Phytochemicals and cancer

Abstract

Epidemiological studies showing a protective effect of diets rich in fruits and vegetables against cancer have focused attention on the possibility that biologically-active plant secondary metabolites exert anti-carcinogenic activity. This huge group of compounds, now collectively termed 'phytochemicals', provides much of the flavour and colour of edible plants and the beverages derived from them. Many of these compounds also exert anti-carcinogenic effects in animal models of cancer, and much progress has been made in defining their many biological activities at the molecular level. Such mechanisms include the detoxification and enhanced excretion of carcinogens, the suppression of inflammatory processes such as cyclooxygenase-2 expression, inhibition of mitosis and the induction of apoptosis at various stages in the progression and promotion of cancer. However, much of the research on phytochemicals has been conducted in vitro, with little regard to the bioavailability and metabolism of the compounds studied. Many phytochemicals present in plant foods are poorly absorbed by human subjects, and this fraction usually undergoes metabolism and rapid excretion. Some compounds that do exert anti-carcinogenic effects at realistic doses may contribute to the putative benefits of plant foods such as berries, brassica vegetables and tea, but further research with human subjects is required to fully confirm and quantify such benefits. Chemoprevention using pharmacological doses of isolated compounds, or the development of 'customised' vegetables, may prove valuable but such strategies require a full risk-benefit analysis based on a thorough understanding of the long-term biological effects of what are often surprisingly active compounds.Phytochemicals: Anti-carcinogenic activity: Molecular effects: Chemoprevention A review by the author and colleagues was published in 1994 (Johnson et al. 1994) that explored the potential anticarcinogenic effects of a range of biologically-active secondary plant metabolites commonly present in human diets, and tentatively considered whether such compounds, now commonly referred to collectively as 'phytochemicals', might usefully be regarded as a new class of micronutrients. The interest in these compounds was stimulated partly by the work of pioneers in this field such as Wattenberg (1975a,b), who first demonstrated the principles of chemoprevention by plant constituents in animal models, and partly by the wealth of epidemiological evidence then emerging for protective effects of diets rich in fruits and vegetables against a variety of cancers (Block et al. 1992). A great deal of new evidence has become available in the last decade, and awareness of the importance of plant foods in the prevention of chronic disease in general has grown apace (Daviglus et al. 2005;Houston et al. 2005;He et al. 2006). The aim of the present paper is to review some important aspects of emerging knowledge about the anti-carcinogenic effects of plant secondary metabolites at the cellular and molecular levels,...

Plant secondary metabolites and gut health: the case for phenolic acids

“…Over 25 000 terpenoids have been identified (6) and they are classified according to the degree of isoprene incorporation, i.e. hemiterpenes (C5), monoterpenes (C5) 2 , sesquiterpenes (C5) 3 , diterpenes (C5) 4 , sesterpenes (C5) 5 , triterpenes (C5) 6 through to higher polymers such as rubber (> 100). In addition to being biosynthesised as part of plants' host defence, flowers emit terpenes to attract pollinating insects (12) .…”

Antioxidant Activity of <i>Moringa oleifera</i> Extracts

“…Free radical reactions take place in the human body and food systems can causing injury and death [1]. Free radicals are one of the main factors which necessary to cause DNA mutation, which is involve in the initiation stage of carcinogenesis [2]. Reactive Oxygen Species (ROS) are constantly produced in human body by normal metabolic system.…”

Dietary Habits Contributing to Breast Cancer Risk Among Iranian Women

“…Some studies reported the no significant associations between vegetable or fruit intake and breast cancer risk (Van Gils et al, 2005, Jung et al, 2013, but others revealed a reduction in risk of breast cancer by high intake of fruits, vegetable (Sangrajrang et al, 2013)and fruits and vegetables combined (Aune et al, 2012) especially among women who were low or most physically active (Kruk, 2014). It has been suggested that phytochemicals in vegetables could decrease the level of cyclin E (Nguyen et al, 2008) and nuclear factor-kappaB (Johnson, 2007;Ahmad A et al, 2011) and consequently, reduce the risk of developing breast cancer.…”