Kumar S Nishanth, Mohandas C, Nambisan Bala, Sreerag R S, Jayaprakas C A
Division of Crop Protection/Division of Crop Utilisation, Central Tuber Crops Research Institute, Sreekariyam, Thiruvananthapuram, 695017, India,
Folia Microbiol (Praha). 2014 May;59(3):197-202. doi: 10.1007/s12223-013-0282-2. Epub 2013 Oct 5.
In continuation of our search for new antimicrobial secondary metabolites from Bacillus cereus associated with rhabditid entomopathogenic nematode, a new microbial diketopiperazine, cyclo(L-Pro-D-Arg), was isolated from the ethyl acetate extract of fermented modified nutrient broth. The chemical structures of the isolated compounds were identified based on their 1D, 2D NMR and high-resolution electrospray ionisation-mass spectroscopy data. Antibacterial activity of the compound was determined by minimum inhibitory concentration and disc diffusion method against medically important bacteria, and the compound was recorded to have significant antibacterial activity against test bacteria. The highest activity was recorded against Klebsiella pneumoniae (1 μg/mL). Cyclo(L-Pro-D-Arg) was recorded to have significant antitumor activity against HeLa cells (IC50 value 50 μg/mL), and this compound was recorded to have no cytotoxicity against normal monkey kidney cells (VERO) up to 100 μg/mL). To the best of our knowledge, this is the first time that cyclo(L-Pro-D-Arg) has been isolated from a microbial natural source.
在我们继续从与小杆科昆虫病原线虫相关的蜡样芽孢杆菌中寻找新的抗菌次生代谢产物的过程中，从发酵改良营养肉汤的乙酸乙酯提取物中分离出一种新的微生物二酮哌嗪，环（L-脯氨酸-D-精氨酸）。根据分离化合物的一维、二维核磁共振和高分辨率电喷雾电离质谱数据确定其化学结构。通过最小抑菌浓度和纸片扩散法测定该化合物对医学上重要细菌的抗菌活性，该化合物对测试细菌具有显著的抗菌活性。对肺炎克雷伯菌的活性最高（1μg/mL）。环（L-脯氨酸-D-精氨酸）对宫颈癌细胞（IC50值为50μg/mL）具有显著的抗肿瘤活性，并且该化合物在高达100μg/mL时对正常猴肾细胞（VERO）无细胞毒性。据我们所知，这是首次从微生物天然来源中分离出环（L-脯氨酸-D-精氨酸）。
