Phytonutrients Flashcards
Phytonutrients
Phytonutrients (phytochemicals) are chemical compounds produced by plants which are beneficial to human health and help prevent various diseases:
* Phytonutrients give foods taste, fragrance, colour and other characteristics.
* They promote health and fight disease.
* There are over 25,000 different phytonutrients.
* Phytonutrients are found in fruits, vegetables, tea, nuts, grains, beans, herbs and spices. These nutrients can be incorporated into one’s diet for their highly therapeutic properties.
Phyto = from Greek phyton ‘plant’.
The origins of phytonutrients
The origins of phytonutrients:
* All organic compounds are normally a by-product of glycolysis or photosynthesis.
* All products have their own specific set of enzymes for production.
* These products can be divided into primary and secondary metabolites.
Glycolysis
Glycolysis:
* Metabolic process to break down sugars & releasing energy in form of ATP.
Glyco from Greek glykys, ‘sweet’; Lysis from Greek lysis, ‘setting free’, ‘releasing’
Biosynthesis
Biosynthesis:
* Bio from Greek bios ‘life’.
* Synthesis from Greek ‘synthesis’ putting together.
Photosynthesis
Photosynthesis:
* Production of glucose and oxygen from water and CO2 catalysed by sunlight.
Photo: From Greek ‘light’
Isolated constituents and synergistic interactions
Consider: Phytonutrients look at isolated constituents and do not consider the synergistic interactions between phytonutrients of the whole plant:
* They don’t account for the energetic or traditional applications.
* Isolated constituents can lead to side effects that would not normally apply. For example:
o Carotenoids, found in foods such as carrots. Beta-carotene (a carotenoid) was found to worsen the outcome of lung cancer patients who smoke when given as an isolated supplement.
o The health benefits of carotenoids are seen in their whole food form (where the antioxidants can recycle each other).
Carotene from Latin carota ’carrot’ — an orange-coloured hydrocarbon
Plant Compounds: Primary Metabolites
Primary metabolites:
* Are compounds necessary for plant survival such as carbohydrates, proteins, lipids, enzymes and chlorophyll.
Metabolites = products of metabolism or substances essential to metabolism
Plant Compounds: Secondary Metabolites
Secondary metabolites:
* Are synthesised by the plant in reaction to its environment —an adaptive response.
* Evolve to facilitate the survival of the plant.
* Deter predators and protect from infection.
Plant Compounds: Roles of secondary metabolites in Plants
Roles of secondary metabolites in plants include:
* Protection against herbivores, plant pathogens and against other plants.
* Protection against physical stressors such as ultraviolet light.
* Signals for communication and to attract pollinators.
Herbivore from Latin herba ‘a plant’ + vorare ’devour’ ,=‘plant-eating animal’
Plant Compounds: Roles of secondary metabolites in humans
Roles of secondary metabolites in the human body include the potential to:
* Function as antioxidants (e.g. quercetin, abundant in red onions).
* Regulate the cell cycle.
* Increase detoxification of carcinogenic and other toxic compounds.
* Reduce DNA damage (e.g. lycopene in tomatoes).
* Mimic or interact with hormones and other body chemistry (e.g. lignans in flaxseeds can support oestrogen levels when low).
Antioxidants = protect cells against free radical damage
Phytonutrients and the Environment
The interaction the plant has with the environment is important for the production of phytonutrients:
* Organic plants have higher phytonutrient levels —as they have to protect themselves in their environment as they don’t get ‘support’ from pesticides, fertilisers and ‘perfect’ conditions.
* Plants respond to the environment they grow in. As a result different chemotypes can occur within one variety or species of plants.
Chemotype = a chemically distinct entity of a plant with differences in the composition of the secondary metabolite
Differences in phytonutrients
Difference in phytonutrients in plants can be due to:
* Chemotype of plant.
* Soil and water conditions.
* Fungi and mycorrhizae.
* Insect friends and foes.
* Climate.
* Seasonal cycles.
* Variability of plant part.
* Bacteria, virus and pathogens.
* Humans and other animals around them.
mycorrhizae = a symbiotic association between a fungus and a plant —important for plant nutrition and soil biology
Toxic Phytonutrients
Are all phytochemicals helpful for the human body?
* No! Some phytochemicals are dangerous or toxic to the body.
* Examples: Many of the alkaloid class of phytochemicals form the basis of pharmaceutical drugs such as:
o Morphine: Comes for the opium poppy.
o Vinblastine: Comes from African violets.
o Digoxin: Found in foxglove.
* All of the above can be used as drugs.
* Caution: They are very poisonous in the wrong dose or if you eat raw plant!
Vinblastine = chemo drug, Digoxin = heart failure drug
Phytonutrients in foods (less toxic)
Less harmful examples contained in food:
* Solanine and chaconine—alkaloids from the nightshade family. Excessive levels can be toxic as they possess anticholinesterase activity.
* Caffeine (an alkaloid) can be toxic in high doses. It has a strong effect on cognition, blood pressure, sleep and endurance.
* Phytates (found in beans, grains and legumes) may prevent the absorption of minerals (e.g. zinc, iron, calcium).
* However, this so-called ‘anti-nutrient’ effect of phytates can be manifested only when large quantities of phytates are consumed.
anticholinesterase = blocks the activity of the enzyme that breaks acetylcholine down
Phytonutrients Classifications
Phytonutrients are classified according to different chemical compounds and their properties. They are grouped as follows:
See diagram in notes.
Phenol = any compound with a hydroxyl group linked directly to a benzene ring
