Chemistry of Natural Drugs Lecture 6 PDF

Chemistry of Natural Drugs Dr. Thukaa Z. Abdul-Jalil Lec 6 On the earth, the green plants are the main source for natural drugs, where many plants accumulate many organic substances have economically as chemical feed stocks or raw materials for various scientific and commercial applications. These o...

Chemistry of Natural Drugs Dr. Thukaa Z. Abdul-Jalil Lec 6 On the earth, the green plants are the main source for natural drugs, where many plants accumulate many organic substances have economically as chemical feed stocks or raw materials for various scientific and commercial applications. These organic substances are synthesis (Anabolism ) and degradation (catabolism )to form another organic substances by series of chemical reactions, these chemical reactions on the whole are named Metabolism , therefore these organic substances are classified as primary and secondary metabolites. Primary Metabolites Properties: 1-These substances are formed by photosynthesis process (anabolism). 2- They have a high molecular weight. 3- They are found in high concentration in the cells of plant. 4-They are source for energy. 5-They have structural and functional roles in the plant. Ex: Different sugars (glucose, sucrose…etc.), amino acids, fatty acids, nucleic acids (DNA, RNA), and their derivatives proteins. Secondary Metabolites Properties: 1-These substances biosynthetically derived from primary metabolites by two main pathways: A. Shikimic acid pathway. B. Acetate mevalonate pathway. 2- They have a small molecular weight. 3-They are found in a small concentration in the cells of plant. 4- They are not a source for energy. 5- They have no apparent clear function in a plant, but often they have an ecological role. Ex: For human, these secondary substances are economically useful, because they are used as drugs like digoxin. Photosynthesis Process: In one of the most important biological process occurred on the earth because it is only source for oxygen, by this process the green plants take the photon and convert it to chemical energy and then the plants use this energy to form different organic compounds, this process consist of 2 classes of reactions: 1-Light reactions: the main function of these reactions is production 2 types of chemical energy and they are NADPH, ATP addition to give O2. 2NADP +3ADP+3H3PO4+2H2O Light 2NADPH+3ATP+O2+2H++3H2O 2-Dark reactions: They are enzymatic reactions that utilize the energy from the light reactions to fix carbon dioxide into sugar, where in these reactions carbon dioxide reacts with the compound RUDP ( Ribulose 1,5-phosphate) to give 2 molecules of PGA (3-phosphoglyceric acid). CO2+RUDP ** 2PGA * ** The enzyme: Ribulose diphosphate carboxylase. *PGA: This compound is the first organic compound produced from photosynthesis. Then occurred a series of reactions named ( Calvin cycle or Calvin –Benson cycle).By this cycle ,the plant formed the first bond sugar (Fructose-6-phosphate), then this sugar converted to sucrose, the sucrose is the first sugar formed in photosynthesis and it is the main transport material in plant and is the usual precursor for oligo- and polysaccharide synthesis and a number of reactions occurred on it. OR hydrolysis by invertase enzyme to formed monosaccharide (glucose & fructose) which play very important roles in the synthesis of secondary metabolites. Carbohydrate and related compounds UDP + Sucrose – P Sucrose - Pi photosynthesis Fructose – 6 – P Glucose – 6 - P Glucose – 1- P Fructose + Pi Sucrose +UDP Fig 1: pathways of sucrose biosynthesis UTP UDP – Glucose – Pi Basic metabolic pathways for primary and secondary metabolites