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, 1H 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.

A polyacrylamide with capsaicin‐derived monomers (AM–MAA–AMPS–HMBA–SMA; AMAHS) was synthesized and investigated as a novel environment‐friendly polymer inhibitor for Q235 mild steel at 25°C in 1 M HCl solution. The inhibition efficiency was evaluated by weight loss measurements, electrochemical experiments, and surface investigation methods as well as by theoretical calculations. Experimental results indicated that the efficiency of AMAHS was up to 94.86% at the concentration of 2 g/L. Electrochemical tests and surface morphology analysis showed that AMAHS served as a mixed‐type corrosion inhibitor, which could be adsorbed and self‐assembled on the surface of mild steel forming a highly hydrophobic protective film (contact angle of 172°). Density functional theory calculations revealed that heteroatoms in AMAHS, such as O, N, S, are active sites in forming coordination bonds with surface iron atoms. In addition, hydrophobic groups played an important role in protecting the metal surfaces from corrosion media.

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