Department of Microbiology, Natural Products Research Center, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand.
J Food Prot. 2010 Oct;73(10):1907-12. doi: 10.4315/0362-028x-73.10.1907.
Edible natural products, either standardized plant extracts or pure compounds, provide unlimited opportunities as safe new antimicrobial agents. This study investigated the antibacterial properties of ethanolic extract from Rhodomyrtus tomentosa (Ait.) Hassk. leaves against Bacillus cereus. Preliminary screening to evaluate the activities of the extract used a paper disc diffusion method against 65 food isolates. The extract produced large inhibition zones in all isolates, ranging from 10 to 18 mm. The results were confirmed by MIC and MBC (16 to 64 and 32 to 256 μg/ml, respectively). Rhodomyrtone, a purified compound, exhibited MIC and MBC at 0.5 and at 2 to 8 μg/ml, respectively. The antimicrobial activity of the extract on vegetative cells and endospores of a representative B. cereus isolate (MIC=32 μg/ml) was assessed by enumerating viable cells at different time intervals up to 24 h. At 2 MICs and 4 MICs, a reduction in the viability of the bacterial cells and endospores was at least 3 log within 6 to 8 h and 2 h after incubation, respectively. Application of the extract in precooked rice and tuna steak demonstrated that after exposure to 16 MICs and 32 MICs, the numbers of viable cells and endospores in both model systems were reduced by at least 2 log within 12 and 6 h, respectively. Since the extract consistently produced remarkable activity against both cells and endospores, it could be used as an alternative food additive for controlling B. cereus without compromising food safety.
食用天然产物，无论是标准化植物提取物还是纯化合物，都为安全的新型抗菌剂提供了无限的机会。本研究调查了罗地玫瑰（Ait.）哈斯克叶乙醇提取物对蜡状芽孢杆菌的抗菌特性。初步筛选评估提取物活性采用纸片扩散法对 65 种食品分离株进行。提取物在所有分离株中均产生了 10-18mm 的大抑制带。结果通过 MIC 和 MBC（分别为 16-64 和 32-256μg/ml）得到证实。罗地玫瑰酮，一种纯化的化合物，MIC 和 MBC 分别为 0.5 和 2-8μg/ml。通过在不同时间间隔（最长 24 小时）计数活菌来评估提取物对代表性蜡状芽孢杆菌分离株（MIC=32μg/ml）的营养细胞和内生孢子的抗菌活性。在 2MIC 和 4MIC 下，细菌细胞和内生孢子的活力分别在 6-8 小时和 2 小时后降低至少 3 个对数。在预煮米饭和金枪鱼牛排中的提取物应用表明，在暴露于 16MIC 和 32MIC 后，在这两种模型系统中，活细胞和内生孢子的数量在 12 和 6 小时内分别减少至少 2 个对数。由于提取物对细胞和内生孢子均表现出显著的活性，因此它可用作控制蜡状芽孢杆菌的替代食品添加剂，而不会影响食品安全。
