The composition and partial structure of silky oak gum Item Type text; Thesis-Reproduction (electronic) Authors Harris, Leland, 1924- Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 03/10/2021 00:08:40 Link to Item http://hdl.handle.net/10150/319578 THE COMPOSITION AND PARTIAL STRUCTURE OF SILKY OAK GUM by Leland Harris A Thesis submitted to the faculty of the Department of Chemistry in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in the Graduate College, University of Arizona 1952 Approved Seci^-Lucf;/ TABLE OF CONTENTS Page INTBODWCTION . 1 SILKY OAK GUM . .. ' 5 A» Source of the Gum . : » . 5 B. Physical Appearance of the Gum 5 C » Qualitative Analysis of the Untreated Gum . 6 1. Test for the Methoxy Group 0 6 2. Test for Methyl Pentoses . .* # . .. 6 3. Naphthoresorcinol Test for Hexuronic Acid „ J 4. Spectroscopic Analysis of the Ash 7 D, Qualitative Tests for Sugars . 7 1. Introduction ................. 7 2. Test for L-arabinose 8 3. Test for D-xylose » . ........... 8 4. Test for D-galactose . ........... 8 5= Fermentation Test for the Absence of D-glucose, D-msmnose, and D-fructose . ■ 9 - 6 . Paper Chromatographic Detection of Sugars . 9 E. Methods of Quantitative Analysis ....... 14 1. Moisture Determination. 14 2. Ash Determination ............. 14 3. Uronic Acid Determination ......... 14 4. Pentosan Determination .......... 14 223111 5. Methylpentosan •Determination « . ... 15 60 Methoxyl Determinations . » . 16 PURIFICATION, FRACTIONATION, AID ANALYSIS OF SILKY OAK OUD$ ® • ® ® o e . e o - o e . o 6 o e . e e e o * © 1 Y A® Purification of Silky Oak Gum » . 1 7 - B. Fractionation of the Purified Cum . , ® , . 17 0. Preparation of Free Acid from Silky Oak Gum© 18 D. Solubility of the Crude Gum, Purified Frac­ tions# and the Gum Acid . » => . » . » . 19 ■ E= Analysis of the Crude Gum, Free Gum Acid, and the Various Purified Fractions » „ . 20 F. Analysis of Unpurified and Purified Silky® . Oak Gum and Gum Acid, Table I® © © ® © . 21 G© Discussion of Results in Table I© © © . © © 22 HYDROLYSIS OF THE GUM, ISOLATION, IDENTIFICATION, AND ANALYSIS OF THE PRODUCTS 23 A. Method Used in Hydrolysis of Gum and Isolation ’ of the Products . v © . © © © © . 23 B. Hydrolysis for 2.5 Hours at 80° C© in a 4 per . cent Solution of Sulfuric Acid © . © © . 23 C© Hydrolysis of the Free Gum Acid for 2 Hours at 65° C . in a 2 per cent Solution of Sulfuric Acid © © . © . © . 26 D. Hydrolysis of Fraction A, for 3©5 Hours at 80° C. in a 3=5 per cent Solution of Sul­ furic Acid . © © © . © © . © . „. © 27 E. Hydrolysis for 13 Hours at 98° C. in a 4 per cent Solution of Sulfuric Acid © © © © 30 Page F. Hydrolysis of the Free Gum Acid for 15 Hours at 98° C. in a 4 per cent Solution of Sulfuric Acid . „ ...... 31 Q. Hydrolysis of the Gum Acid for 18 Hours at 98° C „ in a 4 per cent Solution of Sulfuric Acid .. .... 32 H. Hydrolysis of Barium Salts 3 and 5 for 6 Hours at 98° 0. in a 2 per cent Solu­ tion of Sulfuric Acid . 34 I. Analysis of Barium Salts from Hydrolysis of Silky Oak Gum, Table II. ...... 36 J. Discussion of Results of the Analysis of the Barium Salts. ........... 37 'K. Sugars-Obtained by Hydrolysis of the Gum 37 L. Identification of the Uronic Acid in Silky Oak Gum ...... ... „ 38 SXJMMARy o o a o . o o e e . » . a o o » e e 4 l BIBLIOGRAPHY .................. 43 ACKNOWLEDGMENT . The author wishes to express his sincere apprecia­ tion and gratitude to Dr. Ernest Anderson for his un­ tiring as s is tance and encouragement - during the course of this investigation. - : THE COMPOSITION AND PARTIAL STRUCTURE OF SILKY OAK GUM V \ INTRODUCTION , '' v - ' ' ;■ In recent years much work has been done on the prop­ erties and chemical composition of plant gums at this Uni­ versity under the direction of Dr. Ernest Anderson and Dr. Lila Sands. The first of the papers to be published on plant gums from the University of Arizona appeared in 1925. In this publication the authors described the occur- rence, appearance/ some physical and chemical properties Ofv c&olla gum and mesquite gum which are found in South- western United States, Due to the large amounts of mesquite gum available in this part .of the country and the interesting chemistry in­ volved in its investigation, the work continued along this line. In the latter part of 1925 and 1926 articles ap­ peared which described the preparation of L-arabinose from mesquite gum and the compositloh of this gum. 5 The re- suits of these articles indicated that mesquite gum consists of 50 per cent L-arabinose, 18.7 per cent D-galactose and 13 per cent of an aldehyde