Bioactive components isolated from composted agricultural biomasses have been receiving progressive attention, because they may improve the antibiotic susceptibility of drug resistant bacterial strains. Here, three different humic substances (HS) were isolated from composted artichoke (HS-CYN) and pepper (HS-PEP) wastes, and from coffee grounds (HS-COF), and characterized by infrared spectrometry, NMR spectroscopy, thermochemolysis–GC/MS, and high-performance size-exclusion chromatography. The antibacterial activity of HS was evaluated against some pathogenic bacterial strains, while their bioactivity was determined by a germination assay on basil (Red–Violet variety) seeds. HS-CYN and HS-PEP exhibited the largest antioxidant activity and most significant antimicrobial capacity against some gram-positive bacterial strains, such as Staphylococcus aureus and Enterococcus faecalis. The same HS determined a significant increase of both root and epicotyls in seed germination experiments. The bioactivity of HS was related not only to their specific molecular composition but also to the conformational stability of their suprastructures. Specifically, the greatest bioactive and antimicrobial properties were related to the largest abundance of hydrophobic aromatic and phenolic components and to a more rigid conformational arrangement, that, in turn, appeared to be related to a small fragmentation degree of lignin structures. Our results showed that extraction of bioactive HS from green composts may be a sustainable and eco-compatible way to valorise agricultural byproducts. HS may be indeed exploited as substrates to produce novel materials not only to improve plant productivity but also for medical applications.

中文翻译：

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堆肥农业生物质腐殖质的抗菌和抗氧化特性

从堆肥的农业生物质中分离出的生物活性成分已经受到越来越多的关注，因为它们可以提高耐药菌株的抗生素敏感性。在这里，从堆肥洋蓟 (HS-CYN) 和胡椒 (HS-PEP) 废物以及咖啡渣 (HS-COF) 中分离出三种不同的腐殖质 (HS)，并通过红外光谱、核磁共振光谱、热化学分解-GC 对其进行了表征/MS 和高性能尺寸排阻色谱。HS 对一些致病菌株的抗菌活性进行了评估，而它们的生物活性是通过对罗勒（红紫罗兰品种）种子的发芽测定来确定的。HS-CYN 和 HS-PEP 对一些革兰氏阳性菌株表现出最大的抗氧化活性和最显着的抗菌能力，如金黄色葡萄球菌和粪肠球菌。相同的 HS 确定了种子萌发实验中根和上胚轴的显着增加。HS的生物活性不仅与其特定的分子组成有关，还与其超结构的构象稳定性有关。具体而言，最大的生物活性和抗微生物特性与最大丰度的疏水芳香族和酚类成分以及更刚性的构象排列有关，而这又似乎与木质素结构的小碎裂程度有关。我们的研究结果表明，从绿色堆肥中提取生物活性 HS 可能是一种可持续和生态兼容的方式来评估农业副产品的价值。