Synthesis and Anti-Oomycete Activity of 1-Sulfonyloxy/Acyloxydihydroeugenol Derivatives

Design, synthesis, and anti-oomycete activity of 3-acyloxymaltol/ethyl maltol derivatives

Twenty 3-acyloxymaltol/ethyl maltol derivatives (7a-j and 8a-j) were synthesized and evaluated in vitro for their anti-oomycete activity against Phytophthora capsici, respectively. Among all of twenty derivatives, more than half of the compounds 7f, 7h, 8a-h and 8j had anti-oomycete activity higher than the positive control zoxamide (EC50 = 22.23 mg/L), and the EC50 values of 18.66, 20.32, 12.80, 16.18, 10.59, 14.98, 16.80, 10.36, 15.32, 12.64, and 13.59 mg/L, respectively. Especially, compounds 8c and 8f exhibited the best anti-oomycete activity against P. capsici with EC50 values of 10.59 and 10.36 mg/L, respectively. Overall, hydroxyl group of maltol/ethyl maltol is important active modification site.

Synthesis of new trypanocidal agents from the hybridisation of metronidazole and eugenol analogues

Nitroimidazole compounds are well-known bioactive substances, and the structural activity relationship has been reported whereby the position of the nitro group within the imidazole ring has a large influence on the activity. This study focuses on synthesising new trypanocidal agents from the hybridisation of metronidazole with different natural phenols (eugenol, dihydroeugenol and guaiacol). Two different coupling methodologies have been explored in order to analyse the influence of the connector on bioactivity: i) classic direct esterification (AD compounds) and ii) "click" chemistry using a triazole connector (AC compounds). The in vitro trypanocidal tests show good results for both AC and AD hybrid compounds against both epimastigote and trypomastigote forms of T. cruzi. In silico studies showed positive data for most of the synthesised compounds and, in general present low toxicological risks. The AC compounds present lower ClogP (lipophilicity) values than those found for the AD series and higher TPSA (topological polar surface area) values, suggesting lower lipophilicity may be related to the presence of the triazole connector. The AD series compounds have higher Drug Score values than the AC series derivatives, suggesting better general properties for a pharmacological action.

Design, synthesis and anti-oomycete activity of 2-acyloxyhinokitiol derivatives

In order to explore novel natural product-based anti-oomycete agent, ten 2-acyloxyhinokitiol derivatives (5a-j) were designed and synthesised, and structurally confirmed by 1H NMR,13C NMR, HRMS, and melting point. The stereochemical configuration of compound 5f was unambiguously confirmed by single-crystal X-ray diffraction. Furthermore, we evaluated the target compounds 5a-j as anti-oomycete activity against a serious agricultural disease of Phytophthora capsici. Among the ten hinokitiol ester derivatives tested, four compounds 5d, 5g, 5h and 5j had anti-oomycete activity higher than the positive control zoxamide (EC50 = 23.59 mg/L), and the EC50 values of 18.90, 20.62, 13.61 and 21.29 mg/L, respectively. Especially compound 5h exhibited the best anti-oomycete activity against P. capsici with EC50 value of 13.61 mg/L. Overall, the anti-oomycete activities of 2-acyloxyhinokitiol derivatives is higher than that of 2-sulfonyloxyhinokitiol derivatives. The results laid a good foundation for the subsequent synthesis of hinokitiol ester derivatives with significant anti-oomycete activity.

Semisynthesis, anti-oomycete and anti-fungal activities of ursolic acid ester derivatives

Using ursolic acid (UA) as the lead compound, thirteen UA ester derivatives (3 and 7a-l) were synthesized by modifying their C-3 and C-28 positions, respectively, and their structures were well characterized by 1H NMR, 13C NMR, HRMS and melting points. Furthermore, we evaluated the anti-oomycete and anti-fungal activities of these compounds against Phytophthora capsici and Fusarium graminearum in vitro. The results showed that compound 7h exhibited prominent anti-oomycete and anti-fungal activities, and the median effective concentration (EC50) values of 7h against P. capsici and F. graminearum were 70.49 and 113.21 mg/L, respectively. This study suggested that the anti-oomycete and anti-fungal activities of esters synthesized by introducing acyloxy group at C-3 position of UA was more conspicuous than that of esters synthesized by introducing benzyloxy group at C-28 position. This result will pave the way for further modification of UA to develop potential new fungicides.

