A Nematode Crude Extract Acts as an Elicitor of the Nematocidal Activity of Nematophagous Fungi Liquid Culture Filtrates Against Haemonchus contortus (Nematoda: Trichostrongylidae)

AIM

This study was designed to investigate if culturing nematophagous fungi (NF) in the presence of a Haemonchus contortus larva crude extract (HcCE) enhances the nematocidal activity of nematophagous fungi liquid culture filtrates (NFCF).

MATERIALS AND METHODS

Four NF Arthrobotrys oligospora, A. musiformis, Duddingtonia flagrans and Clonostachys rosea were cultured in flasks (n = 5) containing Czapek-Dox broth medium (CDB) in the presence or absence of HcCE. NFCF recovered by filtration of each fungus (200 mg/mL) were assessed on H. contortus infective larvae (L3) using 96-well micro-titer plates (n = 4). Additionally, CDB and water were considered negative controls, while Ivermectin acted as a positive control. After 48 h confrontation, ten 10-μL aliquots of each well were deposited on slides and observed under the microscope (40 ×). Dead and alive larvae in the aliquots were quantified, and a mortality rate (MR) was estimated.

RESULTS

The MR of the different NFCF was greatly enhanced by the presence of HcCE. The four NF incubated in the absence of HcCE showed low mortality percentages from 8.2 to 25.8%; in contrast, when the assessed NF growth in the presence of HcCE showed a lethal activity ranging from 66.8 to 80.5%. Only C. rosea showed a moderate increase in the presence of the elicitor (42.7%).

CONCLUSION

This study shows evidence about the HcCE enhances the production of nematocidal activity in NFCF. Future studies should be performed to elucidate the compounds responsible of the nematocidal activity that could have important implications in the control of sheep haemonchosis.

Bacillus thuringiensis toxins with nematocidal activity against the pinewood nematode Bursaphelenchus xylophilus

The pine wilt disease is caused by the pinewood nematode Bursaphelenchus xylophilus and it results in serious ecological and economic losses. Therefore, effective prevention and control methods for the pinewood nematode are urgently required. Bacillus thuringiensis (Bt), a widely used microbial insecticide, produces toxins that are toxic to several species of parasitic nematodes, however, its effects on B. xylophilus have not been determined. In this study, Cry5Ba3, App6Aa2, Cry12Aa1, Cry13Aa1, Cry14Aa1, Cry21Aa3, Cry21Fa1, Xpp55Aa1, and Cyt8Aa1 toxins' nematocidal activity against B. xylophilus was evaluated, six toxins with high toxicity were identified: App6Aa2 (LC₅₀ = 49.71 μg/mL), Cry13Aa1 (LC₅₀ = 53.17 μg/mL), Cry12Aa1 (LC₅₀ = 58.88 μg/mL), Cry5Ba3 (LC₅₀ = 63.99 μg/mL), Xpp55Aa1 (LC₅₀ = 65.14 μg/mL), and Cyt8Aa1 (LC₅₀ = 96.50 μg/mL). The six toxins caused shrinkage and thinning of the intestinal cells, contraction of the intestine from the body wall, vacuolization, and degenerated appearance of the pinewood nematodes. The results of this study provide basic information to study the action mechanism of nematocidal toxins on the pinewood nematode and direction for the use of nematocidal toxins in the biological control of B. xylophilus.

Design, synthesis, and biological activity of novel 1,2,4-oxadiazole derivatives

Background

Plant diseases seriously threaten food security, it is urgent to discover efficient and low-risk chemical pesticides. 1,2,4-Oxadiazole derivatives exhibit broad spectrum of agricultural biological activities. For discovering novel molecules with excellent agricultural activities, novel 1,2,4-oxadiazole derivatives were synthesized and evaluated for their agricultural activities.

