These page includes:

• An introduction to the work of the EuroFIR project in relation to bioactives

• A link to the EuroFIR Synthesis Report on Plant Bioactives ("Plant Foods and Health: Focus on Bioactives", see bottom of this page)

• Some basic information about the different classes of bioactives that have been identified

Food consists of a complex mixture of a wide variety of components, many of which are biologically active. Some components, identified some time ago, have been classified as nutrients and these are essential for growth, maintenance and repair of the body. More recently scientists have identified biologically active substances in plants that have proven (e.g. cholesterol lowering effects of phytosterols) or potential beneficial effects on health. Evidence is growing that these plant constituents, also termed phytochemicals or phytonutrients, may help reduce the risk of chronic diseases such as cancer, coronary heart disease, stroke and perhaps Alzheimer’s disease.

Bioactive substances are present in plants for a reason; many influence the colour and flavour of plant foods, or the structure and function, and others such as glucosinolates are part of the plant’s defense system. In particular phytochemicals may be consumed via leaves, stems, roots, tubers, buds, fruits, seeds and flowers, and plant derived foods and drinks (such as tea, coffee, alcoholic beverages).

There are various classes of phytochemicals, including:

• flavonoids – found in a range of plant derived foods. Major sources include tea, wine, onions, apples and berries.

• glucosinolates from Cruciferous vegetables

• phenolic acids in tea and coffee for example

• carotenoids (some of which are precursors of vitamin A) prevalent in red, green and orange fruits and vegetables.

Within each class of phytochemical there are a number of sub-classes, for example flavonols, flavones, flavanones and flavan-3-ols are sub-classes of flavonoids. These sub-classes have the same generic chemical structure, although they are distinguished from each other due to small differences in their chemical structure. Within these sub-categories even more biochemical compounds can be distinguished, for example quercetin and kaempferol are both classified as flavonols.

The various compounds, sub-classes, and classes, have different properties, but in most cases their precise biological function in humans is as yet unknown. Plausible mechanisms for the beneficial health effects of phytochemicals include: the antioxidant capacity; modification of hormonal profile; anti-inflammatory effects; and modification of lipid profile. However, further knowledge of the absorption, distribution and metabolism of plant derived substances is essential in order to fully understand their potential health benefits.

Another problem in getting sufficient evidence to identify the health benefits of phytochemicals is the lack of information available about the content and concentrations of these substances in foods. Information about food sources and concentrations of these bioactives is not always easy to find and data are often inconsistent and incomplete. However the need for this data is becoming more important to researchers and the food industry alike as interest in the potential health benefits expands, and as consumers show more interest in diet and its potential impact on health and well being. To ensure this information is easily accessible, relevant and usable across Europe, EuroFIR is building on previous EU work to pull together a reliable and valid database of foods detailing the type and quantity of classes of bioactives, including flavonoids, isoflavones, carotenoids, glucosinolates, lignans and phytosterols. A unique feature will be the combination of compositional data with information about their biological effects. More detailed information on the phytochemicals being considered as part of the EuroFIR project is provided below.

Whilst further evidence is being collected about the health benefits of phytochemicals, and the content of phytochemical components in foods, the message to consume a variety of fruit and vegetables each day remains important.

Some basic information about the different classes of bioactives that have been identified:

Flavonoids are a large group of bioactives that are found in a range of plant derived foods. As the illustration below shows, this term encompasses a range of bioactives including: flavanols, anthocyanins, flavonols, flavones, isoflavones and flavanones. Flavonoids are also classed as phenolics and polyphenols.

Flavonoids are involved in diverse processes, such as UV protection, pigmentation, stimulation of nitrogen fixing nodules and disease resistance. It is currently thought that these compounds have the potential to interact with the mechanism of cancer induction at a number of different points. Major sources include tea, wine, onions, and apples.

