications because of the long persistence of triazole fungicide and enantiomeric enrichment in mammals and humans. Chirality 26:784–789, 2014. © 2014 Wiley Periodicals, Inc.     

Enantioselective Degradation of the Chiral Fungicides Metalaxyl and Furalaxyl by Brevibacillus brevis

For almost four decades, the chiral fungicides metalaxyl and furalaxyl have been in use in plant protection on a global scale. Both substances are distributed as racemic mixtures, yet the desirable interference in nucleic acid synthesis of harmful fungi only occurs by the (‐)‐R‐enantiomer. As enantioselective degradation in Scheyern (Germany) and Yaoundé (Cameroon) soils has been documented, the influence of 50 isolated microorganisms on the R/S ratio was investigated. A high‐pressure liquid chromatography method with a chiral column to separate enantiomers of metalaxyl and furalaxyl, and subsequent detection by tandem mass spectrometry, was employed. Only one of these microorganisms, a strain of Brevibacillus brevis, showed an enantioselective degradation pattern in liquid culture; the respective (‐)‐R‐enantiomers were preferably degraded. Moreover, (‐)‐R‐furalaxyl was degraded faster in cultures supplemented simultaneously with both fungicides of the same concentration. Chirality 25:336–340, 2013. © 2013 Wiley‐Liss Inc. Chirality 00:000‐000:, 2013. © 2013 Wiley Periodicals, Inc.     

Enantioselective toxic effects of hexaconazole enantiomers against Scenedesmus obliquus

Enantioselectivity in ecotoxicity of chiral pesticides in the aquatic environment has been a subject of growing interest. In this study, the toxicological impacts of hexaconazole enantiomers were investigated with freshwater algae Scenedesmus obliquus. After 96 h of exposure, the EC₅₀ values for rac‐hexaconazole, (+)‐hexaconazole, and (?)‐hexaconazole were 0.178, 0.355, and 0.065 mg l^?1, respectively. Therefore, the acute toxicities of hexaconazole enantiomers were enantioselective. In addition, the different toxic effects were evaluated when S. obliquus were exposed to 0.2, 0.5, and 1.0 mg l^?1 of rac‐hexaconazole, (+)‐hexaconazole, and (?)‐hexaconazole during 96 h, respectively. The chlorophyll a and chlorophyll b contents of S. obliquus treated by (?)‐hexaconazole were lower than those exposed to (+)‐hexaconazole, whereas the malondialdehyde contents of S. obliquus treated by (?)‐form were higher than those exposed to (+)‐form at higher concentrations. In general, catalase activities were significantly upregulated by exposure to (?)‐enantiomer than (+)‐enantiomer at all three concentrations. However, superoxide dismutase activities exposed to (?)‐hexaconazole were lower than that exposed to (+)‐hexaconazole at 0.2 mg l^?1 and 0.5 mg l^?1. On the basis of these data, the acute toxicity and toxic effects of hexaconazole against S. obliquus were enantioselective, and such enantiomeric differences must be taken into consideration in pesticide risk assessment. Chirality 24:610–614, 2012. © 2012 Wiley Periodicals, Inc.     

Toxicity of A Novel Neonicotinoid Insecticide Paichongding to Earthworm Eisenia fetida

Traditional neonicotinoid insecticides are used worldwide. Paichongding (IPP), as a novel neonicotinoid pesticide, has been widely used in China. However, the ecotoxicity of IPP to non-target invertebrates in soil ecosystem has not been reported yet. In this study, acute toxicity of IPP to earthworm Eisenia fetida, as well as the antioxidant response after IPP exposure, was evaluated. In the filter paper contact test, the LC₅₀ at 24 hr and 48 hr for IPP were 14.98 μg/cm² and 7.59 μg/cm², respectively. In artificial soil test, the LC₅₀ (lethal concentration) at 14 days and 28 days for IPP were 541.07 mg/kg and 238.51 mg/kg, respectively. The LC₅₀ of IPP is much higher than that of traditional neonicotinoid insecticides. However, earthworm body weight assessment demonstrated that the growth of earthworm was inhibited by extended exposure to IPP at sublethal doses. The activities of antioxidative enzymes superoxide dismutase and catalase in earthworms were significantly induced after IPP exposure. Malondialdehyde, a biomarker of lipid peroxidation, was also increased after IPP exposure. Although the results indicated that IPP had potentially adverse effect on earthworms, its toxicity was much lower than traditional neonicotinoids.     

