Determination and isolation of purpurin and mollugin from Rubiae Radix ET Rhizoma based on a monolithic adsorbent prepared by bio-monomer

Abstract

Quinonoids such as purpurin and mollugin contained in Rubiae Radix ET Rhizoma (the dried roots and rhizomes of Rubia cordifolia L.) have been proven as the main active components, exhibiting obvious pharmacological effect. However, in practical studies, it is very difficult to extract and separate purpurin and mollugin from the Rubiae Radix ET Rhizoma, due to the complex composition of the herbal sample, which further affects the pharmacological and toxicological studies of these two active components. In this work, a monolithic adsorbent was prepared using a bio-based monomer of methyleugenol via polymerization, according to the structures of purpurin and mollugin contained in Rubiae Radix ET Rhizoma. The prepared adsorbent exhibiting high permeability, multistage pores and large specific surface area, was used for the online extraction, determination and preparative separation of purpurin and mollugin from Rubiae Radix ET Rhizoma, which was carried out with a solid-phase extraction-high-performance liquid chromatography method. The prepared adsorbent shows good enrichment ability due to the abundant interaction sites, and demonstrates unique performance in the extraction, separation and purification of purpurin and mollugin from Rubiae Radix ET Rhizoma. These results indicated that the prepared solid-phase extraction adsorbent shows good selectivity for purpurin and mollugin from Rubiae Radix ET Rhizoma. The isolated and purified products of purpurin and mollugin from Rubiae Radix ET Rhizoma were identified, which results show the yield is high to 2.11 mg/g and 7.08 mg/g for purpurin and mollugin, respectively, as well as the purity is 98.98% and 98.26% for purpurin and mollugin, respectively. It is worth noting that the present method also demonstrated superior applicability in the matrix-removal of spiked mouse plasma. This method is a highly efficient and simple sample pretreatment method.