Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing 100193, China.
Biomedicine College, Beijing City University, Beijing 100094, China.
Molecules. 2023 Jun 11;28(12):4697. doi: 10.3390/molecules28124697.
Sweet mogrosides are not only the primary bioactive ingredient in fruits that exhibit anti-tussive properties and expectorate phlegm, but they are also responsible for the fruit's sweetness. Increasing the content or proportion of sweet mogrosides in fruits is significant for improving their quality and industrial production. Post-ripening is an essential step in the post-harvest processing of fruits, but the underlying mechanism and condition of post-ripening on quality improvement need to be studied systematically. Therefore, this study analyzed the mogroside metabolism in fruits under different post-ripening conditions. We further examined the catalytic activity of glycosyltransferase UGT94-289-3 . The results showed that the post-ripening process of fruits could catalyze the glycosylation of bitter-tasting mogroside IIE and III to form sweet mogrosides containing four to six glucose units. After ripening at 35 °C for two weeks, the content of mogroside V changed significantly, with a maximum increase of 80%, while the increase in mogroside VI was over twice its initial amount. Furthermore, under the suitable catalytic condition, UGT94-289-3 could efficiently convert the mogrosides with less than three glucose units into structurally diverse sweet mogrosides, i.e., with mogroside III as the substrate, 95% of it can converted into sweet mogrosides. These findings suggest that controlling the temperature and related catalytic conditions may activate UGT94-289-3 and promote the accumulation of sweet mogrosides. This study provides an effective method for improving the quality of fruits and the accumulation of sweet mogrosides, as well as a new economical, green, and efficient method for producing sweet mogrosides.
甜苷是具有镇咳、祛痰作用的果实中的主要生物活性成分，也是果实具有甜味的原因。增加果实中甜苷的含量或比例，对于提高果实的品质和工业生产具有重要意义。后熟是果实采后处理的重要步骤，但后熟对果实品质改善的内在机制和条件还需要系统研究。因此，本研究分析了不同后熟条件下果实中的甜苷代谢，并进一步研究了糖基转移酶 UGT94-289-3 的催化活性。结果表明，果实的后熟过程可以催化苦味甜苷 IIE 和 III 的糖苷化，形成含有四到六个葡萄糖单元的甜苷。在 35°C 下后熟两周后，甜苷 V 的含量变化显著，最大增加了 80%，而甜苷 VI 的增加超过了初始量的两倍。此外，在适宜的催化条件下，UGT94-289-3 可以有效地将少于三个葡萄糖单元的甜苷转化为结构多样的甜苷，即，以甜苷 III 为底物，95%可以转化为甜苷。这些发现表明，控制温度和相关的催化条件可能会激活 UGT94-289-3，促进甜苷的积累。本研究为提高罗汉果品质和甜苷积累提供了一种有效的方法，也为甜苷的生产提供了一种新的经济、绿色、高效的方法。
