タイロシンの安定性および抗菌力に及ぼす金属イオンの影響-III : 金属イオンの存在下で起るタイロシンの加熱失活の機作および,その生成物について

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Tylosin, a macrolide class antibiotic, has been reported to be a fairly heat stable substance. In the previous papers1), the antibacterial activity of tylosin was found to be lowered by heating with Fe+++, Al+++ or Sn++ at low acid pH. The present work aimed to elucidate the mechanism of inactivation of tylosin by the action of such metal ions as Fe+++, Al+++ and Sn++ at elevated temperature at low pH, and the identification of a degradation product of tylosin was carried out. Results obtained may be summarized as follows: 1. Inactivation caused by different metal ions ceased at respective constant level after being heated between 15 minutes and 3 hours at 100°C with each 300 ppm of test metal ions (Table 1). 2. With a lower metal concentration, the rate of inactivation of tylosin ran parallel with the increase in concentration, however, beyond a certain limit, the rate of inactivation kept at a constant level. The maximum level of inactivation of tylosin were 60% with Fe+++, 46% with Al+++ and 41% with Sn++, respectively (see Tables 2 and 3). The inactivation of tylosin caused by metal ions depended much upon the pH value of test solution. When the pH value of test solution containing Fe+++ was adjusted to 2.5, there occurred no marked change in the rate of inactivation nevertheless the presence of 1.6 to 100 fold amount of Fe+++ against tylosin in terms of molecular weight (Table 5). The antibacterial activity of an acid degradation product with Fe+++ was found to correspond with that of 0-mycaminosyl tylonolide (O. M. T.), a degradation product of tylosin (Table 6 and Fig. 5). 3. No appreciable change in the antibacterial activity of O. M. T. was noted when it was heated at 100°C for 1 hour in the presence of each 300 ppm of Fe+++, Al+++ or Sn++ (Table 4). 4. The products obtained from tylosin, desmycosin or O. M . T. by heating with equimol amount of Fe+++ in acid condition were found to correspond to O. M. T. by the thin layer chromatography (Figs. 1 and 2). The melting point of this degradation product of tylosin with Fe+++ was found to be 117°C which coincided with that of standard O. M. T., in addition, no appreciable change in the melting point was noted when both of the product and standard O. M. T. were mixed together. The pattern of infrared spectrum of this product was coincident to that of O. M. T. The aforementioned facts might indicate that the product is O. M. T. 5. The mechanism of decreasing in the tylosin activity by heating with such metal ions as Fe+++, Al+++ or Sn++ would be the following; firstly, tylosin will convert into desmycosin by liberating mycarose (at pH less than 5), and secondly, the resultant desmycosin will lose mycinose to convert into O. M. T. by the action of metal ions, especially at pH less than 3.
公益社団法人日本水産学会の論文

タイロシンの安定性および抗菌力に及ぼす金属イオンの影響-III : 金属イオンの存在下で起るタイロシンの加熱失活の機作および,その生成物について

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