Abstract: The crystal structure of Wangzaozin A was elucidated on the basis of the single-crystal X-ray diffraction analysis. The {X-ray} crystal structure revealed that there were two molecules with a little difference in the bond lengths and bond angles data in least asymmetry unit, and three six-membered rings were in a chair-like conformation, five-membered rings adopted a twist envelope-like conformation in the compound, respectively. The crystal of the compound was in orthorhombic crystal system, space group P2-12-12-1 with accurate lattice constants as follows a=0.664 85(8) nm, b={2.579 6(4) nm}, c={1.047 3(2) nm}, Z=4. The molecules formed extensive networks through the intra-molecular hydrogen bonds O₃-H₃0…O₂, O₃'-H₃0'…O₂' and intermolecular hydrogen bonds O1-H10…O₃, {O1'-H10'…O₃'}, O₂-H₂0…O₄', O₂'-H₂0'…O₄, and arranged along c axis in the crystal. The compound was found to exhibit a significant cytotoxicity against human tumor Bel-7402 and {HO^-8910} cells with (5.32±0.79) and (4.10±1.00) μmol/L in SRB assay, respectively.

Key words: Isodon racemosa(Hemsl) Hara, Wangzaozin A, Diterpenoid Crystal structure, Cytotoxicity