Materials Science and Applied Chemistry doi: 10.1515/msac-2016-0005 26 ©2016 Sarmīte Janceva, Tatjana Dižbite, Gaļina Teliševa, Laima Vēvere, Jeļena Krasiļņikova, Mārcis Dzenis. This is an open access article licensed under the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), in the manner agreed with De Gruyter Open. _______________________________________________________________________________________________ 2016/33 Assessment of Alder Tree Bark Potential as a Renewable Source of Proanthocyanidins in Latvia Sarmīte Janceva 1 , Tatjana Dižbite 1 , Gaļina Teliševa 1 , Laima Vēvere 1 , Jeļena Krasiļņikova 2 , Mārcis Dzenis 3 1 Latvian State Institute of Wood Chemistry, Latvia 2 Rīga Stradiņš University, Latvia 3 Institute of Polymer Materials, Faculty of Materials Science and Applied Chemistry,Riga Technical University, Latvia Abstract – With the purpose to assess potential of alder tree bark as a renewable source of bioactive polyphenolic compounds, antioxidant properties of hydrophilic extracts and proanthocyanidins (PAC) isolated from bark of two alder species (grey alder and black alder) growing in Latvia have been examined employing two test systems, ABTS ●+ , DPPH ● assays. In the tests the high free radical scavenging capacities of the PAC were demonstrated. The polyphenolic nature of the bark PAC opens the possibility of its application as food additive. The PAC has good potential as an antioxidant for mayonnaise. Keywords – Bark, deciduous trees, condensed tannins, proanthocyanidins, free radical scavenging activity, lipid peroxidation, amylase. I. INTRODUCTION Deciduous trees, which are wide spread in Northern Europe, cover approximately 54 % of the total forest area in Latvia. Alnus incana and Alnus glutinosa sp., commonly known as grey alder (GA) and black alder (BA) are fast-growing trees that grow well on poorer soils. The bark constitutes typically 4–10 % of the total weight of deciduous tree stems. Nowadays, the wood bark from logging and wood mechanical processing is used as cheap fuels, soil conditioners and amendments, and as decorative landscape mulching products, though the barks of deciduous tree species contain bioactive chemicals, including the polyphenols [1]. The bark of alder species growing in the Europe, in particular in Latvia, is scarcely explored as a source for obtaining of valuable extractive products. Plant polyphenols have drawn increasing attention due to their antioxidant properties and their marked effects in the prevention of various oxidative stress-associated diseases, such as cancer. Proanthocyanidins (PAC), known also as condensed tannins, are widely distributed in the plant kingdom and belong to a class of polyphenolic compounds that take the form of oligomers or polymers of polyhydroxy flavan3ol units, such as (+)catechin and (−)epicatechin, see Fig. 1 [2]. The high concentration of proanthocyanidins in alder bark makes it a prospective raw material not only for medicine and veterinary, but also for food industrial applications, in particular as food antioxidant additive. Fig. 1. Chemical structure of proanthocyanidine exemplified by procyanidin. At present, an urgent task of food manufacturers that is conditioned by the requests of consumers is substitution of synthetic antioxidants by natural ones. The globalization of food-related diseases, such as diabetes mellitus, as a result of modern life style and increasing consumption of high carbohydrate diets stimulates investigation of plant-originating bioactive compounds for working out special food additives. It is a modern therapeutic approach for treatment of food related diseases that is considered economically beneficial [3]. Our approach is connected with widely spread conception of tree as a green factory producing chemicals as individual compounds or their mixtures that can be used not only for agriculture, but also for food industry and health care. This investigation is focused on plant secondary metabolites, in particular proanthocyanidins, which are biologically active. The aim of present work was screening of alder tree species wide spread in Latvia as potential sources of proanthocyanidins and testing of PAC as an antioxidant for food with the aim to create further new valuable products based on logging and wood mechanical processing waste. II. MATERIALS AND METHODS The bark of black and grey alder was collected in Latvia (Ogre region, 2011). Bark was ground before extraction to pass a 420 μm sieve. Hydrophilic extracts enriched with PAC were isolated from bark using sequential extraction with Accelerated Solvent Extractor (ASE 350, Dionex) at 90 °C (1500 psi) for 20 min using solvents of increasing polarity: hexane, ethyl DE GRUYTER OPEN