Novel Fluorinated 7-Hydroxycoumarin Derivatives Containing an Oxime Ether Moiety: Design, Synthesis, Crystal Structure and Biological Evaluation
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Abstract:
A series of fluorinated 7-hydroxycoumarin derivatives containing an oxime ether moiety have been designed, synthesized and evaluated for their antifungal activity. All the target compounds were determined by 1H-NMR, 13C-NMR, FTIR and HR-MS spectra. The single-crystal structures of compounds 4e, 4h, 5h and 6c were further confirmed using X-ray diffraction. The antifungal activities against Botrytis cinerea (B. cinerea), Alternariasolani (A. solani), Gibberella zeae (G. zeae), Rhizoctorzia solani (R. solani), Colletotrichum orbiculare (C. orbiculare) and Alternaria alternata (A. alternata) were evaluated in vitro. The preliminary bioassays showed that some of the designed compounds displayed the promising antifungal activities against the above tested fungi. Strikingly, the target compounds 5f and 6h exhibited outstanding antifungal activity against B. cinerea at 100 μg/mL, with the corresponding inhibition rates reached 90.1 and 85.0%, which were better than the positive control Osthole (83.6%) and Azoxystrobin (46.5%). The compound 5f was identified as the promising fungicide candidate against B. cinerea with the EC50 values of 5.75 μg/mL, which was obviously better than Osthole (33.20 μg/mL) and Azoxystrobin (64.95 μg/mL). Meanwhile, the compound 5f showed remarkable antifungal activities against R. solani with the EC50 values of 28.96 μg/mL, which was better than Osthole (67.18 μg/mL) and equivalent to Azoxystrobin (21.34 μg/mL). The results provide a significant foundation for the search of novel fluorinated 7-hydroxycoumarin derivatives with good antifungal activity.Keywords:
Alternaria solani
Moiety
EC50
Controlled release (CR) formulations of azoxystrobin (Methyl (E)-2-{2[6-(2-cyanophenoxy) pyrimidin-4-yloxy] phenyl}-3-methoxyacrylate) were prepared using amphiphilic polymers synthesized from PEG and aliphatic mono acids, di acids and aromatic di acid employing encapsulation technique. Antifungal activity of azoxystrobin was carried out against Rhizoctonia solani. Seven CR formulations and commercial formulation of azoxystrobin (25 SC) were screened for their fungicidal activities against R. solani by the poisoned food technique and under field conditions. Most of the developed CR formulations recorded higher efficacy over commercial formulation and controlled the disease infestation. The % inhibition ranged from 55.4–86.0% against Rhizoctonia solani and resulted in a significant reduction of sheath blight.
Rhizoctonia
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Sheath blight
Rhizoctonia
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بیماری لکه موجی یکی از بیماری‌های مهم و رایج بوده که در اکثر گیاهان زراعی و بخصوص خانواده‌ی Solanaceae ایجاد بیماری مینماید. هم اکنون در ایران این بیماری مزارع سیب زمینی را به طور همهگیر تهدید مینماید. در بررسی‌های آزمایشگاهی تاثیر قارچ‌کش‌های ایپرودیون، کلروتالونیل و مانکوزب در غلظت یک پیپی‌ام، در مقایــسه با تری فلوکسی استروبین در غلظت‌های 1 ،2 ،5 و 10 پیپی‌ام روی محیط کشت‌های جامد مختلف شامل PDA و CMA روی دو گونه‌ی Alternaria alternata (Fries) Keissler.و Alternaria solani (Ell. and Mart.) Jones and Grout. مورد بررسی قرار گرفت. نتایج نشان داد که همه‌ی قارچ‌کش‌های مورد آزمون در بازدارندگی این دو گونه موثر و تفاوت‌هایی از نظر میزان سرعت رشد پرگنه دارند. در مرحله‌ی بعدی مقایسه‌ی قارچکش تری فلوکسی استروبین در غلظت‌های 1، 2، 5، 10، 20، 50، 100، 200، 500 و 1000 پی پی‌ام روی دو گونه‌ی مذکور نیز نشان داد که غلظت‌های این قارچکش قادر به بازدارندگی این دو گونه در سطح آزمایشگاه هستند، به طوری که با افزایش غلظت قارچکش، سرعت رشد پرگنه‌ی گونه‌ها کاهش قابل توجهی یافت. بیشترین میزان بازدارندگی در قارچکش تری فلوکسی استروبین با غلظت‌های500 و 1000 پیپی‌ام و کم‌ترین اثر بازدارندگی در تری فلوکسی استروبین با غلظت یک پیپی‌ام مشاهده شد. بررسی تاثیر قارچ‌کش‌های فوق بر میزان اسپورزایی گونه‌ی A. alternata نشان داد که با افزایش غلظت قارچکش میزان اسپورزایی کاهش می‌یابد و بالاترین میزان اسپورزایی در تیمار با قارچکش مانکوزب و کم‌ترین آن در قارچکش تری فلوکسی استروبین با غلظت 1000 پیپی‌ام بود. شاخص‌های رشدی، شامل وزن‌تر و خشک میسلیوم در محیط مایع زاپکس تحت تاثیر قارچکش قرار گرفته و بیشترین وزن تر میسلیوم در تیمار قارچکش مانکوزب و کم‌ترین آن در تیمار تری فلوکسی استروبین با غلظت 1000 پی پی‌ام مشاهده شد.
