Synthesis, Nematicidal Evaluation, and 3D-QSAR Analysis of Novel 1

Aug 26, 2018 - bbbbA series of novel 1,3,4-oxadiazole-cinnamic acid hybrids were synthesized. The bioassays results indicated that the compounds 1, 2,...
0 downloads 0 Views 3MB Size
Download PDF
Article pubs.acs.org/JAFC

Cite This: J. Agric. Food Chem. 2018, 66, 9616−9623

Synthesis, Nematicidal Evaluation, and 3D-QSAR Analysis of Novel 1,3,4-Oxadiazole−Cinnamic Acid Hybrids Jixiang Chen, Yongzhong Chen, Xiuhai Gan,* Baojing Song, Deyu Hu, and Baoan Song* State Key Laboratory Breeding Base of Green Pesticide and Agricultural Bioengineering, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Research and Development Center for Fine Chemicals, Guizhou University, Huaxi District, Guiyang 550025, China

Downloaded via UNIV OF LOUISIANA AT LAFAYETTE on September 26, 2018 at 08:08:42 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

S Supporting Information *

ABSTRACT: A series of novel 1,3,4-oxadiazole−cinnamic acid hybrids were synthesized. The bioassays results indicated that compounds 1, 2, 7, and 8 showed excellent nematicidal activities against Tylenchulus semipenetrans with LC50,48h values of 9.7 ± 1.6, 15.6 ± 2.8, 8.0 ± 0.5, and 19.8 ± 2.9 mg/L, respectively, which were higher than those of avermectin (32.6 ± 4.5 mg/L) and fosthiazate (67.8 ± 1.7 mg/L). Low-toxicity compound 26, with excellent nematicidal activity in vitro (LC50,48h = 8.2 ± 1.2 mg/L), was designed on the basis of the predictive CoMFA (q2 = 0.795, r2 = 0.921) and CoMSIA (q2 = 0.762, r2 = 0.912) models. The control effect of compound 26 was 69.8% at an effective dose of 1.0 g per plant in a field experiment, which was superior to that of fosthiazate (67.2%). This work indicated that 1,3,4-oxadiazole−cinnamic acid hybrids may be used as potential nematicides. KEYWORDS: cinnamic acid derivatives, 1,3,4-oxadiazole moiety, nematicidal activity, Tylenchulus semipenetrans, 3D-QSAR

■

INTRODUCTION Tylenchulus semipenetrans,1 a new nematode species in citrus, delays tree growth, causes leaf wilting, and reduces citrus yields considerably.2−5 When infected trees are removed from a grove, the parasite remains in the soil for several years and can potentially infect new trees.6 Currently, nematode control is mainly achieved using commercial nematicides,7,8 including fosthiazate, ethoprop, oxamyl, and avermectin. However, application of these nematicides over the years has caused problems in the environment and to human health and pest resistance.9,10 Recently, fluopyram has been put onto the market as a highly effective nematicide, but its control costs are high.11 Therefore, a novel, economical, and low-toxicity nematicide must be developed for crop protection. Pesticides screened from natural plants have recently drawn interest worldwide. Some pesticides extracted from natural plants exhibit various characteristics, such as high activity, environmental friendliness, reduced resistance, and decreased pollution.12,13 Thus, the use of natural plants or the structural modification of natural products is an important approach for producing safe pesticides.14−17 Cinnamic acid is an important natural product demonstrating various activities, including antibiofilm,18 antitubercular,19 antifungal,20 and herbicidal21 activities. In addition, cinnamaldehyde displays nematicidal activity against Meloidogyne incognita.22 Cinnamic acid ester derivatives, such as cinnamyl acetate, methyl trans-cinnamate, and ethyl trans-cinnamate, exhibit excellent nematicidal activity against Bursaphelenchus xylophilus.23,24 These results revealed that derivatization of cinnamic acid is an effective approach for developing nematicides. 1,3,4-Oxadiazole derivatives are also important compounds demonstrating broad-spectrum bioactivities, such as insecticidal,25,26 antifungal,27 antitumor,28 and antitubercular activities.29 We previously found that some 1,3,4-oxadiazoles © 2018 American Chemical Society

containing trifluorobutene moieties exhibited good nematicidal activities against T. semipenetrans and Caenorhabditis elegans,30 but the nematicidal activities of the compounds are still low for controlling plant nematode diseases. On the basis of the above reports, we know that cinnamic acid derivatives possess enhanced nematicidal activities compared with that of cinnamic acid. To develop a novel, economical, and low-toxicity nematicide, we combined 1,3,4oxadiazole and cinnamic acid to generate 1,3,4-oxadiazole− cinnamic acid hybrids containing thioether bonding (Figure 1). Nematicidal activity was evaluated in vitro and in the field against T. semipenetrans. Moreover, their CoMFA and CoMSIA models were investigated. This study is the first to report on the nematicidal activity of 1,3,4-oxadiazole− cinnamic acid hybrids.

■

MATERIALS AND METHODS

Chemicals. Cinnamic acids, 1-ethyl-3-(3-(dimethylamino)propyl) carbodiimide hydrochloride (EDC), 1-hydroxybeonztriazole (HOBt), RX (substituted benzyl chloride), methyl sulfate, and diethyl sulfate were purchased from Shanghai Tansoole Chemicals Company, Ltd. (Shanghai, China). Carbon disulfide, sodium hydroxide, potassium hydroxide, magnesium sulfate anhydrous, and all solvents were purchased from Guiyang Yuda Chemical Reagent Company, Ltd. (Guiyang, China). All reagents and solvents were reagent-grade and used without further purification. Instrumental Analysis. Melting points were determined using an X-4 digital melting-point apparatus (Yidian Physical Optical Instrument Company, Ltd. Shanghai, China) and readings were uncorrected. 1H NMR and 13C NMR spectra were recorded on a Received: Revised: Accepted: Published: 9616

June 9, 2018 August 14, 2018 August 25, 2018 August 26, 2018 DOI: 10.1021/acs.jafc.8b03020 J. Agric. Food Chem. 2018, 66, 9616−9623

Article

Journal of Agricultural and Food Chemistry

Figure 1. Design of target compounds.

