Nagatoshi Ide

Nα-(1-Deoxy-d-fructos-1-yl)-l-Arginine, an Antioxidant Compound Identified in Aged Garlic Extract

Aged garlic extract (AGE) has been shown to have antioxidant activity. The organosulfur compounds, S-allyl-L-cysteine and S-allylmercapto-L-cysteine, are responsible, at least in part, for the antioxidant activity of AGE. To identify major active components, we fractionated AGE, using hydrogen peroxide scavenging activity as an antioxidative index. Strong activity in the amino acid fraction was found and the major active compound was identified as N alpha-(1-deoxy-D-fructos-1-yl)-L-arginine (Fru-Arg). Antioxidant activity of Fru-Arg was comparable to that of ascorbic acid, scavenging hydrogen peroxide completely at 50 micromol/L and 37% at 10 micromol/L. Quantitative analysis using the established HPLC system revealed that AGE contained 2.1-2.4 mmol/L of Fru-Arg, but none was detected in either raw or heated garlic juice. Furthermore, it was shown that a minimum of 4 mo aging incubation was required for Fru-Arg to be generated. These findings indicate that the aging process is critical for the production of the antioxidant compound, Fru-Arg. These results may explain some of the variation in benefits among different commercially available garlic preparations.

Scavenging Effect of Aged Garlic Extract and its Constituents on Active Oxygen Species

The effect of aged garlic extract (AGE) and its major organosulphur constituents, S‐allylcysteine (SAC), S‐allylmercaptocysteine (SAMC) and alliin on active oxygen species were examined in an in vitro system. AGE and three compounds have demonstrated a scavenging effect on hydrogen peroxide, and also inhibited the chain oxidation induced by a hydrophilic radical initiator.

Aged Garlic Extract Maintains Cardiovascular Homeostasis in Mice and Rats

Nitric oxide (NO) plays an important role in controlling the physiological functions of the cardiovascular system. However, toxic peroxynitrite is produced by the reaction of NO with superoxide. We investigated the effect of aged garlic extract (AGE) on NO production, and on oxidative stress induced by peroxynitrite. A single dose of AGE temporarily increased NO production by 30-40% between 15 and 60 min after administration to mice. The time course of the fluctuation in NO levels in the AGE-treated group clearly differed from that in a group treated with an inducible NO synthase (iNOS) inducer. A selective constitutive NOS (cNOS) inhibitor overcame the effect of AGE. These results indicate that AGE increases NO production by activating cNOS, but not iNOS. In another experiment, the addition of AGE to a rat erythrocyte suspension reduced the rate of peroxynitrite-induced hemolysis in a concentration-dependent manner, suggesting that AGE protects erythrocytes from membrane damage induced by peroxinitrite. Because an increase in NO derived from cNOS and protection against peroxynitrite are important factors in the prevention of cardiovascular disease, our data strongly suggest that AGE could be useful in preventing cardiovascular diseases associated with oxidative stress or dysfunctions of NO production.

Aged garlic extract inhibits peroxynitrite-induced hemolysis

Abstract Nitric oxide (NO), which is synthesized by constitutive NO synthase (cNOS), plays important roles in physiological functions of the cardiovascular system. However, NO, which is synthesized by inducible NOS, is detrimental when it reacts with superoxide to form peroxynitrite. Peroxynitrite is recognized as a powerful oxidant, and results in vascular or tissue damage. We have previously reported that aged garlic extract (AGE) enhances NO production through cNOS stimulation. In the present study, we determined the effect of AGE, its fractions or constituents on peroxynitrite-induced hemolysis using rat erythrocytes. Incubation of rat erythrocytes with peroxynitrite (300 μM) for 30 min at 37°C caused 4-fold hemolysis. AGE (0.14–0.57 %w/v) added to an erythrocyte suspension was found to reduce peroxynitrite-induced hemolysis in a concentration-dependent manner. Of the AGE fractions, a polar fraction and a low-molecular-weight fraction both suppressed the hemolysis to the same degree as that seen with AGE. S-Allylcysteine, one of the major compounds in AGE, also reduced hemolysis at 1–10 mM dose-dependently. These data indicate that AGE and its compounds protect erythrocytes from membrane damage induced by peroxynitrite, suggesting that AGE could be useful for prevention of cardiovascular diseases associated with oxidative stress or dysfunction of NO production.

Antioxidants in processed garlic: II. Tetrahydro-β-carboline derivatives identified in aged garlic extract

Abstract The antioxidant effects and the changes in concentrations of tetrahydro-β-carboline derivatives (THβCs) identified in aged garlic extract (AGE) were determined using several in vitro assay systems and liquid chromatography mass spectrometry (LC-MS). Our data indicate that THβCs are also potent antioxidants, which increase during the natural aging process of garlic and, thus, may contribute to the biological activities of processed garlic such as AGE.

Antioxidants in processed garlic: I. Fructosyl arginine identified in aged garlic extract

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.