Sulfonate Derivatives Containing a Kakuol Moiety as Potential Fungicidal Candidates: Design, Synthesis and Antifungal Activity Evaluation

As a part of our continuing exploration to discover new potential promising fungicide candidates, eighteen sulfonate derivatives (3a-3r) containing a kakuol moiety were designed and synthesized. Synthetic sulfonate derivatives were tested comprehensively for antifungal activities against four plant pathogenic fungi (Botrytis (B.) cinerea, Valsa (V.) mali, Fusarium (F.) graminearum, Sclerotinia (S.) sclerotiorum), and their structure activity relationships were summarized. Especially, derivatives 3i and 3j exhibited remarkable activity against V. mali, with the inhibition rates of 99.8 and 100%, which were slightly superior to that of carbendazim (98.9%), a reference fungicide. Moreover, derivatives 3a, 3k and 3q possess the broader antifungal spectrum against three tested plant pathogenic fungi with inhibition rates over 60%. Structure-activity relationship (SAR) analysis indicated that the introduction of 2-F or 3-F into the benzene ring would give rise to a remarkable increase of the antifungal activity against V. mali.

Synthesis of novel 18β-glycyrrhetinic acid sulfonate derivatives displaying significant anti-oomycete activity against Phytophthora capsici

Using 18β-glycyrrhetinic acid (GA) as the lead compound, fourteen GA sulphonate derivatives (3a-n) were prepared by modifying its C-3 OH group, and their structures were well confirmed by 1H NMR, 13C NMR, HRMS and melting points. Moreover, we screened the anti-oomycete activity of these compounds against Phytophthora capsici by using the mycelial growth rate method. Among the fourteen GA sulphonate derivatives evaluated, four compounds 3f, 3j, 3k and 3l exhibited more potent anti-oomycete activity than that of the positive control zoxamide (EC50 = 25.17 mg/L), and had the median effective concentration (EC50) values of 23.04, 16.16, 22.55, and 13.93 mg/L, respectively. Especially compound 3l showed the best anti-oomycete activity against P. capsici with EC50 value of 13.93 mg/L. Overall, the introduction of sulfonyloxy groups at the C-3 position of GA has a significant impact on its anti-oomycete activity, and the corresponding derivative activity varies significantly with different substituents R.

Synthesis, Anti-Oomycete and Anti-fungal Activities of Novel Cinchona Alkaloid Derivatives Containing Sulfonate Moiety

Using cinchona alkaloid as the lead compound, twenty-four cinchona alkaloid sulfonate derivatives (1 a-l, 2 a-c, 3 a-c, 4 a-c, and 5 a-c) were designed and prepared by modifying their C9 position, and structurally confirmed by 1 H-NMR, 13 C-NMR, HR-MS and melting points. Moreover, the stereochemical configurations of compounds 1 f and 1 l were unambiguously confirmed by single-crystal X-ray diffraction. Furthermore, we determined the anti-oomycete and anti-fungal activities of these target compounds against Phytophthora capsici and Fusarium graminearum in vitro. The results showed that two compounds 4 b and 4 c exhibited prominent anti-oomycete activity, and the median effective concentration (EC50 ) values of 4 b and 4 c against P. capsici were 22.55 and 16.32 mg/L, respectively. This study suggested that when the C9 position of cinchona alkaloid sulfonate derivatives is in the S configuration and the 6'-position methoxy group is not present, the anti-oomycete activity is superior. In addition, five compounds 1 e, 1 f, 1 k, 3 c and 4 c displayed significant anti-fungal activity, with EC50 values of 43.64, 45.07, 80.18, 48.58 and 41.88 mg/L against F. graminearum, respectively. This result indicates that only when a specific substituent is introduced into the structural framework of the target compound, the corresponding compound exhibits significant inhibitory activity against fungi.

Methods for Fungicide Efficacy Screenings: Multiwell Testing Procedures for the Oomycetes Phytophthora infestans and Pythium ultimum

Oomycetes-borne diseases represent a serious problem for agriculture sustainability due to the high use of chemical products employed for their control. In recent years, increasing concerns on side effects associated with fungicide utilization have led to the reduction of the permissible modes of action, with the remaining ones continuously threatened by the increase of resistant strains in the pathogen populations. In this context, it is mandatory to develop new generation fungicides characterized by high specificity towards the target species and low environmental impact to guarantee the sustainability, productivity, and quality of food production. Fungicide discovery is a lengthy and costly process, and despite these urgent needs, poor description and formalization of high-throughput methodologies for screening the efficacy of active compounds are commonly reported for these kinds of organisms. In this study, a comprehensive picture of two high-throughput practices for efficient fungicide screening against plant-pathogenic oomycetes has been provided. Different protocols using multiwell plates were validated on approved crop protection products using Phytophthora infestans and Pythium ultimum as the model species. In addition, detailed statistical inputs useful for the analysis of data related to the efficacy of screenings are included.