Repellency and toxicity of a CO2-derived cedarwood oil on hard tick species (Ixodidae)

The repellency and toxicity of a CO₂-derived cedarwood oil (CWO) was evaluated against actively questing unfed nymphs of four species of hard ticks: Amblyomma americanum (L.), Dermacentor variabilis (Say), Ixodes scapularis Say, and Rhipicephalus sanguineus (Latreille). Using a vertical climb bioassay for repellency, nymphs of these species avoided a CWO-treated filter paper in proportional responses to treatment concentrations. At 60 min of exposure, I. scapularis nymphs were most sensitive with 50% repellency concentration (RC₅₀) of 19.8 µg cm^?2, compared with RC₅₀ of 30.8, 83.8 and 89.6 µg cm^?2 for R. sanguineus, D. variabilis and A. americanum, respectively. Bioassays determined the lethal concentration for 50% (LC₅₀) and 90% (LC₉₀) mortality of nymphs exposed to CWO in treated vials after 24- and 48-h exposure. After 24 h exposure, the LC₅₀ values were 1.25, 3.45 and 1.42 µg cm^?2 and LC₉₀ values were 2.39, 7.59 and 4.14 µg cm^?2 for D. variabilis, I. scapularis and R. sanguineus, respectively, but had minimal effect on A. americanum. After 48 h exposure, the LC₅₀ values were 4.14, 0.78, 0.79 and 0.52 µg cm^?2, and LC₉₀ values were 8.06, 1.48, 1.54 and 1.22 µg cm^?2 for A. americanum, D. variabilis, I. scapularis and R. sanguineus, respectively. The repellency of CWO on tick species decreased with time. The repellency and toxicity bioassays demonstrated concentration-dependent responses of tick nymphs to the oil, indicating the potential of the CO₂-derived cedarwood oil be developed as an eco-friendly repellent and/or acaricide.

     

PFOS对蚯蚓急性毒性和回避行为的影响

全氟辛烷磺酰基化合物(PFOS)作为一种新型持久性有机污染物,已经成为环境科学和毒理学的研究热点,其对生态环境的影响值得深入研究.本文采用OECD标准滤纸接触法、人工土壤法及自然土壤法研究了PFOS对蚯蚓急性致死作用及回避行为的影响.结果表明： PFOS对蚯蚓的急性毒性作用与染毒时间和染毒浓度相关,试验求得滤纸法48 h、人工土壤法14 d和自然土壤法14 d的LC₅₀值分别为13.64 μg·cm^-2、955.28 mg·kg^-1和542.08 mg·kg^-1;人工土壤和自然土壤中蚯蚓在PFOS的最大试验浓度组160 mg·kg^-1中均表现出显著的回避行为,表明蚯蚓可以明显感知较高浓度PFOS污染土壤并作出回避反应.与急性毒性试验的测试终点LC₅₀相比,蚯蚓行为测试终点对PFOS的反应更为敏感.自然土壤中PFOS对蚯蚓的急性毒性大于人工土壤,相同浓度PFOS作用下,蚯蚓于自然土壤中的回避行为较人工土壤明显.     

Separation and toxicity of salithion enantiomers

Enantioseletive toxicities of chiral pesticides have become an environmental concern recently. In this study, we evaluated the enantiomeric separation of salithion on a suite of commercial chiral columns and assessed the toxicity of enantiomers toward butyrylcholinesterase and Daphnia magna. Satisfactory separations of salithion enantiomers could be achieved on all tested columns, that is, Chiralcel OD, Chiralcel OJ, and Chiralpak AD column. However, the Chiralpak AD column offered the best separation and was chosen to prepare micro‐scale of pure salithion enantiomers for subsequent bioassays. The first and second enantiomers eluted on the Chiralpak AD column were further confirmed to be (?)‐S‐salithion and (+)‐R‐salithion, respectively. The half inhibition concentrations to butyrylcholinesterase of racemate, (+)‐R‐salithion, and (?)‐S‐salithion were 33.09, 2.92, and 15.60 mg/l, respectively, showing (+)‐R‐enantiomer being about 5.0 times more potent than its (?)‐S‐form. However, the median lethal concentrations (96 h) of racemate, (+)‐R‐salithion, and (?)‐S‐salithion toward D. magna were 3.54, 1.10, and 0.36 μg/l, respectively, suggesting that (?)‐S‐salithion was about 3.0 times more toxic than (+)‐R‐form. Racemic salithion was less toxic than either of the enantiomers in both bioassays, suggesting that antagonistic interactions might occur between the enantiomers during the toxication action. This work reveals that the toxicity of salithion toward butyrylcholinesterase and D. magna is enantioselective, and this factor should be taken into consideration in the environmental risk assessment of salithion. Chirality 2009. © 2009 Wiley‐Liss, Inc.     

