Synthesis of 3-carene-derived nanocellulose/1,3,4-thiadiazole-amide complexes with antifungal activity for plant protection

Carane-3,4-diol Derivatives as Potential Water-Based Herbicides

Twelve novel carane-3,4-diol derivatives were designed, synthesized, and evaluated for their herbicidal activities against Lolium multiflorum Lam. and Brassica campestris for the first time. The relationships between the chemical structural factors, including types, the number or the carbon chain length of functional groups, associated with the lipophilicity and the herbicidal activity of the tested compounds were also discussed. The results showed that most of newly synthesized compounds had a dose-dependent, herbicidal activity against the root and shoot growths of Lolium multiflorum Lam. and Brassica campestris. Compared to carane-3,4-diol, most of the target derivatives possessed improved lipophilicity and certain solubilities in representative solvents with different polarities. Particularly, ester derivatives 3a-3b and 3e can be dissolved or dispersed in water, but also displayed higher herbicidal activity against Lolium multiflorum Lam. and Brassica campestris than other ester derivatives. The 50 % inhibitory concentration (IC50) value of compound 3e against shoot growth of Brassica campestris (0.485 mmol/L) was superior to that of commercial herbicide glyphosate (1.14 mmol/L), indicating that the potential application as a water-based herbicide for Brassica campestris control.

An Effective and Promising Strategy for Plant Protection: Synthesis of L-Carvone-Based Thiazolinone-Hydrazone/Nanochitosan Complexes with Antifungal Activity and Sustained Releasing Performance

The development of novel natural product-derived nano-pesticide systems with loading capacity and sustained releasing performance of bioactive compounds is considered an effective and promising plant protection strategy. In this work, 25 L-carvone-based thiazolinone-hydrazone compounds 4a~4y were synthesized by the multi-step modification of L-carvone and structurally confirmed. Compound 4h was found to show favorable and broad-spectrum antifungal activity through the in vitro antifungal activity evaluation of compounds 4a~4y against eight phytopathogenic fungi. Thus, it could serve as a leading compound for new antifungal agents in agriculture. Moreover, the L-carvone-based nanochitosan carrier 7 bearing the 1,3,4-thiadiazole-amide group was rationally designed for the loading and sustained releasing applications of compound 4h, synthesized, and characterized. It was proven that carrier 7 had good thermal stability below 200 °C, dispersed well in the aqueous phase to form numerous nanoparticles with a size of~20 nm, and exhibited an unconsolidated and multi-aperture micro-structure. Finally, L-carvone-based thiazolinone-hydrazone/nanochitosan complexes were fabricated and investigated for their sustained releasing behaviors. Among them, complex 7/4h-2 with a well-distributed, compact, and columnar micro-structure displayed the highest encapsulation efficiency and desirable sustained releasing property for compound 4h and thus showed great potential as an antifungal nano-pesticide for further studies.

Synthesis, Antifungal Activity, 3D-QSAR and Controlled Release on Hydrotalcite Study of Longifolene-Derived Diphenyl Ether Carboxylic Acid Compounds

Twenty-two novel longifolene-derived diphenyl ether-carboxylic acid compounds 7a-7v were synthesized from renewable biomass resources longifolene, and their structures were confirmed by FT-IR, ¹H NMR, ¹³C NMR, and HRMS. The preliminary evaluation of in vitro antifungal activity displayed that compound 7b presented inhibition rates of 85.9%, 82.7%, 82.7%, and 81.4% against Alternaria solani, Cercospora arachidicola, Rhizoctonia solani, and Physalospora piricola, respectively, and compound 7l possessed inhibition rates of 80.7%, 80.4%, and 80.3% against R. solani, C. arachidicola, P. piricola, respectively, exhibiting excellent and broad-spectrum antifungal activities. Besides, compounds 7f and 7a showed significant antifungal activities with inhibition rates of 81.2% and 80.7% against A.solani, respectively. Meanwhile, a reasonable and effective 3D-QSAR mode (r² = 0.996, q² = 0.572) has been established by the CoMFA method. Furthermore, the drug-loading complexes 7b/MgAl-LDH were prepared and characterized. Their pH-responsive controlled-release behavior was investigated as well. As a result, complex 7b/MgAl-LDH-2 exhibited excellent controlled-releasing performance in the water/ethanol (10:1, v:v) and under a pH of 5.7.