Introduction to Polyphenols
Polyphenols are bioactive phytochemicals, found in abundance in the outer layers of plants (skins and shells) and less in their inner parts.
Polyphenols are considered by the scientific community as critical and important factors in the development of multi-purpose drugs due to their vascular-cardioprotective, anti-inflammatory, anti-diabetic and anti-cancer effects.
The bioactive properties of polyphenols have been extensively investigated in human health, with their proven antioxidant properties helping to repair oxidative cell damage, homeostasis of plasma lipoproteins and reduction of inflammatory markers.
There are over 8,000 different polyphenols and they are contained in various mixtures in plant foods, such as extra virgin olive oil, tea, wine, chocolate, fruits, vegetables, etc. Also, in their natural state we find them in relatively high concentrations in the by-products of the processing units of the agro-industrial complex, such as those of the oil mills, the juicing facilities, the wineries, etc.
Oxidative Stress – Polyphenols
Oxygen-free radicals are natural byproducts of energy production in the cells of aerobic organisms and, if not removed in time, they cause oxidative damage to cell bio-molecules including lipids, proteins and nucleic acids.
The cells of aerobic organisms have antioxidant enzymes, which remove oxygen free radicals, but some basic antioxidants do not synthesize or produce them in sufficient quantity and must be taken by food.
Exposure to environments with accumulated environmental factors and pollutants due to human activities, such as ultraviolet light, ionizing radiation, heavy metals, pesticides, air pollutants, etc. adversely affects cellular functions and leads to oxygen-free-radicals production.
The overproduction of oxygen-free radicals and at the same time the possible insufficiency of the antioxidant defense mechanisms of the organisms, leads to an excess of oxygen-free radicals and the manifestation of oxidative stress.
Environmental factors, through oxidative stress, contribute significantly to a wide range of respiratory, neurological, cardiac and reproductive diseases, and to some benign and non-benign metabolic, degenerative and neoplastic diseases.
Given the pollution and current environmental conditions, the addition of natural bioactive antioxidants to the diet of any kind of aerobic organism is an urgent requirement to meet the increased need of preventing oxidative damage and the effects of oxidative stress on health and productivity.
Olive fruit contains many phenolic compounds, of which the main ones are: Hydroxytyrosol, Tyrosol, Oleuropein, Ligstroside, Oleacein, Oleocanthal, Pinoresinol, 1-Acetoxypinoresinol, Luteolin, etc.
There are other phenolic components found in olives, such as aromatic acids (caffeic acid, vanillic acid, coumaric acid, ferulic acid, hydroxybenzoic acid, proto-catechic acid, gallic acid, gentisic acid, sicicic acid, phenylacetic acid, etc.), the compounds thymol, carvacrol and the flavonoids (camphorol, apigenin and quercetin…).
The phenolic compounds of the olive are found in different concentrations, combinations and proportions, depending on the species of the genus Olea Europaea L., the place where it grows, the soil parameters, etc.
Olive polyphenols have been shown to have a protective effect on human health when found in an appropriate concentration. They are to a vaious extent involved in the treatment of oxidative stress, the prevention of heart attacks, the prevention of inflammatory syndromes and the protection of the nervous system.
Recovery of olive polyphenols
In addition to olive products, olive phenolic compounds are found in relatively high concentrations in the by-products of olive-oil mills. They are recovered from them as a natural and representative mixture of olive phenolic compounds, where hydroxytyrosol and tyrosol make up at least 20%. The presence of approximately 4% terpenic acids, which have serious and proven hepatoprotective and anti-cancer properties, is also important.
Hydroxytyrosol – Tyrosol
Hydroxytyrosol (2- (3,4-dihydroxyphenyl) -ethanol) is one of the main phenolic constituents of olive products as well as of olive by-products.
Studies to determine the amount of hydroxytyrosol absorbed by the mammalian digestive tract with isotopic labeling estimate that digestibility reaches 99% of total intake with olive oil and 75% of intake with an aqueous solution.
In recent decades, it has been documented that the phenolic compound hydroxytyrosol is an important food-drug agent with a contribution to the protection against metabolic imbalances, cardiovascular and neoplastic diseases, acquired immune deficiency syndrome, neurological diseases, etc.
Hydroxytyrosol – Health Reports
Antioxidant Properties – Immune System
It is considered the most powerful bioactive antioxidant compound after gallic acid, even stronger than the antioxidant vitamins E (α-Tocopherol) and C (Ascorbic acid). It is the phenolic compound with the markedly higher content among the other phenolic compounds found in olive by-products and of course the strongest antioxidant compound among them.
Its activity is related to the binding of “oxygen free radicals” and the prevention of oxidative stress and oxidative damage, which are caused in the cells of aerobic organisms and alter the structure of their organic molecules, such as lipids, proteins and of his DNA
Hydroxytyrosol strengthens the immune system against pathogens, as the body’s immune cells carry many types of receptors. These receptors allow the cellular uptake of hydroxytyrosol that activates through its antioxidant action various enzymes and intracellular mechanisms and triggers the immune response.
Phenolic compounds appear to have important microbiostatic properties as part of a natural set of polyphenolic compounds, found in various plants as a single polyphenolic set.
Most phenol compounds tested in the laboratory for their antimicrobial activity appear to be ineffective against the target bacterial strains and only at high concentrations of 1000 μg/mL was inhibition of microbial activity observed for some of them.
However, under certain conditions, hydroxytyrosol completely inhibited the growth of four target bacterial strains, either Gram-positive or Gram-negative, at concentrations of 400 μg/mL.
Fungi and Hydroxytyrosol
The action of hydroxytyrosol in fungi concerns on one hand its antifungal action and on the other hand the inhibition of the pathogenic action of mycotoxins in the organs they target.
Mycotoxins are a serious health problem worldwide that concerns the health of animals and humans, as exposure to them is associated with many serious pathological syndromes such as carcinogenesis, chronic poisoning, etc.
They are also a serious problem for the health and safety of agricultural products, feed and food, as they cause enormous damage each year due to the degradation and destruction of contaminated food and feed.
Mycotoxins of particular importance for public health and the quality of feed and food are mainly the aflatoxins (AFs) and ochratoxins (OTs), but also fumonisins (Fs), capillaries etc.
Relevant studies confirm that hydroxytyrosol and its relative phenolic analogues act as potent antifungal agents causing lysis of the fungal cell membrane.
While the use of phenolic elements in animal feed, from the aqueous residues of the olive- mill where hydroxytyrosol predominates, seems to completely inhibit the growth of Aspergillus flavus and the production of aflatoxin.B1.