Acute toxicity of tributyltin to encapsulated embryos of a marine gastropod

The marine gastropod Buccinanops globulosus is known to have high imposex incidence in areas moderately polluted by tributyltin (TBT). Acute toxicity was previously studied in adults but no information is known about embryonic intracapsular development. To estimate the potential effects of organotin pollution on the progeny of B. globulosus, acute toxicity tests were conducted on encapsulated and excapsulated pre-hatching embryos. The lethal median concentration estimated for 96?h (LC₅₀ 96?h) in B. globulosus excapsulated embryos was 196.70?µg?TBTCl?L^?1, while in encapsulated embryos it was 2951.28?µg?TBTCl?L^?1. The LC₅₀ 96?h was 15-fold higher for encapsulated embryos compared to excapsulated embryos, denoting egg capsule protection against pollutants from the external environment. Our results show that TBT pollution can have significant effects in molluscs other than the chronic effect of imposex.     

Enantioselective toxicity and degradation of chiral herbicide fenoxaprop-ethyl in earthworm Eisenia fetida

The enantioselective degradation of fenoxaprop-ethyl in ecological indicator earthworm was studied and the main metabolites (fenoxaprop, 6-chloro-2,3-dihydrobenzoxazol-2-one, ethyl-2-(4-hydroxyphenoxy)propanoate, 2-(4-hydroxyphenoxy)propanoic acid) were also monitored on an enantiomeric level. The individual enantiomers of fenoxaprop-ethyl and its three chiral metabolites were prepared to study the acute toxicity to earthworm. Chiral analysis methods were set up based on HPLC–MS/MS with chiralpak IC chiral column. Fenoxaprop-ethyl was not found in earthworms, while the primary metabolite fenoxaprop was in relatively high levels indicating a quick hydrolysis degradation. Fenoxaprop was accumulated almost exclusively with R-enantiomer in earthworms and the bio-concentration factors of R-fenoxaprop and S-fenoxaprop were 1.39 and 0.17 respectively with the enantiomer fraction (EF) values about 0.99. The degradation of R-fenoxaprop in earthworms followed first-order kinetics with half-life of 1.82 day. The other metabolites could not be detected in earthworms. The calculated LC₅₀ values showed ecological indicator earthworm was more sensitive to the four metabolites than fenoxaprop-ethyl. Furthermore, earthworm was more sensitive to the R-form of the chiral metabolites than the S-form and rac-form. The results suggested metabolites and enantioselectivity should be taken into consideration to better predict the exposure concentration and apply ecological indicators in toxicological studies.     

The effects of salinity on acute and chronic nickel toxicity and bioaccumulation in two euryhaline crustaceans: Litopenaeus vannamei and Excirolana armata

We investigated the influence of salinity (5 ppt versus 25 ppt) on acute (96-h LC₅₀) and chronic toxicity (15–30 day LC₅₀) of Ni in two euryhaline crustaceans, the shrimp (Litopenaeus vannamei) and the isopod (Excirolana armata). 96-h LC50 values were 41 μmol L⁻¹ and 362 μmol L⁻¹ for L. vannamei and 278 μmol L⁻¹ and > 1000 μmol L⁻¹ for E. armata at 5 ppt and 25 ppt, respectively. Speciation analysis demonstrated that complexation with anions such as SO₄²⁻, HCO₃⁻ and Cl⁻ at 25 ppt had a negligible effect on reducing the free Ni²⁺ ion component in comparison to 5 ppt. The salinity-dependent differences in acute Ni toxicity could not be explained by differences in Ni bioaccumulation. Therefore, differences in physiology of the organisms at the two salinities may be the most likely factor contributing to differences in acute Ni toxicity. Chronic LC₅₀ values (2.7–23.2 μmol L⁻¹) were similar in the two species, but salinity had no significant effect, indicating that water chemistry and osmoregulatory strategy do not influence chronic toxicity. However chronic (15-day) mortality in both species could be predicted by acute (96-h) Ni bioaccumulation patterns.     

