Xanthomicrol is the main cytotoxic component of Dracocephalum kotschyii and a potential anti-cancer agent Fereshteh Jahaniani, Soltan Ahmed Ebrahimi, Nahid Rahbar-Roshandel, Massoud Mahmoudian * Razi Institute for Drug Research, Iran University of Medical Sciences, Shaheed Hemmat Expressway, P.O. Box 14155-6183, Tehran, Iran Received 22 February 2005; received in revised form 23 April 2005 Available online 9 June 2005 Abstract Spinal-Z, a methanolic mixture of dried powdered seeds of Peganum harmala Linn. and leaf of Dracocephalum kotschyii Boiss. is an Iranian ethno-medical remedy. It has been used for the treatment of various types of cancer for many years. To evaluate the use of Spinal-Z in treatment of cancer, we examined its effects against a panel of malignant cell lines and tumors induced in mice. The in vitro antiproliferative activities of Spinal-Z, the seed extract of P. harmala and the leaf extract of D. kotschyii were deter- mined using the MTT assay. The concentration of the agent required to inhibit cell growth by 50% (IC 50 ) was estimated. In addition, the anti-tumor activities of the remedy and its constituents were investigated. Viability of cells treated with Spinal-Z and its components decreased in a dose dependent manner. Spinal-Z and its components showed cytotoxic effects against all cell lines tested. The leaf extract of D. kotschyii showed a greater preferential cytotoxic effect than the seed extract of P. harmala and Spinal-Z, on all cell lines tested. Harmine showed cytotoxicity against HL60 and K562 cell lines. This could explain the cytotoxic effect of P. harmala on these cells. The leaf extract of D. kotschyii was able to inhibit tumor pro- liferation in mice. The active ingredient in the leaf extract of D. kotschyii appears to be a flavone identified as xanthomicrol. Xant- homicrol was able to inhibit proliferation of a number of malignant cells. The cytotoxic effects of xanthomicrol were more selective towards malignant cells than doxorubicin. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Spinal-Z; Peganum harmala; Dracocephalum kotschyii; Harmine; MTT; Xanthomicrol 1. Introduction Agents that preferentially inhibit proliferation of neo- plastic cells may offer means of developing drugs effec- tive against cancer in human. One of the strategies for finding such agents is screening plant material, especially those which have been reported to have anti-cancer, anti-inflammatory, anti-fungal or anti-bacterial effects (Cordell et al, 1991; Cox and Balick, 1994; Wu et al., 2002). Spinal-Z, is a traditional Iranian anticancer rem- edy (Sobhani et al., 2002). It was used by traditional healers as a plant concoction for the treatment of many forms of cancer in humans. These traditional healers be- lieved that the concoction was especially effective against leukemia and GI tract malignancy. Spinal-Z is an ex- tract consisting of two plants: Peganum harmala Linn. seeds and Dracocephalum kotschyii Boiss leaves (80:20% w/w) (Sobhani et al., 2002). P. harmala, a mem- ber of the family Zygophyllaceae, is a poisonous plant that is native to Iran (Sobhani et al., 2002). Many different pharmacological effects have been attributed to 0031-9422/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.phytochem.2005.04.035 * Corresponding author. Tel.: +98 21 805 8696; fax: +98 21 805 8696/ 8719. E-mail address: masmah99@iums.ac.ir (M. Mahmoudian). www.elsevier.com/locate/phytochem Phytochemistry 66 (2005) 1581–1592 PHYTOCHEMISTRY