While there is no shortage of scientific facts about primary metabolism, secondary metabolism is still largely unexplored. It refers to all metabolic processes that do not directly serve to sustain life. However, the boundary between primary and secondary metabolism is often blurred. It is particularly important in the plant world, but is also relevant for animals and humans. It is still largely unexplored in this respect, which is why this article describes its importance using plants as an example.
What is secondary metabolism?
Pomegranate, in its particular biochemical composition, is considered the best known source of antioxidants to date. Primary metabolism includes all the processes that ensure the vital function of an organism. Primary metabolism synthesizes vital substances such as amino acids, fats and sugars and is the same in almost all living organisms. Components of secondary metabolism are, for example, scents with which the flowers of violets, lilies of the valley or roses attract their pollinators, or the pigments that give fruits color or indicate their degree of ripeness. Secondary metabolism includes all chemical compounds produced by the plants themselves. These are secondary plant constituents, also known as bioactive substances or antioxidants. So far, about 200,000 such substances are known, but they are far from being adequately researched. Secondary substances are the often very conspicuous characteristics of a plant, but they are dispensable for its growth and development. Secondary substances are individual and are often found only in a particular plant species. For example, the “pungents” of pepper are found only in tropical pepper species, and morphine is known only as a secondary in opium poppy. People have known a lot about the healing or even poisonous effects of a wide variety of plants for a long time and, based on accumulated experience, use them as remedies for many diseases. However, why and how some plants could heal and others kill was largely unknown until the first half of the last century. Eventually, chemists also became involved with the various plant constituents. In 1806, the pharmacist Friedrich Wilhelm Sertürner from Paderborn was the first to isolate morphine from opium. It was not until the beginning of biosynthesis research after the Second World War that knowledge grew of the decisive role played by secondary metabolism in the evolution of plants. In this respect, secondary metabolism also ensures the survival of organisms, although not as directly as brisk metabolism does.
Function and task
Today, science agrees, without secondary metabolism, there would be no plant survival. Each plant develops its survival strategy with the help of chemical agents. Predators are fought by deterrence, feeding inhibition or poison. Antibacterial or fungitoxic substances are used against the spread of microbes. All these substances have evolved over the course of evolution, are constantly adapted to changing environmental conditions, and are sometimes reversed from negative to positive. For example, a plant whose toxic barrier an insect has overcome may become its preferred food plant or serve as an egg-laying site, thus becoming a special niche for life. Many studies have shown that the secondary metabolites produced in specialized cell types of plants have an influence on a large number of metabolic processes in humans. Although they are not essential nutrients, a wide variety of health-promoting effects are attributed to them. For this reason in particular, the German Society and all health insurance companies have for years recommended a generous consumption of vegetables and fruit, legumes and nuts, as well as whole grain products. The ingredients of vegetables and fruits are important for us humans because they protect against free radicals with their secondary plant compounds, the antioxidants. To date, research has focused on about 30 of the main plants consumed worldwide and their phytochemicals. Each plant contains a limited but still large number of different substances, for example the apple with 200 to 300 and the tomato with 300 to 350 substances.Compared to fruit, vegetables contain more vitamins as well as secondary plant compounds. The concentration is particularly high in the peel or in the seeds.
Diseases and ailments
If people consume too few of the secondary plant metabolites, deficiency symptoms can develop. In this respect, the substances have a preventive effect. In the case of already existing problems, the intake of the secondary metabolic products can alleviate complaints and diseases. Anthocyanins are a well-known subgroup of polyphenols. They are mainly found in blue, violet, red or blue-black fruits and vegetables. They are contained in many dark blue or red cherries and berries, in eggplants, in red onions and also in red cabbage. Anthocyanins are particularly protective against direct sunlight. Anthocyanins are considered particularly effective antioxidants. They protect our cells from inflammation and degeneration (cancer), for example. Astaxanthin is considered a particularly effective antioxidant. It belongs to the group of carotionoids and gives tomatoes and carrots their red color, for example. For us humans, astaxanthin is important as a power donor and for protecting the skin, joints and especially the eyes (macula) from free radicals. The seeds of grapes contain OPC (oligomeric procyanidins) resveratol and quercetin. All three also belong to the polyphenols. OPC is probably the most powerful antioxidant known. OPC is considered an anti-aging miracle cure for the skin, it can reduce wrinkles and accelerate wound healing. It protects the heart, blood vessels and eyes. Resveratol and quercetin also assist in the fight against cancer, they can lower blood pressure and regulate cholesterol. The pomegranate has always been considered a religious symbol of fertility. Today, this particular fruit is of great scientific interest. The pomegranate is considered to be the best known source of antioxidants due to its special biochemical composition. Not only does it have a particularly high concentration of vitamin C, potassium and vitamin B5 (pantothenic acid), but it also contains many polyphenols and tannins that protect against disease. Intensive research is currently being conducted into its positive effect on protasta and breast cancer. Among the phytoestrogens are lignans (components of flaxseed). They are also believed to have an anti-cancer effect.
