Fructose, glucose and sucrose, as the major soluble sugars and citric and malic acids, as the major organic acids, were identified and determined in kale (Brassica oleraceae L. var. acephala DC., black cabbage) leaves. Fructose was the predominant sugar (2011 mg 100 g(-1) dry wt) identified, followed by glucose (1056 mg 100 g(-1) dry wt) and sucrose (894 mg 100 g(-1) dry wt). The contents of citric and malic acids were at 2213 and 151 mg 100 g(-1) dry wt in the leaves. The 16:0, 18:2n - 6 and 18:3n - 3 fatty acids were the most abundant fatty acids in the leaves. Considering the level of these fatty acids, 18:3n - 3 was found to be the highest (85.3 mu g g(-1) dry wt), contributing 54.0% of the total fatty acid content. Linoleic acid (18:2n - 6), being the second most abundant fatty acid was present at 18.6 mu g g(-1) dry wt, contributing 11.8% of the total fatty acid content. In the seed oil of kale, 22:1n - 9 was the most abundant fatty acid (4198 mu g g(-1) dry wt, 45.7%), with 18:2n - 6 (1199 mu g g(-1) dry wt, 12.3%) and 18:1n - 9 (1408 mu g g(-1) dry wt, 14.8%) being the second next most abundant fatty acids. The most abundant amino acid was glutamic acid (Glu) which was present at 33.2 mg g(-1) dry wt. Aspartic acid, which was the second most abundant amino acid, was present at 27.6 mg g(-1) dry wt and accounted for 10.2% of the total amino acid content of kale leaf. The amino acid content was assessed by comparing the percentages of the essential amino acids in kale leaf versus those of a World Health Organization (WHO) standard protein. The protein of kale leaf compares well with that of the WHO standard. Only one amino acid, lysine, had a score that fell below 100%; the lysine score of kale leaf was 95%. This study attempts to contribute to knowledge of the nutritional properties of the plant. These results may be useful for the evaluation of dietary information. (C) 2005 Published by Elsevier Ltd.