Figure 2. Synthesis of the target compounds, 1−27. = 7.8, 1.5 Hz, 2H, Ph-2,6-H), 7.52 (d, J = 16.5 Hz, 1H, Ph−CHC), 7.43−7.34 (m, 3H, Ph-3,4,5-H), 7.27 (d, J = 16.5 Hz, 1H, Ph−C CH), 3.29 (q, J = 7.8, 2H, S−CH2), 1.35 (t, J = 7.8, 3H, −CH3); 13C NMR (125 MHz, DMSO-d6) δ: 165.59, 163.68, 139.07, 135.18, 130.45, 129.45, 128.38, 110.14, 27.14, 15.37. HRMS (ESI): calcd for C12H12N2OS ([M + H]+), 233.0743; found, 233.0741. Anal. calcd for C12H12N2OS (232.3): C, 62.05; H, 5.21; N, 12.06. Found: C, 62.14; H, 5.20; N, 12.01. In Vitro Nematicidal Activities of 1−25. Collection of Soil Material. Samples were collected as previously described.33 In this study, soil samples were obtained from a citrus orchard in Guangxi Special Crop Research Institute (March 2016) in Guangxi Province, China. Soil samples (10−20 cm deep) were collected from the soil approximately 1 m from the canopy of an infected citrus tree. All samples were immediately transported to a laboratory at the Center for Research and Development of Fine Chemicals, Guizhou University. Extraction and Isolation. Nematodes were isolated using the Baermann funnel method.34 A rubber tube with a sealing clamp was connected to the end of a glass funnel with a diameter of 120 mm. An aliquot (100 g) of the sample was placed on three layers of gauze and then placed on a funnel. The mixture of a sufficient volume of water and soil was stored for 10 h on a funnel and then filtered through a sieve (325 mesh/in.) at room temperature. Nematode suspensions (mixtures of juvenile and adult nematodes) were obtained by backwashing the sieve with a fairly gentle stream of water. In Vitro Test. The test was performed according to a modified method.35 The LC50 values against T. semipenetrans of compounds 1− 25 were tested under different concentrations. All test compounds were dissolved with N,N-dimethylformamide (DMF) and then diluted with Tween 80 (1%). The final concentration of DMF was 0.5% (v/v) in each treatment. Test solution (200 μL) was added into the wells of 48-well plates. Subsequently, a suspension (10 μL) that included approximately 200 living nematodes was added into the above solution. Avermectin and fosthiazate were used as positive

500 MHz spectrometer (JEOL, Tokyo, Japan) with DMSO-d6 or CDCl3 as the solvent and TMS as the internal standard. The course of the reaction was monitored by thin-layer-chromatography analysis on silica gel GF254 (Qingdao Haiyang Chemical Company, Ltd., Qingdao, China), and spots were visualized with ultraviolet (UV) light. Elemental analyses were performed on an Elementar Vario-III CHN elemental analyzer (Elementar Trading Company, Ltd., Shanghai, China). High-resolution mass spectra (ESI TOF (+)) were measured on an LTQ Orbitrap XL (Thermo Scientific, St. Louis, MO). General Procedure. The title compounds were designed and synthesized as presented in Figure 2. The different cinnamyl hydrazides were prepared according to known methods,31 and 2thio-5-styryl-1,3,4-oxadiazoles were synthesized according to a previous method.32 Then, a mixture of the intermediate oxadiazole (2.0 mmol) and sodium hydroxide (2.5 mmol) was stirred in water (8 mL). A solution of 2.0 mmol RX, methyl sulfate, or diethyl sulfate in ethanol (1 mL) was subsequently added into the mixture, which was stirred for another 2 h, and 10 mL water was added when the reaction was completed. The solid was collected through filtration and then purified through crystallization from absolute alcohol to obtain pure title compounds with 75−85% yields. The physical characteristics, 1H NMR spectra, 13C NMR spectra, HRMS spectra, and elementalanalysis data of target compounds 1 and 7 are presented below. (E)-2-(Methylthio)-5-styryl-1,3,4-oxadiazole (1). White solid. MP: 56−57 °C. Yield: 81%. 1H NMR (500 MHz, DMSO-d6) δ: 7.72 (dd, J = 7.9, 1.4 Hz, 2H, Ph-2,6-H), 7.51 (d, J = 16.5 Hz, 1H, Ph−CHC), 7.43−7.34 (m, 3H, Ph-3,4,5-H), 7.27 (d, J = 16.5 Hz, 1H, Ph−C CH), 2.72 (s, 3H, S−CH3); 13C NMR (125 MHz, DMSO-d6) δ: 166.33, 161.91, 142.62, 134.72, 131.20, 129.57, 128.85, 109.46, 43.42. HRMS (ESI): calcd for C11H10N2OS ([M + H]+), 219.0586; found, 219.0582. Anal. calcd for C11H10N2OS (218.2): C, 60.53; H, 4.62; N, 12.83. Found: C, 60.55; H, 4.60; N, 12.82. (E)-2-(Ethylthio)-5-styryl-1,3,4-oxadiazole (7). White solid. MP: 49−50 °C. Yield: 74%. 1H NMR (500 MHz, DMSO-d6) δ: 7.73 (dd, J 9617

