The roots and rhizomes of the plants belonging to the genus Valeriana (Valerianaceae), esecially V. officinalis, are widely used as sedatives in phytomedicine. In herbal supplements containing Valeriana, iridoids are known to be the active ingredients,1 but it was recently reported that some iridoids also show cytotoxic activity.2 Recently, the cell migration is recognized as one of the key targets for the discovery and development of new and effective anticancer drugs.3 In our search for cell migration inhibitors from Sonoran desert plants and their associated microorganisms, a crude extract of V. sorbifolia exhibited cell migration inhibitory activity. Bioassay-guided fractionation of this extract resulted in nine dien-iridoids some of which showed inhibition of metastatic prostate cancer (PC-3M) cell migration at sub-cytotoxic concentrations of which four were shown to be new natural products by physico-chemical methods. It is possible that the cell migration inhibitory activity of some of the dien-iridoids encountered may be related to their cytotoxicity as dien-iridoids were found to be more cytotoxic than their monoen- and saturated analogs.

1.Tang, Y.; Liu, X.; Yu, B. J. Nat. Prod. 2002, 65, 1949-1952.

2.Fukuyama, Y.; Minoshima, Y.; Kishimoto, Y.; Chen, I.-S.; Takahashi, H.; Esumi, T. J. Nat. Prod. 2004, 67, 1833-1838.

3.Fenteany, G.; Zhu, S. Curr. Top. Med. Chem. 2003, 3, 593-616.