Isolation of an in Vitro and ex Vivo Antiradical Melanoidin from Roasted Barley ADELE PAPETTI, § MARIA DAGLIA, § CAMILLA ACETI, § MILENA QUAGLIA, § CESARINA GREGOTTI, † AND GABRIELLA GAZZANI* ,§ Department of Pharmaceutical Chemistry, School of Pharmacy, University of Pavia, Via Taramelli 12, 27100 Pavia, Italy, and Department of Internal Medicine and Therapeutics, School of Medicine, University of Pavia, Piazza Botta 10, 27100 Pavia, Italy The antiradical properties of water-soluble components of both natural and roasted barley were determined in vitro, by means of DPPH • assay and the linoleic acid--carotene system, and ex vivo, in rat liver hepatocyte microsomes against lipid peroxidation induced by CCl 4 . The results show the occurrence in natural barley of weak antioxidant components. These are able to react against low reactive peroxyl radicals, but offer little protection against stable DPPH radicals deriving from peroxidation in microsomal lipids. Conversely, roasted barley yielded strong antioxidant components that are able to efficiently scavenge free radicals in any system used. The results show that the barley grain roasting process induces the formation of soluble Maillard reaction products with powerful antiradical activity. From roasted barley solution (barley coffee) was isolated a brown high molecular mass melanoidinic component, resistant to acidic hydrolysis, that is responsible for most of the barley coffee antioxidant activity in the biosystem. KEYWORDS: Antioxidants; melanoidins; natural and roasted barley; antiradical activity; lipid peroxidation INTRODUCTION Barley (Hordeum Vulgare L.), a prized cereal in ancient Egypt and Babylon, was probably one of the first plants of its type to have been systematically cultivated. It was used for breadmak- ing, for decoction (to which Hippocrates and Galenic ascribed healthy properties), and for the soup with which Romans fed gladiators prior to combat. The Romans considered barley as having a high energy yield, and although in fact it contains less starch than most other cultivated used cereals, it does have a higher content of other carbohydrates (1) that release energy more immediately. Today barley is considered to be a minor cereal and is largely used as fodder. However, it is still important for human nutrition; although it is almost completely supplanted by wheat in breadmaking, pearl barley is often used in the preparation of soup. In germinated form, it is the main ingredient in beer brewing. In recent years, due to its high content in -glucans, tocols, and polyphenols, it has been used in the preparation of functional foods. Furthermore, the secular custom in China of drinking barley or malt coffee instead of traditional coffee as a tasty beverage has greatly spread in Western regions, because children and adults alike are highly susceptible to the negative effects of caffeine. Such beverages use roasted barley, or malt, the composition of which is different from that of natural products. Natural barley grains contain a number of polyphenolic compounds, such as phenolic acids (benzoic and cinnamic acid derivatives) and flavonoids, proanthocyanidins, and tannins (2, 3), all of which are known to possess antioxidant and antiradical properties. These compounds are partially destroyed during the roasting process, which, however, induces the formation of new compounds in roasted grains; of particular note in this respect are polymeric substances that are generally considered to be either caramels, when they do not contain nitrogen, or mel- anoidins, when they incorporate nitrogen atoms. Melanoidins consist of brown compounds that can be detected in biological material and, in particular, in heat-treated foods, where they are the main end products of the Maillard reaction, which in turn comprises a set of consecutive and parallel chemical reactions. The complex structure of melanoidins is largely unknown because polymerization is influenced both by the starting reactans and their concentrations and by the reaction conditions, such as pH, water activity, temperature, reaction time, and solvent used (4-7). Accordingly, most systems or foods (irrespective of whether they differ from, or resemble, each other) co-host a variety of polymeric products, each of which is characterized by differing structure, molecular mass (MM), and elemental composition. These polymeric compounds are classified as low MM or high MM melanoidins depending on their dialysis, as determined by means of 3500 or 12000 Da cutoff membranes. Generally, the MM of such polymeric * Correspondig author (telephone +39 0382 987373; fax +39 0382 422975; e-mail gabriella.gazzani@unipv.it). § Department of Pharmaceutical Chemistry. † Department of Internal Medicine. J. Agric. Food Chem. 2006, 54, 1209-1216 1209 10.1021/jf058133x CCC: $33.50 © 2006 American Chemical Society Published on Web 01/31/2006