DOI: 10.1021/acs.jafc.8b03020 J. Agric. Food Chem. 2018, 66, 9616−9623

Article

Journal of Agricultural and Food Chemistry Table 1. Nematicidal Activities of Compounds 1−25 against Tylenchulus semipenetrans in Vitroa corrected mortality rate ± SD (%)b 1

compound

R

R

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 avermectinc fosthiazatec

H F Br OCH3 Cl Br H Cl OCH3 F H Br H F Cl H F Br H F Cl F Cl H Br  

CH3 CH3 CH3 CH3 CH3 C2H5 C2H5 C2H5 C2H5 benzyl benzyl 4-NO2-benzyl 4-NO2-benzyl 4-NO2-benzyl 4-F-benzyl 4-F-benzyl 4-F-benzyl 4-F-benzyl 4-Cl-benzyl 4-Cl-benzyl 4-Cl-benzyl 3-CH3-benzyl 3-CH3-benzyl 3-CH3-benzyl 3-CH3-benzyl  

24 h 95.2 94.4 51.1 55.2 54.1 50.0 100 57.1 63.6 33.9 41.8 14.6 37.8 17.7 26.0 23.6 22.4 23.4 34.1 36.5 20.8 21.2 24.5 30.4 12.4 59.2 47.1

48 h

± ± ± ± ± ±

2.1 1.3 1.7 1.6 1.3 3.9

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

3.0 2.4 2.1 2.5 1.6 1.9 2.0 2.0 2.8 2.0 2.1 1.9 1.0 2.3 3.9 1.6 0.5 2.8 2.0 1.4

100 100 71.2 70.7 73.5 73.2 100 93.2 72.0 41.8 65.3 28.8 45.2 30.2 40.9 46.6 45.3 34.1 47.4 45.9 46.1 36.4 36.8 44.3 26.4 75.7 69.2

LC50, 48h ± SD (mg/L)

72 h

± ± ± ±

2.1 2.5 2.2 1.0

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

0.7 2.3 1.3 2.3 2.5 3.4 3.8 1.2 1.3 4.2 2.0 1.8 3.3 1.3 2.2 2.5 1.7 1.5 1.7 2.2

100 100 85.7 84.6 86.0 87.8 100 98.8 95.1 66.4 83.2 48.6 70.8 54.1 58.4 74.3 75.4 56.5 77.3 72.9 74.8 56.4 58.1 74.3 45.4 88.2 73.3

± ± ± ±

3.2 2.3 1.4 2.2

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

0.2 1.4 1.2 1.8 4.3 3.2 2.1 3.1 1.1 3.8 1.7 1.8 5.6 1.6 1.7 8.9 1.5 3.5 3.3 1.5

9.7 15.6 45.6 49.4 33.5 33.5 8.0 19.8 37.2 229.3 82.6 608.9 150.7 555.4 269.5 126.6 155.5 443.6 114.1 130.3 155.8 465.6 487.4 128.9 689.4 32.6 67.8

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

1.6 2.8 1.7 0.6 2.2 4.1 0.5 2.9 3.5 0.4 2.1 5.0 6.7 7.4 3.9 0.3 5.7 4.7 2.9 9.6 5.8 9.7 1.4 0.2 2.8 4.5 1.7

a Averages of three replicates. bThe concentration of the test compound is 100 mg/L. cThe commercial nematicide was used for a comparison of activity.

controls, the test solution without compound was used as a negative control. Each concentration was tested in triplicate, and all experiments were repeated three times. The mortality rates of the nematodes as seen under a stereoscopic binocular microscope were recorded after 24, 48, and 72 h. Nematodes were considered dead if their bodies were straight and if they did not move when strongly prodded with a needle.36 The LC50 values of the target compounds were calculated by the probit method.37 The results of the nematicidal activities of the target compounds are summarized in Table 1. Statistical Analysis. Nematode mortality was determined by eliminating natural death according to the Schneider−Orellis formula:38

sponding lowest-energy molecular model. Finally, compound 7 was selected as the template for molecular alignment. Partial-Least-Squares Analysis. There reliable 3D-QSAR models were based on partial least-squares regression. The optimal number of components and cross-validated q2 values were calculated using the leave-one-out method. The statistical parameters standard errors of estimate (SEE) and F-values were calculated using a no-validation method. Generally, a cross-validated q2 > 0.5 and a non-crossvalidated correlation r2 > 0.8 for the model is accepted. CoMFA- and CoMSIA-Color-Map Descriptors. The CoMFA contour maps consisted of two models: the steric field and the electrostatic field. In the steric field, the green contours indicated that bulky groups increase the nematicidal activity, whereas the yellow contours showed that the bulky groups reduce the activity. In the electrostatic field, the red blocks introducing electronegative groups promoted the activity. By contrast, the blue blocks introducing electropositive groups inhibit the biological activity. Relative to the CoMFA model, the CoMSIA model increased the hydrophobic and hydrogen-bond fields. In the hydrogen-bond-acceptor field, magenta polyhedra indicated that increasing the hydrogen-bond receptor enhanced the biological activity, whereas red polyhedra indicated that increasing the amount of donors during hydrogen bonding did not benefit the biological activity. Similarly, in the hydrophobic field, yellow indicated that an increase in the hydrophobic group contributed to an increase in biological activity, whereas white indicated that an increase in the hydrophilic group was beneficial to the biological activity. Field Test. Field trials were carried out in May 2017 in Shuiwei Village, Zhengguo Town, Zengcheng District, Guangdong Province, China. The field was divided randomly into 15 plots.39 The soil was sandy loam, and the organic-matter content was medium. Compound 26 (5% EC) was applied at doses of 0.5, 1.0, and 1.5 g per plant.

corrected mortality (%) mortality of treatment − mortality of control = × 100% 1 − mortality of control

