Myzus persicae (Sulzer) is a crop pest causing serious economic losses around the world. For many decades, the management of M. persicae has relied heavily on chemical pesticides, resulting in the development of resistance, and new compounds with activity against M. persicae are needed. Five novel polyketides, strekingmycins A-E (1-5), were isolated from Streptomyces sp. SA61. Their structures were determined based on MS, NMR, and X-ray diffraction data. Strekingmycins were active against M. persicae between 4.4 and 9.4 μg/mL.

Chloroxaloterpin A (1) and B (2) are two diterpenoids with potent inhibitory activities against spore germination of Botrytis cinerea, which were identified from Streptomyces sp. SN194 as minor products previously. In order to overcome the poor yields, 1 and 2 were synthesized using viguiepinol (3), the major metabolite of Streptomyces sp. SN194, as the precursor compound. Scanning electron microscope and transmission electron microscope observations revealed that after treating B. cinerea spores with 1 and 2, spores were obviously aberrant, the cytoplasm appeared withdrawn, and plasma membranes were blurred. Propidium iodide fluorescence assay indicated that 1 and 2 damaged plasma membranes of B. cinerea spores. In vivo assays showed that compounds 1 and 2 could effectively inhibit the sporulation of B. cinerea on tomato fruits, with sporulation inhibitory rates reaching 98.8% at 100 μg/mL. These findings provide new insights into chloroxaloterpin A and B and demonstrate their potential as lead candidates for novel fungicides.

Pyricularia oryzae causes rice blast, the major destructive disease in nearly all rice fields. In order to obtain highly active compounds against P. oryzae, four new 20-membered macrolides named venturicidins G–J (1–4) were isolated from the culture broth of Streptomyces sp. SN5452 along with two known ones, venturicidins A (5) and B (6). Their structures were determined by the cumulative analyses of nuclear magnetic resonance (NMR) spectroscopy and high-resolution electrospray ionization mass spectrometry (HRESIMS) data. All isolated compounds were evaluated for their antifungal activity against P. oryzae. Interestingly, these compounds exhibited obvious inhibition to mycelial growth and conidial germination of P. oryzae. Remarkably, the EC50 values of venturicidins A (5), B (6), and I (3) against mycelial growth were 0.11, 0.15 and 0.35 µg/mL, and their EC50 values of conidial germination were 0.27, 0.39 and 1.14 µg/mL, respectively. The analysis of structure-activity relationships (SARs) revealed that the methylated positions might be involved in the antifungal activity of venturicidins. These results indicate that the venturicidins are prospective candidates for novel fungicides that can be applied in controlling rice blast.

Bemisia tabaci is one of the most notorious agricultural pests in the world. A vicious circle among insect resistance, dose increased, environment and human body impaired as the overuse of synthetic pesticides are becoming increasingly evident. Entomopathogenic Beauveria sp. is known as an effective natural enemy to control B. tabaci . Therefore, this study aimed to purify and identify the biological compounds from Beauveria sp. LY2 via extensive chromatographic techniques, NMR and MS and evaluated for their insecticidal activities against B. tabaci via contact and feeding assay. The outcome identified that one new cerebroside, cerebroside F ( 1 ), nine known compounds, cerebroside B ( 2 ), bassiatin ( 3 ), methyl 1,4-dihydro-4-oxo-2-quinolinecarboxylate ( 4 ), cerevisterol ( 5 ), 9-hydroxycerevisterol ( 6 ), 6-dehydrocerevisterol ( 7 ), ( 22 E, 24 R)-ergosta-8(14),22-diene-3β,5α,6β,7α-tetrol ( 8 ), melithasterol B ( 9 ) and ergosterol peroxide ( 10 ) were isolated. Among the known compounds, methyl 1,4-dihydro-4-oxo- 2-quinolinecarboxylate ( 4 ) was isolated from natural origin for the first time. It is demonstrable from the results that compounds 3 , 4 and 7 strongly featured insecticidal activities against B. tabaci , being the LC 50 value as 10.59, 19.05, 26.59 μg/mL respectively in contact as well as 11.42, 5.66, 5.65 μg/mL respectively in feeding experiment. Moreover, no adverse effect on plant growth/height or phytotoxicity was observed on pepper, cucumber, tomato and cotton. The data from the current study has provided the foundation for the use of newly purified compounds against Bemisia tabaci as an alternative to synthetic chemical compounds.

