College of Life Sciences, Sichuan Normal University, Longquan, No. 1819 Chen Long Avenue, Chengdu, 610101, People's Republic of China.
Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, People's Republic of China.
Curr Microbiol. 2021 Apr;78(4):1590-1601. doi: 10.1007/s00284-021-02366-3. Epub 2021 Mar 8.
Docynia indica is used as a plant resource for both medicine and food in minority areas of southwestern China and Southeast of Asia, especially Docynia indica leaves, which are often used as a kind of functional tea in daily life. In our previous research, it has found that D. indica is rich in polyphenols (mainly phlorizin (PHZ)). Although PHZ is the first polyphenolic competitive inhibitor of sodium-dependent glucose transporters (SGLTs) to be discovered, the promotion and application of PHZ are limited due to its extremely low bioavailability. As a kind of aglycons, phloretin (PHT) possesses a better bioavailability and bioactivity than PHZ. Therefore, the conversion of PHZ to PHT in D. indica leaves by the method of biotransformation can be applied to solve the above issue. In this study, Aspergillus niger and Eurotium cristatum were used to transform PHZ to PHT in D. indica. Compared with Aspergillus niger, Eurotium cristatum can cause the equimolar conversion of PHZ to PHT. However, Aspergillus niger resulted in the complete degradation of PHZ. In the process of deep fermentation, PHZ in D. indica leaves was gradually biotransformed into PHT, and its content was as high as ~ 12% after fermentation. With the increase of PHT content, the antioxidant and antibacterial activity of Docynia indica leaves increased. By the acute toxicity evaluation, it was confirmed that Docynia indica leaves and Eurotium cristatum fermented leaves were much safer. These results indicate that Eurotium cristatum fermentation has the ability to transform the functional compounds in Docynia indica leaves and increase the antioxidant and antibacterial activity of Docynia indica, thus making it a substitute for PHT and functional tea.
软枣猕猴桃在我国西南和东南亚少数民族地区既是药用植物资源也是食用植物资源，尤其是软枣猕猴桃叶，在日常生活中常被用作一种功能性茶。在我们之前的研究中发现，软枣猕猴桃富含多酚（主要是根皮苷（PHZ））。虽然 PHZ 是发现的第一种对钠依赖性葡萄糖转运体（SGLTs）具有竞争性抑制作用的多酚，但由于其极低的生物利用度，PHZ 的促进和应用受到限制。作为一种糖苷配基，根皮素（PHT）比 PHZ 具有更好的生物利用度和生物活性。因此，通过生物转化的方法将 PHZ 转化为软枣猕猴桃叶中的 PHT 可用于解决上述问题。在这项研究中，黑曲霉和赤曲霉被用于将 PHZ 转化为软枣猕猴桃中的 PHT。与黑曲霉相比，赤曲霉可以使 PHZ 等摩尔转化为 PHT。然而，黑曲霉导致 PHZ 完全降解。在深层发酵过程中，软枣猕猴桃叶中的 PHZ 逐渐被生物转化为 PHT，发酵后其含量高达约 12%。随着 PHT 含量的增加，软枣猕猴桃叶的抗氧化和抗菌活性也随之增加。通过急性毒性评价，证实软枣猕猴桃叶和赤曲霉发酵叶安全性更高。这些结果表明，赤曲霉发酵具有转化软枣猕猴桃叶中功能化合物并增加软枣猕猴桃抗氧化和抗菌活性的能力，从而使其成为 PHT 和功能性茶的替代品。
