Experiments on the synthesis of carotenoid glycosides (original) (raw)

Carotenoids Biosynthesis – a review

Plants synthesized an enormous variety of metabolites that can be classified into two groups based on their functions: primary metabolites, which participate in nutrition and essential metabolic processes within the plant, and secondary metabolites (also referred to as natural products), which influence ecological interactions between plants and their environment. The carotenoids pigments are secondary metabolites of isoprenoid origin. Despite their diversity of functions and structures, all isoprenoids derive from the common five-carbon (C 5) building units isopentenyl diphosphate (IPP) and its isomer dimethylallyl diphosphate (DMAPP). More complex isoprenoids are usually formed by «head-to-tail» or «head-to-head» addition of isoprene units. The most prevalent tetrater-penes (C 40) are carotenoids, which are pigments in many flowers and fruits. In this paper we discuss some aspects of carotenoid biosynthesis. The pathway involves a series of desaturations, cyclizations, hydroxylations, and epoxidations, commencing with the formation of phytoene. The pathway begins with the synthesis of IPP from the mevalonic acid (MVA) pathway and/or methylerythritol 4-phosphate (MEP) pathway. Resumo As plantas sintetizam uma enorme variedade de metabolitos, que podem ser classificados em dois grupos, de acordo com as suas funções: metabolitos primários, que participam na nutrição e processos metabólicos essenciais no interior da própria planta, e metabolitos secundários (também referidos como produtos naturais), os quais influenciam as interacções ecológicas entre as plantas e o ambiente. Os carotenóides são metabolitos secundários derivados do isopreno. O isopentenil-pirofosfato (IPP) é a unidade básica para a biossíntese dos carotenóides. O esqueleto carbonado dos carotenóides é sintetizado por adição sucessiva das unidades em C 5 que vão formar geranil-geranilpirofosfato, intermediário em C 20 que por condensação origina a estrutura em C 40. Recentemente assumia-se que todos os isoprenóides se sintetizavam a partir do acetil-CoA via ácido mevalónico. Estudos recentes mostraram que o percurso metabólico começa com a síntese do IPP via ácido mevalónico (MVA) e/ou via metileritritol 4-fosfato (MEP). Neste trabalho discutem-se os avanços no conhecimento destas diferentes vias metabólicas assim como as enzimas e

Partial synthesis of serum carotenoids and their metabolites

Acta Biochimica Polonica, 2012

Human serum and tissues contain in excess of 12 dietary carotenoids and several metabolites that originate from consumption of fruits and vegetables. Among these are hydroxycarotenoids: (3R,3'R,6'R)-lutein (1), (3R,3'R)-zeaxanthin (2), (3R,6'R)-α-cryptoxanthin (3), and (3R)-β-cryptoxanthin (4). In addition, several dehydration products of 1 have also been identified in human serum, these are: (3R,6'R)-3-hydroxy-3',4'-didehydro-β,γ-carotene (5), (3R,6'R)-3-hydroxy-2',3'-didehydro-β,ε-carotene (6), and (3R)-3-hydroxy-3',4'-didehydro-β,β-carotene (7). Several metabolites of 1 and/or 2, namely, (3R,3'S,6'R)-lutein (3'-epilutein, 8) and (3R,3'S;meso)-zeaxanthin (9) have also been characterized in human serum and ocular tissues. Semi-synthetic processes have been developed that separately transform commercially available 1 into 4 via 7 as well as 1 into 8. While 8 is converted into 2 by base-catalyzed isomerization, 7 is tran...

