Quantification of Fatty Acids from Arctium lappa L. Leaves by ¹³C qNMR and HPLC-CAD

Arctium lappa L. (burdock) leaves is effective in the traditional treatment of stroke. Fatty acids are abundant in burdock leaves, and may play an important role in the treatment of stroke. A new procedure was presented that provides ¹³C NMR-based quantitative measurements of total content, average chain length, average degree of unsaturation, and average polyunsaturation of fatty acids in burdock leaves from five producing areas. The content of five fatty acids in burdock leaves, including α-linolenic acid, linoleic acid, palmitic acid, oleic acid, and stearic acid, were further determined by HPLC-CAD. Among five producing areas, the results of ¹³C qNMR showed that the content of total fatty acids in burdock leaves ranged from 8.62 to 24.51 μmol·g^-1, the average chain length ranged from 19.67 to 23.14, the average degree of unsaturation ranged from 1.19 to 3.91, and the average polyunsaturated moieties ranged from 0.23 to 2.37. The results of HPLC-CAD showed that the contents of α-linolenic acid, linoleic acid, palmitic acid, oleic acid and stearic acid were 0.66 - 6.60 mg·g^-1, 0.38-4.41 mg·g^-1, 0.46-3.55 mg·g^-1, 0.18-0.20 mg·g^-1 and 0.10-0.32 mg·g^-1 respectively. The developed ¹³C qNMR method can accurately determine the total fatty acids content and provide relevant information on the fatty acids structure types in burdock leaves. This method is capable of complementing existing fatty acids quantitative methodologies, circumventing their deficiencies, and its application can be extended to other plants.