Zhu Junhui, Lei Zhiying, Tang Yali, Lu Lixin, Qiu Xiaolin, Pan Liao
School of Mechanical Engineering, Jiangnan University, Wuxi, Jiangsu 214122, China.
School of Mechanical Engineering, Jiangnan University, Wuxi, Jiangsu 214122, China; Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment Technology, Jiangnan University, Wuxi, Jiangsu 214122, China.
Int J Biol Macromol. 2025 Mar;292:139276. doi: 10.1016/j.ijbiomac.2024.139276. Epub 2024 Dec 30.
The antioxidant activity of ε-polylysine (EPL) can be enhanced by grafting phenolic compound caffeic acid (CA) onto its amino groups. To enhance the antioxidant activity of EPL, this study synthesized caffeic acid-ε-polylysine conjugate (CA-EPL) by grafting CA onto EPL using carbodiimide coupling reaction. Fourier transform infrared spectroscopy, H nuclear magnetic resonance (NMR) spectroscopy confirmed the successful conjugation of caffeic acid and ε-polylysine. The ultraviolet-visible absorption spectra, grafting ratio, and Zeta potential data indicate that the molar ratio of CA to EPL has a significant impact on the grafting degree and Zeta potential of the conjugates. In particular, the highest grafting degree and the lowest Zeta potential were obtained when the molar ratio of carboxyl groups in CA to amino groups in EPL was 3:1. Furthermore, the antimicrobial and antioxidant activities of the conjugates were evaluated. The results of antimicrobial activity indicate that the conjugate CA-EPL still exhibits excellent antimicrobial properties. The results of antioxidant activity show a significant increase in the antioxidant activity of the conjugate CA-EPL, which was significantly higher than that of free EPL. In addition, the research results on the antimicrobial mechanism show that CA-EPL has a similar antimicrobial mechanism to EPL: by interacting with the bacterial cell membrane, it disrupts the cell membrane, causing leakage of cell contents, ultimately leading to bacterial death. These results indicate that CA-EPL, as a novel dual-functional active substance, has broad prospects in the food and pharmaceutical industries.
通过将酚类化合物咖啡酸（CA）接枝到ε-聚赖氨酸（EPL）的氨基上，可以增强其抗氧化活性。为了提高EPL的抗氧化活性，本研究采用碳二亚胺偶联反应将CA接枝到EPL上，合成了咖啡酸-ε-聚赖氨酸共轭物（CA-EPL）。傅里叶变换红外光谱、氢核磁共振（NMR）光谱证实了咖啡酸与ε-聚赖氨酸的成功共轭。紫外可见吸收光谱、接枝率和Zeta电位数据表明，CA与EPL的摩尔比对共轭物的接枝度和Zeta电位有显著影响。特别是，当CA中的羧基与EPL中的氨基摩尔比为3:1时，接枝度最高，Zeta电位最低。此外，还对接合物的抗菌和抗氧化活性进行了评估。抗菌活性结果表明，共轭物CA-EPL仍具有优异的抗菌性能。抗氧化活性结果表明，共轭物CA-EPL的抗氧化活性显著提高，明显高于游离EPL。此外，抗菌机制的研究结果表明，CA-EPL与EPL具有相似的抗菌机制：通过与细菌细胞膜相互作用，破坏细胞膜，导致细胞内容物泄漏，最终导致细菌死亡。这些结果表明，CA-EPL作为一种新型的双功能活性物质，在食品和制药行业具有广阔的前景。
