Classes of phenolics have been characterized on the basis of their basic skeleton. Plant adaptation to biotic and abiotic stress involves the stimulation of protective secondary metabolite pathways 57, resulting in the biosynthesis of phenolic antioxidants. Secondary metabolites, drugs, flavours, fragrances, biotechnology introduction plants possess capacity to synthesize different organic molecules called secondary metabolites. Phenols constitute probably the largest group of plant secondary metabolites, varying in size from a simple structure with an aromatic ring to complex ones such as lignins. Phenolic acids are aromatic secondary plant metabolites broadly distributed throughout the plant kingdom. Role of secondary metabolites in defense mechanisms of plants. Pdf response of plant secondary metabolites to environmental. Much attention has been focused on the potential bioactivity and nutritional relevance of several classes of phytochemicals such as flavonoids, carotenoids, phytooestrogens and glucosinolates. Many simple phenols are responsible for taste, for example eugenol. Increased temperature as an abiotic stress may exert a considerable influence on the levels of secondary metabolites in plants.
Pigments such as terpenoid carotenes, phenolics, and flavonoids color flowers and, together with terpene and phenolic odors, attract pollinators. Phenolic compoundsare ubiquitous in plants and these are secondary metabolites which shield the plants against uv radiation or resist the pathogenic the phenolic acids with common biogenetic precursor, shikimic acid. Classification of secondary metabolites plant secondary metabolites are classified into four major categories as classified by british nutrition foundation 12. Alkaloids, glycosides, phen olics, terpenoids secondary metabolites 6.
Plant secondary metabolites can be distinguished roughly into three classes of chemical compounds, namely alkaloids, phenolic compounds and terpenes. Based on their biosynthetic origins, plant natural products can be divided into three major groups. Skeletal formula of solanine, a toxic alkaloid which builds up in potatoes. Plant phenolics and polyphenols are secondary natural metabolites arising. Secondary metabolism is connected to primary metabolism by using building blocks and biosynthetic enzymes derived from primary metabolism. These molecules have activities that could improve or deteriorate health and production. Metabolites are the intermediates and products of metabolism and are usually restricted to small molecules.
They contain benzene rings, with one or more hydroxyl substituents, and range from simple phenolic molecules to highly polymerized compounds 2 figure1. Secondary metabolites, including terpenes, phenolics and nitrogen n and sulphur s containing compounds, defend plants against a variety of herbivores and pathogenic microorganisms as well as various kinds of abiotic. Among these compounds, flavonoids constitute one of the most ubiquitous groups of all plant phenolics. These compounds are the products of secondary metabolism, which is the metabolism of chemicals that occurs irregularly or rarely among plants, and that have no known general metabolic role. Studies indicate that plants exposed to ozone responded with increased transcript levels of enzymes in the phenylpropanoid and lignin pathways 8. All consist of the aromatic ring c6 bonded directly to at least one phenol or more polyphenol hydroxyl groups oh and other substituents, such as methoxyl or carboxyl groups which cause the polar character of the compounds and allow dissolution in water 28. These compounds are an extremely di verse group of natural products synthesized by plants, fungi, bacteria, algae, and animals. A study on the stability of structurally different phenolic compounds in buffers in the ph range 311 revealed that caffeic, chlorogenic, and gallic acid were not stable to high ph. The plant phenolic compounds 8,000 phenolic structures known account for 40% of organic carbon circulating in the biosphere evolution of vascular plants. Terpenes, phenols, flavanoids, alkaloids, sterols, waxes, fats, tannins, sugars, gums, suberins, resin. Of the estimated 400,000 500,000 plant species around the globe, only a small percentage has been investigated phytochemically and the fraction subjected to biological or pharmacological screening is even lower.
Currently, natural products, especially plant secondary metabolites such as isoprenoids, phenolics and alkaloids, have been demonstrated to be the leading providers of novel anticancer agents. Most of secondary metabolites, such as terpenes, phenolic compounds and alkaloids are classified based on their biosynthetic. Abstract plant phenolics and polyphenols are secondary natural metabolites arising biogenetically from either the shikimatephenylpropanoid pathway, which directly provides phenylpropanoids, or the polyketide acetatemalonate pathway, which can produce simple phenols, or both, thus producing monomeric and polymeric phenols and polyphenols, which. In organic chemistry a class of chemical compounds which consist of a hydroxyl group oh directly bonded to an aromatic hydrocarbon group phenolic compounds are the substances containing benzoic molecules with one or several hydroxylic groups and their. Introduction classification of phenolic compounds biosynthesis genetic engineering of the flavonoid biosynthetic pathway databases acknowledgements phenols, polyphenols and tannins. They share the presence of one or more phenol groups as a common characteristic and range from simple structures with one aromatic ring to highly complex polymeric substances. The metabolism can be defined as the sum of all the biochemical reactions carried out by an organism.
Plant based diets contain a plethora of secondary metabolites that may impact on health and disease prevention. Modes of action of plant secondary metabolites and counteraction by mammals toxic plant secondary metabolites negative. Phenolic compounds confer unique taste, flavour, and healthpromoting properties found in vegetables and fruits8. Phenolic compounds are a large and diverse group of molecules, which includes many different families of aromatic secondary metabolites in plants. Although many of the essential oils are terpenes, some are phenolic compounds, for example thymol from thymus spp.
