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BACKGROUND Tobacco sore shin caused by Rhizoctonia solani Kühn is a major soil‐borne fungal disease of tobacco, gradually causing infected stems to become thin and dry, leading to great losses to Chinaʼs tobacco industry. Fungicides with phloem mobility are needed for application to foliage to effectively control root or vascular system pathogens. In this study, phenazine‐1‐carboxylic acid‐valine conjugate (PCA‐Val) with strong phloem mobility was tested for control of tobacco sore shin. In vitro fungicidal activity, systemicity, and in vivo efficacy of PCA‐Val against R. solani in tobacco seedling were evaluated. RESULTS: In vitro fungicidal activity of PCA‐L‐Val against R. solani was lower than that of PCA or PCA‐D‐Val, but the in vivo protective activity and curative activity of PCA‐L‐Val was the highest among these chemicals tested. The systemicity tests in tobacco seedlings revealed that PCA did not possess phloem mobility, while PCA‐L‐Val and PCA‐D‐Val exhibited strong phloem mobility and could be transported and accumulated in the lower part of the seedling as well as throughout the phloem. In addition, we also found that, just like reported hormone amino acid conjugates, PCA‐L‐Val could be hydrolyzed by tobacco seedlings, to release free PCA. CONCLUSIONS: The current research results indicated that PCA‐L‐Val possess good phloem transport in tobacco and promising in vivo antifungal activity against R. solani, which can be used as a phloem‐mobile fungicide against tobacco sore shin in production practice. [ABSTRACT FROM AUTHOR]

Phenazine-1-carboxylic acid (PCA) as a natural product which has significant inhibition effects against many soil-borne fungal phytopathogens in agricultural application and has been registered in China as the fungicide against rice sheath blight. In order to find new higher fungicidal activities lead compounds and develop new eco-friendly agrochemicals, we introduced substructure piperazines which also have high biological activity into PCA, designed and synthesized a series of phenazine-1-carboxylic piperazine derivatives, and their structures were confirmed by 1H NMR and HRMS. Most compounds exhibited certain in vitro fungicidal activities. In particular, Compounds 5r exhibited the activity against all the tested pathogenic fungi, such as Rhizoctonia solani, Alternaria solani, Fusarium oxysporum, Fusarium graminearum, Pyricularia oryzac Cavgra, with the EC50 value of 24.6μM, 42.9μM, 73.7μM, 73.8μM, 34.2μM, respectively, more potent activities than PCA (33.2μM, 81.5μM, 186.5μM, 176.4μM, 37.3μM). This result provided a highly active lead compound for the further structure optimization design. [ABSTRACT FROM AUTHOR]

BACKGROUND: Conjugating an amino acid onto existing fungicidal parent structures has been demonstrated to be an effective way to endow non‐phloem mobile fungicides with phloem mobility. To alter the systemicity of the fungicide PCA (phenazine‐1‐carboxylic acid), 10 amino acids derivatives of this fungicide were designed and synthesized, and their synthesis, characterization, phloem and xylem mobility in Ricinus communis L, and their fungicidal activity in vitro are described. RESULTS: The systemicity experiments in Ricinus communis system demonstrated that all conjugates exhibited obvious phloem mobility compared with non‐phloem‐mobile PCA, and the introduction of an L‐amino acid to PCA more greatly enhanced the phloem mobility. The five D‐amino acid conjugates exhibited higher xylem mobility than that of PCA and of each corresponding L‐amino acid conjugate. Most conjugates were found to exhibit moderate in vitro fungicidal activities against six pathogenic fungi, which were lower than that of PCA. The results of the bioassay showed fungicidal activities of PCA‐amino acid conjugates associated not only with different amino acids, but also with their conformation. Conjugation with D‐amino acid contributed to the in vitro fungicidal activities of PCA‐amino acid conjugates. CONCLUSIONS: The current research offers a new strategy for enhancing the systemicity of non‐phloem‐mobile fungicides and presents some useful information on the effects of introducing amino acids of different steric configurations on the fungicidal activity, phloem and xylem mobility of the parent fungicide. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Taking natural product phenazine-1-carboxamide (PCN) as a lead compound, a series of novel phenazine-1-carboxylic acid diamide derivatives were designed and synthesised. Their structures were confirmed by 1H-NMR and HRMS. The bioassays showed that some of the target compounds exhibited promising in vitro fungicidal activities, and exhibited excellent and selective herbicidal activities. Particularly, compounds c, h, o and s displayed root length inhibition activities against barnyard grass with the rate of more than 80%. Compound c exhibited the best activity among all the target compounds against barnyard grass stalk length with the IC50 value of 0.158 mmol/L, and compound o exhibited the best and wide spectrum inhibition against barnyard grass root length and rape in both root length and stalk length herbicidal activities with its IC50 values of 0.067, 0.048 and 0.059 mmol/L respectively. The analysis of preliminary Structure-Activity Relationships provides the theoretical basis for further design of phenazine-1-carboxylic acid. [ABSTRACT FROM AUTHOR]

