Synthesis and Quantum Chemical Calculation of Benzamide Derivatives Containing Capsaicin and Their Bacteriostatic and Antifouling Properties

Thirteen benzamide derivatives containing capsaicin (BDCCs) have been successfully synthesized via the current method (Friedel-Crafts alkylation reaction). The resultant monomers were characterized by IR, H-1 and C-13 NMR, elemental analysis and HRMS. Characterization results were in agreement with the proposed structures of the products. Quantum chemistry calculation yielded three parameters, namely, Delta epsilon(L-H), HF values (total energy) and dipole that could explain activity, stability and polarity respectively, and the relationship of each parameter with antimicrobial and antifouling performance was also preliminary discussed. The bacteriostatic property of the 13 compounds was evaluated by minimum inhibitory concentration (MIC) and bacteriostatic ring tests. Experimental results indicated that these compounds can inhibit Staphylococcus aureus and Escherichia coli. The antifouling effectiveness of the novel antifoulants was investigated using panel tests at the eighth harbor, Qingdao. Four-month exposure results were compared. The compounds exhibited better antifouling properties than the blank panel without antifouling coating or the panel with a common coating. However, test panels with the antifouling coatings were covered with trace amounts of algae and Balanus because of weakening of antifouling ability over extended periods of time. All results demonstrate that the new compounds synthesized via our method can be applied in environment-friendly antifouling paints.