Analyses on fatty acid composition in Rheum tanguticum from different locations in Qinghai and its principal component analysis

Fatty acid composition in under-ground part of Rheum tanguticum Maxim. ex Balf. from fifteen plots of six counties of Gande,Dari,Banma,Maqin,Tongde and Qilian in Qinghai Province were determined and analyzed by the method of high performance liquid chromatography-fluorescence detection(HPLC-FLD) with pre-column derivatization,and on this basis,principal component analysis on fatty acid composition was carried out. The results show that all of fifteen fatty acids are detected in R.tanguticum from different locations,which includes twelve saturated fatty acids( viz. decanoic acid,undecanoic acid,dodecanoic acid,myristic acid,pentadecanoic acid,palmitic acid,octadecanoic acid,arachidic acid,heneicosylic acid,docosanoic acid,tricosanoic acid and tetracosanoic acid) and three unsaturated fatty acids( viz. linolenic acid,linoleic acid and oleic acid). In which,palmitic acid content is the highest in saturated fatty acids,and linoleic acid content is the highest in unsaturated fatty acids. The content of total fatty acids in R. tanguticum from different locations is 2. 38- 54. 22 μg·g- 1,in which,unsaturated fatty acids account for 17. 31%- 48. 97%. There is an obvious regional difference in fatty acid compositions. The content of total fatty acids in sample from MQ1 plot of Maqin County is the highest,and the proportion of unsaturated fatty acids in sample from QL2 plot of Qilian County is the highest. The result of principal component analysis shows that accumulative contribution rate of the first three principal components is high with a value of 87. 387%,in which,fatty acids with high eigenvector are all even number and long carbon chain fatty acids( with carbon atom number being higher than 12),meaning that even number and long carbon chain fatty acids are characteristic fatty acid composition of R.tanguticum. Comprehensive analysis result indicates that complex and changeable climate and geographical conditions of different regions in Qinghai Province are probably the main factors to cause differences in composition and content of fatty acids in R. tanguticum.