Analogues of the frog skin peptide alyteserin‐2a with enhanced antimicrobial activities against Gram‐negative bacteria

The emergence of strains of multidrug‐resistant Gram‐negative bacteria mandates a search for new types of antimicrobial agents. Alyteserin‐2a (ILGKLLSTAAGLLSNL.NH₂) is a cationic, α‐helical peptide, first isolated from skin secretions of the midwife toad, Alytes obstetricans, which displays relatively weak antimicrobial and haemolytic activities. Increasing the cationicity of alyteserin‐2a while maintaining amphipathicity by the substitution Gly¹¹→ Lys enhanced the potency against both Gram‐negative and Gram‐positive bacteria by between fourfold and 16‐fold but concomitantly increased cytotoxic activity against human erythrocytes by sixfold (mean concentration of peptide producing 50% cell death; LC₅₀ = 24 µm ). Antimicrobial potency was increased further by the additional substitution Ser⁷→Lys, but the resulting analogue remained cytotoxic to erythrocytes (LC₅₀ = 38 µm ). However, the peptide containing d ‐lysine at positions 7 and 11 showed high potency against a range of Gram‐negative bacteria, including multidrug‐resistant strains of Acinetobacter baumannii and Stenotrophomonas maltophilia (minimum inhibitory concentration = 8 µm ) but appreciably lower haemolytic activity (LC₅₀ = 185 µm ) and cytotoxicity against A549 human alveolar basal epithelial cells (LC₅₀ = 65 µm ). The analogue shows potential for treatment of nosocomial pulmonary infections caused by bacteria that have developed resistance to commonly used antibiotics. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.     

Determination of the Enantiomeric Purity of the Antiasthmatic Drug Montelukast by Means of 1H NMR Spectroscopy

In order to define an enantioselective nuclear magnetic resonance (NMR) method for the antiasthmatic drug montelukast, a series of nine easily available products were evaluated as NMR chiral solvating agents (CSAs): D‐dibenzoyltartaric acid, D‐ditoluoyltartaric acid, (+)‐camphorsulfonic acid, (S)‐BINOL, (S)‐3,3’‐diphenyl‐2,2’‐binaphthyl‐1,1’‐diol, (R)‐3,3'′‐di‐9‐anthracenyl‐1,1'′‐bi‐2‐naphthol, (R)‐3,3'′‐di‐9‐phenanthrenyl‐1,1'′‐bi‐2‐naphthol, Pirkle's alcohol, and (?)‐cinchonidine. It was proved that most of the studied agents constitute diastereomeric complexes with both drug enantiomers in CD₂Cl₂ or CDCl₃ solutions, thus permitting the direct ¹H NMR detection of the unwanted S‐enantiomer, even at levels of 0.75%. (?)‐Cinchonidine was found to be the more convenient CSA in terms of NMR enantiodiscrimination power and ease of experimental requirements. The final method was validated and applied to the fast monitoring of the optical purity of montelukast “in‐process” samples, circumventing the need for tedious and slower analytical procedures like enantioselective chromatography or capillary electrophoresis. In addition, a method for the enantiopurity control of the commercial drug (montelukast sodium salt) was also established using (S)‐BINOL as NMR CSA. Chirality 25: 780–786, 2013. © 2013 Wiley Periodicals, Inc.     

