Original ArticleUbiquinone contents in Korean fermented foods and average daily intakes
Introduction
Coenzyme Q10 (CoQ10) or ubiquinone-10 (UQ-10), an endogenous enzyme cofactor produced in all living cells in humans and distributed in cellular membranes, is an essential lipophilic component of the electron transport chain for oxidative phosphorylation, and it is known to be an energy booster and immune-system enhancer (Ernster and Dallner, 1995, Molyneux et al., 2005). Naturally occurring members are the coenzyme Q6–Q10, and the differences in their properties are due to the length of the side chain (Ernster and Dallner, 1995). CoQ10 is produced in the human body in variable amounts depending on the diet or diseases (Overvad et al., 1999). More than 90% of the CoQ10 content in human serum and biological tissues exists in the reduced form ubiquinol-10 (CoQ10H2) (Fig. 1), which is a powerful lipid-soluble antioxidant (Kaikkonen et al., 2002, Miles, 2007). Ubiquinol-10 protects low-density lipoproteins (LDL) from lipid peroxidation by scavenging peroxyl radicals and reducing α-tocopheryl radicals (Stocker et al., 1991, Mohr et al., 1992). The oxidized form (ubiquinone) may be reduced to ubiquinol enzymatically after absorption (Mohr et al., 1992). CoQ10 deficiency has been implicated in several clinical disorders, including chronic heart failure (Molyneux et al., 2008), hypertension (Kumar et al., 2009), Parkinson's disease (Beal, 2004) and malignancy (Portakal et al., 2000). Thus, exogenous CoQ10 may have beneficial effects on human health; i.e., CoQ10 present in food or taken as a dietary supplement appears to act primarily by elevating the coenzyme Q level in blood, where it may function as an antioxidant (Mohr et al., 1992). Despite the presumption that exogenous coenzyme Q may have beneficial effects on human health, only few studies have assessed contents of coenzyme Q in foods (Weber et al., 1997a, Mattila and Kumpulainen, 2001, Pravst et al., 2010). It has been reported that most foods contained ubiquinone and daily intake of CoQ10 was estimated to be 2–20 mg/day (Weber et al., 1997a, Mattila and Kumpulainen, 2001).
Traditionally, Koreans have consumed high quantities of fermented foods to overcome the protein deficiency risk resulting from a rice-based diet (Yoo, 1997). The main substrates used in the commercial or traditional production of the most familiar fermented products in Korea are vegetables (Kimchi), soybean (Doenjang, Cheonggukjang, Kochujang, Soy sauce), and fishes (Jeotgal). The Fermented foods have been placed as an important portion of the diet in Korea. The microflora responsible for this food fermentation is in many cases indigenous and includes strains of lactic acid bacteria (LAB), yeast, and fungi (Table 1) (Cheigh and Park, 1994, Yoo, 1997, Kim et al., 1998a, Ham et al., 2004, Cho and Seo, 2007, Guan et al., 2011).
Meanwhile, a number of microorganisms, including bacteria (e.g. Pseudomonas, Agrobacterium, Paracoccus), moulds (e.g. Aspergillus, Neurospora) and yeasts (e.g. Candida, Rhodotorula, Saitoella) have been reported as CoQ10 producers (Meganathan, 2001, Cluis et al., 2007). In particular, selection studies of wild-type strains showed that photosynthetic bacteria such as Rhodospirillum, Rhodobacter and Pseudomonas are excellent CoQ10 producers, with the highest specific CoQ10 content found in Rhodospirillum (Cluis et al., 2007). Therefore, it could be expected that Korean fermented foods may have higher CoQs, when compared to other foods without fermentation. Because the fermentation process by diverse microorganisms during manufacture might influence the production of CoQs and possibly the distribution of CoQs homologues. However, the contents of total and individual ubiquinone in fermented foods consumed in Korea have not been reported. Thus, the aim of this study is to determine CoQ9 and CoQ10 contents in some fermented food commonly consumed in Korea and estimates the average daily intake of these compounds using both the data generated and a recently published report.
Section snippets
Food samples
Fermented food samples used for analysis were selected considering the ordinary intake of the Korean population. They were obtained from different local markets and traditional shops, and prepared for analysis on the day of purchase or on the following day. Purchased samples were the brands commanding a high share of the domestic market and the best selling brands for fermented foods in Korea. The number of selected items in each food group for fermented foods from traditional and commercial
Ubiquinone contents in Korean fermented foods
There are several types of traditional fermented foods in Korea. The most common Korean fermented foods based on soybean (Doenjang, Kochujang, Cheonggukjang, and Soy sauce), vegetables (Kimchi), and fish (Jeotgal) as shown in Table 1. These fermented foods have an important role in the diet and nutrition of Koreans. The content of CoQ9, CoQ10, and total CoQs (Q9 + Q10) in Korean fermented food items are shown in Table 2. The ubiquinone content in these foods was significantly different between
Conclusions
The present study sought to determine CoQ9 and CoQ10 contents in Korean fermented food groups and estimate the average dietary intake of these compounds using both the data generated and a recently published dietary survey of Korean adults. The total CoQs (Q9 + Q10) content ranged from 5.5 ± 0.6 to 308.5 ± 18.9 μg/g in fermented soybean food group (Doenjang, Kochujang, Chonngukjang, Soy sauce), 110.2 ± 7.4 to 148.2 ± 12.3 μg/g in fermented vegetable food group (Kimchi), and 296.8 ± 11.9 to 315.9 ± 12.6 μg/g in
Acknowledgement
This work was supported by the Sungshin Women's University Research Grant 2009.
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