acid belonging to the glucuronic :acid:.group. \ : y ^ ■ - 0.: / c ■ ' r ; . ■ V - ; 4 2 Further investigation by Anderson and Otis showed that mesquite gum is the inorganic salt of an organic acid cons is ting of f bur itqle cule s of L-arabinose, three mole­ cules of D-galactose-, and one molecule of methoxy-D-gluc- uronic acid united with the loss of seven molecules of water. : .. - . ■ , : , 5 . \ ' .; - ' , ' In 19^6 E. Vi White at the University of Idaho found that one molecule of methoxy-D-glucuronic acid and one of L-arabinose occupy terminal positions in the repeating unit of mesquite g-um. The remaining units of L-arabinose were found to be joined by glycosidic linkage at the first and second carbon atoms while the galactose residues seemed to be trebly linked at the first, third, and sixth positions. White stated that the ratio of L-arabinose to D-gdlactose to methoxy-D-glucuronic acid in mesqulte gum is.4;2:1. In 1932 Anderson published an article summarizing some of the results of the previous investigations of plant gums. He Stated that plant gums are probably pathological products which occur chiefly as salts of. complex organic acids. The hydrolytic products of the gums revealed that ■ they usually consist of either D-glucuronic acid or D-galac turonic acid and several molecules of one or more sugars. The acid and sugars seem to be held together in a large molecule by glycosidic linkages„ In .this publication Ander son described the general method used in separating the ' . .. : ;: 3 products of hydrolysis of the gums. References are also given to the analytical methods used in determining the com­ position of the resulting hydrolytic" products; In 1936 E. Anderson, F . H . Russell and L„ ¥„ Seigle^ suggested that the gum from lemon - tirees is composed of one molecule of a methylated uronic acid plus two molecules of P^galactose plus two molecules of L-arabinose minus five molecules of water. In this case the simple formula seems to be doubled. The researchers stated that lemon gum is not formed from pectic substances nor from hemicelluloses in lemon wood but from some of the simple sugars or poly­ saccharides present in the inner portion of the bark of citrus trees. • ' : • ■ / . -; • : : ' : • 8 ' ’ : ■ ' In 1949> J. K. N. Jones and F . Smith reviewed the studies that have been made on gum arable, damson gum, cherry gum, egg plum gum, inesquite gum, and gum tragacanth. The authors state that the uronic acid component found in gums is usually B-glucuronic acid in the pyranose form. The hexoses, which are usually B-galactose or B-mannose, have the pyranose form, while B-arabinose is in the furahose form and B-xylose is found in the pyranose form 6 The methyl- pentoses found in plant gums are L-rhamnose and L-fucose and these have the pyranose structure. Jones, and Smith state that the significance of the occurrence of so many sugars united by all the known types of glycosidic linkage :: ^ . : /v ’ v;. ; -v.; X: ■ :;7 ^ 4 is not known; unless: it be that they are so constituted as to be able to resist the action of an organism or a series of invading organisms with their accompanying enzyme systems . ' : - v : v , ' - : ' : : : /Y' Recently E. Anderson and H . D .- Ledbetter invest!- ■. gated the composition of sapote gum,, which IS available in Peru. The investigation showed that this polyuronide con­ sists of the calcium and magnesium salts of a methoxyuronic acid to which pentosan material is attached. The only sugars present were D-xylose:and L-arabinose. The complex salt contained approximately one methoxy group to two uronic acid groups and seven anhydro pentose units. It was found that the L-arabinose groups were easily hydrolyzed off the polyuronide in this case, while the D-xylose attached to the uronic acid, presumably by a glyeosidic linkage/ was very difficult to remove even under rigorous conditions of hydrolysis. • , - The present investigation deals with the composition and partial structure of the gum from silky oak, G-revillea . robusta.» The general methods used in the work have been described by Anderson and Bands , and are similar to those used by Anderson and Ledbetter.^ SILKY OAK G1M SOURCE OF THE GUM Originally the name silky oak was used for the timbers of Orites excelsa and Grevillea robusta which grow on the coastal areas in southern Queensland and northern Hew South 10 Wales in Australia. This source of supply has been prac­ tically exhausted and the name is now the standard trade common name for the timber of Cardwellia sublimus. In the United States it is known as lacewood.