Determination of iridoid glucosides for quality assessment of Herba Oldenlandiae by high-performance liquid chromatography.

Herba Oldenlandiae, the dried herb of Oldenlandia diffusa (WILLD.) ROXB. (Family Rubiaceae), is officially listed in the Chinese Pharmacopoeia. In the herbal market, two substitutes originated from O. corymbosa (L.) LAM and O. tenelliflora BL. are commonly used. In light of this, the target in setting up a method for quality assessment of Herba Oldenlandiae is urgently needed. In this article, a simple and reliable high-performance liquid chromatographic (HPLC) method was developed for quantifying asperuloside (1), E-6-O-p-coumaroyl scandoside methyl ester (2) and E-6-O-p-coumaroyl scandoside methyl ester-10-methyl ether (3) in Herba Oldenlandiae derived from O. diffusa. Among them, compound 3 is a new compound isolated from O. diffusa. All these unique compounds were used as markers for the first time in the quality assessment of Herba Oldenlandiae. The results showed that the contents of compounds 1-3 were significantly varied among different samples whilst those of compounds 2 and 3 were found to be lower in contents in the two substitutes of O. diffusa. The analytical method is suitable for quality control of Herba Oldenlandiae and useful in differentiation from its confusable species. The method has been fully validated with satisfactory linearity, accuracy, precision and stability.