Isolation, structural elucidation, and chemical synthesis of 2-hydroxy-3-octadecyl-5-methoxy-1,4-benzoquinone (irisoquin), a cytotoxic constituent of Iris missouriensis.

As part of a continuing effort to provide novel agents of potential value in cancer chemotherapy, 2-hydroxy-3-octadecyl-5-methoxy-1,4-benzoquinone (irisoquin) was identified as a component of Iris missouriensis. This novel species demonstrated cytotoxic activity with cultured KB and P-388 cells (ED50 = 1.8 and 0.03 microgram/mL, respectively). The structure was assigned on the basis of spectral analyses and The structure was assigned on the basis of spectral analyses and confirmed by chemical synthesis. The latter provides a facile method for the production of irisoquin and structural derivatives that may be of value for the examination of structure-activity relationships. A closely related compound, 3-octadecyl-5-methoxy-1,4-benzoquinone (deoxyirisoquin), was also isolated from Iris missouriensis, prepared synthetically, and found to be devoid of cytotoxic activity.