11º Encontro de Química dos Alimentos Isolation and characterization of polysaccharides from Fraxinus angustifolia infusions Vitor M. Martins a,b , Manuel A. Coimbra b a CIMO - Escola Superior Agrária de Bragança, Bragança, Portugal b QOPNA - Universidade de Aveiro, Aveiro, Portugal * vmartins@ipb.pt Palavras chave: infusions; pectic polysaccharides ABSTRACT In Trás-os-Montes region the infusions prepared from the dried leaves of “freixo” (Fraxinus angustifolia) is used for the prevention of high levels of cholesterol, blood pressure and uric acid. In this work, infusions from the dried leaves of “freixo” were prepared and the high molecular weight material (HMWM) was obtained and fractionated. The results evidenced the presence of pectic polysaccharides, frequently referred as biologically active, with distinct proportions of homogalacturonans (HG) and rhamnogalacturonan (RG) domains. Additional work is in progress in order to evaluate the biological activity of the various isolated fractions and to establish a structure-activity relationship. 1. INTRODUCTION A great diversity of plant infusions is being used for medicinal purposes. In Trás-os-Montes region, one of the most used is the one prepared from the dried leaves of the narrow-leafed ash “freixo” (Fraxinus angustifolia). This infusion is used for the prevention of high levels of cholesterol, blood pressure and uric acid [1]. Although, the bioactivity and potential health benefits of the most popular plant infusions, such as Camellia sinensis and Matricaria recutita, are well documented [2, 3], the use of most of them is based on an empirical knowledge transmitted across several generations. The reported health benefits are associated with the extraction of biologically active substances, such as phenolic compounds and polysaccharides, among others. Recent studies have shown that pectic polysaccharides isolated from plant infusions exhibit a number of beneficial therapeutic properties, such as anti-ulcer, anti-tumoral and immunobiological activities, being thought that the mechanisms involved in these effects are due to the modulation of innate immunity and, more specifically, macrophage function [4]. Pectic polysaccharides are a very complex group of heteropolysaccharides composed of homogalacturonan (HG) and rhamnogalacturonan (RG) domains [5]. The HG domain is composed of partially methyl-esterified α-1,4-galacturonic acid residues, which can be interrupted by ramified domains, called rhamnogalacturonan I (RG-I) or rhamnogalacturonan II (RG-II) domains. RG-I consists of a backbone alternating 1,4-linked GalA and 1,2-linked Rhap units. The rhamnose residues are frequently branching points, primarily on position 4. Frequently, Type II arabinogalactans