Usnic acid, a dibenzofuran, was originally isolated from lichens producing secondary metabolites, and is well known as an antibiotic, but is also endowed with several other interesting properties. Thus, the goal of this paper is the design of new usnic acid derivatives and evaluation of their antimicrobial activity. All newly synthesized compounds possess good antibacterial activity with MIC ranging from 1.02–50.93 × 10–2 mmol mL–1 and MBC from 2.05–70.57 × 10–2 mmol mL–1. The most sensitive bacterial species was Staphylococcus aureus, while Pseudomonas aeruginosa and Escherichia coli were the most resistant among the ATCC strains, and MRSA was the most resistant among all tested bacteria (ATCC and clinical isolates). Their antifungal activity was very strong (MIC = 0.35–7.53 × 10–2 mmol mL–1 and MFC = 0.70–15.05 × 10–2 mmol mL–1) – better than those of reference compounds and usnic acid itself. The most sensitive fungal species was Trichoderma viride, while Penicillium versicolor var. cyclopium appeared to be the most resistant. It should be mentioned that in general most of the compounds showed weaker antibacterial activity, but better antifungal properties than usnic acid itself. The results allow us to conclude that the title compounds are good lead compounds for novel more active antibacterial drugs. On the other hand, these compounds are very promising as antifungals.
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机译：松香酸是一种二苯并呋喃，最初是从产生次生代谢产物的地衣中分离出来的，众所周知，它是一种抗生素，但也具有其他一些有趣的特性。因此，本文的目的是设计新的松萝酸衍生物并评估其抗菌活性。所有新合成的化合物均具有良好的抗菌活性，MIC为1.02–50.93×10 –2 mmol mL –1 ，MBC为2.05–70.57×10 –2 mmol mL –1 。最敏感的细菌是金黄色葡萄球菌，铜绿假单胞菌和大肠杆菌在ATCC菌株中耐药性最高，而MRSA在所有测试细菌（ATCC和临床分离株）中耐药性最高。它们的抗真菌活性非常强（MIC = 0.35–7.53×10 –2 mmol mL –1 和MFC = 0.70–15.05×10 –2 mmol mL –1 ）–优于参考化合物和松萝酸本身。最敏感的真菌物种是木霉，木霉青霉。 p似乎是最有抵抗力的。应该提到的是，一般而言，大多数化合物显示出比松萝酸本身更弱的抗菌活性，但具有更好的抗真菌性能。结果使我们得出结论，标题化合物是新型活性更高的抗菌药物的良好先导化合物。另一方面，这些化合物作为抗真菌剂非常有前景。
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