Current Nutrition & Food Science - Volume 5, Issue 4, 2009

Flavonoids are a large group of ubiquitous molecules synthesized by plants. Recent research has revealed that these molecules possess antioxidant activities which prevent free-radical damage to biological molecules like lipids, proteins and DNA, damage which can cause many cardiovascular and neurodegenerative diseases as well as cancer and diabetes. The underlying mechanisms involve metal chelation, free-radical scavenger capacities and inhibition of freeradical producing enzymes. Structure-activity studies have demonstrated common features of flavonoids that are highly important to their different activities. They include their planar structure; the number and position of their hydroxyl groups as well as the presence of the C2-C3 double bond. Many research groups indicated that flavonoids have shown cardioprotective activity, mainly through inhibition of lipid peroxidation. More recently, flavonoids are proven to be effective as anti-cancer agents, through apoptosis by induction of cell cycle arrest and inhibition of key enzymes involved in tumor promotion. Although discrepancies between in vitro and in vivo studies have been found, the elucidation of the mechanisms involved in flavonoid action will have many health benefits to man.

This review is focussed on an update of the validity of ‘Metabolic programming’. The related concepts of critical windows and thrifty phenotype are also analyzed. The present concept of intrauterine growth restriction (IUGR) with its varied entries is considered not only because of the importance of fetal growth assessment but also for the precision that has been given to the neonatal status assessment. Particularly the perinatal nutrition status is approached for an eventual relationship to late obesity. More recent long term studies from well defined prenatal growth positions are analysed in terms of the mentioned programming hypothesis for later health. Finally it is considered how other circumstances such as certain polymorphisms of different genes are related to the developing of obesity.

Lettuce is a popular leafy vegetable and plays an important role in American diet and nutrition. Crisphead lettuce has much lower nutrient content than leaf and romaine types. As the synthesis or absorption of many nutrients is light dependent, the lower nutritional value of crisphead lettuce is due to the enclosure of its leaves in a head structure. In addition to varietal differences, nutritional quality of lettuce may be influenced by environmental factors such as light, temperature, growing season, cultural practices, fertilizer application, and storage conditions. The moisture content of the plant also affects nutrient concentration. Enhancing the nutritional levels of vegetables would improve the nutrient intake without requiring an increase in consumption. Genotypic variation in germplasm suggests that genetic improvement of nutritional value is feasible in lettuce. However, breeding efforts for nutrition are often hampered by the lack of analytical capabilities in most crop improvement programs. Biotechnology has the potential to markedly increase the nutritional value of lettuce. The commercialization of transgenic lettuce may largely depend on progress in transgene expression, public acceptance, economic and marketing challenges, intellectual property issues, and risk assessment.

Polyphenols are among a wide variety of active photochemicals present in the human diet. Basic researches and epidemiological studies have shown the inverse association between risk of cancer, CVDs, diabetes, several age related chronic diseases and intake of diet rich in polyphenols. Recent researches have opened the possibility of dietary polyphenols to be considered as phytomedicine. Most of the studies on the bioactivity of polyphenols have been conducted on animal models and in in vitro systems, direct studies on humans are few and results inconclusive. The bioavailability and biotransformation of polyphenols in humans needs to be studied. The present review provides an update about dietary polyphenols covering their nature, occurrence, bioavailability, and possible health benefits in relation to human diseases.

In addition to their nutritive value, foods provide health benefits or have a role in disease prevention since they contain a wide range of phytochemicals which represent functional or bioactive components. These bioactive molecules present in foods are based on a variety of chemical structures, from carotenoids, through sterols and fatty acids, to different types of polyphenols. In this review, the polyphenols which are common constituents of vascular plants are explored. They are also common constituents of fruits and vegetables, teas and cocoas. The extractable polyphenols, obtainable by solvent extraction of the forest biomass, are of special interest as they are readily available form different types of forest and wood transformation residues. Flavonoids, cinnamic acid derivatives and proanthocyanidins, which share a part of their biosynthetic pathway with lignins, and therefore are associated with “woody” character of the plants, are reviewed along with some non-flavonoids important as food constituents such as stilbenes and hydrolysable tannins. The foods rich in these polyphenols are reviewed along with the forest sources of the same classes of molecules. The emphasis is put on residues of wood transformation such as bark and knotwood as these materials represent particularly rich resources for bioactive polyphenol classes. One of the most notorious bioactive properties of polyphenols is their antioxidant activity. The most important results on antioxidant capacity of forest trees extracts are presented and compared to those obtained for the extracts from healthy foods rich in polyphenols. These results are discussed also in relation to total phenol content of the studied extracts. Finally, the results on the application of selected types of polyphenols or extracts from forest biomass in prevention and/or treatment of diseases which are related to oxidative stress, cardiovascular disease, Alzheimer and cancer, are presented. It is clear from all discussed results, that the forest biomass in general and the residues of wood transformation in particular, represent the important natural resources of bioactive polyphenols. These residues have a real potential to be used as raw materials for the development of food supplements and/or functional foods which can enhance the animal and human health by disease prevention. They are also applicable for cosmetics and pharmaceutical products development, but their application in disease prevention remains more straightforward.