Alternaria solani
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A total of 740 Mycosphaerella graminicola strains were isolated between 2000 and 2002 from winter wheat F1 or F2 leaves showing Septoria leaf blotch lesions (SLB) collected mainly at the soft dough stage in fungicide trials, analysing at 12 locations in Belgium the possibilities and risks associated with the use of epoxiconazole and azoxystrobin at various doses, mixtures and application dates. Fungicide sensitivity tests were performed in microtitre plates on potato dextrose broth amended with various concentrations of azoxystrobin. A wide range of sensitivity to azoxystrobin was observed, with EC50 values ranging for 735 strains between 0.002 to 0.7 microg/ml, the highest frequency gradually shifting from EC50 classes 0.01 and 0.02 microg/ml azoxystrobin in 2000 to EC50 classes 0.02 and 0.04 microg/ml in 2002. No clear selection effect of particular fungicide use strategies was observed. Among the 382 strains isolated in 2002, five originating from 2 locations, showed azoxystrobin EC50 values >1 microg/ml. On medium amended with 100 microg/ml salicylhydroxamic acid (SHAM), 58% of the 2002 strains were strongly inhibited, which affected adequate azoxystrobin ED50 determination. This suggests widespread occurrence of M. graminicola strains relying in vitro on the alternative respiration pathway. In the presence of SHAM, strains 339 and 880 showed azoxystrobin EC50 values of 3 and >30 microg/ml, respectively. This high level of resistance to a QoI fungicide was confirmed by analysing mycelium growth inhibition on PDA. Cross-resistance to trifloxystrobin and kresoxim-methyl was demonstrated. Greenhouse assays on wheat plants revealed that control of QoI resistant strains by azoxystrobin is decreased, compared to control of sensitive ones. This highlights the risk of resistance to QoI fungicides also in M. graminicola populations, although up to now no decrease in field performance was noticed. It is recommended to delay build up of QoI resistance by an integrated approach, combining optimised fungicide use with the choice of SLB resistant cultivars and the application of farming practices promoting stubbles break down and so the reduction of the teleomorph stage.
EC50
Strobilurin
Mycosphaerella graminicola
Salicylhydroxamic acid
Graminicola
Tebuconazole
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Alternaria solani
EC50
Botrytis
Fusarium solani
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Azoxystrobin is a common fungicide used by farmers of Solanaceous crops against Alternaria solani, but there was growing concern about decreased sensitivity with repeated applications. In 2002 and 2003, monitoring of A. solani from commercial potato fields in Wisconsin indicated increased frequency and a statewide distribution of isolates with decreased in vitro sensitivity to azoxystrobin. Mean effective concentration in inhibiting spore germination by 50% values gathered in 2002 and 2003 were approximately 20-fold higher than baseline isolates of A. solani collected in 1998 from fields that had never been treated with azoxystrobin. This sensitivity decrease was correlated with site-specific mutations in the cytochrome b detected by quantitative real-time polymerase chain reaction. The F129L and the G143A substitution have been shown to cause a reduction in sensitivity or resistance, respectively, to quinone outside inhibitors. All of the recovered A. solani isolates collected in 2002 and 2003 were wild type at position 143. However, all three mutations responsible for the F129L substitution (TTA, CTC, and TTG) were detected in our samples. In addition, the frequency of this amino acid substitution in A. solani isolates was statistically different across sampling sites and years, indicating that sensitivity changes depended on specific disease management practices.
Alternaria solani
Spore germination
Strobilurin
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Toxicity measurement of 6 fungicides on Rhizoctonia solani was studied by measuring growth rate of pathogen in vitro.The results showed that all of the 6 fungicides inhibited the growth of R.solani.Among them,Tolclofos methyl showed the best,EC50 was 0.042 mg/kg.Then was Carbendazim,EC50 was 0.044 mg/kg.A significant positive correlation was found between the fungicide concentration and inhibition.
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Growth inhibition
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Sundravadana, S., Alice, D., Kuttalam, S., and Sami yappan, R. 2007. Azoxystrobin activity on Rhizoctonia solani and its efficacy against rice sheath blight. Tunis ian Journal of Plant Protection 2: 79-84. Sheath blight, caused by Rhizoctonia solani is one of the major diseases affecting rice crop. We investigated the effect of azoxystrobin on R. solani growth (in vitro) and its efficacy against rice she ath blight, under field conditions. The results reveale d that azoxystrobin at 1, 2, and 4 ppm, completely inhibited mycelial growth of R. solani. Field study showed that foliar spray of azoxystrob in at 125, 250, and 500 g/ha significantly suppressed (> 64%) the d evelopment of sheath blight and enhanced yield leve l (> 60%). For controlling sheath blight disease, the optimum rate of azoxystrobin was 125 g/ha. Our results showed also that there was no residue in ri ce matrices at harvest time and no phytotoxicity at the highest concentration of azoxystrobin (500 g/ha).
Sheath blight
Rhizoctonia
Phytotoxicity
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Root rot
Fusarium solani
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The indoor toxicity of eight fungicides on Alternaria alternata was tested by the growth rate method.The results showed that the eight fungicides had different levels inhibitory effect on the growth of pathogen mycelium of Alternaria alternata under experimental levels,in which the 10% of difenoconazole WP was the best effect with 7.45 μg/ mL of EC50;the 15% of hymexazol WP and 25% of prochlora EC were followed,whose the EC50 were 16.26 μg/mL and 23.57 μg/mL,respectively;the 80% of chlorothalonil WP was the worst with 111.71μg/mL of EC50.
EC50
Chlorothalonil
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