Secondary plant substances

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Secondary plant substances (also secondary metabolites , secondary plant constituents , phytochemicals , also called phytamines in naturopathic areas ) are certain chemical compounds that are produced by plants neither in the energy metabolism nor in the anabolic ( anabolic ) or in the catabolic ( catabolic ) metabolism . They are only produced in special cell types and differ from primary plant substances in that they are not essential for the plant .

Secondary plant substances are natural substances and are of great importance to humans. Often times, plants are grown just for the sake of these compounds. Their biosynthetic pathways are summarized under the term secondary metabolism . Secondary metabolites are derived from products of the anabolic and catabolic metabolism, mainly carboxylic acids , carbohydrates and amino acids . The secondary metabolism cannot always be clearly delineated. This is due to the fact that primary and secondary metabolism often use common reaction steps and the same enzyme systems. The decision as to whether it is a primary or a secondary metabolic product can only be made by considering the function that the substance has in the plant organism.

The most important groups of plant secondary compounds are, classified according to their chemical structure:

Although chlorophyll is only produced in photosynthetically active parts of the plant, it does not belong to the secondary plant substances, as it is essential for the plant to live.

meaning

Since the production of phytochemicals can be very different in different plant species, their investigation is of great importance for taxonomy . Because they are limited in time and space, and are often produced depending on environmental conditions, their investigation is important for understanding cell differentiation in plants. Secondary plant substances such as B. Alkaloids and terpenes form chemically very different structures and are therefore of enormous importance for humans, especially in pharmacology and chemical synthesis .

Significance for the plant organism

The function of secondary phytonutrients for the plant was unexplained for a long time. It was assumed that secondary metabolic pathways served to render useless or toxic metabolic by-products or end products of the primary metabolism harmless, because the compounds could not be assigned a direct role in metabolism . Today it is believed that phytonutrients have important ecological tasks. It is assumed that secondary plant substances have developed as a result of intensive interaction between plants and their environment - especially predators. Many plant secondary substances serve the plant as effective chemical defense substances against herbivores and pathogens . On the other hand, secondary metabolites attract pollen-spreading insects and seed-spreading fruit-eaters as coloring and flavoring substances .

Plants use secondary metabolites

Many of the defense substances are poisonous not only for the enemies of the plants , but also for the plants themselves. In order to avoid self-destruction, three essential strategies have evolved in plants:

Structural formula of Alliin
garlic
  1. The substances accumulate in special cells or tissues . For example, resin collects in the resin ducts, alkaloids are stored in special hairs or scales, and secondary metabolites very often accumulate in the vacuole . The substances are only released when the tissue is destroyed.
  2. The plants form non-toxic precursors and a specifically matching enzyme system that is located in other compartments of the cell or in special cells. Only when the compartments dissolve due to injury do the enzymes come into contact with the substances and form the actual toxic defense substances. Example: alliin in garlic.
  3. The plants only produce protective substances in response to an infection. These protective substances are called phytoalexins . Their formation is limited only to the place of infection. The formation of phytoalexins is triggered by special signal substances ( elicitors ).

Adaptations to secondary plant substances

Despite the sophisticated and diverse connections, certain animals have repeatedly adapted to them or developed a tolerance for them. Such animals are called food specialists. You can absorb the ingredients with food and make them usable for yourself, neutralize them or simply excrete them again. Some animals are able to store toxic substances in their own body by means of sequestration in order to protect themselves from their predators in this way. An interesting example of this is the monarch butterfly , which can store cardiac glycosides ( cardenolides ). These secondary substances cause paralysis and vomiting in its predator, the blue jay . After a short time the birds learn to avoid the strikingly colored butterflies.

Importance to humans

Secondary plant substances are also known as phytamines ( ancient Greek φ Pflanzeτον phyton 'plant') in the naturopathic field , as some of them could offer health benefits as part of the diet. So far, the following effects are known, some of which are controversial (e.g. antioxidant in connection with a health benefit):

effect Fabrics
Lowering blood pressure Reserpine in Rauwolfia serpentina , polyphenols in pomegranate
Therapy of heart failure Cardiac glycosides, in particular cardenolides from Digitalis purpurea and Digitalis lanata
Reduction of thrombi Sulfides in garlic
Lowering blood sugar levels Phytin in grain
Promote digestion Polyphenols in spices
Antimicrobial effects Phenolic acids in fruits
Anti-inflammatory Saponins in legumes , oats, and some vegetables ; Flavonoids in almost all plants
Lowering cholesterol Phytosterols in almost all plants, saponins
Inhibition of carcinogenesis z. B. carotenoids in green-leaved vegetables, protease inhibitors (toxic in higher doses) in potatoes, nuts, cereals, legumes; Pomegranate polyphenols such as punicalagin and other ellagitannins , crosmin , gallic acid and ellagic acid
antioxidant Flavonoids , lipoic acid
estrogenic effects Phytohormones , phytoestrogens .

