HPLCによる生乳中メラトニンの定量 [in Japanese] Quantitative Analysis of Melatonin in Raw Milk by HPLC [in Japanese]
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We report results of quantitative analysis using a precolumn derivatization method for melatonin extracted from raw milk. The extraction method is described as follows.<BR>The raw milk, obtained from 43-month-old Holstein cows, was incubated with papain at 45°C for 30 minutes. The enzyme reaction was stopped by the addition of trichloro acetic acid and then the reaction mixture centrifuged. The melatonin in the supernatant was extracted with chloroform, after which, the chloroform layer was washed with water and evaporated to dryness. For the derivatization of melatonin, 150μL of aqueous 2mol/L Na<SUB>2</SUB>CO<SUB>3</SUB>, 100μL 100mmol/L H<SUB>2</SUB>O<SUB>2</SUB>, 50μL 1mmol/L CuSO<SUB>4</SUB>, and 700μL water were added to the residue, and the mixture was then heated in water (94-96°C) for 6 minutes. The melatonin derivative was extracted with ethyl acetate, evaporated to dryness, dissolved in aqueous 15% (v/v) CH<SUB>3</SUB>CN, and then subjected to HPLC analysis. When standard melatonin was added to raw milk, the recovery rate was 85.3±7.3% (mean S.D. n=5). The 43-month-old Holstein cows were milked at noon and night, on January, February, and March 2006. In January, melatonin content in raw milk was determined to be 5.7pg/mL in diurnal milk and 42.3pg/mL in nocturnal milk. In February and March, melatonin content in nocturnal milk decreased to 22.3 and 14.8pg/mL, respectively. These results suggest that the present method is suitable for determination of melatonin contained in raw milk.
- NIPPON SHOKUHIN KOGYO GAKKAISHI
NIPPON SHOKUHIN KOGYO GAKKAISHI 54(3), 113-117, 2007-03-15
Japanese Society for Food Science and Technology