Antioxidant Phytochemicals: Dietary Phenolics
new theory about mechanism of action

Chronic diseases like diabetes, heart disease, arthritis, cognition diseases and cancer have been linked to "oxidation" of "cellular molecules" such as proteins, lipids and DNA. This is where damaging modified oxygen molecules attach to molecules in cells and cause damage and inflammation. This is why "antioxidants" have received so much media attention because they help to prevent or remove the damaging oxygen molecules from interacting with cellular molecules before they cause damage and lead to disease. Some of the most important antioxidants are phytochemicals, especially the phenolic antioxidants, found in plant foods (e.g grapes, berries,olives,soy), herbs (e.g oregano) and spices (e.g cinnamon,cumin,turmeric).

A new theory has been put forward by nutrition scientists (Professor Shetty and Professor Wahlqvist which will be published in the next issue of APJCN March 2004) about how these dietary phenolic antioxidants may be using an alternate energy producing pathway (pentose phosphate pathway) which also involves an amino acid (proline) to stimulate this antioxidant response. This also means that foods high in protein, containing the amino acid proline and proline precursors (e.g fish, legumes), may help support the phenolic-linked antioxidant response. This is an interesting theory. Until the details about the pathway are worked out, remember to eat a variety of plant foods, to use herbs and spices and where possible to eat fish and legumes.

Preventive management of diseases and phytochemicals: A New Perspective

Kalidas Shetty, PhD, Department of Food Science, University of Massachusetts, Amherst, MA 01003, USA (e-mail: kalidas@foodsci.umass.edu)

In a recent insightful article in APJCN Professor Mark Wahlqvist ( Wahlqvist, M.L. (2002) Asia Pacific J. Clin Nutrition, 2002; 11(S): S759-S762) stated that the combination of immuno-deficiency, inflammatory process and nutritional status that is characteristic of infective and food-borne illness is more evident in chronic diet- and environment-influenced chronic diseases such as diabetes, obesity, cardiovascular disease, cancer, arthritis and neuro-degeneration diseases. These chronic diseases tend to be oxidation-linked and may manifest in communities around the world, irrespective of income. In addressing the challenges of the above diseases, a significant role for dietary phytochemicals is emerging. Phytochemicals are required from a spectrum of diet for at least their antioxidant role, if not for other properties, to protect tissues from activities that manifest themselves into what we call chronic disease. Among the diverse groups of phytochemicals, phenolic antioxidants and antimicrobials from dietary plants are being targeted for designed dietary intervention to manage major oxidation-linked diseases such as diabetes, cardiovascular diseases, arthritis, cognition diseases and cancer. Foods containing phenolic phytochemicals are also being targeted to manage bacterial infections associated with chronic diseases such as peptic ulcer, urinary tract infections, dental caries and food-borne bacterial infections. In our extensive review ("A Model for the Role of Proline-Linked Pentose-Phosphate Pathway in Phenolic Phytochemical Biosynthesis and Mechanism of Action for Human Health and Environmental Applications; A Review" by Kalidas Shetty from University of Massachusetts, Amherst, USA & Mark L. Wahlqvist, Monash University, Melbourne, Australia in APJCN, March/April, 2004) we have offered a novel and an integrated perspective about how dietary phenolic phytochemicals (from fruits, vegetables, beverages, herbs and spices and their products) can have an important role in preventive management of chronic oxidation and infectious diseases. In our model for role of dietary phytochemicals in preventive management of diseases we have focused on how phenolic phytochemicals at the cellular level could counter oxidation-linked biochemical reactions and in particular how an alternative mode of energy metabolism through the use of proline (an amino acid) may be more important for providing energy and reducing equivalents such as NADPH2 (involved as co-factor in anabolic reactions in cells, including antioxidant
response pathway) for stimulating protective antioxidant response. An interesting aspect of our model is that the role of phenolic phytochemicals in preventive management of diseases also integrates a role for easily and readily assimilated sources of protein foods (particularly legume and fish proteins) for improved antioxidant response through the proline-linked metabolism.

From our initial investigations we have specifically proposed that the proline-linked pentose-phosphate pathway may be critical for modulating protective antioxidant response pathways in diverse biological systems, including biochemical and cellular pathways important for human health. The proposed proline-linked pentose-phosphate pathway model provides a mechanism for understanding the mode of action of phenolic phytochemicals and proteins from the diet in modulating antioxidant pathways and provides avenues by which dietary approaches may manage oxidation-linked chronic and infectious diseases. The model also has implications for the development of antimicrobial phenolic phytochemicals against bacterial pathogens in an era of increasing antibiotic resistance and for improved strategies for drug discovery and design. Further this model also has relevance for designing clonal phytochemical profiles of single genetic origin and for improving fungal and yeast-based food bioprocessing for designing functional foods. In terms of environmental challenges the model provides strategies for environmental bioremediation using plant and microbial systems, as well as for improving agricultural and food production systems in harsh environments.

January 2004