Nishanth Kumar S, Dileep C, Mohandas C, Nambisan Bala, Ca Jayaprakas
Division of Crop Protection/Division of Crop Utilization, Central Tuber Crops Research Institute, Sreekariyam, Thiruvananthapuram, 695017, India.
J Pept Sci. 2014 Mar;20(3):173-85. doi: 10.1002/psc.2594. Epub 2013 Dec 19.
A new microbial cyclic dipeptide (diketopiperazine), cyclo(D-Tyr-D-Phe) was isolated for the first time from the ethyl acetate extract of fermented modified nutrient broth of Bacillus sp. N strain associated with rhabditid Entomopathogenic nematode. Antibacterial activity of the compound was determined by minimum inhibitory concentration and agar disc diffusion method against medically important bacteria and the compound recorded significant antibacterial against test bacteria. Highest activity was recorded against Staphylococcus epidermis (1 µg/ml) followed by Proteus mirabilis (2 µg/ml). The activity of cyclo(D-Tyr-D-Phe) against S. epidermis is better than chloramphenicol, the standard antibiotics. Cyclo(D-Tyr-D-Phe) recorded significant antitumor activity against A549 cells (IC50 value: 10 μM) and this compound recorded no cytotoxicity against factor signaling normal fibroblast cells up to 100 μM. Cyclo(D-Tyr-D-Phe) induced significant morphological changes and DNA fragmentation associated with apoptosis in A549 cells. Acridine orange/ethidium bromide stained cells indicated apoptosis induction by cyclo(D-Tyr-D-Phe). Flow cytometry analysis showed that the cyclo(D-Tyr-D-Phe) did not induce cell cycle arrest. Effector molecule of apoptosis such as caspase-3 was found activated in treated cells, suggesting apoptosis as the main mode of cell death. Antioxidant activity was evaluated by free radical scavenging and reducing power activity, and the compound recorded significant antioxidant activity. The free radical scavenging activity of cyclo(D-Tyr-D-Phe) is almost equal to that of butylated hydroxyanisole, the standard antioxidant agent. We also compared the biological activity of natural cyclo(D-Tyr-D-Phe) with synthetic cyclo(D-Tyr-D-Phe) and cyclo(L-Tyr-L-Phe). Natural and synthetic cyclo(D-Tyr-D-Phe) recorded similar pattern of activity. Although synthetic cyclo(L-Tyr-L-Phe) recorded lower activity. But in the case of reducing power activity, synthetic cyclo(L-Tyr-L-Phe) recorded significant activity than natural and synthetic cyclo(D-Tyr-D-Phe). The results of the present study reveals that cyclo(D-Tyr-D-Phe) is more bioactive than cyclo(L-Tyr-L-Phe). To the best of our knowledge, this is the first time that cyclo(D-Tyr-D-Phe) has been isolated from microbial natural source and also the antibacterial, anticancer, and antioxidant activity of cyclo(D-Tyr-D-Phe) is also reported for the first time.
首次从与小杆目昆虫病原线虫相关的芽孢杆菌属N菌株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环状二肽（二酮哌嗪），环（D-酪氨酸-D-苯丙氨酸）。通过最小抑菌浓度和琼脂平板扩散法测定该化合物对重要医学细菌的抗菌活性，该化合物对受试细菌具有显著的抗菌作用。对表皮葡萄球菌（1微克/毫升）的活性最高，其次是奇异变形杆菌（2微克/毫升）。环（D-酪氨酸-D-苯丙氨酸）对表皮葡萄球菌的活性优于标准抗生素氯霉素。环（D-酪氨酸-D-苯丙氨酸）对A549细胞具有显著的抗肿瘤活性（IC50值：10微摩尔），且该化合物在高达100微摩尔时对正常成纤维细胞的因子信号没有细胞毒性。环（D-酪氨酸-D-苯丙氨酸）在A549细胞中诱导了与凋亡相关的显著形态变化和DNA片段化。吖啶橙/溴化乙锭染色的细胞表明环（D-酪氨酸-D-苯丙氨酸）诱导了凋亡。流式细胞术分析表明环（D-酪氨酸-D-苯丙氨酸）没有诱导细胞周期停滞。在处理过的细胞中发现凋亡效应分子如半胱天冬酶-3被激活，表明凋亡是细胞死亡的主要方式。通过自由基清除和还原能力活性评估抗氧化活性，该化合物具有显著的抗氧化活性。环（D-酪氨酸-D-苯丙氨酸）的自由基清除活性几乎与标准抗氧化剂丁基羟基茴香醚相同。我们还比较了天然环（D-酪氨酸-D-苯丙氨酸）与合成环（D-酪氨酸-D-苯丙氨酸）和环（L-酪氨酸-L-苯丙氨酸）的生物活性。天然和合成的环（D-酪氨酸-D-苯丙氨酸）具有相似的活性模式。虽然合成环（L-酪氨酸-L-苯丙氨酸）的活性较低。但在还原能力活性方面，合成环（L-酪氨酸-L-苯丙氨酸）的活性比天然和合成的环（D-酪氨酸-D-苯丙氨酸）显著。本研究结果表明环（D-酪氨酸-D-苯丙氨酸）比环（L-酪氨酸-L-苯丙氨酸）具有更高的生物活性。据我们所知，这是首次从微生物天然来源中分离出环（D-酪氨酸-D-苯丙氨酸），并且首次报道了环（D-酪氨酸-D-苯丙氨酸）的抗菌、抗癌和抗氧化活性。