A new approach to the synthesis of glycosides

Pure and Applied Chemistry, 1993

An new approach towards glycosides, which obviates the use of promoters and depends upon the acihty of the glycosyl acceptor is proposed to achieve regioselective glycosidation. Glycosylidene mbenes, generated under thermal or photolytic conditions from 0benzylated or 0-acylated 1-azi-glycoses, or from glycono-l,5-(or 1,4)-lactone tosylhydrazones react with hydroxy compounds to yield glycosides. The preparation of these precursors, their structure, their thermal stability, and their products of thermolysis are discussed. A mechanism is proposed to explain and predict the reaction of 1-azi-glycoses with mono-, di-, and triols. Protonation of the carbene in the o-plane leads to an ion-pair, which cannot immediately form glycosides. The fate of this ion pair depends upon the pK of the glycosyl acceptor, inter-and intramolecular hydrogen bonds, the direction of H-bonds, the presence of a neighbouring group at C(2), the configuration of the glycosyl acceptor, the solvent, and the temperature. Strongly acidic hydroxy compounds give glycosides in high yields and stereoselectively. Successful regio-and stereoselective glycosidation of diols and triols depends strongly upon intra-(and inter)molecular hydrogen bonds, both between the hydroxy goups of the acceptor and between functional groups of the donor and hydroxy groups of the acceptor. This is illustrated by a number of significant cases. For some of them, regioselectivity is complementary to the one observed in glycosidations of the Koenigs-Knorr-type, for others it is not. Reasons for this are discussed. Other cases present the preferential glycosylation of secondary hydroxy groups in the presence of a primary one, and the selective formation of aD -glycosides of M A C and GlcNAc. Intramolecular reactions of alkoxyalkyl carbenes are illustrated by a new method for the formation of benzylidene acetals under basic conditions, and by a new synthesis of homobenzofurans. New reactions, leading to the formation of C,C bonds at the anomeric centre are presented: the synthesis of spiro-oxiranes, of dialkoxy-spiro-cyclo opanes, and of the first glycosylated, enantiomdcally pure derivatives of Cmbuckminst&erene.

Goldacre Review: Carotenoids in nature: insights from plants and beyond

Functional Plant Biology, 2011

Carotenoids are natural isoprenoid pigments that provide leaves, fruits, vegetables and flowers with distinctive yellow, orange and some reddish colours as well as several aromas in plants. Their bright colours serve as attractants for pollination and seed dispersal. Carotenoids comprise a large family of C40 polyenes and are synthesised by all photosynthetic organisms, aphids, some bacteria and fungi alike. In animals carotenoid derivatives promote health, improve sexual behaviour and are essential for reproduction. As such, carotenoids are commercially important in agriculture, food, health and the cosmetic industries. In plants, carotenoids are essential components required for photosynthesis, photoprotection and the production of carotenoid-derived phytohormones, including ABA and strigolactone. The carotenoid biosynthetic pathway has been extensively studied in a range of organisms providing an almost complete pathway for carotenogenesis. A new wave in carotenoid biology has re...

Carotenoid metabolism: New insights and synthetic approaches

Frontiers in Plant Science

Carotenoids are well-known isoprenoid pigments naturally produced by plants, algae, photosynthetic bacteria as well as by several heterotrophic microorganisms. In plants, they are synthesized in plastids where they play essential roles in light-harvesting and in protecting the photosynthetic apparatus from reactive oxygen species (ROS). Carotenoids are also precursors of bioactive metabolites called apocarotenoids, including vitamin A and the phytohormones abscisic acid (ABA) and strigolactones (SLs). Genetic engineering of carotenogenesis made possible the enhancement of the nutritional value of many crops. New metabolic engineering approaches have recently been developed to modulate carotenoid content, including the employment of CRISPR technologies for single-base editing and the integration of exogenous genes into specific “safe harbors” in the genome. In addition, recent studies revealed the option of synthetic conversion of leaf chloroplasts into chromoplasts, thus increasing ...

Carotenoids and Some Other Pigments from Fungi and Yeasts

Metabolites

Carotenoids are an essential group of compounds that may be obtained by microbiological synthesis. They are instrumental in various areas of industry, medicine, agriculture, and ecology. The increase of carotenoids’ demand at the global market is now essential. At the moment, the production of natural carotenoids is more expensive than obtaining their synthetic forms, but several new approaches/directions on how to decrease this difference were developed during the last decades. This review briefly describes the information accumulated until now about the beneficial effects of carotenoids on human health protection, their possible application in the treatments of various diseases, and their use in the food and feed industry. This review also describes some issues that are linked with biotechnological production of fungal and yeasts carotenoids, as well as new approaches/directions to make their biotechnological production more efficient.

Carotenoids: Potent to Prevent Diseases Review

Natural Products and Bioprospecting, 2020

Carotenoids are the phytochemicals known for their biological activities. They are found in nature in the form of plants, algae, fungi and in microorganisms. This is the major group having two different structure one with oxygen and without oxygen. The Present article aims to present these molecules as a new therapeutic agent, as it has unrealized efficiency to prevent and reduce the symptoms of many diseases like cancer, neurodegenerative diseases such as Alzheimer, cerebral ischemia, diabetes associated with obesity and hypertension, ophthalmic diseases and many more. It can be utilized in the form of dietary supplement as nutraceutical and pharmaceutical compounds. Yet more research and developing test knowledge is needed to make it available to the humans. In this article its sources, biosynthesis, properties, applicability and commercialization of pigments from naturally produced sources are discussed. Graphic Abstract