Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia.
Institute of Pharmaceutical Sciences, Department of Pharmacognosy, University of Graz, Universitätplatz 4, 8010 Graz, Austria.
Int J Food Microbiol. 2020 Sep 2;328:108664. doi: 10.1016/j.ijfoodmicro.2020.108664. Epub 2020 May 18.
To control Pseudomonas and Shewanella as important psychrotrophic spoilage bacteria in fish meat, we used ethanolic extracts of oregano (Origanum vulgare subsp. vulgare) and nettle (Urtica dioica), with phytochemical characterisation of the extracts and their bioactive compounds. Liquid chromatography coupled with photodiode array detection and electrospray ionisation-mass spectrometry was used for qualitative compositional determination of the extracts. Four main compounds were identified in the oregano extract, with rosmarinic acid the most abundant, followed by three glycosylated phenolics, one of which is reported for the first time in O. vulgare: 4'-O-β-d-glucopyranosyl-3',4'-dihydroxybenzyl-4-hydroxybenzoate. Six main compounds were identified in the nettle extract, as caffeoylmalic acid and five flavonoid glycosides. These oregano and nettle ethanolic extracts showed in-vitro antimicrobial activities against selected Pseudomonas and Shewanella strains in broth and fish meat homogenate when evaluated at two inoculum concentrations. The antimicrobial activities were more pronounced for the nettle extract at the lower inoculum concentration, and for both the Shewanella strains. Growth inhibition in the fish meat homogenate was evaluated at 3.13 mg/mL and 1.56 mg/mL at 5 °C. Again, the nettle extract showed greater antimicrobial activity, which was seen as the lowest maximum growth rate, followed by the oregano extract, which was inhibitory only at 3.13 mg/mL. Finally, the extracts were applied to fish meat that was then stored at 5 °C for 9 days. Evaluation here was for the counts of the mesophilic, psychrotrophic, Pseudomonas and HS producers. These confirmed the better antimicrobial effects of the nettle extract, especially against the HS-producing bacteria, which included Shewanella. Both of the extracts were rich in glycosides of flavonoids and phenolic acids. The enzymatic activities of the Pseudomonas and Shewanella spoilage bacteria and their actions on the phenolic glycosides from natural sources will be further investigated.
为了控制鱼类肌肉中重要的嗜冷腐败菌假单胞菌和希瓦氏菌，我们使用了牛至（Origanum vulgare subsp. vulgare）和荨麻（Urtica dioica）的乙醇提取物，并对提取物及其生物活性化合物进行了植物化学特性分析。采用液相色谱-光电二极管阵列检测-电喷雾电离-质谱联用技术对提取物进行定性成分测定。在牛至提取物中鉴定出 4 种主要化合物，其中迷迭香酸含量最丰富，其次是 3 种糖基化酚类化合物，其中 1 种在牛至中首次报道：4'-O-β-d-吡喃葡萄糖基-3'，4'-二羟基苯甲基-4-羟基苯甲酸酯。在荨麻提取物中鉴定出 6 种主要化合物，如咖啡酰柠檬酸和 5 种类黄酮糖苷。当在两种接种浓度下评估时，这两种牛至和荨麻乙醇提取物在肉汤和鱼肉匀浆中对选定的假单胞菌和希瓦氏菌菌株表现出体外抗菌活性。在较低的接种浓度下，荨麻提取物的抗菌活性更为明显，对两种希瓦氏菌菌株也是如此。在 5°C 时，在鱼肉匀浆中评估了 3.13 mg/mL 和 1.56 mg/mL 的生长抑制。同样，荨麻提取物表现出更强的抗菌活性，其最大生长速率最低，其次是牛至提取物，仅在 3.13 mg/mL 时具有抑制作用。最后，将提取物应用于鱼肉中，然后在 5°C 下储存 9 天。在此评估中，计数了嗜温菌、嗜冷菌、假单胞菌和 HS 产生菌。这证实了荨麻提取物的更好的抗菌效果，特别是对包括希瓦氏菌在内的 HS 产生菌。这两种提取物都富含类黄酮和酚酸的糖苷。还将进一步研究腐败菌假单胞菌和希瓦氏菌的酶活性及其对天然来源的酚糖苷的作用。
