Abstract:

In order to validate whether or not frosted mulberry leaves have better quality, the flavonoids of mulberry leaves
were identified by high performance liquid chromatography-mass spectrometry (HPLC-MS), the contents of four main
components, namely chlorogenic acid, rutin, isoquercitrin, and astragalin were simultaneously determined by HPLC and
the content of 1-deoxynojirimycin (DNJ) was assayed by pre-column derivatization HPLC with fluorescence detection.
We investigated dynamic changes in the flavonoid composition and the contents of four individual flavonoids and DNJ in
mulberry leaves across seasons. The results showed that the contents of flavonoids in mulberry leaves were lower in July
and August when temperature was high and reached their maximum in November or October after frost. The DNJ content
of mulberry leaves in July and August reached its maximum and then decreased in September or October with declining
temperature to its minimum after frost. It is concluded that alkaloids may contribute little to the functions of mulberry leaves
in evacuating wind-heat, clearing away lung-heat and moistening dryness. The medicinal components of frosted mulberry
leaves may be associated with flavonoids. This study can provide a theoretical basis for elucidating scientific connotation of
frosted mulberry leaves.

Key words: mulberry leaves, secondary metabolites, high performance liquid chromatography-mass spectrometry(HPLC-MS), frost, dynamic change