Analysis of 3D-QSAR Models. Data Set of 3D-QSAR. In this work, the CoMFA and CoMSIA models were analyzed using SYBYLX 2.1 (Tripos Inc., St. Louis, MO) on the basis of their experimental pLC50 values. Eighteen compounds were randomly selected from the target compounds as a training set, and the remaining compounds were used as the testing set (Table 2). The training set was used to structure the CoMFA and CoMSIA models, whereas the testing set was applied to validate the models. Molecular-Descriptor Calculation and Alignment. To obtain reliable 3D-QSAR models, we calculated all molecular descriptors as follows: First, energy minimization was performed using the Tripos force field, Gasteiger−Hückel charge, and Powell conjugate-gradient algorithm with a convergence criterion of up to 0.005 kcal/mol/Å. Second, each molecule continued to be optimized using the geneticalgorithm-conformational-search method to determine the corre9618

DOI: 10.1021/acs.jafc.8b03020 J. Agric. Food Chem. 2018, 66, 9616−9623

Article

Journal of Agricultural and Food Chemistry Table 2. Experimental and Predicted Results of pLC50 Values for CoMFA and CoMSIA CoMFA compound 1 2 3 4 5 6d 7 8 9 10 11 12d 13 14 15d 16 17 18d 19 20 21d 22 23d 24 25d

LC50 (mg/L) 9.7 15.6 45.6 49.4 33.5 33.5 8.0 19.8 37.2 229.3 82.6 608.9 150.7 555.4 269.5 126.6 155.5 443.6 114.1 130.3 155.8 465.6 487.4 128.9 689.4

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

1.6 2.8 1.7 0.6 2.2 4.1 0.5 2.9 3.5 0.4 2.1 5.0 6.7 7.4 3.9 0.3 5.7 4.7 2.9 9.6 5.8 9.7 1.4 0.2 2.8

CoMSIA

LC50 (mmol/L)

exptla

predictedb

relative errorc

predicted

relative error

0.04 0.06 0.15 0.17 0.13 0.11 0.03 0.07 0.14 0.73 0.28 1.46 0.44 1.55 0.78 0.41 0.47 1.13 0.35 0.38 0.43 1.42 1.42 0.42 1.78

4.35 4.18 3.81 3.70 3.88 3.97 4.46 4.13 3.85 3.13 3.55 2.84 3.35 2.81 3.11 3.39 3.33 2.95 3.46 3.43 3.37 2.85 2.85 3.38 2.75

4.38 3.98 4.00 3.77 4.00 3.99 4.38 3.99 3.76 3.20 3.61 3.05 3.31 2.91 3.30 3.56 3.16 3.31 3.58 3.17 3.31 2.93 3.06 3.35 3.09

−0.03 0.20 −0.19 −0.07 −0.12 −0.02 0.08 0.14 0.09 −0.07 −0.06 −0.21 0.04 −0.10 −0.19 −0.17 0.17 −0.36 −0.12 0.26 0.06 −0.08 −0.21 0.03 −0.34

4.43 4.03 4.00 3.77 3.98 3.94 4.36 3.92 3.71 3.19 3.59 3.06 3.28 2.88 3.37 3.61 3.22 3.39 3.54 3.15 3.30 2.99 3.14 3.38 3.16

−0.08 0.15 −0.19 −0.07 −0.10 0.03 0.10 0.21 0.14 −0.06 −0.04 −0.22 0.07 −0.07 −0.26 −0.22 0.11 −0.44 −0.08 0.28 0.07 −0.14 −0.29 −0.00 −0.41

a

Experimental pLC50. bPredicted by CoMFA. cExptl/predicted. dTest-set samples.

Fosthiazate (5% EC), as a positive control, was applied at an effective dose of 1.0 g per plant, and the test solution without agent was used as a negative control. In the growing season of the 5 year old citrus trees, different concentrations of test agents were poured onto the roots. One month after application, 15 citrus-disease indexes were investigated and graded by the five-spot-sampling method in every plot. Each concentration was tested in triplicate, and the experiment was repeated three times. The root-knot index was graded as follows: level 0, knotless roots; level 1, root knots accounted for 1−25% of the root system; level 3, root knots accounted for 26−50% of the root system; level 5, root knots accounted for 51−75% of the root system; and level 7, root knots accounted for 76−100% of the root system. The control efficiency of 26 is summarized in Table 3.

Table 3. Control Efficiency of the Testing Agent against Tylenchulus semipenetrans in the Field treatment 26a

fosthiazatea negative control a

root‐knot index ∑ (number of diseased plants × corresponding grade value) = total number of diseased plants × 7

effective dose (grams per plant)

root-knot index

control efficiency (%)

0.5 1.0 1.5 1.0 

14.9 11.1 8.9 12.1 38.7

59.4 69.8 75.8 67.2 

Concentration of 5% of the emulsifiable concentrate.

the pH (5−6) and obtain (E)-5-styryl-1,3,4-oxadiazole-2thiols. Finally, the compounds were prepared from reaction with the corresponding RX, dimethyl sulfate, or diethyl sulfate. Nematicidal Activity. In Vitro Nematicidal Activity. Table 1 displays the nematicidal activities of compounds 1− 25 against T. semipenetrans. Some of the target compounds demonstrated worthwhile nematicidal activities against T. semipenetrans. Compounds 1 and 7 (Figure 3) exhibited remarkable nematicidal activities at 100 mg/L after 24, 48, and 72 h, wherein mortality rates were 95.2, 100, and 100% for compound 1; and 100, 100, 100% for compound 7. To study the relationship between the structures and activities of the compounds, the LC50 values of some target compounds were also evaluated after 48 h. The results are listed in Table 1. Compounds 1, 2, 7, and 8 demonstrated excellent nematicidal activities, with LC50 values of 9.7 ± 1.6, 15.6 ± 2.8, 8.0 ± 0.5, and 19.8 ± 2.9 mg/L at 48 h, respectively, which were higher than those of avermectin (32.6 ± 4.5 mg/L) and fosthiazate (67.8 ± 1.7 mg/L).

