Secondary metabolites - phytochemicals

Summary

The world of secondary metabolites, also called phytochemicals, is complex. There is a lack of specific research and studies to understand the various modes of action. Current studies show that a varied, balanced diet with plenty of different colored plant-based foods has a positive effect on numerous and various aspects of health in the human organism. Phytocemicals play a particularly essential role in the defense against diseases and for the microbiome in the human gut.

Secondary metabolites are found in vegetables, fruits, pulses, seeds, nuts and cereal products and give our food its color, aroma and taste. They are absent in all animal foods. In order to exploit the full potential of phytochemicals, you should focus on the wide variety of vegetables, fruits, nuts, seeds, grains and legumes and include as many colors of the rainbow in your meal plan as possible.

Plant-based foods should be eaten raw and unprocessed whenever possible or at least be prepared in a gentle way. Industry and relevant public institutions communicate this knowledge little or not at all. The reasons for this may be a lack of interest in communicating the benefits of a diet that is close to nature. The impression could prevail that economic interests are far too important. As a result, people remain inadequately informed by public authorities. In the approximately 600 food descriptions (ingredients of our recipes), we therefore mention the effects of secondary metabolites wherever possible.

You can find these approximately 600 foods directly using the search function on each page or as a link in the recipes. In this article, we have highlighted active ingredients in purple and foods in green.

Basics

Plants form primary and secondary metabolites. Primary metabolites, such as carbohydrates, proteins and fats as well as micronutrients etc., are used for basic processes (growth, development) and are essential for energy metabolism.

Not all secondary metabolites are necessary (essential) for the growth and direct maintenance of plants, but give the plant decisive advantages. They are formed through various biochemical syntheses of the primary metabolism. Hence their name.

Secondary metabolites benefit plants and us in different ways by fulfilling certain ecological functions. Environmental factors such as light, temperature, other living organisms and nutrient availability influence their synthesis by the plants. Certain secondary metabolites (or groups) or their combinations are often characteristic of individual plant species. Plant secondary metabolites are internationally also referred to as phytochemicals or phytonutrients.

Functional variety for plants

Due to their antibiotic, antifungal and antiviral properties, secondary metabolites play a decisive role as a defense mechanism against pathogens in the interaction of plants with their environment. Thanks to their physiological properties, secondary metabolites protect plants from external influences such as pathogenic microorganisms.

Other plant secondary metabolites deter herbivorous insects through an unpleasant odor, repulsive taste or toxic effects. In addition, phytochemicals act as fragrances to attract animals such as insects and birds to pollinate or disperse the seeds. Some secondary metabolites protect plants from UV radiation and oxygen radicals and regulate growth. Plant secondary metabolites are indispensable for the survival of a species.

Effects and benefits for humans

Naturopathy has been using the effects of phytochemicals since early human history, specifically in spices, extracts, medicines, incense and dyes as well as foods. Nowadays, modern science uses various highly developed, sensitive analytical methods to identify the bioactive substances in phytochemicals and researches their diverse effects on humans. Researchers have so far identified around 100'000 different substances in secondary metabolites, although the number of plants analyzed to date is still relatively small.

Our organism uses a variety of nutrients. The three macronutrients carbohydrates, fats (fatty acids) and proteins (i.e. nitrogen compounds) are essential. Around 30 micronutrients such as minerals, trace elements, vitamins (salts or electrolytes) and water are also essential. In addition, approximately 10'000 secondary metabolites are known to date, which are extremely important for the quality and utility value of numerous plant foods in the human organism. Every day, humans consume around 1,5 g of phytochemicals. However, the Western diet only provides a fraction of this.

Current studies show that, in addition to essential nutrients and dietary fiber, phytochemicals influence numerous processes in the human metabolism and thus make a significant health-promoting contribution and have a preventive effect against various diseases. The number of secondary metabolites that contain anticancer active substances is strikingly high. Secondary metabolites also have a positive effect on the human intestinal microflora, as they selectively promote the growth of certain bacteria. This is why they are also known as "probiotics".

