plant nutraceuticals

Chapter 32 The plant nutraceuticals

A number of plant nutraceuticals are common food constituents, and extracts of many others are used as nutraceuticals.

There are a number of definitions of nutraceuticals, but the first and most straightforward is that coined by De Felice, of the Foundation of Innovation in Medicine, who defined a ‘nutraceutical’ as a ‘food, or parts of a food, that provide medical or health benefits, including the prevention and treatment of disease’.

Nutraceuticals are rarely legally classed as medicines, but instances exist in certain countries for particular entities, for example coenzyme Q10 in Japan and melatonin in the UK. This consequent lack of regulation for most nutraceuticals has resulted in a number of poor quality products being available on the market.

There are a number of sources of nutraceuticals, including basic human and mammalian metabolites, dietary components of plant and animal origin, synthetic constituents and plant secondary metabolites; increasingly, they are also produced by microbial fermentation. Arguably the greatest number are derived from plants and are used either as single purified components, such as resveratrol, purified multi-component products, such as pycnogenol, or whole plant foods, such as flaxseed. The most researched nutraceuticals of plant origin are those derived from soy and tea, but large numbers of scientific and medical publications relate to the constituents of grapes and wine, and also the many plants rich in polyphenolic components. Table 32.1 lists plant sources and therapeutic activities of a number of commercially available single-component nutraceuticals, which often occur in a number of plants. Various purified multi-component nutraceuticals are also obtained from specific plants (Table 32.2). Those from grape, soy and tea could realistically be obtained from the diet. Increasingly, a number of foods are being promoted as sources of nutraceuticals specifically for consumers who prefer eating a healthy diet instead of taking supplements; Table 32.3 depicts a wide variety of such products. The last group of nutraceuticals occurs in the plant kingdom either widely, such as coenzyme Q10 and S-adenosylmethionine (SAMe), or only in a few specific plants but at insubstantial levels, and are therefore not suitable for realistic incorporation in the diet. These latter nutraceuticals are often produced by chemical or biotechnological synthesis (Table 32.4).

Table 32.1 Single-component nutraceuticals.

Table 32.2 Multi-component products.

Table 32.3 Dietary sources of nutraceuticals.

Table 32.4 Nutraceuticals present in plants but commercially obtained from other sources.

The range of therapeutic applications is wide, encompassing many areas in which conventional pharmaceuticals treat only the symptoms of the disease state. A number of these nutraceuticals have been shown to treat the underlying cause of the illness, e.g. α-linolenic acid. As a consequence of this, many nutraceutical manufacturers and pharmaceutical companies are increasingly investigating the possibility of formulating and marketing plant based nutraceuticals.

Many of the nutraceuticals owe their activities to antioxidant activity (activity is highlighted in Tables 32.1–32.4), but this may not be the full story. It has been claimed that many also have other activities, including enhancement or inhibition of Phase I and II metabolizing enzymes, and modulation of DNA repair.

In addition to the increasing number of clinical trials being published to support the use of plant nutraceuticals, evidence is accumulating regarding synergistic interactions, adverse effects, and quality of commercially available single and multicomponent nutraceuticals.