Synthesis and Structure-Activity Relationship Studies of Novel Aryl Sulfonamides and Their Activity against Human Breast Cancer Cell Lines

A series of structural analogs of aryl sulfonamide hybrid compounds were synthesised and their cytotoxic activity was evaluated against three human breast cancer cell lines (MCF-7, MDA-MB-231 and Hs 578T). The compounds were designed through electronic, hydrophobic and steric modifications using the chemical structure of N-{4-[(2-hydroxy-3-methoxy-5-propylphenyl)sulfamoyl]phenyl}acetamide (referred to as compound 7) as a starting point to then assess a structure-activity relationship (SAR) study. From the data generated, we observed that compounds 9, 10 and 11 (which have modifications in the substituents of the aryl sulfonamide), efficiently reduced the cell viability of MCF-7 and MDA-MB-231 cell cultures. Based on initial data, we selected compounds 10 and 11 for further investigations into their antiproliferative and/or cytotoxic profile against MDA-MB-231 cells, and we noted that compound 10 was the most promising compound in the series. Compound 10 promoted morphological changes and altered the dynamics of cell cycle progression in MDA-MB-231 cells, inducing arrest in G1/S transition. Taken together, these results show that the dihydroeugenol-aryl-sulfonamide hybrid compound 10 (which has an electron withdrawing nitro group) displays promising antiproliferative activity against MDA-MB-231 cell lines.

Synthesis of hinokitiol sulfonate derivatives and their anti-oomycete and nematicidal activities

In order to explore novel natural product-based anti-oomycete and nematicidal agents, sixteen unreported 2-sulfonyloxyhinokitiol derivatives were prepared using the principle of active splicing, and structurally confirmed by proton nuclear magnetic resonance (1H NMR), carbon-13 nuclear magnetic resonance (13C NMR), high-resolution mass spectrometry (HRMS), and melting point. Moreover, we evaluated the title compounds as anti-oomycete and nematicidal agents against two serious agricultural pests of Phytophthora capsici and Meloidogyne incongnita. Among the sixteen hinokitiol esters tested: (1) Compounds 3a and 3m exhibited the most potent anti-oomycete activity compared to zoxamide against P. capsici, and the median effective concentration (EC50) values of 3a, 3m, and zoxamide were 18.64, 21.11, and 23.15 mg/L, respectively; Further studies showed that the existence of seven membered ring and carbonyl group was the necessary condition for the high anti-oomycete activity of hinokitiol. (2) Compounds 3n and 3p exhibited more promising nematicidal activity than hinokitiol, and the median lethal concentration (LC50) values of 3n, 3p and 1 against M. incongnita were 0.2111, 0.2079, and 0.3933 mg/L, respectively. This result will pave the way for further modification of hinokitiol to develop potential new fungicides and nematicides.

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.

Synthesis and Anti-Oomycete Preliminary Mechanism of Sulfonate Derivatives of Ethyl Maltol

To discover novel molecules with unique mechanism against plant pathogenic oomycetes, sixteen new sulfonate derivatives of ethyl maltol (3a-p) were synthesized by structural modification of 2-ethyl-3-hydroxy-4H-pyran-4-one, and their anti-oomycete activity against a serious agricultural disease, Phytophthora capsici Leonian was determined in this study. Among all tested compounds, derivatives 3e, 3m and 3p exhibited the most potent anti-oomycete activity against P. capsici with EC₅₀ values of 19.40, 21.04 and 31.10 mg/L, respectively; especially 3e and 3m showed the best promising and pronounced anti-oomycete activity than zoxamide (EC₅₀ =26.87 mg/L). The results further proved that 4-tert-butylphenylsulfonyl group, 3-nitro-4-chlorophenylsulfonyl group and 8-quinolinesulfonyl group introduced at the hydroxy position of ethyl maltol or maltol were necessary for obtaining the most potent compounds. Further mechanism studies of P. capsici treated with 3e demonstrated that this compound can affect the growth of mycelia by disrupting the integrity of the membrane, and the higher the concentration of the compound is, the greater the degree of membrane integrity damage. These important results will pave the way for further modification of ethyl maltol to develop potential new fungicides.

Synthesis and Anti-Oomycete Activity of Sulfonate Derivatives of Fenjuntong

In order to discover highly active fungicides, sixteen novel sulfonate derivatives of Fenjuntong were synthesized by structural modification of 2'-hydroxybutyrophenone, and their anti-oomycete activity against Phytophthora capsici Leonian was determined in this study. Among all tested compounds, compound 3b displayed more significant anti-oomycete activity than the precursor Fenjuntong against P. capsici, and the EC₅₀ values of 3b and Fenjuntong were 84.50 and 517.25 mg/L, respectively. By comparing the anti-oomycete activity of compounds 3a-p, I-a-p, and II-a-p, the following conclusions were drawn: (1) Hydroxy group is well tolerated, and sulfonylation of hydroxy group enhances its anti-oomycete activity. (2) The proper length of the ketone carbonyl chain is very important for their anti-oomycete activity. (3) The presence of a site methoxy group in the structural skeleton is closely related to the anti-oomycete activity. These important results will pave the way for further modification of Fenjuntong to develop potential new fungicides.