Journal of the Science of Food and Agriculture J Sci Food Agric (in press) DOI: 10.1002/jsfa.2347 MALDI-TOF MS characterization of proanthocyanidins from cranberry fruit (Vaccinium macrocarpon) that inhibit tumor cell growth and matrix metalloproteinase expression in vitro Catherine C Neto, 1∗ Christian G Krueger, 2 Toni L Lamoureaux, 1 Miwako Kondo, 1 Abraham J Vaisberg, 3 Robert AR Hurta, 4 Shannon Curtis, 4 Michael D Matchett, 4 Horace Yeung, 4 Marva I Sweeney 4 and Jess D Reed 2 1 Department of Chemistry and Biochemistry, University of Massachusetts–Dartmouth, North Dartmouth, MA, USA 2 Department of Animal Sciences, University of Wisconsin–Madison, Madison, WI, USA 3 Laboratorios de Investigaci ´ on y Desarrollo de Ciencia y Tecnolog´ ıa y Departamento de Microbiolog´ ıa, Universidad Peruana Cayetano Heredia, Lima, Peru 4 Department of Biology, University of Prince Edward Island, Charlottetown, PEI, Canada Abstract: Proanthocyanidin-rich extracts were prepared by fractionation of the fruit of the North American cranberry (Vaccinium macrocarpon). In vitro growth inhibition assays in eight tumor cell lines showed that selected fractions inhibited the growth of H460 lung tumors, HT-29 colon and K562 leukemia cells at GI 50 values ranging from 20 to 80 μg ml -1 . Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) of one of these fractions found it to be composed of polyflavan-3-ols, which are primarily tetramers through heptamers of epicatechin containing one or two A-type linkages. Whole cranberry extract and the proanthocyanidin fractions were screened for effect on the expression of matrix metalloproteinases in DU 145 prostate carcinoma cells. The expression of MMP-2 and MMP-9 was inhibited in response to whole cranberry extract and to a lesser degree by the proanthocyanidin fractions.  2005 Society of Chemical Industry Keywords: cranberry; proanthocyanidins; anticancer; lung tumors; matrix metalloproteinases INTRODUCTION The North American cranberry (Vaccinium macrocar- pon Ait. Ericaceae) is of growing public interest as a functional food due to a variety of potential health benefits linked to the diverse nature of phytochemi- cals in the fruit. The long-time practice of consuming cranberry juice for the prevention of urinary tract infections has now been linked to the ability of cran- berry proanthocyanidins to inhibit adhesion of E. coli bacteria responsible for these infections. 1 Cranberry antioxidant quality and quantity rank highly among fruit. 2 This is due largely to the content of flavonols, anthocyanins and proanthocyanidins, many of which have been found effective in preventing oxidative pro- cesses including low-density lipoprotein oxidation. 3,4 Cranberry extract also decreased oxidative damage to rat neurons in a stroke model. 5 The anticancer properties of cranberries and the nature of chemopreventive compounds in the fruit have been the subject of recent investigation, since sev- eral groups of phytochemicals plentiful in Vaccinium can be expected to have an impact on cancer-related processes. Cranberry extracts were observed to inhibit proliferation of MCF-7 and MDA-MB-435 breast cancer cells 6,7 but these reports did not identify the active constituents. Using bioassay-guided fractiona- tion, we recently isolated from whole cranberry fruit two phenolic esters of the pentacyclic triterpene ursolic acid, which selectively inhibited the growth of several types of tumor cells in vitro, 8 particularly MCF-7. Cranberry flavonoids may also play a role in chemo- prevention. Flavonoid-rich fractions from Vaccinium species including cranberry inhibited ODC expression while inducing the xenobiotic detoxification enzyme ∗ Correspondence to: Catherine C Neto, Department of Chemistry and Biochemistry, University of Massachusetts–Dartmouth, North Dartmouth, MA, USA E-mail: cneto@umassd.edu Contract/grant sponsor: UMass Dartmouth Cranberry Research Program (Received 24 May 2005; accepted 1 July 2005)  2005 Society of Chemical Industry. J Sci Food Agric 0022–5142/2005/$30.00