The bioavailability of individual phytochemicals is very complex and also depends heavily on the method of preparation. It is therefore important to consciously select plant-based foods according to their degree of ripeness, origin (wild forms, old varieties), degree of processing, regionality and seasonality.

Depending on the dosage, phytochemicals can have harmful or beneficial effects on human health. The boundary between the health-promoting and pharmacological effects of some secondary metabolites is blurred. Their spectrum of action in the human organism is diverse and includes anticarcinogenic (antitumor), antimicrobial, antioxidant, antithrombotic, immunomodulating, anti-inflammatory, blood pressure regulating, cholesterol-lowering and digestive effects. Evidence for these effects is provided by various observational studies in in-vitro tests and animal experiments.

General characteristics of secondary metabolites

Secondary metabolites occur specifically in certain taxonomic plant groups in various plant parts such as seeds, blossoms, fruits, leaves, stems, bark, rhizomes and roots in rather small quantities. They vary according to plant species, stage of development and environmental conditions. They often exhibit considerable structural diversity and manifest themselves in a wide range of closely related structures. Structurally similar compounds or those with similar building principles do not necessarily have identical biological features. Secondary metabolism is scientifically regarded as the "playground of evolution".

Certain secondary metabolites vary during specific stages of plant development, e.g. the content of menthone and menthol in the essential oil of young peppermint plants changes as they grow. Similarly, the alkaloid content in fruits of tomato plants decreases as they ripen. In some cases, the plant only produces certain phytochemicals when external stimuli are present. Plants can also absorb substances produced by soil fungi and chemically convert them into plant secondary metabolites.

After their formation, secondary metabolites are deposited in specific places. Lipid-soluble compounds are found in specialized glandular hairs, oil cells or chromoplasts, while water-soluble secondary metabolites such as glycosides and alkaloid salts are often found in the vacuoles of special cell types, such as the glands of lactiferous plants. The site of synthesis and storage of phytochemicals are often not identical. The ability to synthesize certain secondary metabolites can be gained or lost through mutations.

Variety of chemical structures

Secondary metabolites are extremely diverse in terms of their chemical properties. Therefore, the classification of secondary metabolites requires precise knowledge of often complexly interwoven biochemical biosynthetic pathways. Metabolic pathways of secondary metabolites rarely follow linear processes, but rather appear as multidimensional metabolic grids. Intermediate products of a metabolic pathway are used and incorporated in a variety of ways - building blocks of other metabolic networks also occur. Thus, an overly strict separation of primary and secondary metabolic products makes little sense.

Classification according to structural similarities, taking biogenetic aspects into account, leads to a kind of "family tree" of phytochemicals. The chemical structure of most phytochemicals follows the biogenetic rules of isoprene, acetate and amino acids.

Main groups of secondary metabolites

Research has so far defined over 80'000 structures of secondary metabolites from higher plants alone, which can be summarized into the following few main groups.

• Isoprenoids (terpenoids, terpenes, steroids, saponins, carotenoids)

• Alkaloids (proto-, pseudo-, and true alkaloids)

• Polyphenols (phenolic acids, flavonoids, phytoestrogens)

• Organic sulfur-containing compounds (glycosides, sulfides)

• Other nitrogenous compounds

Classification of secondary metabolites

Below you will find the most important representatives of the main groups of phytochemicals for human nutrition, their occurrence in plant foods including their health-promoting effects:

Main group of isoprenoids

Isoprenoids are divided into terpenoids, terpenes, steroids, saponins and carotenoids. They are a large and very diverse group of natural secondary metabolites with important features for medicine, nutrition and industry. They are the starting material for many natural plant and animal products. Isoprenoids are lipophilic compounds based on the structural building block isoprene, which consists of five carbon atoms (C₅H₈).