× 100 control effect (%) negative‐control root‐knot index − treatment root‐knot index = negative‐control root‐knot index × 100

Data were analyzed using Duncan’s reciprocal-Doppler-tolerance (DMRT) method.

■

RESULTS AND DISCUSSION Synthesis. The desired cinnamic hydrazides were easily prepared from cinnamic acid via the reaction of hydrazine hydrate with acetonitrile in the presence of HOBt and EDC. These were subsequently reacted with carbon disulfide, and the mixture was acidified using dilute hydrochloric acid to adjust 9619

DOI: 10.1021/acs.jafc.8b03020 J. Agric. Food Chem. 2018, 66, 9616−9623

Article

Journal of Agricultural and Food Chemistry

Figure 3. Nematocidal activities of compounds 1, 7, and 26 against Tylenchulus semipenetrans at 100 mg/L in vitro.

Figure 4. Plots of experimental and predicted pLC50 for the (A) CoMFA and (B) CoMSIA models.

Analysis of 3D-QSAR Models. Analysis of Modeling Results. Table 2 displays the predicted and experimental pLC50 values of the target compounds. The q2 values were 0.795 and 0.762 for the CoMFA and CoMSIA models, respectively, and the r2 values were 0.921 and 0.912. The SEE of the CoMFA and CoMSIA models were 0.147 and 0.161, respectively, and the corresponding F-values were 54.290 and 33.540. Generally, internal validations of cross-validated values (q2 > 0.5) and non-cross-validated coefficient values (r2 > 0.8) were commonly applied as 3D-QSAR models. Figure 4 displays the correlations between the predicted and experimental pLC50 values of the CoMFA and CoMSIA models. The predicted pLC50 values were consistent with the experimental values within an acceptable error range as verified by the reliability of the models. CoMFA-Color-Map Analysis. As shown in Figure 5A,B, the steric field of CoMFA (Figure 5A) showed some yellow contours adjacent the R position, and the bulky groups in this area inhibited the nematicidal activity. This finding suggests that the compounds with aromatic rings exhibited poor nematicidal activity compared with the corresponding compounds with alkyl groups. These results agreed with the following findings: 1 (R1 = 4-H, R = CH3, LC50,48h = 9.7 ± 1.6 mg/L, 0.04 mmol/L) > 11 (R1 = 4-H, R = benzyl, LC50,48h = 82.6 ± 2.1 mg/L, 0.28 mmol/L), 2 (R1 = 4-F, R = CH3, LC50,48h = 15.6 ± 2.8 mg/L, 0.06 mmol/L) > 10 (R1 = 4-F, R = benzyl, LC50,48h = 229.3 ± 0.4 mg/L, 0.73 mmol/L), 5 (R1 = 4-Cl, R = CH3, LC50,48h = 33.5 ± 2.2 mg/L, 0.13 mmol/L) > 15 (R1 = 4-Cl, R = 4-F-benzyl, LC50,48h = 269.5 ± 3.9 mg/L,

Figure 5. CoMFA contour maps of (A) steric and (B) electrostatic fields.

0.78 mmol/L), and 3 (R1 = 4-Br, R = CH3, LC50,48h = 45.6 ± 1.7 mg/L, 0.15 mmol/L) > 25(R1 = 4-Br, R = 3-CH3-benzyl, LC50,48h = 689.4 ± 2.8 mg/L, 1.78 mmol/L). Figure 5B shows the CoMFA map of the electrostatic field, wherein many red contours are found near the aromatic ring, particularly in the 4position. This observation suggests that the small-sterichindrance electron-withdrawing groups in the region enhance the nematicidal activity, as shown with the following results: 2 (R1 = 4-F, R = CH3, LC50,48h = 15.6 ± 2.8 mg/L, 0.06 mmol/ L) > 5(R1 = 4-Cl, R = CH3, LC50,48h = 33.5 ± 2.2 mg/L, 0.13 mmol/L) > 3 (R1 = 4-Br, R = CH3, LC50,48h = 45.6 ± 1.7 mg/ 9620

DOI: 10.1021/acs.jafc.8b03020 J. Agric. Food Chem. 2018, 66, 9616−9623

Article

Journal of Agricultural and Food Chemistry

Figure 6. CoMSIA contour maps of (A) steric, (B) electrostatic, (C) H-bond-acceptor, and (D) hydrophobic fields.

