Phytochemicals, biological effects

Agerbirk N, Vos M, Kim JH, Jander G (2009) Indole glucosinolate breakdown and its biological effects. Phytochem Rev 8 101-120... 

Many bioactive phytochemicals were systematically studied after their fractionation and characterization from many vegetables and fruits. New biological effects such as the differentiation-inducing activity of carotenoids— particularly vitamin A—were described in the 1930s. In addition, several experimental results suggested that various carotenoids might serve as dietary chemopreventive agents [6] because of their ability to quench excited molecules and excess radicals. 

Examples of phytochemicals and their biological effects include isothiocyanates and sulforaphane which are found in vegetables such as broccoli and have been shown to trigger enzyme systems that block or suppress cellular DNA damage and reduce tumor size in animal studies (4) Allylic sulfides, found in onions and garlic, can enhance immune function, increase the production of enzymes that help to excrete carcinogens, decrease the proliferation of tumor cells, and reduce serum cholesterol levels (5). Isoflavonoids in soy have also been shown to reduce serum cholesterol levels in humans (6). 

Before considering the bioavailability of phytochemicals in a food matrix and relating these to biological effects in humans, it is important and necessary to understand that phytochemicals are mostly minor plant constituents whose concentration varies considerably according to, for example, seasonal and agronomic factors, the variety, age, and part of the plant examined. Such variability can lead to serious problems of interpretation of results from epidemiologal studies or human intervention trials if the dose of the phytochemical applied is not determined. 

In summary, pine nut shows promise in lowering cholesterol and therefore risk for CVD. The research is at times contradictory and sometimes shows detrimental effects. This is possibly due to the use of animal models that are inherently and sometimes unknowingly limited in (heir appUcabihty to human diseases. Additional animal and human studies are required to understand the effects of pine nut or its individual components, such as pinolenic acid, on plasma lipids and ultimately CVD risk. It deserves mention that other chemical components in pine nut oils such as phytochemicals may contribute to its observed biological effects, and other components in the nut such as dietary fiber may also have potential cholesterol-lowering activity. Additional research is essential to investigate other components in pine nut and its effects on blood lipids. 

Details about structure, biosynthesis, and classification of phenolics are described in the other chapters in this handbook. Plant phenolics have a distinctive ability to form non-covalent, intermolecular complexes with each other and with both large and small molecules. Recognition of the antioxidant activities of many polyphenols has established correlation with the health benefits by such compounds [34]. This leads to the development of commercial products containing free-radical-scavenging phytochemical mixtures, for example, Pycnogenol (procyanidin extracted from Pinus maritima). Table 82.2 represents a list of polyphenolic compounds used in nutraceuticals and their biologic effects on human health. 

A scientific revival of and a new interest in resin glycosides caused by the discovery of novel biological effects, e.g., antibacterial, cytotoxic, phytotoxic activities, could be observed during the last two decades. This development has stimulated again phytochemical research on these compounds. 

There is inereasing interest in the biological effects of phenolic compounds and recent research has shown that these phenolic phytochemicals possess excellent antioxidant properties. Evidence was found that diets rich in Ifuit and vegetables appear to protect against oxidation-linked diseases such as cardiovascular disease (CVD), diabetes, and some forms of cancer (Block et al. 1992 Hertog et al. 1993 Paganga et al. 1999 Serdula et al. 1996 Shetty 1997, 2001, 1999 Shetty and Labbe 1998). 

Section 7.2 deals with issues related to secondary metabolites (phytochemicals) from lichen. Lichen compounds and extractives because they possess some biological effects will form also the focus of this section. How they influence biological host and agents would be described briefly in the latter part of this section with proper X-ray of various reported agents of lichen otigm that display antiviral activities. The exact sources of these compounds and extractives would be fully elucidated. Here, we will lightly also mention yet-to-be-validated lichen-derived compounds with speculated or rumored antiviral property. This perhaps may inspire further comprehensive screening of such to fully validate their claims. 

The discovery that, in industrialised societies, diets deficient in fruits and vegetables can effectively double the risk of developing many different types of cancer has focused renewed attention on the beneficial properties of these foods (Block e/a/., 1992 Patterson ef a/., 1990 Southon and Faulks, 2002). As we have seen, plant foods are rich in micronutrients, but they also contain an immense variety of biologically active secondary metabolites providing colour, flavour and natural toxicity to pests and sometimes humans (Johnson et ah, 1994). The chemistry and classification of such substances is still a matter for much research and debate, but this has not prevented attempts to isolate and exploit substances that have variously been termed protective factors , phytoprotectants , phytochemicals and nutraceuticals . Phytochemical compounds include ... 

UV-C technology is widely used as an alternative to chemical sterilization and microorganism reduction in food products (Lamikanra 2002 Fan and others 2008). Ultraviolet light also induces biological stress in plants and defense mechanisms in plant tissues with the consequent production of phytochemical compounds (Lee and Kader 2000). Phytoalexin accumulation could be accompanied by other inducible defenses such as cell-wall modifications, defense enzymes, and antioxidant activity, which have been reported with health benefits (Gonzalez-Aguilar and others 2007). It is well documented that UV-C irradiation has an effect in secondary metabolism. 

Sea animals are rich in soluble dietary fibers, proteins, minerals, vitamins, antioxidants, phytochemicals, and polyunsaturated fatty acids, with low caloric value. Polysaccharides from marine animals have been reported to possess biological activities with potential medicinal values in addition to their current status as a source of dietary fibers and prebiotics. Moreover, they have a lot of dietary fiber, which lowers blood cholesterol, and iodine, which improves metabolism, vascular and cardiac action, body temperature, and perspiration regulation, and are effective in... 

Nielsen, I.L.F., Nielsen, S.E., Ravn-Haren, G., and Dragsted, L.O., Detection, stability and redox effects of black currant anthocyanin glycosides in vivo positive identification by mass spectrometry, in Biologically-Active Phytochemicals in Food Analysis, Metabolism, Bioavailability and Function, Pfannhauser, W., Fenwick, G.R., Khokhar, S., Eds., Royal Society of Chemistry, Cambridge, U.K., 2001, pp. 389-393. 

Epidemiological studies show an association between low to moderate consumption of red wine and reduced risk for CHD. This phenomenon is known as the French paradox and may be mediated, in part, by the phytochemical resveratrol. The mechanism underlying the cardiomodulatory effects of this polyphenol has not been completely elucidated but may be partly attributable to the broad spectrum of biological responses it elicits. 

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