The isoprenoid groups are classified according to the number of isoprene units. Chemically speaking, all other derivatives are made up of isoprene units and occur as hydrocarbon, alcohol, glycoside, ether, aldehyde, ketone, carboxylic acid or ester compounds. The combinations and arrangements of isoprene units (isoprene rule) lead to various terpenoids, terpenes (mono-, di-, sesqui- and triterpenes) and subsequently to steroids, saponins and carotenoids (tetraterpenes). Depending on the number of isoprene residues, a distinction is made between monoterpenes consisting of two, sesquiterpenes consisting of three, diterpenes consisting of four, triterpenes consisting of six and tetraterpenes consisting of eight isoprene molecules. These can be arranged in rings or chains.

The biological function of isoprenoids is very diverse. For example, they serve as pigments, just as certain carotenoids are essential for photosynthesis in plants. Gibberellins function as hormones, while others act as defense substances, components of membranes, of signal transduction networks or as photoprotective substances. Due to the different chemical and physical characteristics of isoprenoids, no general statements can be made regarding their medical and therapeutic significance. Studies show effects on the heart and circulation (cardioactive steroids), anti-inflammatory effects (sesqui- and triterpenes) and digestive effects due to bitter substances (mono-, di-, triterpenes).

Terpenoids

Terpenoids are a modified class of terpenes with oxygenated hydrocarbons that have oxidized methyl groups at different positions and different functional groups. Terpenoids are divided into alcohols, aldehydes, esters, ethers, epoxides, ketones and phenols. Examples of terpenoids include carvacrol, citronellal, geraniol, linalool, linalyl acetate, menthol, piperitone and thymol. Due to their bitter taste and sticky, sometimes poisonous properties, terpenes and terpenoids have a repellent effect on many herbivores and thus protect the plant from feeding damage. The sticky and poisonous resins also seal plant wounds and prevent infections. Terpenes and terpenoids can undergo aromatic and sensory changes when exposed to light and oxygen, resulting in a tallowy, castor oil like taste.

Terpenoids are found in many spices and medicinal plants, such as basil, mugwort, savory, birch leaves, tarragon, fennel, lady's mantle, cloves, golden nettle, kaffir lime leaves, garlic, bay leaves, marjoram, lemon balm, oregano, parsley, peppermint (Moroccan mint, spearmint), rosemary, sage, chives, star anise and thyme. They also occur in various fruits such as clementines, limes, olives, oranges, blackcurrants, black elderberries, black pepper, juniper berries and nuts such as pine nuts, hemp nuts and walnuts. Terpenoids have anticarcinogenic, antiallergic, antibacterial and antioxidant effects in the human organism.

Terpenes

They are divided into mono-, di-, tri- and sesquiterpenes and terpenoids. Terpenes and terpenoids have versatile structures. Terpenes such as pinene, myrcene, limonene or terpinene consist of simple hydrocarbon compounds. Due to the large number of terpenes and their diverse structural variants, there are several possible classifications for terpenes in the scientific literature. The more lipophilic mono- and sesquiterpenes are mainly found as components of essential oils, the hydrophilic mono- and triterpenes in the form of glycosides (iridoids, saponins, steroids).

Terpenes are extracted from a wide variety of plants, including eucalyptus, peppermint, lemongrass, lemon and thyme. They are widely used as raw materials in the pharmaceutical, food and cosmetics industries. Furthermore, they play an important role in the growth, development and physiological processes of plants and their reaction to their environment. Terpenes also have anticarcinogenic, antioxidant, anti-inflammatory, antibacterial and anti-allergenic properties.

Monoterpenes

Monoterpenes consist of two isoprene molecules and are found in various parts of coniferous plants, vegetables, fruits and herbs. Many essential oils belong structurally to monoterpenes, such as pinene, myrcene, limonene, terpinene, carvacrol, carvone, eugenol, geraniol and thymol. They act as fragrances in plants to attract pollinating insects or repel predators. Monoterpenes are added to many food products as flavorings, fragrances and natural preservatives or act as natural insecticides and fungicides.

