Selective enrichment of ailanthone from leaves of ailanthus altissima by tandem reverse phase/molecularly imprinted solid phase extraction

Abstract

The biological activity of extracts from Ailanthus altissima is mainly due to the presence of ailanthone, a compound belonging to the quassinoid class. Recently, attention has been paid to its strong cytostatic activity. However, the extraction of ailanthone is based on very long and demanding procedures, which keep the price of the commercial product very high. Thus, the development of selective adsorbents for the purification of ailanthone from A. altissima leaves extracts could help in reduce the costs of production. In this work, we describe the rational design of a molecularly imprinted polymer selective for ailanthone based on the screening of a 96-members not-imprinted polymeric library to rapidly identify pre-polymerization mixtures able to generate MIPs with enhanced binding properties. A 4-vinylpyridine-co-trimethylolpropane trimethacrylate polymer showed high binding towards ailanthone. It was used to prepare an imprinted polymer with acetonitrile showed interesting binding affinity (Keq = 18.3 × 103 L mol−1), high imprinting factor (IF = 3.8) and fast binding kinetics (kass = 0.390 min−1, kdis = 0.021 mol L−1 min−1). The imprinted polymer was used to develop a successful purification protocol of extracts from Ailanthus altissima leaves. The purification was based on the combination of a preliminary clean-up of Soxhlet extracts onto a reverse phase-C18 cartridge and the subsequent isolation of ailanthone by a molecularly imprinted solid phase extraction. This approach allowed efficiently purifying the ailanthone contained in aqueous or methanolic Soxhlet extracts with high yields compared to the quantities reported in literature (water: 0.756 ± 0.027 mg g−1; methanol: 0.770 ± 0.030 mg g−1). Moreover, it allows processing sample volumes up to 15 mL without significant losses of the target compound.