L, 0.15 mmol/L) > 4 (R1 = 4-OCH3, R = CH3, LC50,48h = 49.4 ± 0.6 mg/L, 0.17 mmol/L) and 17 (R1 = 4-F, R = 4-F-benzyl, LC50,48h = 155.5 ± 5.7 mg/L, 0.47 mmol/L) > 15 (R1 = 4-Cl, R = 4-F-benzyl, LC50,48h = 269.5 ± 3.9 mg/L, 0.78 mmol/L) > 18 (R1 = 4-Br, R = 4-F-benzyl, LC50,48h = 443.6 ± 4.7 mg/L, 1.13 mmol/L). CoMSIA-Color-Map Analysis. Figure 6 shows the four types of contour maps for CoMSIA. Figure 6A,B shows the stericand electrostatic-field maps, respectively. The results of the steric- and electrostatic-field maps for the CoMSIA models were consistent with those for the CoMFA models. Figure 6C exhibits the hydrogen-bond-acceptor contour map for the CoMSIA model. Two large blocks of red contour maps were observed in R and in the oxadiazole ring, indicating that the hydrogen-bond-acceptor groups located in these positions enhance the nematicidal activity (16 (R1 = 4-H, R = 4-Fbenzyl, LC50,48h = 126.6 ± 0.3 mg/L, 0.41 mmol/L) > 13 (R1 = 4-H, R = 4-NO2-benzyl, LC50,48h = 150.7 ± 6.7 mg/L, 0.44 mmol/L)). Figure 6D displays the hydrophobic-field (CoMSIA) contour maps. A white polyhedra was observed in the R position, demonstrating that hydrophobic groups exhibited reduced activity in that position. Design of the New Compounds and Nematicidal Activity. As shown in the steric fields of the CoMFA and CoMSIA models, there are yellow patches at approximately two carbon atoms from the R group, which indicate that the introduced group in that position should not be too long. As shown by the CoMSIA electrostatic field, there are blue patches near the R group, indicating that the electropositive group introduced into this position is active. Thus, an electronegative group at the R1 position and a short-chain and positively charged group at the R position should be introduced to increase nematicidal activity, and vice versa. Therefore, two new compounds were designed: 26 (R1 = 4-F, R = C2H5, LC50,48h = 8.2 ± 1.2 mg/L) and 27 (R1 = 4-OCH3, R = 4-F-benzyl, LC50,48h = 947.5 ± 4.4 mg/L). The nematicidal activity of compound 26 was superior to those of avermectin (LC50,48h = 32.6 ± 4.5 mg/L) and fosthiazate (LC50,48h = 67.8 ± 1.7 mg/L). This conclusion was consistent with the analysis of the CoMFA and CoMSIA models. The control efficiency of compound 26 on the citrus nematode disease caused by T. semipenetrans were evaluated in the field, and the results are shown in Table 3. The results indicated that compound 26 possessed a potent inhibitory effect on citrus nematode disease at 30 days after application to the roots. At effective doses of 0.5, 1.0, and 1.5 g per plant, the control effects were 59.4, 69.8,

and 75.8%, respectively, which were superior to that fosthiazate (67.2%) at the same effective dose of 1.0 g per plant. Toxicity. Rats were used for acute oral-, dermal-, and inhalation-toxicity tests by the Toxicology Center of Guizhou Medical University (approval number 20161020), according to Pesticide Registration Toxicology Test Methods (GB156701995). Meanwhile, New Zealand white rabbits were selected for acute skin- and eye-irritation tests, and guinea pigs were chosen for skin-allergy (sensitization) tests. Compound 26 shows extremely low toxicity in rats (acute oral LD50 > 5000 mg/kg, acute dermal and inhalational LD50 > 2000 mg/kg), rabbits (no acute skin or eye irritation), and guinea pigs (no skin allergies, but the positive control, 2,4-dinitrochlorobenzene, has 100% skin allergy). The commercial nematicides thiazophos (90 day oral dose >20.0 mg/kg) and avermectin (acute oral LD50 = 61.8 mg/kg, acute dermal LD50 > 1670 mg/ kg) are highly or moderately toxic to rats.40,41 In summary, novel 1,3,4-oxadiazole−cinnamic acid hybrids were designed and synthesized, and their nematicidal activities were evaluated against T. semipenetrans. Some of these compounds revealed strong nematicidal activities. The CoMFA and CoMSIA models showed that small-sterichindrance groups promote nematicidal activity. Compound 26, with low toxicity, was designed on the basis of the 3DQSAR models, and this compound exhibited excellent nematicidal activity. This study is the first to report 1,3,4oxadiazole−cinnamic acid hybrids as nematicides.

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jafc.8b03020. Characterization data, 1H and 13C NMR spectra, HRMS, and elemental analysis for intermediates and title compounds; molecular alignment result; statistical parameters for the CoMFA and CoMSIA models; toxicity data for compound 26 (PDF)

■

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (X.G.). *Tel.: 86-851-88292170. Fax: 86-851-88292170. E-mail: [email protected] (B.S.). ORCID