Limonene and carvone are currently the most intensively studied monoterpenes with antitumor properties against stomach, breast and lung cancer. Limonene is the main component of citrus oil and caraway oil. It is also found in numerous plants, such as valerian, basil, bitter oranges, dill, spruce, ginger, hemp, cardamom, pine, garlic, coriander, bay leaf, mint, nutmeg, parsley, rosemary, celery, fir and juniper.

Diterpenes

Diterpenes consist of four isoprene units. Among them are forskolin, ginkgolides and vitamin A. Forskolin is involved in a number of functions in the body. Among other things, it helps to improve blood circulation and strengthens cardiac functions. The health benefits of ginkgo (ginkgo) are mainly due to its ginkgolides content; ginkgolide-B in particular increases blood circulation in the brain and can also protect against allergies.

Cafestol and kahweol are natural diterpenes that are extracted from coffee beans and are mainly present in unfiltered coffee in the form of fatty esters. Some studies have confirmed that coffee diterpenes, especially cafestol, can effectively increase human blood lipid and low-density lipoprotein cholesterol (LDL) levels. This represents a potential risk for the development of some cardiovascular diseases. However, other studies show that moderate consumption of coffee (3 to 5 cups/day) reduces the risk of cardiovascular diseases. Many studies are designed to be able to sell a particular food more frequently - there are studies that work with "target-oriented methods". Smoking has also been touted as beneficial like that.

Sesquiterpenes

Sesquiterpenes consist of three isoprene units and are found mainly in essential oils of plants, where they perform important biological functions, e.g. abscisic acid as a phytohormone, rishitin as a phytoalexin, farnesol as a pheromone, sirenin as a plant sex pheromone and cnicin (benedict herb) as a bitter substance. Individual representatives are e.g. farnesol, nerolidol (neroli oil), caryophyllene (clove oil), cedrol and santalol. The structural diversity of sesquiterpenes is also reflected in the various groups (hydroxyl, methyl, carbonyl, epoxide) and groupings (allene, ether, lactone) that occur.

Triterpenes

Triterpenes consist of six isoprene units. Among others, they include limonoids (in citrus fruits). They have anticarcinogenic, antiviral, antibacterial and fungicidal properties. A well-known triterpene is squalene, which serves as a precursor for the production of steroids. This substance is a component of vegetable and fish oils and is found in e.g. olive oil and wheat germ oil. Squalene is an antioxidant and also has antibacterial, antifungal and antitumor properties. With regard to the isoprene rule, the triterpenes show some irregularities.

The tetracyclic triterpenes consist of four isoprene units that fuse to form a closed ring system. Compounds within these compounds are also known as steroids. The sterols are derived from the steroids. An important sterol is, for example, cholesterol, which is an essential building block for biomembranes. Some well-known examples of phytosterols are beta-sitosterol (β-sitosterol), campesterol and stigmasterol. Phytosterols have a cholesterol-lowering effect and prevent cardiovascular diseases. Epidemiological and experimental studies indicate a protective role of beta-sitosterol in the development of some types of cancer. They show anti-carcinogenic effects in breast, colon and prostate cancer, among others. Beta-sitosterol also has an anti-oxidative activity and reduces the risk of arteriosclerosis. Phytosterols are found in particular in seeds, nuts and vegetable oils such as linseed, sesame, soybeans, sunflower seeds, pumpkin seeds and corn oil.

Saponins are another well-known group of triterpenes with foam-forming properties. Saponins are glycosides of steroids or triterpenes. An exact classification remains controversial. The foam-forming ability of saponins is due to the combination of a hydrophobic (fat-soluble) sapogenin and a hydrophilic (water-soluble) sugar part. Saponins have a bitter taste. Due to their ability to inhibit the division rates, DNA synthesis and growth of tumor cells in the colon, they reduce the risk of developing colon cancer. They also have an anti-inflammatory and cholesterol-lowering effect. Some saponins are poisonous - they are known as sapotoxins.