Enantioselective Toxic Effects and Degradation of Myclobutanil Enantiomers in Scenedesmus obliquus

Research on the enantioselective environmental behavior of chiral pesticides has been a hot spot of environmental chemistry recently. In this study, the acute toxicity of myclobutanil enantiomers was investigated with the aquatic algae Scendesmus obliquus. After exposure for 96 h, the EC₅₀ values for (?)‐myclobutanil, rac‐myclobutanil and (+)‐myclobutanil were 3.951, 2.760, and 2.128 mg/L, respectively. The photosynthetic pigment (chlorophyll a, chlorophyll b, and carotenoids) and antioxidant enzyme activities catalase (CAT) were determined to evaluate the different toxic effects when S. obliquus were exposed to 1.5, 5 and 15 mg/L of rac‐myclobutanil, (?)‐myclobutanil, and (+)‐myclobutanil for 96 h, respectively. In addition, the degradation of myclobutanil enantiomers in S. obliquus was also studied. Myclobutanil in the medium inoculated with algae degraded faster than in the uninoculated medium. The degradation of (?)‐myclobutanil was faster than that of (+)‐myclobutanil at a concentration of 3 mg/L. On the basis of these data, the acute toxicity and toxic effects of myclobutanil against S. obliquus were concluded to be enantioselective, and such enantiomeric differences should be taken into consideration in pesticide risk assessment. Chirality 25:858–864, 2013. © 2013 Wiley Periodicals, Inc.     

Effects of Manduca sexta allatostatin and an analogue on the peach-potato aphid Myzus persicae (hemiptera: aphididae) and degradation by enzymes in the aphid gut

The oral toxicity of the C‐type allatostatin, Manduca sexta allatostatin (Manse‐AS) and the analogue δR³δR⁵Manse‐AS, where R residues were replaced by their D‐isomers, were tested against the peach‐potato aphid Myzus persicae by incorporation into an artificial diet. Both peptides had significant dose‐dependent effects on mortality, growth, and fecundity compared with control insects. The analogue, δR³δR⁵Manse‐AS, had an estimated LC₅₀ of 0.31 µg/µl diet and was more potent than Manse‐AS (estimated LC₅₀ of 0.58 µg/µl diet). At a dose of 0.35 µg δR³δR⁵Manse‐AS/µl diet, 76% of the aphids were dead after 6 days and all were dead after 10 days. In comparison, three times the dose of Manse‐AS was required to achieve 74% mortality after 8 days and 98% mortality after 16 days. The degradation of both peptides by extracts prepared from the gut of M. persicae was investigated. The estimated half‐life of Manse‐AS, when incubated with the gut extract from M. persicae, was 31 min. Degradation was due to a cathepsin L‐like cysteine protease, carboxypeptidase‐like activity, endoprotease activity with glutamine specificity, pyroglutamate aminopeptidase activity, and possibly trypsin‐like proteases. The half‐life of the δR³δR⁵ Manse‐AS analogue was enhanced (73 min) with the D‐isomers of R appearing to prevent cleavage around the R residues by cathepsin L‐like cysteine proteases or from trypsin‐like proteases. The greater stability of the analogue may explain its increased potency in M. persicae. This work demonstrates the potential use of Manse‐AS and analogues, with greater resistance to enzymatic attack, in aphid control strategies. © 2010 Wiley Periodicals, Inc.     

Enantiomerization and Enantioselective Bioaccumulation of Metalaxyl in Tenebrio molitor Larvae

The enantiomerization and enantioselective bioaccumulation of metalaxyl by a single dose of exposure to Tenebrio molitor larvae under laboratory condition were studied by high‐performance liquid chromatography tandem mass spectroscopy (HPLC‐MS/MS) based on a ChiralcelOD‐3R [cellulosetris‐tris‐(3, 5‐dichlorophenyl‐carbamate)] column. Exposure of enantiopure R‐metalaxyl and S‐metalaxyl in Tenebrio molitor larvae exhibited significant enantiomerization, with formation of the R enantiomers from the S enantiomers, and vice versa, which might be attributed to the chiral pesticide catalyzed by a certain enzyme in Tenebrio molitor larvae. Enantiomerization was not observed in wheat bran during the period of 21 d. In addition, bioaccumulation of rac‐metalaxyl in Tenebrio molitor larvae was enantioselective with a preferential accumulation of S‐metalaxyl. These results showed that enantioselectivity was caused not only by actual degradation and metabolism but also by enantiomerization, which was an important process in the environmental fate and behavior of metalaxyl enantiomers. Chirality 26:88–94, 2014. © 2013 Wiley Periodicals, Inc.     

