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Marine-Based Carbohydrates as a Valuable Resource for Nutraceuticals and Biotechnological Application
Published in Se-Kwon Kim, Marine Biochemistry, 2023
Rajni Kumari, V. Vivekanand, Nidhi Pareek
It is classified on the basis of molecular size and degree of polymerization into monosaccharides, disaccharides, oligosaccharides, and polysaccharides (Knudsen et al., 2013). Monosaccharides are the simplest sugar and have the chemical formula (CH2O)n, where n is the number of carbon atoms in a molecule (Vaclavik et al., 2008), that cannot be further hydrolyzed. The rest of the other saccharides are linked by glycosidic bonds and hydrolyzed into simpler units. For example, fructose, galactose, and glucose are the main source of energy preferentially utilized by the brain and red blood cells (Ferrier, 2014). Disaccharides comprise two monomer sugar units linked by glycosidic bonds. Sucrose, lactose, trehalose, and maltose belong to disaccharides. Oligosaccharides are composed of a few monosaccharide units (2 to 20 units) (Roberfroid and Slavin, 2000) which are soluble in 80% ethanol, but intestinal enzymes are unable to digest them. Fructo-oligosaccharides, galacto-oligosaccharides, and mannan-oligosaccharides are examples of oligosaccharides (Englyst et al., 2007). Polysaccharides belong to high-molecular-weight polymeric monosaccharide units, and the degree of polymerization ranges from 70,000 to 90,000, depending on the type of polysaccharide (BeMiller, 2018). They are neither sweet in taste nor utilized directly like other carbohydrates. They may be linear (starch, cellulose) or branched (amylopectin, glycogen), homopolysaccharides (cellulose, glycogen) or heteropolysaccharides (hyaluronic acid, arabinoxylans) (Slavin, 2012).
Chemopreventive Agents
Published in David E. Thurston, Ilona Pysz, Chemistry and Pharmacology of Anticancer Drugs, 2021
Quercetin (Figure 12.8) is widely distributed in the plant kingdom and is mainly found in the outer parts and leaves in the form of aglycones and glycosides. In the latter, one or more sugar groups are bound to the phenolic groups via glycosidic bonds. Its name is associated with the Latin “quercetum” (meaning oak forest) and the genus Quercus to which oak trees belong. In its pure form quercetin is a yellow crystalline powder (Figure 12.9A) that is virtually insoluble in water but will dissolve in aqueous alkaline solutions. It has a reputation for providing health benefits, including as a chemopreventive agent, and many brands of supplements are available in health food stores worldwide (Figure 12.9B).
Phytochemicals from Traditional Medicinal Plants
Published in Hafiz Ansar Rasul Suleria, Megh R. Goyal, Masood Sadiq Butt, Phytochemicals from Medicinal Plants, 2019
R. N. Raji, A. Vysakh, D. Suma, M. K. Preetha, M. S. Latha
Glycosides are sugars that are chemically bound to any functional group via a glycosidic bond; the sugar group termed as glycone and the nonsugar group termed as aglycone. Plants usually store glycosides in their inactive form and are hydrolyzed to their active forms. Glycosides are classified on the basis of the glycone involved, by the type of glycosidic bond and by the aglycone in the moiety. The most important function carried out by glycosides is signal transduction (Table 1.5).99
Natural polymeric nanocarriers in malignant glioma drug delivery and targeting
Published in Journal of Drug Targeting, 2021
Yuan Gao, Rui Wang, Lixia Zhao, Anchang Liu
Dextran is a common unbranched polysaccharide and is widely explored as raw materials of medical products due to its excellent biodegradability, non-antigenicity, biocompatibility and non-immunogenicity. Its main chain is composed of monomer ɑ-D-glucose. Generally, ɑ-(1→6) glycosidic bond is the core bonding bond while ɑ-(1→4) or ɑ-(1→3) glycosidic bonds exist as the initial end of the branch chain [75]. The structure of the dextran is shown in Figure 4. Polymer–drug conjugates refer to the combination of drugs and polymer-carriers via different chemical bonds. Dextran-based polymer–drug conjugates are typically linked by ester or amide bond, which could affect hydrolysis or enzymolysis in vivo, and enhance the stability and release kinetics of drugs [76]. Han et al. [88] designed an RVG peptide liganded multi-targeting micelles (RVG-Dex-PTX) bypass the BBB, and then reach brain glioma. Carboxylated dextran was first made through a reaction between dextran and succinic anhydride conjugated with PTX via ester bond later. Results showed better anticancer activity in vivo and in vitro than monomer drugs. Li et al. [89] facilely synthesised a polysaccharide-di-drugs conjugate Dex-g-(DOX + BTZ)/cRGD via the one-pot Schiff base reaction between oxidised dextran (Dex-CHO) and c(RGD) and DOX, and boronic esterification between Dex-CHO and bortezomib (BTZ). The formed polysaccharide conjugate could be self-assembled into micelle with a diameter at around 80 nm in an aqueous condition and released DOX and BTZ simultaneously triggered by the acidic condition.
Targeting glyco-immune checkpoints for cancer therapy
Published in Expert Opinion on Biological Therapy, 2021
Glycans are carbohydrate-containing molecules which play an important role in several biological functions, including cell adhesion, metabolism, and immune surveillance [5,6]. Glycans can be found in the extracellular matrix as free chains of glycosaminoglycans, at the cell surface in the form of glycoproteins and glycolipids, and as intracellular glycosylated proteins [6–8]. Glycosylation is an enzymatic process that generates glycosidic bonds. This process takes place predominantly in the endoplasmic reticulum and in the Golgi apparatus and it involves the coordinated action of several glycosyltransferases and glycosidases [6,8]. Given the importance of glycans, it is not surprising that glycosylation is controlled at several levels, including gene expression and localization of glycosyltransferases and glycosidases, and substrate availability [6,8].
Resistant starch, microbiome, and precision modulation
Published in Gut Microbes, 2021
Peter A. Dobranowski, Alain Stintzi
Starch is synthesized in the amyloplast and chloroplast organelles of plants, forming mixtures of amylose and amylopectin. These molecules both consist of chains of glucose subunits linked by α-1,4- and α-1,6-glycosidic bonds, but differ in their chain length (i.e. degree of polymerization; DP) and branching (α-1,6 bonds). Amylose possesses a DP below 6,300 glucose subunits, almost entirely (>99.3%) bonded by α-1,4-glycosidic linkages.16 Conversely, amylopectin forms much larger molecules (DP up to 26,500) with dense networks of short chains (mean DP 15–18) branching from longer chains (mean DP 48 to 60).16 The intra- and intermolecular interactions of amylose and amylopectin impart starch granules with a complex hierarchical structure (Figure 1).