Saponins are found in many different plant species in nutrient-rich tissue such as roots, tubers, leaves, flowers and seeds. They occur in various legumes (edamame, peas, peanuts, green beans, chickpeas, lentils, alfalfa, mung beans, broad beans, soybeans), vegetables (eggplant, cassava or manioc, Chinese water chestnut, fennel, jackfruit, potato, garlic, chestnut, asparagus, star fruit, tomato), cereals (oats) and pseudocereals (amaranth, quinoa). Due to their foaming effect, saponins are also used as additives in cosmetics and food production. The name of some herbs refers to their foaming properties, such as soapwort, soap root, soap bark and soapberry. Saponins are also found in various medicinal plants, such as birch blossoms, fenugreek seeds, borage, epazote, lady's mantle, ginseng, ground ivy, golden nettle, garlic rocket, chestnuts, melissa, moringa, rosemary, sage, ribwort, licorice and chickweed.

Carotenoids

Carotenoids consist of eight isoprene units (isoprene building blocks). They belong to the group of tetraterpenes and are a very extensive group of substances. To date, around 750 carotenoids have been identified. Of these, around 50 exhibit a "vitamin A effect". At least 18 different carotenoids have been identified in the human organism. Carotenoids are naturally occurring, fat-soluble, yellow, orange to red dyes.

Carotenes (pure hydrocarbons) and xanthophylls (oxygenated derivatives) form the two main groups of carotenoids. Carotenoids are mainly found in the photosynthetically active tissues of plants and algae and are bound to chromoplasts, which are responsible for the coloration of many flowers and fruits. The most important task of carotenoids in plants is the absorption and transfer of light energy to chlorophyll. Carotenoids are highly sensitive to the effects of oxygen, oxidizing substances and light.

Carotenes give fruits and vegetables their yellow-orange or red color (α- and β-carotene), while xanthophylls (astaxanthin, beta-cryptoxanthin) are mainly found in yellow and dark green foods. Carotenoids such as β-carotene (beta-carotene), lycopene, lutein, zeaxanthin, β-cryptoxanthin (beta-cryptoxanthin) and α-carotene (alpha-carotene) are the most abundant. Lycopene occurs in higher concentrations in various fruits and vegetables like jackfruit, tomatoes, watermelon, pink grapefruit, pink guava, papaya, peppers, sea buckthorn, goji berries and in some medicinal drugs such as rosehip, orange marigolds, willowherb and porcini mushrooms - and is more effective as a radical scavenger than other carotenoids. Lutein is found in all green plants - in larger quantities in nettle, nasturtium, marigold, cabbage, dandelion, turnip, spinach, chard, red algae, palm oil and watercress.

The concentration of carotenoids in plants is highly dependent on the variety, season, degree of ripeness, growing, harvesting and storage conditions, method of preparation and varies in different parts of a plant. The outer leaves of cabbage contain over 100 times more lutein and β-carotene than the inner leaves. Carotenoids influence various processes of food intake, distribution, metabolism and excretion in the human organism. Epidemiological studies show that α-carotene, β-carotene, canthaxanthin, lutein and lycopene suppress the formation of cancer cells, i.e. have an anti-carcinogenic effect.

High concentrations of carotenoids in the blood reduce the risk of cardiovascular diseases and damage to the retina. Through their interaction with free radicals, they also protect against cell damage that contributes to skin ageing, support the immune system and inhibit arteriosclerosis (lipid-lowering). In the cells of the small intestine wall, β-carotene is converted into vitamin A, which plays an important role in the visual process. β-carotene is found together with α- and γ-carotene in carrots, pumpkins, corn, oranges and probably in most green plants. In addition, β-carotene and most other carotenoids can be produced synthetically and are approved as colorants in food and pharmaceutical products.