Enantioselective Metabolism and Interference on Tryptophan Metabolism of Myclobutanil in Rat Hepatocytes

Myclobutanil, (RS)‐2‐(4‐chlorophenyl)‐2‐(1H‐1, 2, 4‐triazol‐1‐ylmethyl) hexanenitrile is a widely used triazole fungicide. In this study, enantioselective metabolism and cytotoxicity were investigated in rat hepatocytes by chiral HPLC‐MS/MS and the methyl tetrazolium (MTT) assay, respectively. Furthermore, tryptophan metabolism disturbance in rat hepatocytes after myclobutanil exposure was also evaluated by target metabolomics method. The half‐life (t1/2) of (+)‐myclobutanil was 10.66 h, whereas that for (?)‐myclobutanil was 15.07 h. Such results indicated that the metabolic process of myclobutanil in rat hepatocytes was enantioselective with an enrichment of (?)‐myclobutanil. For the cytotoxicity research, the calculated EC₅₀ (12h) values for rac‐myclobutanil, (+)‐ and (?)‐myclobutanil were 123.65, 150.65 and 152.60 µM, respectively. The results of tryptophan metabolites profiling showed that the levels of kynurenine (KYN) and XA were both up‐regulated compared to the control, suggesting the activation effect of the KYN pathway by myclobutanil and its enantiomers which may provide an important insight into its toxicity mechanism. The data presented here could be useful for the environmental hazard assessment of myclobutanil. Chirality 27:643–649, 2015. © 2015 Wiley Periodicals, Inc.     

Strategy Approach for Direct Enantioseparation of Hyoscyamine Sulfate and Zopiclone on a Chiral αl‐Acid Glycoprotein Column and Determination of Their Eutomers: Thermodynamic Study of Complexation

Rapid and simple isocratic high‐performance liquid chromatographic methods with UV detection were developed and validated for the direct resolution of racemic mixtures of hyoscyamine sulfate and zopiclone. The method involved the use of α_l‐acid glycoprotein (AGP) as chiral stationary phase. The stereochemical separation factor (?) and the stereochemical resolution factor (R_s) obtained were 1.29 and 1.60 for hyoscyamine sulfate and 1.47 and 2.45 for zopiclone, respectively. The method was used for determination of chiral switching (eutomer) isomers: S‐hyoscyamine sulfate and eszopiclone. Several mobile phase parameters were investigated for controlling enantioselective retention and resolution on the chiral AGP column. The influence of mobile phase, concentration and type of uncharged organic modifier, ionic strength, and column temperature on enantioselectivity were studied. Calibration curves were linear in the ranges of 1–10 µg mL^‐1 and 0.5–5 µg mL^‐1 for S‐hyoscyamine sulfate and eszopiclone, respectively. The method is specific and sensitive, with lower limits of detection and quantifications of 0.156, 0.515 and 0.106, 0.349 for S‐hyoscyamine sulfate and eszopiclone, respectively. The method was used to identify quantitatively the enantiomers profile of the racemic mixtures of the studied drugs in their pharmaceutical preparations. Thermodynamic studies were performed to calculate the enthalpic ΔH and entropic ΔS terms. The results showed that enantiomer separation of the studied drugs were an enthalpic process. Chirality 28:49–57, 2016. © 2015 Wiley Periodicals, Inc.     

