Pectic substances molecular structures

Pectic Substances. Part 111. Composition of Apple Pectin and the Molecular Structure of the Araban Component of Apple Pectin, E. L. Hirst and J. K. N. Jones,/. Chem. Soc., (1939) 454-460. 

Polyuronides may be defined as polysaccharides that contain one or more uronic acid units in their molecular structures. They have a frequent and wide occurrence in nature. Much of the carbohydrate material in plants belongs to the group. It includes all pectic materials and plant gums and many plant mucilages, hemicelluloses and gel-forming substances and some microbial polysaccharides. These substances are to be looked for in water-soluble plant exudates and mucilages, as well as in water and alkaline extracts of most plant materials. This review will be limited to the polyuronides occurring in plants. 

The first structural studies of soluble pectic substances in grapes are relatively recent. Pioneering work was carried out by Villetaz et al. (1981), Brillouet (1987), Saulnier and Thibault (1987) and Saulnier et al. (1988). Continuing studies have identified detailed molecular structures and linked them to known pectic substances in plants. 

These substances have molecular structures similar to those of the lateral branches of acid pectic substances, consisting of arabinan and type 11 arabinogalactan. 

For a century the development of pectin chemistry was severely handicapped by the aim of investigators to identify its structure in terms of a constant, relatively small molecular size . It is clear today that any sample of a pectic substance is in reality a mixture of polygalacturonic acids of various... 

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