Quantitative determination of five glucosyloxybenzyl 2-isobutylmalates in the tubers of Gymnadenia conopsea and Coeloglossum viride var. bracteatum by HPLC.

Glucosyloxybenzyl 2-isobutylmalates are one group of important active constituents in the tubers of Gymnadenia conopsea R. Br. and Coeloglossum viride (L.) Hartm. var. bracteatum (Willd.). For the purpose of quality evaluation of these two Chinese herbal medicines, it is necessary to use a rapid and reliable assay that is suitable for the determination of their active constituents. A high-performance liquid chromatography method is firstly developed for the simultaneous quantification of five glucosyloxybenzyl 2-isobutylmalates in the tubers. The analytes including dactylorhin B, dactylorhin E, loroglossin, dactylorhin A, and militarine are isolated from the tubers of G. conopsea. The compounds are separated on an Agilent Hydrosphere C(18) (150 x 4.6 mm i.d., 5 microm) column using a mobile phase of acetonitrile-water including 0.3% acetic acid (adjusted with 36% acetic acid) with gradient elution at a flow rate of 1.0 mL/min. Detection is set at a UV wavelength of 221.5 nm. The recovery of the method is 97.7-101.0%, and linearity (r > 0.9998) is obtained for all the analytes. The assay is successfully applied to determine the contents of the analytes in the tubers of G. conopsea and C. viride var. bracteatum collected from different regions of China.