Urtica dioica traces of zeaxanthin or between 20 – 60 mg / kg of dry matter. Nettle contains ascorbic acid (vitamin C), riboflavin (vitamin B), pantothenic acid, vitamin K and tocopherols (vitamin E). The highest vitamin contents can be found in the leaves. In laying hens, nettle can be used as an egg yolk colorant instead of artificial pigments or other natural pigments (derived from marigold for yellow). Nettle has high carotenoid contents, especially lutein, β-carotene and zeaxanthin, of which lutein and zeaxanthin act as yellow pigments. Feeding as little as 6.25 g dry nettle per kg feed is as effective as
Chemistry of ascorbic acid the presence of free metal ions can not only promote but also initiate free radical reactions, thus making it a potentially dangerous pro-oxidative compound in certain metabolic contexts. Ascorbic acid and its sodium, potassium, and calcium salts are commonly used as antioxidant food additives. These compounds are water-soluble and, thus, cannot protect fats from oxidation: For this purpose, the fat-soluble esters of ascorbic acid with long-chain fatty acids (ascorbyl palmitate or ascorbyl stearate) can be used as food antioxidants. It creates volatile compounds when mixed with glucose and amino acids in 90 °C. It is a cofactor in tyrosine oxidation.