Phytochemicals are defined as bioactive plant chemical in fruits, vegetables, grain, and other plant foods that protect plants against bacteria, viruses, and fungi.
Phytochemical is derived from the Greek word “Phyto,” which means plant. The consumption of a large amount of brightly coloured fruits and vegetables (yellow, orange, red, green, white, blue, purple), whole grain/cereals, and beans have been linked to reducing the risk of major chronic diseases.
A large number (>5000) of individual phytochemicals have been identified, but a large percentage still remain undiscovered.Phytochemicals are compounds found in plant food that appear to have a variety of activities.
Major activities of Phytochemicals and benefits of Phytochemicals
- Acting as antioxidants
- Altering the effect of the hormone oestrogen
- Helping to fight cancer-causing agents
- Limiting inflammation
- Limiting blood clotting
- Helping to reduce blood cholesterol levels
- Enhancing immune function
- Antibacterial
- Antiallergic
- Antispasmodic
Phytochemicals also help in preventing ageing, diabetes, osteoporosis, cancer and heart diseases, induce apoptosis, diuretic, CNS stimulant, analgesic, protects from UVB-induced carcinogenesis, immunomodulator and carminative.
Evidence with respect to cancer and cardiovascular disease suggests that phytochemicals may play a significant part in protection against the development of these diseases. This association has been drawn from the strong correlation that exists between a high dietary intake of fruit and vegetables and a reduction in the incidence of these diseases. This has led nutritionists to investigate the components in fruits and vegetables (phytochemicals) that may give this protection.
The majority of foods, such as whole grains, beans, fruits, vegetables and herbs, contain phytochemicals. Among these, fruits and vegetables are significant sources of phytochemicals. These phytochemicals, either alone or in combination, have tremendous therapeutic potential in curing various ailments.
Phytochemicals with nutraceutical properties present in food are of enormous significance due to their beneficial effects on human health since they offer protection against numerous diseases.
More than 25,000 phytonutrients are found in plant foods. We take a look at some important phytonutrients — and their potential health effects:
1.Polyphenols
Polyphenols are naturally occurring compounds found largely in fruits, vegetables, cereals and beverages. Legumes and chocolate also contribute to the polyphenolic intake. These molecules are secondary metabolites of plants and are generally involved in defence against ultraviolet radiation or aggression by pathogens.
The epidemiological studies provide convincing evidence that a diet rich in antioxidants is associated with a lower incidence of degenerative diseases.
Phenols protect plants from oxidative damage. They have also been studied extensively as antioxidant protectants for human beings and play a beneficial role in reducing the risk of coronary heart disease, diabetes, hypertension and some types of cancer.
The major sources of dietary polyphenols are cereals, legumes (barley, maize, nuts, oats, rice, sorghum, wheat, beans and pulses), oilseeds (rapeseed, canola, flaxseed and olive seeds), fruits, vegetables and beverages (fruit juices, tea, coffee, cocoa, beer and wine).
2.Carotenoids
Carotenoids are highly pigmented, yellow, orange and red, are present in fruits and vegetables. When consumed by birds are incorporated into the yolk of eggs. Carotenoids comprise two types of molecules, carotenes and xanthophylls. The antioxidant properties of carotenoids have been suggested as being the main mechanism by which they afford their beneficial effects.
3.Limonoids
These are terpenes present in citrus fruit. Limonoids, with diverse structures and a broad range of bioactivities, has been an attraction for both natural product and synthesis chemists. They provide chemotherapeutic activity by inhibiting I detoxification enzymes in the liver.
D-Limonene, the commonest monocyclic monoterpene, found within orange peel oil, inhibits pancreatic carcinogenesis induced in experimental models and also provides protection to lung tissue.
4.Phytosterols
Phytosterols compete with cholesterol in the intestine for uptake, and aid in the elimination of cholesterol from the body.
Saturated phytosterols appear to be more effective than unsaturated compounds in decreasing cholesterol concentrations in the body. Their actions reduce serum or plasma total cholesterol and low-density lipoprotein (LDL) cholesterol.
5.Glucosinolates
Glucosinolates are present in cruciferous vegetables and are activators of liver detoxification enzymes. These chemicals are responsible for the pungent aroma and bitter flavour of cruciferous vegetables. The sprouts of certain crucifers, including broccoli and cauliflower, contain higher amounts of glucoraphanin (the glucosinolate of sulforaphane) than do the corresponding mature plants.
