The invention relates to a
puerarin monocrystal and a preparation method thereof. The
puerarin monocrystal is named
crystal form A, the CCDC number is 708830, the
crystal structure is asymmetrical, each
crystal cell contains two asymmetrical molecules, i.e. molecule a and molecule b, each of which carries a molecular crystal water, and moreover, the binding sites of the crystal waters are different. The crystal water of the molecule a and a hydroxyl group on a
benzene ring carry out
hydrogen bonding, the crystal water of the molecule b and a
carbonyl group on a flavone mother
nucleus carry out
hydrogen bonding, the
hydroxymethyl group of the glucose of the molecule a is at the position of an equatorial bond and perpendicular to a
ring plane, the
oxygen atom of the
hydroxymethyl group is in a saccharide
ring plane, the
hydroxymethyl group of the glucose of the molecule b is at the position of an axial bond and perpendicular to a
ring plane, the
hydrogen on the rest
pyranose carboatomic ring is an axial bond, the hydroxyl group is positioned at an equatorial bond, and the molecular formulas of the molecule a and the molecule b are the same, i.e. C21H20O9.H2O. The
absolute configuration of the
puerarin monocrystal is an asymmetrical isomer. The
melting point of the puerarin monocrystal is increased, and the
heat stability is remarkably enhanced compared with
powder. The average purity of the puerarin crystal form A reaches 99.8 percent, higher than 99.1 percent of average purity of bulk pharmaceutical chemicals, and the quality is remarkably increased.