Result

Bioassays results showed that the title compounds exhibited moderate nematocidal activity against Meloidogyne incognita and anti-fungal activity to Rhizoctonia solani. It’s worth noting that compounds 5m, 5r, 5u, 5v, 5x and 5y showed strong antibacterial effects on Xanthomonas oryzae pv. oryzae (Xoo), with EC₅₀ values of 36.25, 24.14, 28.82, 19.44, 25.37 and 28.52 μg/mL, respectively, superior to bismerthiazol (BMT, EC₅₀ = 77.46 μg/mL) and thiodiazole copper (TDC, EC₅₀ = 99.31 μg/mL). Compounds 5p, 5u and 5v exhibited excellent antibacterial ability against Xanthomonas oryzae pv. oryzicola (Xoc), with EC₅₀ values of 31.40, 19.04 and 21.78 μg/mL, respectively, better than that of BMT (EC₅₀ = 68.50 μg/mL) and TDC (EC₅₀ = 91.05 μg/mL). In addition, compound 5v exerted moderate antibacterial effects on rice bacterial leaf blight.

Conclusions

Twenty-six novel 1,2,4-oxadiazole derivatives were obtained and their biological activities were evaluated. Compound 5u and 5v exhibited excellent antibacterial activity Xoo and Xoc. These results indicated that 1,2,4-oxadiazole derivatives containing a trifluoromethyl pyridine moiety could be as potential alternative templates for discovering novel antibacterial agents.

Nematocidal activity of 6-O-octanoyl- and 6-O-octyl-d-allose against larvae of Caenorhabditis elegans

The nematocidal activities of the fatty acid esters of d-allose were examined using the larvae of C. elegans. Among the fatty acid esters, 6-O-octanoyl-d-allose (3) showed significant activity. 6-O-octanoyl-d-glucose (5) showed no activity, indicating that the D-allose moiety is essential for the nematocidal activity of 3. A nonhydrolyzable alkoxy analog 6-O-octyl-d-allose (6) also showed activity equivalent to that of 3.

Galloyl derivatives from Caesalpinia coriaria exhibit in vitro ovicidal activity against cattle gastrointestinal parasitic nematodes

Gastrointestinal nematodes (GIN) are responsible for enormous economic losses worldwide. The use of anthelmintic drugs reduces the parasitic burden in ruminants. However, the excessive use of these drugs triggers anthelmintic resistance in these parasites, which leads to a worrisome inefficacy of most of the commercially available antiparasitic drugs. Caesalpinia coriaria is an arboreal legume possessing medical properties, although the antiparasitic potential of this plant against animal parasitic nematodes has not yet been studied. The aim of this study was to assess the in vitro ovicidal activity of a hydro-alcoholic extract (HA-E) from C. coriaria fruits against GIN and to identify the compounds responsible for this activity through an egg hatch inhibition (EHI) assay. GIN eggs obtained from cattle faeces were used in bio-guided assays. The HA-E was subjected to a liquid-liquid extraction using water and ethyl acetate to obtain two fractions, an organic fraction (EtOAc-F, 27% yield) and an aqueous (Aq-F, 73% yield) fraction. The chromatographic fractionation of the EtOAc-F (2 gr) was performed on a glass column packed with silica gel and eluted with dichloromethane/methanol with 10% ascending polarity. The bioactive compounds were analysed using high-performance liquid chromatography (HPLC) with UV detection, nuclear magnetic resonance (NMR) spectroscopy and mass spectroscopy (MS). The HA-E extract and the EtOAc-F showed ovicidal activity at a LC₅₀ of 0.92 and 0.16 mg/mL, respectively. A concentration-dependant effect was observed in both treatments. Chromatographic fractionation of the EtOAc-F, allowed for the isolation and characterisation of three important compounds: methyl gallate (1), gallic acid (2) and an unidentified compound (UC). The bioactive molecules (2 and UC) displayed an ovicidal activity close to 100% at 1 mg/mL concentration. The results of this work show that gallic acid (2) isolated from C. coriaria fruits is responsible for its ovicidal activity. The use of Caesalpinia coriaria could be explored in future studies as an environmentally-friendly alternative for the control of GIN in ruminants.

