Synthesis of amide derivatives containing capsaicin and their antioxidant and antibacterial activities.

The capsaicin in hot peppers is an important biological active substance that is widely used in food and medicine. In this work, six capsaicin derivatives such as N-(4-Hydroxy-3-acetophenone benzyl)acrylamide (A), 2-hydroxy-3-(octyloxy)phenyl-5-acrylamidemethylbenzene phenyl methanone (B), N-(2,5-dihydroxybenzene)acetamide (C), N-(5-acetamidemethyl benzene-2,4-dihydroxybenzene)acetamide (D), 4-acetamideme thylbenzene-2-benzylphenol (E), and N-(2-methyl-4-hydroxy-5-methylthiobenzene)acetamide (F) were synthesized via the Friedel-Crafts (F-C) alkylation reaction and were characterized using IR, 1 H NMR, and HRMS. The antioxidant activity of compounds was evaluated using the reducing power and DPPH radical (DPPH·) scavenging assays, and Vitamin C (Vc) was used as a control. The antibacterial activity was tested using minimum inhibition concentration (MIC) and antibacterial rate assays, and Escherichia coli and Staphylococcus aureus were used as the tested strain. The results showed that all six capsaicin derivatives had certain antioxidant and antibacterial activities, and the activities increased with increasing mass concentration. The best properties were obtained for compounds C and F; the antioxidant activity of compound C was similar to Vc and the MIC of compound F was 0.0313 mg/ml, its antibacterial rate was greater than 99% at 3 mg/ml. PRACTICAL APPLICATIONS: As a vegetable, peppers can be eaten fresh or processed to other forms such as pepper powder or pepper jam, and it is very popular because of its long history, unique flavor, and special functions. Our current study shows that capsaicin derivatives have good antioxidant and antibacterial activities, and therefore, the present study of capsaicin derivatives with good activity provides a good foundation for future applications in natural food additives and medicine.