Flavonols are the most widespread of the flavonoids. Quercetin, kaempferol and myricetin are all biochemical compounds classified as flavonols. Flavonols are found in onions, kale, broccoli, apples, cherries and berries, tea and red wine. These compounds have potential anti-mutagenic, anti-carcinogenic and anti-hypertensive effects.

Isoflavones are found throughout the plant kingdom but significant levels are only found in a limited number of plants. Genistein and daidzein are just two isoflavones which are recognized to have an influence on our health, and it has been suggested may have a role in reducing the incidence of prostate and breast cancers in humans because their structure appears to mimic the steroidal hormone oestradiol. For this reason, they are also termed phytoestrogens. The principal source of isoflavones is legumes, in particular the soya bean.

Of the other flavonoids:

• flavanols (sometimes called flavan-3-ols), e.g. catechins and their derivatives and proanthocyanidins, sometimes referred to as procyanidins or tannins are found in tea, apples, apricots, cherries, red wine and cocoa, for example

• flavones (e.g. apigenin, luteolin) are found for example in parsley, thyme and celery

• anthocyanidins (e.g. cyanidin, pellargonidin) are found in red and purple fruits such as grapes and cherries

• flavanones (e.g. hesperetin and naringenin) are found in citrus fruit, and derivatives such as the dihydrochalcone phloretin present in apples

A number of other groups of non-flavonoid phenolic/polyphenolic bioactive compounds are found in foods in addition to flavonoids. These include various phenolic acids (including hydroxycinnamates such as caffeic acid from coffee and ferulic acid from cereal brans), simple phenols (e.g. benzoic acid, vanillin), capsaicins (e.g. capsaicin in chilli peppers, zingerone in ginger) and stilbenes (e.g. the phytoestrogen resveratrol in red wine).

Phenolic acids may also be classified as hydroxybenzoic acid derivatives. Benzoic acid and salicylic acid come under this category. The manufactured compound acetyl salicylic acid (aspirin) has well characterised health effects, protecting against coronary heart disease, stroke and some intestinal cancers. It is possible that food salicylates may also demonstrate such effects, although levels found in foods are generally low and therefore may not have any biological significance.

Lignans have been suggested to be another type of phytoestrogen (due to their weak oestrogenic activity). As with other phytoestrogens, lignans are thought to play a role in reducing the risk of cancers related to oestrogen activity. Lignans can be found in wholegrain products, seeds, fruits and berries.

Carotenoids are classified as tetraterpenes, a form of terpenoid, of which there are many structurally diverse compounds. Lycopene and lutein are types of carotenoid. Carotenoids work alongside chlorophyll in photosynthesis, extending the range of light absorbed by the photosynthetic pigments, which is why many plant foods containing carotenoids are red or orange. In humans carotenoids are important dietary anti-oxidants, and are thought to be involved in reducing the risk of some forms of cancer. There is also evidence a protective effects of carotenoids against UV induced erythema (reddening of the skin). Evidence for a protective effect against skin cancer is currently weak. Orange vegetables, fruit with orange flesh and tomato and tomato products are the main sources of carotenoids.

Plant sterols are also categorized as a terpenoid. Plant sterols have become well recognized through their proven ability, in the form of plant sterol and stanol esters, to reduce plasma cholesterol levels when incorporated into foods such as spreads. Their action hinges on their very low absorption rates and their structural similarity to cholesterol and hence their competition in the gut for dietary and endogenous cholesterol, reducing uptake of cholesterol from the diet.

Cruciferous vegetables, such as sprouts, broccoli and cabbage, contain glucosinolates. When glucosinolate-containing vegetables are chewed, sliced or crushed, the glucosinolates break down and form isothiocyanates, which have been shown in in vitro experiments to induce potentially anti-carcinogenic defence mechanisms. Hence, when cruciferous vegetables are eaten, the biologically active isothiocyanates are released and are available for interactions with the colonic epithelial cells and for uptake into the circulation via the colonic mucosa.

More information on bioactive compounds can be found in the 4th Synthesis Report of EuroFIR 'Plantfoods and Health: Focus on Plant Bioactives'.