为了筛选出对温室白粉虱Trialeurodes vaporariorum具有增效作用的农药复配组合,室内采用玻璃管饲喂法测定了辣椒碱与吡虫啉、溴氰虫酰胺、苦参碱复配对温室白粉虱初羽化成虫的联合毒力,并以共毒因子法与共毒系数法对各复配组合的联合毒力进行评价.试验结果表明,共毒因子大于20的配比共6组,进一步细化配比后筛选出共毒系数大于120的复配组合,其中14组具有增效作用,辣椒碱分别与吡虫啉、溴氰虫酰胺、苦参碱按287∶1、1 558∶1、423∶1复配时增效作用最显著,其共毒系数分别为257.89、255.65、248.80,LC50分别为31.83、128.07、98.87 mg/L.辣椒碱与吡虫啉按287∶1复配为最佳复配组合.

In this work, the antibacterial substances in Aspergillus flavipes ASD isolated from soil were identified and the biological activities of its secondary metabolites were evaluated. The crude dichloromethane extract from ASD fermentation broth was purified by silica gel column chromatography, gel column chromatography and semi-prepared high performance liquid chromatography. The isolated pure compounds were characterized by nuclear magnetic resonance spectrum and high resolution mass spectrometry and were compared with literature reported data. The structures were further confirmed by X-ray single crystal diffraction data. The fungicidal activities of the 2 isolated compounds against 9 pathogenic fungi, such as Phytophthora capsici, Exserohilum turcicum and Colletatrichum graminicola, etc, were determined by the method of pesticide plate dilution and mycelial growth rate. The results show that sulochrin and 4,5-dimethyl resorcinol were 农药学学报 2020, 22 Chinese Journal of Pesticide Science http://www.nyxxb.cn 收稿日期:2019-07-31;录用日期:2019-11-15. 基金项目:国家重点研发计划项目 (2017YFD0201100);辽宁省农业攻关及产业化项目 (2018103003);辽宁省自然科学基金 (20180550692). 作者简介:王辉,女,副研究员,E-mail:wanghui118000@sohu.com;刘长远,共同通信作者 (Co-author for correspondence),男,研 究员,从事园艺作物病害研究,E-mail:lcylns@163.com;王琦,通信作者 (Author for correspondence),男,教授,从事植物病害生物 防治,E-mail:wangqi@cau.edu.cn isolated from ASD. Sullocrin has a good control effect on P. capsici, E. turcicum and C. graminicola. 4,5-Dimethyl resorcinol has good control effect on P. capsici. They had no obvious effect or no inhibitory effect on 6 strains, such as Botrytis cinerea, Cercospora zeae-maydis and Curvularia lunata.

Two novel depsipeptides xenematides F and G (1, 2), were isolated from entomopathogenic Xenorhabdus budapestensis SN84 along with a known compound xenematide B. The structures of the two new molecules were elucidated using NMR, MS and Marfey’s method. The xenematide G (2) contains α-aminoheptanoic acid, a non-protein amino acid that is rarely found in secondary metabolites from entomopathogenic bacteria. Xenematides F and G were tested for antibacterial activity. Xenematide G (2) exhibited moderate antibacterial activity.

For decades, plant parasitic nematodes have caused serious damage to crop production. Most nematicides are banned because of their negative impacts on the environment and public health. The repeated application of the few commercially available nematicides has caused more incidences of nematicide resistance. To seek novel nematicides, seven linear peptides named rhabdopeptides I-O, 1-7, were isolated from culture broth of Xenorhabdus budapestensis SN84. The structures of the peptides were elucidated on the basis of extensive mass spectrometry (MS), and nuclear magnetic resonance analyses. 3, 4, and 7 were novel compounds. 1, 2, 5, and 6 were isolated and purified for the first time, despite being previously elucidated from an extract mixture based on labeling and MS experiments. All seven compounds were tested for their nematicidal activities against the second-stage juveniles (J2) of Meloidogyne incognita using 24-microwell plates. Rhabdopeptide J, 2, demonstrated strong inhibitory activity with an LC50 value of 27.8 μg/mL. Rhabdopeptide K, 3, and M, 5, showed moderate inhibitory activity with LC50 values of 46.3 and 42.4 μg/mL, respectively.

Members of genus Xenorhabdus are symbiotically associated with entomopathogenic nematodes of genus Steinernema . Herein, we describe the isolation and purification of four novel metabolites, xenocyloins G-J (1–4), from liquid cultures of Xenorhabdus bovienii SN52 by extensive column chromatography and semi-preparative HPLC. Chemical structures of the xenocyloin derivatives were determined based on comprehensive NMR spectra and HR-ESI-MS analyses. All compounds exhibited significant collagen-induced anti-platelet aggregation activities, among which xenocyloin H (2) exhibited the strongest activity with an inhibition rate of 96.0 ± 0.1% at a concentration of 50 μM. The xenocyloin G (1) and H (2) exhibited anti-platelet activities with IC 50 values which were 31.7 ± 4.4 μM and 27.5 ± 3.5 μM respectively; whilst under similar conditions the IC 50 value for aspirin was 289.5 ± 15.7 μM, nearly ten times less than 1 and 2.

