Medicinal crude drug for reducing blood sugar

The invention relates to a medicinal crude drug for reducing blood sugar. The active component of the crude drug is a compound shown as a formula I, or acid addition salt of the compound such as phosphate or solvate of the compound such as aquo-complex, and the crude drug also comprises optional impurity D and impurity N, wherein, relative to the free alkali of the compound of formula I, the content of the impurity D is less than 0.5%, and the content of the impurity N is less than 0.5%. The invention also relates to a medicine composition prepared by the crude drug, a preparation method for the crude drug and the application of the crude drug. The crude drug can be used for preventing or curing diabetes mellitus II, hyperglycemia, insulin resistance, obesity and high blood pressure as well as complication of the diabetes mellitus II, hyperglycemia, insulin resistance, obesity and high blood pressure.