Baoan Song: 0000-0002-4237-6167 9621

DOI: 10.1021/acs.jafc.8b03020 J. Agric. Food Chem. 2018, 66, 9616−9623

Article

Journal of Agricultural and Food Chemistry Funding

growth inhibitory effect against Spodoptera litura. J. Agric. Food Chem. 2011, 59, 6004−6010. (17) Chen, J. T.; Su, H. J.; Huang, J. W. Isolation and identification of secondary metabolites of Clitocybe nuda responsible for inhibition of zoospore germination of Phytophthora capsici. J. Agric. Food Chem. 2012, 60, 7341−7344. (18) De Vita, D.; Simonetti, G.; Pandolfi, F.; Costi, R.; Di Santo, R.; D’Auria, F. D.; Scipione, L. Exploring the anti-biofilm activity of cinnamic acid derivatives in Candida albicans. Bioorg. Med. Chem. Lett. 2016, 26, 5931−5935. (19) Talath, S.; Gadad, A. K. Synthesis, antibacterial and antitubercular activities of some 7-[4-(5-amino-[1,3,4]thiadiazole-2sulfonyl)-piperazin-1-yl] fluoroquino- lonic derivatives. Eur. J. Med. Chem. 2006, 41, 918−924. (20) Bisogno, F.; Mascoti, L.; Sanchez, C.; Garibotto, F.; Giannini, F.; Kurinasanz, M.; Enriz, R. Structure-antifungal activity relationship of cinnamic acid derivatives. J. Agric. Food Chem. 2007, 55, 10635− 10640. (21) Vishnoi, S.; Agrawal, V.; Kasana, V. K. Synthesis and structureactivity relationships of substituted cinnamic acids and amide analogues: a new class of herbicides. J. Agric. Food Chem. 2009, 57, 3261−3265. (22) Caboni, P.; Aissani, N.; Cabras, T.; Falqui, A.; Marotta, R.; Liori, B.; Ntalli, N.; Sarais, N.; Sasanelli, N.; Tocco, G. Potent nematicidal activity of phthalaldehyde, salicylaldehyde, and cinnamic aldehyde against Meloidogyne incognita. J. Agric. Food Chem. 2013, 61, 1794−1803. (23) Park, I. K.; Park, J. Y.; Kim, K. H.; Choi, K. S.; Choi, I. H.; Kim, C. S.; Shin, C. H. Nematicidal activity of plant essential oils and components from garlic (Allium sativum) and cinnamon (Cinnamomum verum) oils against the pine wood nematode (Bursaphelenchus xylophilus). Nematology 2005, 7, 767−774. (24) Kong, J. O.; Lee, S. M.; Moon, Y. S.; Lee, S. G.; Ahn, Y. J. Nematicidal activity of cassia and cinnamon oil compounds and related compounds toward Bursaphelenchus xylophilus (Nematoda: Parasitaphelenchidae). J. Nematol. 2007, 39, 31−36. (25) Wang, B. L.; Zhu, H. W.; Ma, Y.; Xiong, L. X.; Li, Y. Q.; Zhao, Y.; Zhang, J. F.; Chen, Y. W.; Zhou, S.; Li, Z. M. Synthesis, insecticidal activities, and SAR studies of novel pyridylpyrazole acid derivatives based on amide bridge modification of anthranilic diamide insecticides. J. Agric. Food Chem. 2013, 61, 5483−5493. (26) Tok, F.; Kocyigit-Kaymakcioglu, B.; Tabanca, N.; Estep, A. S.; Gross, A. D.; Geldenhuys, W. J.; Becnel, J. J.; Bloomquist, J. R. Synthesis and structure-activity relationships of carbohydrazides and 1,3,4-oxadiazole derivatives bearing an imidazolidine moiety against the yellow fever and dengue vector. Pest Manage. Sci. 2018, 74, 413− 421. (27) Liu, F.; Luo, X. Q.; Song, B. A.; Bhadury, P. S.; Yang, S.; Jin, L. H.; Xue, W.; Hu, D. Y. Synthesis and antifungal activity of novel sulfoxide derivatives containing trimethoxyphenyl substituted 1,3,4thiadiazole and 1,3,4-oxadiazole moiety. Bioorg. Med. Chem. 2008, 16, 3632−3640. (28) Bondock, S.; Adel, S.; Etman, H. A.; Badria, F. A. Synthesis and antitumor evaluation of some new 1,3,4-oxadiazole-based heterocycles. Eur. J. Med. Chem. 2012, 48, 192−199. (29) Dhumal, S. T.; Deshmukh, A. R.; Bhosle, M. R.; Khedkar, V. M.; Nawale, L. U.; Sarkar, D.; Mane, R. A. Synthesis and antitubercular activity of new 1,3,4-oxadiazoles bearing pyridyl and thiazolyl scaffolds. Bioorg. Med. Chem. Lett. 2016, 26, 3646−3651. (30) Chen, X. W.; Gan, X. H.; Chen, J. X.; Chen, Y. Z.; Wang, Y. J.; Hu, D. Y.; Song, B. A. Synthesis and nematicidal activity of novel 1,3,4-oxadiazole (thiadiazole) thioether derivatives containing trifluorobuten moiety. Youji Huaxue 2017, 37, 2343−2351. (31) Zhang, X. N.; Breslav, M.; Grimm, J.; Guan, K. L.; Huang, A. H.; Liu, F. Q.; Maryanoff, C. A.; Palmer, D.; Patel, M.; Qian, Y.; Shaw, C.; Sorgi, K.; Stefanick, S.; Xu, D. W. A new procedure for preparation of carboxylic acids hydrazides. J. Org. Chem. 2002, 67, 9471−9474. (32) Li, P.; Hu, D. Y.; Xie, D. D.; Chen, J. X.; Jin, L. H.; Song, B. A. Design, synthesis, and evaluation of new sulfone derivatives

The authors are grateful to the National Natural Science Foundation of China (No. 21672044), the Subsidy Project for Outstanding Key Laboratory of Guizhou Province in China (No. 20154004), the Key Agricultural Technologies R&D Program of Guizhou University in China (No. 2016047), and the Collaborative Innovation Center for Natural Products and Biological Drugs of Yunnan for supporting the project (No. 201225). Notes

The authors declare no competing financial interest.

■

ABRREVIATIONS USED EDC, 1-ethyl-3-(3-(dimethylamino)propyl) carbodiimide hydrochloride; CoMFA, comparative molecular-field analysis; CoMSIA, comparative molecular-similarity-index analysis

