Abstract: The interaction between the chemical components of hypoglycemic effective traditional Chinese medicine and H2O especially the hydrogen bond has been investigated theoretically to discuss the effect of the interaction to medicine molecular geometric structures and properties,because H2O must be involved in the process when the medicine molecules play a role in the body.Gaussian 09 program package was employed to optimize the geometric structures of H2O,effective chemical components in Bidens pilosa  L.(a kind of widely used hypoglycemic effective traditional Chinese medicine) luteolin,okanin,quercitin and 6,7,3′4′-tetrahydroxy auroe and complexes between them and H2O on B3LYP level,and the geometric parameters,dipole moment,charge distribution and the interaction energy were obtained at the same computational level.In addition,the charge distribution was firstly analyzed to know the electronic environment of hydrogen bond,then the geometrical parameters were analyzed to know the characteristic of hydrogen bonds and the interaction energy to know the stability of hydrogen bonds along with the conclusion.It turned out that all the four molecules selected herein can form stable hydrogen bond with H2O,and at the same time the charge distribution and geometrical parameters of medicine molecules changed under the effect of hydrogen bonds,among which the hydrogen bond length of luteolin-H2O is 1.936,Okanin-H2O is 1.805,Quercitin-H2O is 1.827 ,and 6,7,3′4′-tetrahydroxy auroe-H2O is 1.812,and the bond energy values of luteolin and quercitin between H2O are the maximum ones because both the two adjacent hydroxyls of the two medicine molecules are tending to form hydrogen bond with H2O.

Key words: traditional Chinese medicine molecules, hydrogen bond, Bidens pilosa L., quantum chemistry