Novel 1,3,4-Oxadiazole Derivatives Containing a Cinnamic Acid Moiety as Potential Bactericide for Rice Bacterial Diseases

• Main Authors: Shaobo Wang, Xiuhai Gan, Yanju Wang, Shaoyuan Li, Chongfen Yi, Jixiang Chen, Fangcheng He, Yuyuan Yang, Deyu Hu, Baoan Song
• Format: Article
• Language: English
• Published: MDPI AG 2019-02-01
• Series: International Journal of Molecular Sciences
• Subjects: 1,3,4-oxadiazole derivatives; cinnamic acid; bacterial diseases; antibacterial activity; 3D-QSAR; real-time quantitative PCR
• Online Access: https://www.mdpi.com/1422-0067/20/5/1020

Rice bacterial leaf blight and leaf streak are two important bacterial diseases of rice, which can result in yield loss. Currently, effective antimicrobials for rice bacterial diseases are still lacking. Thus, to develop highly effective and low-risk bactericides, 31 novel 1,3,4-oxadiazole derivatives containing a cinnamic acid moiety were designed and synthesized. Bioassay results demonstrated that all compounds exhibited good antibacterial activities in vitro. Significantly, compounds <b>5r</b> and <b>5t</b> showed excellent antibacterial activities against <i>Xanthomonas oryzae</i> pv. <i>oryzae</i> (<i>Xoo</i>) and <i>X. oryzae</i> pv. <i>oryzicola</i> (<i>Xoc</i>), with the 50% effective concentration (EC₅₀) values of 0.58 and 0.34, and 0.44 and 0.20 &#956;g/mL, respectively. These compounds were much better than thiodiazole copper (123.10 and 161.52 &#956;g/mL) and bismerthiazol (85.66 and 110.96 &#956;g/mL). Moreover, compound <b>5t</b> had better protective and curative activities against rice bacterial leaf blight and leaf streak than thiodiazole copper and bismerthiazol in vivo. Simultaneously, the in vivo efficacy of the compounds was demonstrated by real-time quantitative PCR to quantify bacterial titers. In addition, a three-dimensional quantitative structure&#8315;activity relationship model was created and presented good predictive ability. This work provides support for 1,3,4-oxadiazole derivatives containing a cinnamic acid moiety as a potential new bactericide for rice bacterial diseases.