■

REFERENCES

(1) Inserra, R. N.; Vovlas, N.; O’Bannon, J. H. A classification of Tylenchulus semipenetrans biotypes. J. Nematol. 1980, 12, 283−287. (2) Irshad, U.; Mukhtar, T.; Ashfaq, M.; Kayani, M. Z.; Kayani, S. B.; Hanif, M.; Aslam, S. Pathogenicity of citrus nematode (Tylenchulus semipenetrans) on Citrus jambhiri. J. Anim. Plant Sci. 2012, 22, 1014− 1018. (3) Javed, N.; Javed, M.; Ilyas, M. B.; Khan, M. M.; Haq, M. I. Reaction of various citrus stocks (germ plasm) against citrus root nematode (Tylenchulus semipenetrans Cobb.). Pak. J. Bot. 2008, 40, 2693−2696. (4) Fattah, F. A.; Saleh, H. M.; Aboud, H. M. Parasitism of the citrus nematode, Tylenchulus semipenetrans, by Pasteuria penetrans in Iraq. J. Nematol. 1989, 21, 431−433. (5) Baines, R. C.; Miyakawa, T.; Cameron, J. W.; Small, R. H. Infectivity of two biotypes of the citrus nematode on citrus and on some other hosts. J. Nematol. 1969, 1, 150−159. (6) O’Bannon, J. H.; Tarjan, A. C. Preplant fumigation for citrus nematode control in Florida. J. Nematol 1973, 5, 88−95. (7) Liu, T.; Meyer, S. L. F.; Chitwood, D. J.; Chauhan, K. R.; Dong, D.; Zhang, T. T.; Li, J.; Liu, W. C. New nematotoxic indoloditerpenoid produced by Gymnoascus reessii za-130. J. Agric. Food Chem. 2017, 65, 3127−3132. (8) Oka, Y.; Shuker, S.; Tkachi, N. Systemic nematicidal activity of fluensulfone against the root-knot nematode Meloidogyne incognita on pepper. Pest Manage. Sci. 2012, 68, 268−275. (9) Qin, S. J.; Gan, J. Y.; Liu, W. P.; Becker, J. O. Degradation and absorption of fosthiazate in soil. J. Agric. Food Chem. 2004, 52, 6239− 6242. (10) Meher, H. C.; Gajbhiye, V. T.; Chawla, G.; Singh, G. Virulence development and genetic polymorphism in Meloidogyne incognita (Kofoid & White) Chitwood after prolonged exposure to sublethal concentrations of nematicides and continuous growing of resistant tomato cultivars. Pest Manage. Sci. 2009, 65, 1201−1207. (11) Hungenberg, H.; Fuersch, H.; Rieck, H.; Hellwege, E. Use of fluopyram for controlling nematodes in crops. U.S. Patent US20160270394A1, 2016. (12) Isman, M. B. Botanical insecticides, deterrents, and repellents in modern agriculture and an increasingly regulated world. Annu. Rev. Entomol. 2006, 51, 45−66. (13) Chitwood, D. J. Phytochemical based strategies for nematode control. Annu. Rev. Phytopathol. 2002, 40, 221−249. (14) Regnault-Roger, C.; Philogene, B. J. R. Past and current prospects for the use of botanicals and plant allelochemicals in integrated pest management. Pharm. Biol. 2008, 46, 41−52. (15) Isman, M. B. Botanical insecticides: for richer, for poorer. Pest Manage. Sci. 2008, 64, 8−11. (16) Zhou, Y. Y.; Luo, S. H.; Yi, T. S.; Li, C. H.; Luo, Q.; Hua, J.; Liu, Y.; Li, S. H. Secondar metabolites from Glycine soja and their 9622

DOI: 10.1021/acs.jafc.8b03020 J. Agric. Food Chem. 2018, 66, 9616−9623

Article

Journal of Agricultural and Food Chemistry containing a 1,3,4-oxadiazole moiety as active antibacterial agents. J. Agric. Food Chem. 2018, 66, 3093−3100. (33) Ryss, A. Y. The simplest “field” methods for extractin of nematodes from plants, wood, insects and soil, with additional description how to keep extracted nematodes alive for a long time. Parazitologiia 2017, 51, 57−67. (34) Kerfahi, D.; Park, J.; Tripathi, B. M.; Singh, D.; Porazinska, D. L.; Moroenyane, I.; Adams, J. M. Molecular methods reveal controls on nematode community structure and unexpectedly high nematode diversity, in svalbard high arctic tundra. Polar Biol. 2017, 40, 765− 776. (35) Montasser, S. A.; Ei-Wahab, A. E. A.; Abd-Elgawad, M. M. M.; Abd-EI-Khair, H.; Faika, F. H. K.; Hammam, M. M. A. Effects of some fungi and bacteria as bio-control agents against citrus nematode Tylenchulus semipenetrans Cobb. J. Appl. Sci. Res. 2012, 8, 5436−5444. (36) Wang, G. L.; Chen, X. L.; Deng, Y. Y.; Li, Z.; Xu, X. Y. Synthesis and nematicidal activity of 1,2,3-benzotriazin-4-one derivatives against Meloidogyne incognita. J. Agric. Food Chem. 2015, 63, 6883−6889. (37) Dang, Q. L.; Kim, W. K.; Nguyen, C. M.; Choi, Y. Y.; Choi, G. J.; Jang, K. S.; Park, M. S.; Lim, C. H.; Luu, N. H.; Kim, J. C. Nematicidal and antifungal activity of annonaceous acetogenins from Annona squamosa against various plant pathogens. J. Agric. Food Chem. 2011, 59, 11160−11167. (38) Kumari, S.; Singh, R.; Kumar, A.; Walia, R. K. Synthesis and nematicidal bioevaluation of substituted 2H-1-benzopyrane-2-ones and their carbamate derivatives against root−knot nematode (Meloidogyne javanica). Asian J. Chem. 2014, 26, 3139−3143. (39) Qiao, K.; Shi, X. G.; Wang, H. Y.; Ji, X. X.; Wang, K. Y. Managing root-knot nematodes and weeds with 1,3-dichloropropene as an alternative to methyl bromide in cucumber crops in China. J. Agric. Food Chem. 2011, 59, 2362−2367. (40) Zhang, X. F.; Ren, R.; Wu, Y. P.; Zhang, Y.; Li, B. X. Acute toxicity test of avermectin. Chin. J. Public. Health. 2005, 21, 984−984. (41) Li, B. C.; Deng, L.; Zhou, N. Toxic effects of fosthiazate feeding for 90 days in rats. Chin. J. Comp. Med. 2014, 24, 49−53.

9623

DOI: 10.1021/acs.jafc.8b03020 J. Agric. Food Chem. 2018, 66, 9616−9623