| The consumption of dry beans has been correlated with the inhibition of several chronic diseases such as cardiovascular disease, type II diabetes mellitus, obesity and cancer. Dry beans contain a variety of phytochemicals (phytic acid, saponins, oligosaccharides, and phenolic compounds) that may confer these health benefits. Phenolic compounds have been shown to possess anti-cancer activity and other health promoting effects. Phenolic compounds in raw common dry beans have been studied, however, beans must be heat-treated (i.e. cooked) before consumption and there is little known about the types and amounts of phenolic compounds found in cooked beans.;Hydroxybenzoic acids and hydroxycinnamic acids were identified in the four cooked dry common beans. The hydroxybenzoic acids found were p-hydroxybenzoic acid, vanillic acid, and syringic acid and total concentrations ranged from 3 to 12 mg per 100 g bean flour. Protocatechuic acid was only identified in black, pinto and red beans. The hydroxycinnamic acids identified were p-coumaric acid, caffeic acid, ferulic acid, and sinapic acid in total concentrations ranging from 11 to 36 mg per 100 g bean flour. Acid hydrolysis of the beans liberated greater quantities of hydroxybenzoic acids while alkaline hydrolysis liberated greater quantities of hydroxycinnamic acids. Only black, pinto, and red beans contained the flavan-3ol (+)-catechin (0.3 to 3 mg per 100 g bean flour) and the flavonols quercetin and kaempferol (7 to 67 mg per 100 g bean flour).;Since dry beans may contain other colon cancer inhibiting compounds in addition to phenolic compounds, cooked navy beans were fractionated into an aqueous-ethanol soluble fraction (navy bean extract mix, NBEM; concentrated in saponins, oligosaccharides, and phenolic compounds) and an aqueous-ethanol insoluble fraction (navy bean residue, NBR; concentrated in fiber and protein) to narrow the search for which components inhibit the development of colon cancer. A control diet and diets containing either cooked navy beans or its fractions were fed to azoxymethane (AOM) injected mildly diabetic, obese mice (ob/ob; B6.V-Lepob/J). This mouse model has not been previously used to evaluate the effect of dietary ingredients on chemically induced colon carcinogenesis.;The ob/ob mouse did not have the desired sensitivity to AOM to be recommended for widespread use to test dietary ingredients for colon tumor inhibiting potential. The low tumor incidence in the control fed animals weakened the statistical power to differentiate colon cancer inhibition potential between the extract (NBEM) and the residue (NBR). Nevertheless, compounds contained in the aqueous-ethanol extract of navy beans (NBEM) reduced tumor incidence by 100% compared to the control diet. Additionally, the inhibition of chemically induced colon carcinogenesis in ob/ob mice fed navy bean and navy bean fractions was accompanied by a downregulation in the expression c-fos in the colonic mucosa. c-Fos is required for normal cell cycle progression and proliferation but is overexpressed in some cancers. The downregulation of c-fos expression in the colon of ob/ob mice fed the navy bean and navy bean fractions may inhibit carcinogenesis by maintaining normal colon crypt cell homeostasis. |
