Determination of Phylloquinone and Menaquinones in Foods by Hplc

High-performance liquid chromatographic (HPLC) methods for determining vitamin K contents in oils and margarines, vegetables, fruits and berries, cereals and animal products were developed. These methods were applied to analysing phylloquinone and menaquinone in a total of 87 food items. In addition, the 2 ́,3 ́-dihydrovitamin K1 contents of a few margarines and hydrogenated oils were determined, and variation in the phylloquinone contents of plant products were investigated. The quantification of vitamin K compounds was made after solvent extraction, which was optimised separately for each food group, and chromatographic purification. In the case of animal products with high fat contents, lipase treatment was used as an extra purification step. The phylloquinone contents of plant products were analysed by HPLC with electrochemical detection, whereas fluorescence detection after reduction with metallic zinc was applied for determination of animal products. The identification of menaquinones was confirmed with LC-MS. Phylloquinone was the dominant vitamin K form in foods analysed here; dihydrovitamin K1 and menaquinones probably play no significant role in vitamin K nutrition in Finland. The highest phylloquinone contents were found in green vegetables, oils and margarines; a remarkable variation was observed in these items. There are several possible reasons, such as genetic factors and processing conditions, for this. In the case of animal products this study concentrated mainly on the developing a validated and documented analytical method for determining their phylloquinone and menaquinone contents. Thus, only a few items were analysed. The vitamin K contents of meat, fish and dairy products were generally low and long-chain menaquinones were found only in livers, cheese and soured whole milk. The estimated average daily intake of vitamin K was 120 μg/day, of which 30% is derived from oils and margarines, 35% from various vegetables and the rest from cereals, fruits, berries and animal products. Because a fairly high variation especially in the consumption of vegetables among individuals is to be expected, the daily dietary intake of vitamin K may vary considerable.