Legumes in combination with other products are the staple food for a large part of the world population, especially the low-income fragment, because their seeds provide valuable amounts of carbohydrates, fiber, and proteins, and have an important composition of essential amino acids, the sulphured amino acids being the limiting ones. Furthermore, legumes also have nonnutritional compounds that may decrease the absorption of nutrients or produce toxic effects; however, it has been reported that depending on the dose, these nonnutritional compounds also have different bioactivities as antioxidant, hypolipidemic, hypoglycemic, and anticarcinogenic agents, which have been proven in scientific studies. It has been observed that in countries with a high consumption of legumes, the incidence of colorectal cancer is lower. Some studies have shown that legume seeds are an alternative chemopreventive therapy against various cancers especially colon; this was verified in various animal models of induced by azoxymethane, a colon specific carcinogenic compound, in which a diet was supplemented with different concentrations of beans, lentils, chickpeas, or soybeans, mostly. These studies have proven the anticancer activity of legumes in early stages of carcinogenesis. Therefore, it is important to review the information available to elucidate the chemopreventive mechanisms of action of legume compounds.

Recently, an increased interest in antioxidant activity and health-improving capacity of cactus pear has been registered. The antioxidant capacity of the pulp of cactus-pear fruits has been previously assessed. In this work, total phenolics, flavonoids and tannins of peel and seeds of four cactus pear cultivars were examined as well as their antioxidant capacity. Tannins were the major phenolics in cactus pear seeds accounting for almost fifty percent for all cultivars. Analysis of variance revealed that ripeness, cultivar, and its interaction had highly significant effect on the total phenolics, tannin, and flavonoid contents of cactus pear peel. With regard to the seeds, only the stage of ripeness and interaction (ripeness stage x cultivar) were significant on total phenolics and tannins contents. The flavonoid content in seeds was not affected by any of the factors or their interactions. The antioxidant capacity was higher in the peel than in the seeds. Generally, fruits with light-green or yellow-brown peel have higher antiradical activity and Trolox equivalent antioxidant capacity (TEAC) values compared with those with red-purple peel. Cactus pear by-products can indeed be exploited as a good and cheap source of natural antioxidants. Recentemente, existe um crescente interesse na atividade antioxidante e na capacidade de melhora da saúde da palma forrageira. A capacidade antioxidante das polpas dos frutos da palma forrageira foi avaliada anteriormente. Neste trabalho, compostos fenólicos, flavonoides e taninos da casca e sementes de quatro cultivares da palma forrageira foram examinados, assim como a sua capacidade antioxidante. Os taninos foram os principais compostos fenólicos nas sementes da palma forrageira, representando quase 50% de todos os cultivares. A análise de variância revelou que a maturação, o cultivar e sua interação tiveram um efeito altamente significativo sobre o conteúdo dos fenóis totais, taninos e flavonoides da pele da palma forrageira. Em sementes, apenas o estágio de maturação e a interação (estágio de maturação x cultivar) foram significativos em fenólicos totais e taninos. O teor de flavonoides de sementes não foi afetado por nenhum dos fatores ou suas interações. A capacidade antioxidante foi maior na pele do que nas sementes. Geralmente, as frutas com casca verde-clara ou amarelo-marrom apresentam maior atividade antirradical e maior valor de capacidade antioxidante equivalente a Trolox (TEAC), quando comparadas com os frutos vermelho-púrpura. De fato, os subprodutos da palma forrageira podem ser explorados como uma fonte boa e barata de antioxidantes naturais