One new indole derivative, chloroindole (1), one new diketone, streptoone A (2), two new ketonic acids, streptoones B (3) and C (4), and one known macrolide antibiotic, X-14952B (5), were isolated from Streptomyces sp. SN0280. Extensive NMR, HRESIMS, and IR analysis was used to elucidate their structures. Streptoone A (2) displayed antibacterial activity (MIC value of 7.81 μg/mL) against Clavibater michiganensis, comparable with the positive control streptomycin (MIC value of 7.81 μg/mL). Streptoone B (3) showed antifungal activity (MIC value of 15.63 μg/mL) against Phytophthora capsici (positive control carbendazol MIC value of 7.81 μg/mL). These molecules provide new templates for the potential treatment and management of these phytopathogens.

Members of genus Xenorhabdus are symbiotically associated with entomopathogenic nematodes of genus Steinernema . Herein, we describe the isolation and purification of four novel metabolites, xenocyloins G-J (1–4), from liquid cultures of Xenorhabdus bovienii SN52 by extensive column chromatography and semi-preparative HPLC. Chemical structures of the xenocyloin derivatives were determined based on comprehensive NMR spectra and HR-ESI-MS analyses. All compounds exhibited significant collagen-induced anti-platelet aggregation activities, among which xenocyloin H (2) exhibited the strongest activity with an inhibition rate of 96.0 ± 0.1% at a concentration of 50 μM. The xenocyloin G (1) and H (2) exhibited anti-platelet activities with IC 50 values which were 31.7 ± 4.4 μM and 27.5 ± 3.5 μM respectively; whilst under similar conditions the IC 50 value for aspirin was 289.5 ± 15.7 μM, nearly ten times less than 1 and 2.

Members of genus Xenorhabdus are symbiotically associated with entomopathogenic nematodes of genus Steinernema. Herein, we describe the isolation and purification of four novel metabolites, xenocyloins G-J (1–4), from liquid cultures of Xenorhabdus bovienii SN52 by extensive column chromatography and semi-preparative HPLC. Chemical structures of the xenocyloin derivatives were determined based on comprehensive NMR spectra and HR-ESI-MS analyses. All compounds exhibited significant collagen-induced anti-platelet aggregation activities, among which xenocyloin H (2) exhibited the strongest activity with an inhibition rate of 96.0 ± 0.1% at a concentration of 50 μM. The xenocyloin G (1) and H (2) exhibited anti-platelet activities with IC50 values which were 31.7 ± 4.4 μM and 27.5 ± 3.5 μM respectively; whilst under similar conditions the IC50 value for aspirin was 289.5 ± 15.7 μM, nearly ten times less than 1 and 2.

[目的]对链霉菌Streptomyces sp.SN194的次生代谢产物进行分离和纯化,发现对辣椒疫霉具有抑制作用的化合物.[方法]通过硅胶柱层析、凝胶柱层析和HPLC制备,得到纯化合物.利用ESI-MS、1H NMR和13C NMR等图谱分析的方法鉴定化合物的结构;采用菌丝生长速率法测定化合物对辣椒疫霉的抑制作用.[结果]得到对辣椒疫霉有抑制作用的4种二萜类化合物Viguiepinol、Oxaloterpin C、Oxaloterpin D和Oxaloterpin E,其中Oxaloterpin D活性最强(EC50值为21.44 mg/L).[结论]4种二萜类化合物对辣椒疫霉有抑制作用,值得进一步的研究.

采用硅胶柱层析、凝胶柱层析和半制备高效液相色谱技术对线虫共生菌Xenorhabdus budapestensis SN19 的次生代谢产物进行分离纯化,得到2个单体化合物.通过波谱综合解析和文献数据对照分别鉴定为xenematides C(1)和xenematides E(2),其中化合物2为新化合物,化合物1对番茄灰霉病菌具有较强的抑制作用(EC50=22.71 μg/mL).

Botrytis cinerea is a serious phytopathogen affecting a wide range of crops around the world. Many fungicides targeting Botrytis cinerea have failed due to the pathogen's genetic plasticity. In an effort to search for new fungicides from natural products, two new diterpenoids, named chloroxaloterpin A, 1, and B, 2, were isolated from culture broth of Streptomyces sp. SN194 along with four known diterpenoids, viguiepinol, 3, and oxaloterpins C-E, 4-6. Their structures were elucidated based on extensive MS, NMR, and X-ray crystallography analyses. Both the [(2-chlorophenyl)amino]carbonyl carbanic acyl group in 1 and the 2-[(2-chlorophenyl)amino]-2-oxo-acetyl group in 2 are discovered in natural products for the first time. All six compounds were tested against Botrytis cinerea, and chloroxaloterpin A, 1, and B, 2, demonstrated strong inhibitory activity against spore germination with EC50 of 4.40 and 4.96 μg/mL, respectively.