Enantioselective Bioaccumulation of Diniconazole in Tenebrio Molitor Larvae

The enantioselective bioaccumulation of diniconazole in Tenebrio molitor Linne larva was investigated with liquid chromatography tandem mass spectrometry based on the ChiralcelOD‐3R[cellulose tri‐(3,5‐dimethylphenyl carbamate)] column. In this study we documented the effects of dietary supplementation with wheat bran contaminated by racemic diniconazole at two dose levels of 20 mg kg^‐1 and 2 mg kg^‐1 (dry weight) in Tenebrio molitor. The results showed that both doses of diniconazole were taken up by Tenebrio molitor rapidly in the first few days, the concentrations of R‐enantiomer and S‐enantiomer at high doses reached the highest level of 0.55 mg kg^‐1 and 0.48 mg kg^‐1, respectively, on the 1^st d, and the concentrations of them obtained a maxima of 0.129 mg kg^‐1 and 0.128 mg kg^‐1 at low dose, respectively, on the 3^rd d, which means that the concentration of diniconazole was proportional to the time of achieving the highest accumulated level. It afterwards attained equilibrium after a sharp decline at both 20 mg kg^‐1 and 2 mg kg^‐1 of diniconazole. The determination results from the feces of Tenebrio molitor demonstrated that the extraction recovery (ER) values of the high dose group were higher than that of the low dose group and the values were all above 1; therefore, it could be inferred that enantiomerization existed in Tenebrio molitor. Additionally, the biota accumulation factor was used to evaluate the bioaccumulation of diniconazole enantiomers, showing that the bioaccumulation of diniconazole in Tenebrio molitor was enantioselective with preferential accumulation of S‐enantiomer. Chirality 25:917–922, 2013. © 2013 Wiley Periodicals, Inc.     

Chemical Constituents and Insecticidal Activities of Ajania fruticulosa Essential Oil

The insecticidal activity and chemical constituents of the essential oil from Ajania fruticulosa were investigated. Twelve constituents representing 91.0% of the essential oil were identified, and the main constituents were 1,8‐cineole ( 41.40% ), (+)‐camphor ( 32.10% ), and myrtenol (8.15%). The essential oil exhibited contact toxicity against Tribolium castaneum and Liposcelis bostrychophila adults with LD₅₀ values of 105.67 μg/adult and 89.85 μg/cm², respectively. The essential oil also showed fumigant toxicity against two species of insect with LC₅₀ values of 11.52 and 0.65 mg/l, respectively. 1,8‐Cineole exhibited excellent fumigant toxicity (LC₅₀ = 5.47 mg/l) against T. castaneum. (+)‐Camphor showed obvious fumigant toxicity (LC₅₀ = 0.43 mg/l) against L. bostrychophila. Myrtenol showed contact toxicity (LD₅₀ = 29.40 μg/cm²) and fumigant toxicity (LC₅₀ = 0.50 mg/l) against L. bostrychophila. 1,8‐Cineole and (+)‐camphor showed strong insecticidal activity to some important insects, and they are main constituents of A. fruticulosa essential oil. The two compounds may be related to insecticidal activity of A. fruticulosa essential oil against T. castaneum and L. bostrychophila.     

Synergistic activity of Bacillus thuringiensis δ‐endotoxin and TMOF against Culex pipiens and Spodoptera littoralis larvae

Trypsin Modulating Oostatic Factor (TMOF) is a decapeptide hormone that inhibits the biosynthesis of digestive enzymes in the mosquito midgut. The hormone inhibits food digestion and ultimately leads to starvation and death. It has been used as a biological insecticide to control mosquitoes. In an attempt to increase the insecticidal activity of TMOF, a combination of CryIC (δ‐endotoxin from Bacillus thuringiensis) and TMOF was determined. Eight recombinant proteins fused with GST (glutathione‐S‐transferase) were expressed in Escherichia coli cells. Their insecticidal activities were determined against Culex pipiens and Spodoptera littoralis larvae. Purified GST‐TMOF and its analogue GST‐YDPAS exhibited a moderate toxicity on C. pipiens larvae with LC₅₀ of 145.9 and 339.9 μg/mL, respectively. Unexpectedly, no mortality was observed in first instar larvae of S. littoralis. Puirified GST‐TMOF and GST‐YDPAS together with Bt toxin showed a synergistic toxic effect on both Culex and Spodoptera larvae. In the presence of 100 μg/mL GST‐TMOF and GST‐YDPAS, the median lethal concentration of entomocidus on culex larvae decreased from 52.1 to 16.7 and 31.9 μg/mL, respectively. Likewise, GST‐TMOF and GST‐YDPAS incorporated with 0.07 μg/cm² of enotmocidus showed insecticidal activity against S. littoralis with LC₅₀ of 16.4 and 21.9 μg/cm². The E. coli lysates containing GST‐CryIC and its 3′‐truncated version showed low toxicity against the lepidopteran insect (10.8 and 16.6 μg/cm²) compared to 0.15 μg/cm² of the native crystalline form of CryIC. Similarly, the mosquitocidal activity of the recombinant Bt toxins was low.