Determination of folate vitamers in food and in Italian reference diet by high-performance liquid chromatography.

A trienzyme treatment (conjugase, alpha-amylase, protease) followed by affinity chromatography and reversed-phase HPLC with UV and fluorescence detection was performed for the quantification of folate vitamers in legumes (chickpea and beans), processed meats (salami Milano and Parma ham) and in an Italian reference diet. This method allowed a good separation of six folate vitamers: 5-methyltetrahydrofolate, 5-formyltetrahydrofolate, folic acid, 10-formylfolic acid, 10-formyldihydrofolate and tetrahydrofolate within 30 min. Recovery, reproducibility and limits of detection of the method are reported. HPLC results were 24-52% lower than the microbiological assay findings.

Effect of folic acid supplementation on folate status and formate oxidation rate in mink (Mustela vision).

We investigated the folate-dependent toxicity of formate to mink to better understand the use of formic acid in fur animal feeds. Folic acid supplementation (0, 1, 5, 10, and 20 mg/kg of DM) in the feed of weanling mink for 4 wk resulted in hepatic tetrahydrofolate (H4folate) concentrations of 3.94, 8.51, 9.15, 10.4, and 15.0 nmol/g, respectively (SE 1.03). Oxidation tests in metabolic chambers, preceeding a single injection of sodium [14C]formate (500 mg/kg BW), showed that the nonsupplemented mink oxidized formate into CO2 at a rate 37% less than that of the supplemented mink. The oxidation rate increased with supplementation level and was maximal, 54.2 mEq.kg1.h1 (SE 3.0), at 10 mg of folate/kg; at the highest level of supplementation (20 mg/kg), CO2 production tended to be lower. Concentration of hepatic 14C increased with the hepatic H4folate, and its accumulation continued after the highest point of oxidation. These observations indicate that mink oxidize formate readily but at a slightly lower rate than do rats. However, if extra folate is not supplemented in the feed during the period of early intensive growth, hepatic H4folate level may decline to the levels found in humans and monkeys, which are susceptible to formate accumulation. Average daily weight gain improved with each increase in supplementation of folic acid; however, only the differences between the nonsupplemented diet and the two highest levels of the vitamin reached statistical significance (P < .05).

Liquid chromatographic determination of folate monoglutamates in fish, meat, egg, and dairy products consumed in Finland.

A liquid chromatographic (LC) method with fluorescence and UV detection was used to determine the folate contents of fish, meat, fish and meat products, chicken, eggs, and milk consumed in Finland. 5-Methyltetrahydrofolate, tetrahydrofolate, 5-formyltetrahydrofolate, 10-formylfolic acid, and folic acid from 24 commodities obtained from supermarkets, retail stores, and different outlets in the Helsinki area were analyzed. Pooled samples were extracted at pH 6.0 in the presence of antioxidants and deconjugated with hog kidney deconjugase. Very low levels of folates were detected in meat and meat products. Fresh fish, fish sticks, and chicken meat contained reasonable amounts (3-13 micrograms/100 g) of tetrahydrofolate and 5-methyltetrahydrofolate. Egg yolk contained high concentrations of 5-methyltetrahydrofolate (140-150 micrograms/100 g); 10-formylfolic acid was also detected (14-17 micrograms/100 g). Between-species differences in folate monoglutamate distributions were observed. The highest levels of tetrahydrofolate, > 5 micrograms/100 g, were found in chicken meat and fillets of rainbow trout, whitefish, and baltic herring. Tetrahydrofolate was most abundant in fresh fish. LC was well suited for analyzing folate compositions of meat, fish, and other foods of animal origin. Recovery of added folates ranged from 49 to 96%.