Abstract
In this study, using the botanical active component thiochromanone as the lead compound, a total of 32 new thiochromanone derivatives containing a carboxamide moiety were designed and synthesized and their in vitro antibacterial activities against Xanthomonas oryzae pv. oryzae (Xoo), Xanthomonas oryzae pv. oryzicolaby (Xoc), and Xanthomonas axonopodis pv. citri (Xac) were determined, as well as their in vitro antifungal activities against Botryosphaeria dothidea (B. dothidea), Phomopsis sp., and Botrytis cinerea (B. cinerea). Bioassay results demonstrated that some of the target compounds exhibited moderate to good in vitro antibacterial and antifungal activities. In particular, compound 4e revealed excellent in vitro antibacterial activity against Xoo, Xoc, and Xac, and its EC50 values of 15, 19, and 23 μg/mL, respectively, were superior to those of Bismerthiazol and Thiodiazole copper. Meanwhile, compound 3b revealed moderate in vitro antifungal activity against B. dothidea at 50 μg/mL, and the inhibition rate reached 88%, which was even better than that of Pyrimethanil, however, lower than that of Carbendazim. To the best of our knowledge, this is the first report on the antibacterial and antifungal activities of this series of novel thiochromanone derivatives containing a carboxamide moiety.
Highlights
Plant bacterial and fungal diseases have posed serious threats in agricultural production and in spite of the best control efforts of plant pathologists, continue to contribute to heavy crop losses worldwide each year [1,2]
We reported a series of novel thiochromanone derivatives containing a sulfonyl hydrazone moiety (Figure 1) with moderate to good antibacterial activities against Xanthomonas oryzae pv. oryzae (Xoo), Xanthomonas oryzae pv. oryzicolaby (Xoc), and Xanthomonas axonopodis pv. citri (Xac) [16]
In the 13C NMR spectra for compound 4d, a singlet at 168.30 ppm indicated the presence of C=O in the thiochromanone group; a doublet at 159.79 and 157.41 ppm indicated the presence of C=O; a singlet at 149.88 ppm indicated the presence of C=N in the thiochromanone group
Summary
Plant bacterial and fungal diseases have posed serious threats in agricultural production and in spite of the best control efforts of plant pathologists, continue to contribute to heavy crop losses worldwide each year [1,2]. Thiochromanone, a kind of chromone compound, is an important botanical active component with extensive biological activities, including antiviral [7], antibacterial [8,9], antifungal [8,10,11,12], herbicidal [13,14], and insecticidal [15] activity. Carboxamides, as important nitrogen-containing compounds in organic synthesis, have attracted considerable attention due to their broad range of biological activities, including antiviral [17], antibacterial [18,19], antifungal [20,21,22], herbicidal [23], and insecticidal [24,25] activity. In this study, using the botanical active component thiochromanone as the lead compound, a series of new thiochromanone derivatives containing a carboxamide moiety were designed and synthesized. We determined the in vitro antibacterial activities of the derivatives against Xoo, Xoc, and Xac as well as their in vitro antifungal activities against Botryosphaeria dothidea (B. dothidea), Phomopsis sp., and Botrytis cinerea (B. cinerea)
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