Synthesis of novel 3/5(3,5)-(di)nitropaeonol hydrazone derivatives as nematicidal agents

Synthesis of paeonol hydrazone derivatives and their anti-oomycete, anti-fungal, and nematicidal activities

BACKGROUND

The natural product paeonol is a rich and sustainable natural bioresource, and its derivatives have various unique biological efficacy. As is well known, Schiff bases are a class of organic compounds with a wide range of biological activities, including anti-fungal, insecticidal, anti-viral, and nematicidal.

RESULTS

To discover biorational natural product-based pesticides, nine intermediates (2-10), 12 sulfonylhydrazones (11a-11c, 12a-12c, 13a-13c, and 14a-14c) and 20 benzylidene hydrazones (18a-18r, 19a, and 20a) were synthesized by structural modification of paeonol, and their structures were characterized by proton nuclear magnetic resonance (1H NMR), carbon-13 (13C) NMR, and high-resolution mass spectrometry (HRMS). The stereochemical configurations of compounds 14a, 18d, and 18r were unambiguously confirmed by single-crystal X-ray diffraction. Furthermore, bioactivities of these compounds as anti-oomycete, anti-fungal, and nematicidal agents against three serious agricultural pests, Phytophthora capsici, Fusarium graminearum, and Heterodera glycines were evaluated. Among all tested compounds: (i) compound 7 exhibited promising anti-oomycete against Phytophthora capsici, with a half maximal effective concentration (EC50) value of 15.81 mg L-1; (ii) compounds 2, 7, 10, and 19a displayed promising anti-fungal against F. graminearum, with EC50 values of 12.22, 14.72, 23.39, and 33.10 mg L-1, respectively; (iii) ten compounds (12a-12c, 14c, 18g-18j, 18m, and 19a) showed significant nematicidal activity against H. glycines, with median lethal concentration (LC50) values all less than 30.00 mg L-1. Especially for compound 18g, its LC50 value is the smallest, at 12.65 mg L-1.

CONCLUSION

The research results indicate that introducing nitro groups at the C5 position of paeonol, or introducing halogens at both C5 and C3 positions, can significantly enhance its biological activity against Phytophthora capsici, F. graminearum, and H. glycines. © 2024 Society of Chemical Industry.

Exploring Soybean Resistance to Soybean Cyst Nematode

Resistance to the soybean cyst nematode (SCN) is a topic incorporating multiple mechanisms and multiple types of science. It is also a topic of substantial agricultural importance, as SCN is estimated to cause more yield damage than any other pathogen of soybean, one of the world's main food crops. Both soybean and SCN have experienced jumps in experimental tractability in the past decade, and significant advances have been made. The rhg1-b locus, deployed on millions of farm acres, has been durable and will remain important, but local SCN populations are gradually evolving to overcome rhg1-b. Multiple other SCN resistance quantitative trait loci (QTL) of proven value are now in play with soybean breeders. QTL causal gene discovery and mechanistic insights into SCN resistance are contributing to both basic and applied disciplines. Additional understanding of SCN and other cyst nematodes will also grow in importance and lead to novel disease control strategies.

Synthesis of paeonol ester derivatives and their insecticidal, nematicidal, and anti-oomycete activities

BACKGROUND

Paeonol is extracted and isolated as a rich and sustainable natural bioresource from the root bark of Paeonia suffruticosa, the derivatives of which exhibit numerous biological activities. It is well known that ester compounds play a very important role in pest control, such as organophosphorus, carbamate and pyrethroid pesticides.

RESULTS

To discover biorational natural product-based pesticides, three series of (60) paeonol ester derivatives (7a-t, 8g,p, 9g,p, 10g-j,n-u, 11g,u, 12g,u, 13a-p, 14b,c, and 15b,c) were prepared by structural modification of paeonol, and their structures were well characterized by proton nuclear magnetic resonance (¹ H-NMR), carbon-13 nuclear magnetic resonance (¹³ C-NMR), high-resolution mass spectrometry (HRMS), and melting point. Furthermore, we assessed the compounds as insecticidal, nematicidal, and anti-oomycete agents against three serious agricultural pests, Mythimna separata, Heterodera glycines, and Phytophthora capsici. Among all tested compounds: (i) compound 8p showed more significant insecticidal activity than toosendanin, and the final mortality rates of 8p and toosendanin against M. separata (1 mg mL^-1 ) were 70.4%, and 51.9%, respectively; (ii) compound 7a exhibited more promising nematicidal activity than paeonol, and the median lethal concentration (LC₅₀ ) values of 7a and 1 against H. glycines were 15.47 and 50.80 mg L^-1 , respectively; (iii) compounds 7n and 13m displayed more significant anti-oomycete activity compared to zoxamide against Phytophthora capsici, and the median effective concentration (EC₅₀ ) values of 7n, 13m, and zoxamide were 23.72, 24.51, and 26.87 mg L^-1 , respectively; and the protective effect of the compounds against Phytophthora capsici in vivo further confirmed the effectiveness of the agents.

CONCLUSION

This study suggested that the introduction of a nitro at the C5 or C3 position of paeonol could improve its bioactivity against M. separata, H. glycines, and Phytophthora capsici. © 2022 Society of Chemical Industry.