Carotenoids are found in various vegetables (broccoli, chili, kale, kohlrabi, pumpkins, corn, horseradish tree, peppers, spinach, tomatoes, sweet potato, asparagus, savoy cabbage), fruits (apricots, apple, avocado, banana, dates, durian, grapefruit, goji berries, guava, coconut, kumquat, lime, mandarin, mango, melon, orange, papaya, peach, watermelon, lemon, plum), berries (goji berries, sea buckthorn), pulses (chickpeas), nuts (peanuts, hemp, pumpkin seeds), cereals (kamut), pseudocereals (quinoa), herbs (fenugreek, safflower, nasturtium, garlic rocket, lupins, chives, parsley, willowherb, meadow chervil), spices (fenugreek leaves, mace, saffron, mustard), medicinal plants (arnica, dandelion, marigold, pansy), oils (from hemp, olives, oil palm, rapeseed), algae (arame algae, red algae, wakame, laminaria algae) as well as honey.

Main group of alkaloids

The group of alkaloids is the second largest group of plant secondary metabolites with approximately 12'000 described substances, of which approx. 75 % occur in higher plants. It is difficult to divide this large class of substances into subgroups; the main aspects of classification are biogenesis, structural relationship and botanical origin. Alkaloids are nitrogenous derivatives of amino acids such as ornithine, arginine, lysine, phenylalanine, tyrosine and tryptophan. Most alkaloids contain one or more nitrogen rings as their basic structure. However, there are also a number of non-heterocyclic alkaloids, including the phenethylamine alkaloids like mescaline, ephedrine and adrenaline. Depending on which amino acid is the source of biosynthesis, there are three groups: Protoalkaloids, pseudoalkaloids and "true alkaloids".

Protoalkaloids

Protoalkaloids include basic (alkaline) or neutral reacting secondary metabolites in which the nitrogen atom is not integrated into a heterocycle. They are formed directly from amino acids, for example by decarboxylation. Representatives of this group are for example ephedrine and tyramine. Alkaloids derived from the amino acids lysine, phenylalanine, tyrosine, tryptophan or ornithine are considered "true" alkaloids in this classification.

Pseudoalkaloids

Pseudoalkaloids are alkaloids that are not products of amino acid metabolism and are therefore structurally related to other natural substances, such as steroid alkaloids, which include the toxic solanine.

"True alkaloids"

Many plants that contain alkaloids are poisonous and have a bitter taste that protects the plants from predators. Medical basic research is interested in the molecular mechanism of action of alkaloids with the aim of developing new drugs. There are many alkaloids that are used in medicine, such as morphine, taxol and penicillin. Alkaloids include many stimulants, hallucinogens and sedatives. Therefore, they act on certain functional centers, resp. the central nervous system, like caffeine (caffeine), codeine or morphine. Coffee plants produce caffeine mainly as an insecticide to protect their seedlings from being eaten by insects - for humans, it has a stimulating effect. Caffeine is found in over 60 plants such as coffee, tea, cocoa and guarana. Theobromine is the most important alkaloid in coffee, tea and cocoa, resp. chocolate. Piperine also belongs to the alkaloid group and is responsible for the pungent taste of pepper.

Main group of polyphenols

The group of polyphenols is one of the most important groups of natural substances in the plant kingdom. Phenols are aromatic compounds that carry one or more free OH-groups (hydroxy groups) on an aromatic ring system. They occur frequently and have a high structural diversity and functional significance. Due to the large number of phenols and their very different chemical constitution, no general statements can be made about their physico-chemical properties here. Phenols are found almost everywhere in foodstuffs and luxury foods of plant origin - often in considerable concentrations as bioactive substances such as colorants, flavorings and tanning agents. These protect plants from predators, attract pollinating insects or filter UV-B radiation.

Polyphenols have an antioxidant activity, support cognitive functions and reduce the risk of heart diseasse and certain types of cancer. Due to their anti-inflammatory properties, polyphenols can also modify the interaction between muscle and immune cells. They are found in a variety of plant species.

Polyphenols include phenolic acids (such as caffeic acid), flavonoids and phytoestrogens.

Phenolic acids

Studies show that phenolic acids have a protective effect against cancer of the stomach, oesophagus, skin and lungs. They also have antimicrobial and antioxidant potential, which has been studied intensively, particularly in connection with fruit juices.