Novel amide derivatives containing 1,3,4-thiadiazole moiety: Design, synthesis, nematocidal and antibacterial activities

A series of novel amide derivatives containing 1,3,4-thiadiazole moiety were synthesized and their bioactivities were evaluated. The compound 34 exhibited good nematocidal activities against Meloidogyne incognita in vitro and in vivo, the LC₅₀ value and control effect were 6.5 mg/L and 83.3%, respectively. Meanwhile, it exhibited exciting antibacterial activities against Xanthomonas oryzae pv. oryzae, Xanthomonas campestris pv. citri, and Ralstonia solanacearum, the EC₅₀ values were 0.4, 6.7 and 5.1 mg/L, respectively, which were better than positive controls. The curative and protection activities under the greenhouse conditions of compound 34 against rice bacterial blight were 47.9 and 55.8%, respectively. The structure-activity relationship were analyzed in detail.

A phytochemical investigation of Stemona parviflora roots reveals several compounds with nematocidal activity

Twelve undescribed compounds including six phenanthrene derivatives (parviphenanthrines A-F), two stilbene derivatives (parvistilbines A-B), three esters (parviesters A-C), and one sesquiterpenoid (parvidiol A) were isolated from the roots of Stemona parviflora, together with twenty-two known ones. The structures of the undescribed compounds were elucidated based on the analyses of their spectroscopic data. The absolute configuration of parviphenanthrine A was determined by the quantum ECD calculations. Parviphenanthrines A and E, stemanthrene A, stilbostenin E, 4-hydroxy-benzenepropanol-α-benzoate, and (E)-4-hydroxycinnamic acid methyl ester showed nematocidal activity against Meloidogyne incognita with IC₅₀ values of 14.02 ± 0.32, 2.51 ± 0.13, 17.10 ± 0.65, 2.05 ± 0.07, 4.22 ± 0.31, and 1.07 ± 0.05 μM, respectively.

Synthesis, nematocidal activity and docking study of novel chiral 1-(3-chloropyridin-2-yl)-3-(trifluoromethyl)-1H-pyrazole-4-carboxamide derivatives

A series of novel chiral fluorinated pyrazole carboxamides derivatives were designed and synthesized. All these title compounds were confirmed by NMR and MS. The primarily nematocidal activity results indicated that some of them exhibited good control efficacy against the tomato root-knot nematode disease caused by Meloidogyne incognita. The docking results indicated that compound 5n interact with amino acid residue Tyr 121, Trp 279 of AchE via hydrogen bond.

Production, characterization, gene cloning, and nematocidal activity of the extracellular protease from Stenotrophomonas maltophilia N4

A rhizosphere strain of the bacterium Stenotrophomonas maltophilia N4 secretes the serine protease PN4, whose molecular mass is approximately 42 kDa. The optimal temperature for the enzyme activity of the 11-fold purified protein was 50°C and the optimal pH was 10.5. The activity of the enzyme was strongly inhibited by specific serine protease inhibitors, which allowed for its classification as an alkaline serine protease family. Ca(2+) ions stimulated the activity of the protease PN4, while Mg(2+) ions stabilized its activity, and Zn(2+) and Cd(2+) ions strongly inhibited its activity. The enzyme has broad substrate specificity. For example, it is able to hydrolyse casein, keratin, albumin, haemoglobin, and gelatin, as well as the insoluble modified substrates azure keratin and azocoll. The gene that encodes the 1740 bp precursor form of the enzyme (accession number: LC031815) was cloned. We then deduced that its amino acid sequence includes the region of the conserved domain of the S8 family of peptidases as well as the catalytic triad Asp/His/Ser. The bacterial culture fluid as well as the purified protease PN4 demonstrated biocidal activity with regard to the nematodes Caenorhabditis elegans and Panagrellus spp.