A third view characterizes secondary metabolism as an integral part of. Primary, secondary metabolites, photosynthetic capacity. More than 8,000 phenolic plant compounds exist as secondary metabolites in plants and have various physiological activities tsao, 2010, many of which have been developed as pharmaceuticals. Phenolics are most abundant secondary metabolites of plants ranging from simple molecules such as phenolic acid to highly polymerized substances such as tannins.
Plant secondary metabolites plants produce as amazing diversity of low molecular weight compounds. Nowadays, phenolic acids are receiving considerable attention because of their reported protective role against cancer and heart disease. In fact, grasslands, especially those with high dicotyledonous plant species, present a large, pharmacologically active reservoir of secondary metabolites e. Most of the natural phenols are derived from secondary plant metabolism of the shikimic acid pathway, malic acid pathway or both.
The role they play in the plant is not, to date, well known or understood, but it may. Secondary metabolism produces a large number of specialized compounds estimated 200,000 that do not aid in the growth and development of plants but are required for the plant to survive in its environment. Plants are sessile organisms and, in order to defend themselves against exogenous abiotic constraints, they synthesize an array of secondary metabolites which have important physiological and ecological effects. Analytical methods for analyse secondary metabolites. Secondary metabolism plant phenolics phenolic classes ecological and. The term phenolic acids, in general, designates phenols that possess one carboxylic acid functionality. Phenolic acids, including gallic acid, benzoic acids and cinnamic acids, constitute a major group of plant secondary metabolites. Secondary metabolites, also known as phytochemicals, natural products or plant constituents are responsible for medicinal properties of plants to which they belong. The role of plant secondary metabolites in mammalian.
Induced plant secondary metabolites for phytopatogenic. Phenolic compounds are secondary metabolites, which are produced in the shikimic acid of plants and pentose phosphate through phenylpropanoid metabolization 1. The current work aimed to characterize the phenolic secondary metabolites of s. Some of the organic compounds like carbohydrates, fats, proteins, nucleic acids, chlorophylls, hemes are required for their basic metabolic processes and found throughout the plant kingdom. Biological activity of secondary plant metabolites human health activity of natural phenolic compounds scientific papers dins nic d c d oids d ns dzin ol n ols antiviral effect x x x x antimicrobial effect x x x x protection of cell membranes x x x affect to fatty acid metabolism x x x affect nolevel in plasma x x antiallergenic effect x. All terpenoids, including both primary metabolites and more than 25,000 secondary compounds, are derived. Journal of soil science and plant nutrition 2012, 12 4, 893911 induced plant secondary metabolites for phytopatogenic fungi control. Stress and defense responses in plant secondary metabolites. Phenolics probably constitute the largest group of plant secondary metabolites. Secondary metabolites in plants biology encyclopedia. Secondary metabolites are divided into three major groups plant secondary metabolites can be divided into three chemically distinct groups.
Large number of phenolic compounds occur in plants as secondary metabolites which perform the following functions. Quantitative hplc analysis of phenolic acids, flavonoids. These four categories include terpenoids such as carotenoids, sterols, cardiac glycosides and plant volatiles, phenolics such as lignans, phenolic acid, tannins, coumarins, lignins. Toxic psm generally enter the animal via absorption from the gastrointestinal tract and exert their effects via their lipophilicity, causing them to reside in membranes disrupting membrane function, or they enter the cells. Enhanced experession of secondary metabolites in plants. Unique carbon skeleton structures are basic properties of plant secondary metabolites. These phenolics are the most abundant secondary metabolites in plants and can be classified into nonsoluble compounds such as condensed tannins, lignins, cellwall. Plant secondary metabolites can be classified into four major classes. Predictions of global increased temperature are for 1. Phenolic compounds constitute one of the main classes of secondary metabolites. Introduction and role of phenolic secondary metabolites. Kossel in 1891 implies that while primary metabolites are present in every living cell capable. Pdf plant phenolics and polyphenols are secondary natural metabolites arising biogenetically from either the shikimatephenylpropanoid pathway.
The aromatic amino acid phenylalanine, synthesized in the shikimicacid pathway, is the common precursor of phenol containing amino acids and phenolic. Introduction classification occurrence synthesis defense 2. Secondary metabolites are not necessary for a cell organism to live, but. Plants make a variety of less widely distributed compounds such as morphine, caffeine, nicotine, menthol, and rubber. Phenolic compound an overview sciencedirect topics. Current approaches for enhanced expression of secondary. Secondary metabolites may also inhibit the growth of competitor plants allelopathy. To evaluate its antioxidant activity in vivo, the nematode caenorhabditis elegans was used, since it is a wellestablished model suitable to study stress resistance, aging, and longevity. Phenolic compounds have long been associated with a variety of biochemical and pharmacological properties including antioxidant, antiviral, anticancer, and anti. By their nature, plants protect themselves by producing some compounds called as secondary metabolites. They are widespread in plants where they contribute significantly to the color, taste and flavor of many herbs, foods.