Keywords: Flazin, soy sauce, HL-60, DNA fragmentation, TUNEL *To whom correspondence should be addressed. E-mail: umekawa@bio.mie-u.ac.jp
IntroductionSoy sauce is a representative Japanese seasoning known worldwide. Soy sauce is classified into five (Koikuchi, Usukuchi, Tamari, Sashikomi, and Shiro) according to Japanese Agricultural Standard (Kataoka, 2005). Typical Koikuchi soy sauce involves the fermentation of soybeans and wheat in a 1:1 ratio. A variety of biological functions have been reported for Koikuchi soy sauce, including the blood pressurelowering effect of nicotinamine (Kinoshita et al., 1993) and the arteriosclerosis-controlling activity of polyamine. In contrast, the main raw ingredient of Tamari soy sauce is soybean, with wheat as a minor ingredient (Kataoka, 2005). The physiological effects of Tamari soy sauce are not well understood.Soy sauce is not only a delicious seasoning, characterized by a mellow odor and taste, but exhibits a number of physiological activities, such as an antioxidative effect (Aoshima and Ooshima, 2009), blood pressure-lowering effect, and an action that alleviates allergic symptoms (Kobayashi et al., 2004, Kobayashi, 2005. The aim of the present study was to refine 1-[5-(Hydroxy-methyl)furan-2-yl]-9H-pyrido [3,4-b] indole-3-carboxylic acid (Flazin) from the main body of collected soy sauce (Gessner et al., 1988) and to examine the cellular effects of this compound.Flazin was first separated from sake lees as a crystal during the manufacture of synthetic sake (Gessner et al., 1988) and has been found to exhibit strong fluorescence (Li et al., 2011). Flazin was also discovered as a cluster of dark green microcrystals in rice vinegar during a research study on soy sauce (Gessner et al., 1988). The structure of Flazin was determined by Nakatsuka et al. (1986). Flazin comprises tryptophan and 5-hydroxymethyl-2-furfural, and is generated through processes of oxidation and dehydration. It was later discovered as a metabolic product of a marine microorganism (Shaaban et al., 2007).The aim of this study was to examine the physiological function of Flazin. The results demonstrate that Flazin from Tamari soy sauce inhibits the proliferation of human promyelocytic leukemia cells at least in part due to its apoptotic activity against the cells.
Materials and MethodsRegents The soy sauces used in the present study were a gift from Sanjirushi Corp (Japan). HL-60 cells, which are human promyelocytic leukemia cells, were obtained from the three replicates. The concentration of Flazin was 65.1 ± 15.9 μg/mL in Koikuchi soy sauce and 232.0 ± 18.4 μg/mL in Tamari soy sauce (Fig. 1) The cell suspensions were then incubated for 24 h in a CO 2 incubator. Untreated cell suspensions were used as negative controls. Cell proliferation was determined after 3 h using a kit (CCK-8 kit, DOJINDO, Japan) and absorbance was measured at 450 nm using a microplate reader (BIO-RAD, Model-550, Japan). Experiments were performed in triplicate.
Preparation of FlazinThe diethyl ether extraction sample from e...