A simultaneous determination and monitoring of vitamin K1 (phylloquinone) and vitamin K2 (menaquinone) in vegetable drinks and natto sold on the Korean market

A simultaneous sample preparation for vitamins K1 (phylloquinone) and K2 (menaquinones MK4 and MK7) was developed for vegetable drinks and natto by solvent extraction optimization for each matrix. Vitamin K has shown several health benefits, but no simple method exists for its rapid identification and quantification in food samples. The recovery rates were in the range 81.26–104.40%, with relative standard deviations between 0.46 and 4.10%. Monitoring studies were conducted on vegetable drinks and natto products sold on the Korean market. The range of vitamin K1 in vegetable drinks was 0 (not detected)–69 μg/100 g, and the range of vitamin K2-MK7 in natto was 285–1221 μg/100 g. The vitamin K2 content in natto was generally 2–4 times higher in frozen products than the content in refrigerated products. This method may be implemented in laboratories to save time and reduce the costs of disposable materials.