Phenazine-1-carboxylic acid (PCA) is a natural product that has been proven effective against a number of soil-borne fungal phytopathogens and registered for biofungicide against rice sheath blight in China. In order to improve the phloem mobility of phenazine-1-carboxylic acid (PCA), four PCA derivatives were designed and synthesized by conjugating PCA with l -alanine methyl ester, d -alanine methyl ester, l -alanine and d -alanine respectively. In vitro and planta bioassays results showed that conjugates L-PAM and D-PAM exhibited higher fungicidal activities against Rhizoctonia solani Kuhn than PCA while L-PA and D-PA were less active than PCA. The concentration of conjugates in Ricinus communis phloem sap was determined by HPLC. The results showed that only L-PA exhibited phloem mobility among these conjugates, and its concentration in Ricinus communis phloem sap increased with the increase of time (the maximum concentration was 12.69 μM within 5 h). However, the results of pot experiments showed that L-PA and other conjugates didn't exhibited the inhibition for the growth of Rhizoctonia solani Kuhn in the lower leaves after treatment in the upper leaves of rice seedlings. This may be due to the poor plant absorbility for them or their too little amount of accumulation in the lower leaves. [ABSTRACT FROM AUTHOR]

Phenazine-1-carboxylic acid (PCA) as a natural product widely exists in microbial metabolites of Pseudomonads and Streptomycetes and has been registered for the fungicide against rice sheath blight in China. To find higher fungicidal activities compounds and study the effects on fungicidal activities after changing the carboxyl group of PCA, we synthesized a series of PCA derivatives by modifying the carboxyl group of PCA and their structures were confirmed by 1 H NMR and HRMS. Most compounds exhibited significant fungicidal activities in vitro . In particular, compound 6 exhibited inhibition effect against Rhizoctonia solani with EC 50 values of 4.35 mg/L and compound 3b exhibited effect against Fusarium graminearum with EC 50 values of 8.30 mg/L, compared to the positive control PCA with its EC 50 values of 7.88 mg/L ( Rhizoctonia solani ) and 127.28 mg/L ( Fusarium graminearum ), respectively. The results indicated that the carboxyl group of PCA could be modified to be amide group, acylhydrazine group, ester group, methyl, hydroxymethyl, chloromethyl and ether group etc . And appropriate modifications on carboxyl group of PCA were useful to extend the fungicidal scope. [ABSTRACT FROM AUTHOR]

Rice sheath blight caused by Rhizoctonia solani Kühn is a major fungal disease that plagues commercially grown rice. Occurring mainly in leaf sheaths and leaves, the disease leads to great losses in food production. β -amino-butyric acid (BABA) has been demonstrated to activate an induced resistance response and is a potent inducer of broad-spectrum disease resistance in different plant species. In this study, β -amino-butyric acid conjugate of phenazine-1-carboxylic acid (PCA) with prominent induced resistance to rice sheath blight was tested. The in vitro fungicidal activity, as well as in vivo efficacy, systemicity, induced resistance and defense enzyme activity of BABA conjugate of PCA against R. solani in rice seedlings was systematically evaluated. The results indicated that in vitro fungicidal activity of PCA- β -aminobutyric acid (4e) against R. solani was lower than that of PCA, but in vivo curative ability of 4e was the highest among all tested compounds. The systemicity tests in rice seedlings revealed that PCA did not possess phloem mobility, while 4e exhibited moderate phloem mobility but much lower than α -amino-butyric acid conjugate of PCA (4d). In addition, Compound 4e showed the highest induced activity against rice sheath blight. The observed effects of defense enzymes help to explain this high level of induced activity. The current research results indicate that in rice seedlings, BABA conjugate of PCA induce observable resistance to rice sheath blight and exhibit moderate phloem mobility, which could be used as an induced resistance fungicide against rice sheath blight in commercial rice production. The BABA conjugate of PCA might provide a useful example of induced resistance to R. solani. [Display omitted] • β -amino-butyric conjugates of phenazine-1-carboxylic acid (PCA) were designed and synthesized. • PCA- β -amino-butyric acid possess high induced resistance to rice sheath blight. • PCA- β -amino-butyric acid exhibited moderate phloem mobility. • PCA- β -amino-butyric acid retains certain fungicidal activity. [ABSTRACT FROM AUTHOR]

Phenazine-1-carboxylic acid (PCA) is a natural product that has been characterized by special chemical structures, interesting bioactivities and has been registered for fungicide against rice sheath blight in China. Phloem mobility is of great significance to long-distance transport of systemic pesticides in plants. In order to improve the phloem mobility and bioactivities of PCA, seventeen PCA-amino acid ester conjugates were designed and synthesized by conjugating PCA with different amino-acid esters. The conjugates were evaluated for their fungicidal activities against Rhizoctonia solani Kuhn and their phloem mobility was determined by HPLC. Results showed that conjugates a , b , c , d , e , l , m and p (EC 50 values between 5.35 and 18.85 μg/mL) were more active than PCA (25.66 μg/mL). In particular, conjugates l and m exhibited the best fungicidal activities against Rhizoctonia solani Kuhn (EC 50 values of them were 6.47 μg/mL and 5.35 μg/mL respectively). All these conjugates didn’t have phloem mobility. [ABSTRACT FROM AUTHOR]