Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/4/2003
Publication Date: 8/1/2004
Citation: Kurilich, A.C., Britz, S.J., Clevidence, B.A., Novotny Dura, J. 2003. Isotopic labeling and lc-apci-ms quantification for investigating absorption of carotenoids and vitamin k1 from kale. Journal of Agricultural and Food Chemistry.51(7):4877-4889.
Interpretive Summary: Phytonutrients from fruits and vegetables not only help individuals to meet daily requirements, but can also improve health by protecting against many diseases, including cancer, cardiovascular disease and age-related macular degeneration. Regardless of the nutrient content of a plant-derived food, the ability of those plant-derived nutrients to impart health benefits depends on the gastrointestinal tract's ability to extract the nutrients from the plant material. It is difficult to determine the effectiveness of the intestine in absorbing a given nutrient: if one samples blood, the newly ingested nutrient has mixed with previously circulating nutrients, and if one measures fecal nutrient loss, one cannot be sure that the bacteria in the intestine did not alter the amount of nutrient in the feces. We have developed several new methods which in combination offer a unique method for determining absorption of a nutrient from a plant-derived food. We have grown kale with a tag called carbon-13. Further, we have developed new laboratory methodology to detect tagged beta-carotene, lutein, vitamin A, and vitamin K in human blood. We then fed the tagged kale to an adult volunteer and measured the rise and fall of the tagged nutrients in that subject's blood. In sum, we have developed new methods for tagging nutrients in plants and measuring the tagged nutrients in blood, and we have conducted a feeding study to show the feasibility of our new method. This new method will be useful to scientists who study nutrient bioavailability.
Technical Abstract: The ability to study bioavailability of nutrients from plant-based foods is an important step in determining the potential health impact of those nutrients. This work describes a new method for studying bioavailability of nutrients from green, leafy vegetables by labeling the nutrients in kale with carbon-13, feeding the labeled kale to an adult volunteer, and analyzing plasma samples for lutein, beta-carotene, retinol, and phylloquinone using LC-APCI-MS. Results showed that conditions for producing atmospheric intrinsically labeled kale had no detrimental effect on plant growth. Lutein, retinol, and phylloquinone were successfully analyzed simultaneously using LC-APCI-MS. An additional solid phase extraction step was required for beta-carotene to remove a co-eluting interference. Analysis of plasma samples showed that labeled lutein peaked in plasma at 11 hrs (0.23 mmolar), beta-carotene peaked at 8 hrs (0.058 mmolar) and 24 hrs (0.062 mmolar), retinol peaked at 24 hrs (0.10 mmolar) and phylloquinone peaked at 7 hrs (3.0 nmolar). This method of labeling green, leafy vegetables with carbon-13 was successful for producing clearly defined kinetic curves for labeled lutein, beta-carotene, retinol, and phylloquinone.