Determination of five major iridoid glucosides in Flos Lonicerae by high-performance liquid chromatography coupled with evaporative light scattering detection

This study presents a new HPLC method using evaporative light scattering detection for the simultaneous determination of five major iridoid glucosides, namely 7-epi-loganin, sweroside, loganin, 7-epi-vogeloside, and secoxyloganin in Flos Lonicerae, an important traditional Chinese medicinal herb. The optimal conditions of separation and detection were achieved on a C18 analytical column with an isocratic mobile phase consisting of methanol–water (30:70, v/v) containing 0.5% acetic acid at the flow-rate of 1.0 ml/min, temperature for the detector drift tube set at 90 °C and the nitrogen flow-rate of 2.6 l/min. The limit of detection (S/N=3) is less than 35.1 μg/ml and the limit of quantification (S/N=10) is less than 140.1 μg/ml. All calibration curves show good linear regression (r2>0.996) within test ranges. This method provides good reproducibility for the quantification of the major iridoid glucosides in four Lonicera species with overall intra- and inter-day variation of less than 5% and 9%, respectively. The assay was successfully applied to quantify the main iridoid glucosides in the herb and to identify the botanical origin of Flos Lonicerae.