Flavonoids

Flavonoids occur in a wide variety of chemical structures in all higher plants. However, they are absent in bacteria, algae and fungi, as well as in the entire animal kingdom.

These substances have anti-allergic, anti-inflammatory, antiviral, antimicrobial, antioxidant and anticarcinogenic effects. Medicinal drugs containing flavonoids and some pure substances are particularly useful therapeutically and are used as vein remedies, cardiovascular agents, diuretics, spasmolytics, liver therapeutics and for gastrointestinal complaints. Flavonoids are found in berries, citrus fruits, tea and cocoa. Onions and kale are particularly rich in flavonols. In addition to juices, red wine and black tea contain flavonoids. In general, the flavonoid content in processed foods is only about half as high as in fresh, unprocessed foods due to leaching of the substances.

Flavonoids are divided into different classes such as flavanones, flavones, flavanonols, flavonols and anthocyanins. Flavones and flavonols occur in plants in different variants, including as glycosides.

Anthocyanins are water-soluble plant pigments that occur in the cell sap of almost all higher plants and give flowers, leaves and fruits an intense red, purple or blue color. Anthocyanins have anti-inflammatory properties. This effect is based on their ability to influence various biochemical processes in the body. Anthocyanins are also found in roots. Berries (such as açaí berries, chokeberries, cherries, blue grapes and blueberries) and red cabbage are rich in anthocyanins.

Phytoestrogens

Phytoestrogens are chemically classified as polyphenols and are divided into three structural classes: isoflavones, lignans and coumestans. Isoflavones are found in various legumes, especially in soy products. Lignans occur particularly in cereals and linseed, sesame, sunflowers, peanuts, oily fruits and various fruits and vegetables such as apples, pears, cherries, peaches, fennel, broccoli, onions and garlic. Coumestans are found especially in vegetable sprouts such as soybean sprouts, alfalfa, clover and cabbage.

Phytoestrogens protect plants from damage caused by UV radiation. They influence the growth and stress levels of plants. They also have the ability of reducing fertility in grazing and flying herbivorous predators. In the human body, oestrogens can have hormonal effects. Phytoestrogens are considered to be potentially beneficial to human health. In particular, they are said to alleviate menopausal symptoms, improve bone health, inhibit the development of breast and prostate cancer and ultimately reduce the risk of cardiovascular diseases in women.

Main group of organic sulfur-containing compounds

Sulphides are sulphur-containing compounds in onion and leek plants - e.g. alliin in garlic, onions, chives, shallots, leeks and wild garlic - and in various cabbage plants. Enzymatic or thermal decomposition of the main active ingredients produces characteristic odors, such as in garlic. Sulphides have an antimicrobial and protective effect against various types of cancer such as stomach cancer. They improve the taste of food and have a positive effect on digestion, the immune system and the formation of blood lipids and cholesterol.

Glucosinolates contain sulphur and contribute significantly to the typical smell and taste of mustard, horseradish, cabbage and other members of the cruciferous family. The actual active ingredients are the enzymatic degradation products isothiocyanates, thiocyanates and indoles. Studies on animals have shown antitumor effects against stomach, breast, liver and lung cancer. They also influence the metabolization of endogenous estrogens and thus protect against estrogen-related cancers such as breast and endometrial cancer. Glucosinolates also have an antimicrobial effect and lower blood pressure and cholesterol.

Main group of other nitrogen-containing compounds

The structural and chemical relationship of many nitrogen-containing secondary metabolites is still unsettled. This also includes a number of non-proteinogenic amino acids.

Reminder:

Despite the complexity of the topic, the following applies in practice: prefer a varied, plant-based and seasonal diet with organic food that is as unprocessed as possible. This will allow you to benefit optimally from the many positive effects of phytochemicals. As the plant secondary metabolites are often found in the outer layers, peel vegetables and fruits with consideration. As a vegan or omnivore, please read the article "A vegan diet can be unhealthy. Nutrition mistakes".

Many of our newly edited food descriptions provide you with specific information on which of the secondary metabolites are most prominently represented in the food discussed.