Prenylflavone derivatives from Broussonetia papyrifera, inhibit the growth of breast cancer cells in vitro and in vivo

Two new prenylflavones 5,7,3',4'-tetrahydroxy-3-methoxy-8-geranylflavone (1) and 5,7,3',4'-tetrahydroxy-3-methoxy-8,5'-diprenylflavone (2), as well as four known ones, uralenol (3), papyriflavonol A (4), broussoflavonol B (5) and broussochalcone A (6) were isolated and purified from an ethyl acetate-soluble extract of the barks of Broussonetia papyrifera. Their structures were determined with the spectroscopic methods including HR-EI-MS, 1D and 2D NMR. We found that compounds 2-6 showed potent anti-proliferation effects on ER-positive breast cancer MCF-7 cells in vitro. The IC50 values of compounds 2 and 5 were 4.41 and 4.19 mu M respectively after the treatment of 72 h. We also found that compounds 2 and 5 strongly down-regulated expression concentrations of estrogen receptor-alpha (ER-alpha) and were able to inhibit tumor growth in a xenograft model of the human breast cancer line BCAP-37 in vivo. Our results demonstrated that prenylflavones from B. Papyrifera exhibit potent anti-tumor activity. (C) 2013 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved.