黄芪茎叶总皂苷提取物的抑菌活性研究

本文采用滤纸片法和倍比稀释法测定黄芪茎叶不同成分对6种供试菌的抑菌圈直径和最小抑菌浓度（minimal inhibitory concentration，MIC），分析了黄芪茎叶资源的抑菌活性，并通过测定大肠杆菌的生长曲线及菌悬液中大分子物质的含量，初步阐述了黄芪茎叶的抑菌机理。结果表明，黄芪茎叶总皂苷对6种供试菌均具有明显的抑菌活性，尤其是对大肠杆菌的MIC值可达12.5 μg/mL；黄芪茎叶总黄酮仅对2种供试菌具有明显抑菌活性，MIC值均为93.8 μg/mL；黄芪茎叶总多糖无抑菌活性。黄芪茎叶皂苷类提取物的加入可严重抑制大肠杆菌的生长，使菌悬液中核酸物质含量增大，表明黄芪茎叶皂苷可通过破坏菌体细胞膜的完整性、致使大分子物质外溢而发挥抑菌作用。本研究为黄芪茎叶作为一种天然防腐剂在食品保鲜与贮藏领域的应用提供了理论依据。
In this study, the antibacterial activity of the stems and leaves of Astragalus membranaceus (denoted as AMSL herein) was explored through testing the inhibition zone diameter and the minimum inhibitory concentration (MIC) of different components on six test bacteria by the filter paper method and double dilution method respectively. Besides, the antibacterial mechanism of AMSL was preliminarily described by measuring the growth curve of Escherichia coli and evaluating the influence of AMSL on the release of macromolecular substances in the suspension. The results showed that the total saponins of AMSL had obvious antibacterial activities against the six test bacteria, especially its effect on Escherichia coli with the MIC value of 12.5 μg/mL. The total flavonoids had significant antibacterial activities against only two test bacteria with the MIC values of 93.8 μg/mL, and the total polysaccharides had no activity. After the extract of AMSL saponins was added to the bacterial suspension, the growth of Escherichia coli was severely inhibited and the content of macromolecules such as nucleic acids in the bacterial suspension increased, indicating that the AMSL exerted bacteriostatic action mainly by destroying the integrity of the cell membrane which caused the macromolecular substances to overflow. This study provides a theoretical basis for the application of AMSL as a natural preservative in the field of food preservation and storage.