Classification of nutraceuticals based on chemical nature
This classification permits nutraceuticals to be categorized under molecular/elemental groups. This preliminary model includes several large groups, which then provide a bases for sub-classification or subgroups, and so on. One way to group nutraceuticals grossly is as follows:
- Isoprenoid derivatives
- Phenolic substances
- Fatty acids and structural lipids
- Carbohydrates and derivatives
- Amino acid-based substances
- Microbes
- Minerals
Isoprenoid Derivatives (Terpenoids):
Isoprenoids and terpenoids are terms used to refer to the same class of molecules. These substances are one of the largest groups of plant secondary metabolites. Many popular nutraceutical families comes under this group such as carotenoids, tocopherols, tocotrienols, simple terpenes and saponins. This group is also referred to as isoprenoid derivatives because isoprene is the principal building block molecule which is synthesized from acetyl coenzyme A (CoA).
Phenolic Compounds:
Phenolic compounds are also considered secondary metabolites. The base for family of molecules is a phenol structure, which is a hydroxyl group on an aromatic ring. From this structure, larger molecules are formed viz., anthocyanins, coumarins, isoflavones, flavonones, flavonols, tannins, and lignin.
Carbohydrates and Derivatives:
Ascorbic acid (Vitamin C) is the glucose derivative and functions as an antioxidant. Many plants produce some oligosaccharides which functions as prebiotic substances. Several plant polysaccharide families are not readily available energy sources for humans as they are resistant to secreted digestive enzymes. These polysaccharides are grouped together along with lignin to form one of the most recognizable nutraceutical families — dietary fibres. The non-starch polysaccharides are further divided into homogeneous and heterogeneous polysaccharides, as well as into soluble and insoluble substances.
Fatty Acids and Structural Lipids:
Fatty acids and/or their derivatives include the ω-3 PUFA found in higher amounts in plants, fish, and other marine animals, and conjugated linoleic acid (CLA) produced by bacteria in the ruminants.
Amino Acid-Based:
This group includes intact protein (i.e., soy protein), polypeptides, amino acids, and nitrogenous and sulphur amino acid derivatives. A few amino acids are also being investigated for their nutraceutical potential now a days. Among these amino acids is arginine, ornithine, taurine, and aspartic acid. Arginine has been considered to be cardioprotective since it is a precursor molecule for the vasodilating substance nitric oxide (NO). Also, arginine may reduce atherogenesis. The nonprotein amino acid taurine may also have blood pressure-lowering as well as antioxidant properties. Other examples are isothiocyanates, indole-3-carbinol, allyl sulfur compounds, and capsaicinoids. Another nutraceutical amino acid-derived molecule is folic acid, which is believed to be cardioprotective by minimizing homocysteine levels. Other members of this group would include the tripeptide glutathione and choline.
Microbes (Probiotics):
Other groups of nutraceuticals include molecules or elements, whereas probiotics includes live bacteria. A good probiotic must be resistant to acid conditions of the stomach, bile, and digestive enzymes normally found in the human gastrointestinal tract; able to colonize the human intestine; be safe for human consumption; and have scientifically proven efficacy. Among the bacterial species recognized as having functional food potential are Lactobacillus acidophilus, L. plantarum, L. casei, Bifidobacterium bifidum, B. infantis, and Streptococcus salvarius subspecies thermophilus. Some yeasts have been noted as well, including Saccharomyces boulardii.
Minerals:
Several minerals have been recognized for their nutraceutical potential and thus have been included under functional foods. Among the most evident is calcium with relation to bone health, colon cancer, and perhaps hypertension and cardiovascular disease. Potassium has also been found to reduce hypertension and thus improve cardiovascular health. A couple of trace minerals have also been found to have nutraceutical potential such as copper, selenium, manganese, and zinc. All these trace minerals have antioxidant property. Copper, zinc, and manganese are components of superoxide dismutase (SOD) enzymes, whereas selenium is a component of glutathione peroxidase. Certainly, more research is required in the area of trace elements in view of their metabolic relationships to other nutrients and the potential for toxicity.
Let us summarize
Thus we have seen the classification of functional foods and nutraceuticals according to source/origin, nutrient/non nutrient, organ/organ system, modifications in foods, specific functional components, mechanism of action and chemical nature of food. According to source or origin, functional foods are classified as plant foods, animal foods and microbial foods. According to nutrient and nutrient, functional foods are classified as nutrient viz., lipids, Vitamins and minerals. According to organs, functional foods have been classified according to beneficial effects on Gastrointestinal tract, Cardiovascular system, Kidney: Immune System and Skeletal system. According to modifications, the foods are classified as: Fortified foods, Enriched foods, Enhanced foods and Altered foods. According to mechanism of action, they are classified as antioxidant, antibacterial, antihypertensive, antihypercholesterolemic, antiaggregate, anti-inflammatory, anticarcinogenic and osteoprotective. According to chemical nature of foods nutraceuticals have been classified as Isoprenoid derivatives, Phenolic substances, Fatty acids and structural lipids, Carbohydrates and derivatives, Amino acid-based substances, Microbes and Minerals.
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