A novel high-performance liquid chromatography (HPLC) method using 2-(9-oxoacridin-10(9H)-yl) acetohydrazide (OAAH) as pre-column labeling reagent was applied to the analysis of fatty acids in four kinds of Dendrobium species for the first time. The reaction of OAAH with fatty acids could proceed easily and quickly in the presence of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC) as condensing reagent within 20 min. The derivatives exhibit excellent fluorescence property with excitation and emission wavelengths of 255 and 420 nm, respectively. The 20 fatty acid derivatives were separated on a SB C18 reversed-phase column with gradient elution. Good linear correlations were observed for all fatty acids with correlation coefficients of >0.996. When 50 mg of sample was used for analysis, the detection limits at a signal-to-noise ratio of 3 were in the range of 0.10–0.42 µg/g. Free fatty acids and total fatty acids in four kinds of Dendrobium species were analyzed by the developed method. The results indicated that the main fatty acids in Dendrobium species were unsaturated linoleic acid (C18:2n-6) and saturated hexadecanoic acid. This work provides a useful tool for the safety assessment and quality control of Dendrobium species.
Practical applications: Dendrobium species, the stems of which can be used for medical purpose or as health foods, are precious plants in China. Their significant medical effects have recently attracted increasing attention. However, there is little research on the fatty acid composition of Dendrobium species. The proposed method provided a sensitive method for the HPLC analysis of FFAs and TFAs in four kinds of Dendrobium species. This is the first report of the fatty acid compositions of Dendrobium species. It would be helpful for the comprehensive safety or quality assessment of Dendrobium species.