[Analysis of dynamic changes of flavonoids and alkaloids during different drying process of Morus alba leaves]

To find out dynamic changes of flavonoids and alkaloids in Morus alba leaves by analyzing influence of different drying method and drying degrees, in order to provide evidence for quality evaluation of Morus alba leaves.

Different drying methods, programmed temperature methods and constant temperature methods were adopted to dry Morus alba leaves samples respectively. Contents of flavonoids and alkaloids were analyzed by HPLC-PDA and LC-TQ/MS respectively.

It's shown obviously that the content of flavonoids were influenced heavily by different drying methods. Methods that suitable for flavonoids were freezing-dried > shade-dried > dried > sun-dried > microwave-dried > infrared-dried; Methods that suitable for alkaloids were freezing-dried > shade-dried > dried > sun-dried > infrared-dried > microwave-dried. The 55 -65 degrees C group was shown to be the lowest in both flavonoids and DNJ while the 85 - 95 degrees C group was shown to be the best for DNJ. For fagomine, the 45 degrees C group was shown to be the lowest concentrations while the 95 - 105 degrees C group was shown to be the highest. Samples with different moisture were shown to be different in content of flavonoids and alkaloids. And samples with 10% moisture contain highest flavonoids while those with 30% - 50% moisture contain lowest flavonoids. Content of DNJ and fagomine raised as moisture decreasing. In addition, the 55 - 65 degrees C group was better than the 95 -105 degrees C one in alkaloids content.

The results provide optimal drying methods and condition for drying Morus alba leaves, and foundations for uncovering biochemical transform of Morus alba leaves.