7.Fibres
Most plant foods in their native state contain indigestible residues that used to be classified as crude fibre but are currently classified as dietary fibre.
Dietary fibre is not a single entity but consists of a wide range of complex polysaccharides such as cellulose, gums, mucilage, hemicellulose and lignin’s with different chemical, physiochemical and physiological properties.
These foods have been shown to be useful in reducing blood glucose levels in diabetes, in reducing blood cholesterol levels for treatment of cardiovascular disease and also in preventing bowel cancer.
Dietary fibre components exert their beneficial effects mostly by way of their swelling properties, and by increasing transit time in the small intestine. Consequently, they reduce the rate of release of glucose and its absorption, thus helping in the management of Type 2 diabetes.
DF components also bind bile salts, thereby promoting cholesterol excretion from the body and thus reducing blood cholesterol levels,and food toxins in the gut to reduce their toxicity.
8.Polysaccharides
Polysaccharides widely exist in plants, microorganisms, algae and animals. They are essential biomacromolecules in life activities and play important roles in cell–cell communication, cell adhesion and molecular recognition in the immune system.
Plant polysaccharides have shown diverse biological activities such as wound healing, , stimulation of the immune system, treatment of tumours and effects on the haematopoietic system.
Conclusion
Scientific data has supported the nutritional and medical importance of phytonutrients/phytochemicals for the prevention and treatment of several diseases.
The ‘novel’ nutraceuticals of plant origin may evolve to be considered a vital aspect of dietary disease-preventive food components in future
List of Phytochemicals,sources and beneficial actions
| Family and Examples | Examples of good food Sources | Beneficial Actions |
| Carotenoids Beta-carotene Lycopene Lutein zeaxanthin | Yellow-orange and dark-green fruit and vegetables Red-pink vegetables Dark-green vegetables Green and yellow orange fruits and vegetables | Antioxidant activity Cancer protection Immune system function Protection against prostate cancer Protection against macular degeneration (eye disease) |
| Flavanols Quercetin Resveratrol | Tea, onions, berries, grapes, apples Grapes, wine, peanuts | Strong antioxidant Activity Anti-inflammatory activity Anti-cancer properties Reduction of damage to arteries caused by certain blood fats |
| Catechins | Green tea, black tea | Strong antioxidant activity Prevention of formation of cancer-causing Agents |
| Anthocyanins | Blue-purple fruits and vegetables | Strong antioxidant activity Mild antibacterial Agent |
| Isoflavones Genistein | Soybeans and soy products (e.g. soy milk, tofu), other beans and legumes | Sharing activities of the hormone oestrogen such as reducing symptoms of menopause and assisting bone health May also interfere with oestrogen synthesis and reduce risk of breast cancer |
| Lignin | Flax-seeds, pumpkin seeds, sesame seeds, bran and wholegrains, beans | As above |
| Phenolic acids Capsaicin Ellagic acid Curcumin | Hot peppers/chillies Raspberries, strawberries, red grapes and kiwifruit Mustard, turmeric | Regulates blood clotting Increases enzymes that get rid of cancer causing agents Anti-inflammatory properties Blocks cancer causing agents |
| Terpenes | Citrus fruit (especially skins) | Neutralises cancer causing agents Reduces growth of cancers |
| Saponins | Soybeans, legumes, some herbal compounds | May reduce blood cholesterol levels May reduce growth of cancers |
| Phytates | Wholegrains and bran, nuts, oats, soybeans, and seeds | Binds to minerals to prevent free-radical production—may have anti-cancer outcomes |
| Indoles and Isothiocyanates | Cruciferous vegetables (cabbage, broccoli, cauliflower, Brussels sprouts) | Increases enzymes that get rid of cancer-causing agents Reduces the growth of cancers |
| Allicin | Onion, garlic, leeks, chives | Antibacterial and antiviral activity Blood-thinning activity |
| Phytosterols | Soybeans and other plants—now added to a range of ‘functional foods’ such as margarines | Has cholesterol-like activity, reducing the absorption of food cholesterol and lowering blood cholesterol |
Classification of Phytochemicals
