Cryptocin和5ʹ-epi-cryptocin的立体构型及抗菌活性

在活性追踪的指导下,从一株落羽杉内生真菌Pezicula neosporulosa SC1337玉米发酵物中分离得到两个tetramic acid类抗菌活性化合物5?-epi-cryptocin (1)和cryptocin (2),通过核磁共振(NMR)谱、质谱分析和X-射线单晶衍射确定了它们的绝对构型。本文首次从同一真菌代谢产物中分离得到这对差向异构体,并报道了化合物1的晶体结构和2的NMR数据。活性测试表明化合物1和2对金黄色葡萄球菌、耐甲氧西林金黄色葡萄球菌有中等强度的抑制活性,MIC均为30 μg/mL;载样量为200 μg时两者对灰巨座壳菌、稻绿核菌和新月弯孢霉的抑菌圈半径均为7.5、5.0和2.0 mm,对意大利青霉和指状青霉均未显示抑菌圈,说明这对差向异构体的5?-位构型差异对其抗菌活性无明显影响。

Absolute configuration and antimicrobial activities of cryptocin and 5ʹ-epi-cryptocin

Under the guidance of bioassay, 5?-epi-cryptocin (1) and cryptocin (2) were isolated from the corn culture of an endophytic Pezicula neosporulosa SC1337 derived from Taxodium distichum. Their absolute configurations were determined by comprehensive spectroscopic analysis including NMR and HRESI-MS, as well as X-ray crystallographic data. Both of these two epimers were first simultaneously obtained from metabolite of the same fungus. Crystallography structure of 1 and the NMR data of 2 were reported for the first time. Both of 1 and 2 showed moderate antibacterial acitivities against Staphylococcus aureus, methicillin-resistant S. aureus and Ralstonia solanacearum with MIC of 30 μg/mL. At the dose of 200 μg per paper disk, these two compounds show the same inhibition zone of 7.5, 5.0 and 2.0 mm respectively against Magnaporthe grisea, Ustilaginoidea virens and Curvularia lunata, but inactive on Penicillium italicum and P. digitatum. The data showed that configuration of C-5? had no significant effect on the antimicrobial activities in these two epimers.