Antioxidants in processed garlic

International Congress Series 1245 (2002) 447 – 448

Antioxidants in processed garlic I. Fructosyl arginine identified in aged garlic extract Nagatoshi Ide a,*, Kenjiro Ryu a, Kozue Ogasawara a, Takashi Sasaoka a, Hiromichi Matsuura a, Shin-ichiro Sumi a, Hiromichi Sumiyoshi a, Benjamin H.S. Lau b a

Healthcare Research Institute, Wakunaga Pharmaceutical Co., Ltd., 1624 Shimokotachi, Koda-cho, Takata-gun, Hiroshima 739-1195, Japan b Department of Microbiology and Molecular Genetics, School of Medicine, Loma Linda University, Loma Linda, CA 92350, USA

Abstract Both fresh and processed garlic (Allium sativum L.) have shown a variety of biological activities including antioxidant, cancer prevention, liver protection, immunomodulation and reduction of cardiovascular disease risk factors. In the present study, the antioxidant effects and the change in concentration of fructosyl arginine (Fru-Arg) identified in aged garlic extract (AGE) were determined using several in vitro assay systems and high-performance liquid chromatography (HPLC). Our data indicate that Fru-Arg is a potent antioxidant, which forms and increases during the natural aging process and, thus, may contribute to the biological activities of processed garlic. D 2002 Elsevier Science B.V. All rights reserved. Keywords: Maillard reaction products; Aged garlic extract; Antioxidant; Fructosyl arginine; Amadori compound

1. Introduction Aged garlic extract (AGE) is a uniquely manufactured form of garlic produced by a more than 10-month natural aging process, which has demonstrated a variety of biological activities including antioxidant, cancer-preventing, lipid-lowering and anti*

Corresponding author. Tel.: +81-826-45-2331; fax: +81-826-45-4351. E-mail address: [email protected] (N. Ide).

0531-5131/02 D 2002 Elsevier Science B.V. All rights reserved. PII: S 0 5 3 1 - 5 1 3 1 ( 0 2 ) 0 0 9 5 4 - 8

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N. Ide et al. / International Congress Series 1245 (2002) 447–448

aging properties. In the present study, antioxidant effects of Fru-Arg (Fig. 1), an Amadori compound identified in AGE, were determined using several in vitro assay systems. Also, HPLC analyses were performed to determine the change in concentration of the compound during the natural aging process.

2. Results and discussion Incubation of low-density lipoprotein (LDL) with Cu2+ at 37 jC and 5% CO2 for 24 h resulted in its peroxidation and an increase of thiobarbituric acid reactive substances (TBARS). The formation of TBARS was significantly inhibited by adding Fru-Arg to the incubation mixture. The exposure of pulmonary artery endothelial cells (PAEC) to 0.1 mg/ml oxidized LDL (Ox-LDL) at 37 jC and 5% CO2 for 24 h resulted in release of lactate dehydrogenase, an indicator of cell membrane damage, and increased TBARS. Pretreatment of PAEC with Fru-Arg inhibited these changes. According to a fluorometric assay, coincubation of murine macrophages with FruArg and Ox-LDL inhibited the release of peroxides dose-dependently. In a cell-free system, Fru-Arg directly scavenged hydrogen peroxide. HPLC analyses showed that Fru-Arg cannot be detected in raw garlic, but this Amadori compound forms and increases during the natural aging process. These data suggest that Fru-Arg, which forms and increases during the natural aging process, is a potent antioxidant which may contribute to the biological activities of processed garlic such as AGE (Fig. 1).

Fig. 1. Chemical structure of Fru-Arg identified in aged garlic extract.