Many phytochemicals are poisonous for humans and animals. These naturally occurring toxins include, for example, the alkaloids such as nicotine or atropine . The individual ingredients with potential health benefits can also be toxic in high doses. Some of these natural poisons can, however, be used pharmacologically, such as the poison of the deadly nightshade, atropine, the alkaloids of the opium poppy (including morphine , codeine , papaverine and noscapine ) or the diterpenoids from yew species (Taxol A = paclitaxel ). In many cases, natural substances serve as the lead structure for new types of active ingredients, in which the basic structure is optimized in the direction of improved effectiveness and reduced side effects.

literature

  • Katharina Munk (ed.): Basic studies in biology - botany . Spektrum Verlag, Heidelberg 2001.
  • P. Schopfer, A. Brennicke: Plant physiology. 6th edition. Elsevier, 2005, ISBN 3-8274-1561-6 .
  • Jefferey B. Harborne, Herbert Baxter: Phytochemical Dictionary- A Handbook of Bioactive Compounds from Plants . Taylor & Frost, London 1983.
  • Newman Lansky RA: Punica granatum (pomegranate) and its potential for prevention and treatment of inflammation and cancer. In: Journal of Ethnopharmacology . 109, 2007, pp. 177-206.
  • Walter de Gruyter: Pschyrembel Dictionary Naturopathy . Berlin / New York 1996, ISBN 3-11-014276-7 .
  • Deutschlandfunk, consultation hour , October 12, 2010, Radiolexikon , Renate Rutta: Secondary Plant Substances (online) (October 14, 2010)

Individual evidence

  1. See also Karl-Heinz Kubeczka: Comparative Investigations on the Biogenesis of Volatile Products of Secondary Metabolism , I .: Investigations on Ruta graveolens L. In: Flora, Abt. A. Volume 158, No. 5, 1967, pp. 519-544 .
  2. Antioxidants: helpers against free radicals. Retrieved May 10, 2020 .
  3. RJ Vakil: Antihypertensive affects of Rauwolfia. In: British Health Journal. 11, 1949, pp. 350-355.
  4. Hildebert Wagner: Pharmaceutical Biology. Volume 2: Drugs and their ingredients. Gustav Fischer Verlag, Stuttgart 1980.
  5. Christoph Gardener et al .: Effect of Raw Garlic vs Commercial Garlic Supplements on Plasma Lipid Concentrations in Adults With Moderate Hypercholesterolemia: A Randomized Clinical Trial. In: Archives of Internal Medicine . - / 167/2007, pp. 346-353.
  6. FH Erfurt Bioactive substances in vegetables (PDF; 337 kB).
  7. M. Aviram et al .: Pomegranate juice consumption for 3 years by patients with carotid artery stenosis reduces common carotid intima-media thickness, blood pressure and LDL oxidation. ( Memento of the original from December 22, 2015 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. In: Clinical nutrition. Volume 23, Number 3, June 2004, pp. 423-433. doi: 10.1016 / j.clnu.2003.10.002 . PMID 15158307 . @1@ 2Template: Webachiv / IABot / www.wonderfulpomegranateresearch.com
  8. B. Watzl, C. Leitzmann: Bioactive substances in food. 3rd, unchanged edition. Hippokrates, Stuttgart 2005, ISBN 3-8304-5308-6 .
  9. ^ Bernhard Watzl, Gerhard Rechkemmer: Basic knowledge updated: Flavonoide. In: Nutrition review. 48, issue 12, 2001. (PDF).
  10. ^ W. Ling, PJ Jones: Dietary Phytosterols, A Review of Metabolism, Benefits and Side Effects. In: Life Sciences . 57 (3), 1995, pp. 195-206. PMID 7596226 .
  11. UGB: Carotenoids: Red and yellow keep you fit
  12. UGB: Phytoestrogens - foods with hormonal effects
  13. Plants on the warpath. from EU.LEN-SPIEGEL 5-6 / 2010, p. 38.