Gram-scale purification of faradiol from common marigold

Common marigold (Calendula officinalis L.) is one of the most widely used medicinal plants in the European folk medicine with confirmed anti-inflammatory activity. The biological activity of the flowers is related to their triterpenoid content. The pharmacologically important triterpenoids are alcohols (monools, diols and triols). Diols, such as faradiol, calenduladiol and maniladiol and their mono- and diesters are characteristic compounds of this plant with remarkable antiphlolgistic activity. Faradiol monoester is the most relevant principle for the clinical efficacy of the drug, due to its quantitative prevalence. However, the unesterified faradiol, which is not present in the extract, is the most active member of the Calendula triterpenoids. The anti-inflanmmatory activity of marigold is related to the inhibition of the proinflammatory cytokines and COX-2 [2]. Although the pharmacological properties of faradiol make this molecule very promising for further pharmacological testing, phytochemical studies have mainly focused on the isolation of its ester derivatives and there are no methods in the literature for its quick and simple isolation from plant material [3]. The aim of our work was to develop a method which allows the gram-scale production of faradiol from marigold. Calendula officinalis flowers were extracted with methanol. The extract was subjected to hydrolysis using 1 M KOH. After precipitation with BaCl2, a solvent-solvent partitioning using CH2Cl2 resulted in the faradiol-enriched organic layer. Further separation was carried out by MPLC on silica gel, using a gradient of cyclohexane – diethyl ether. The final purification, which was performed by preparative HPLC using a C-18 stationary phase and a MeOH – H2O gradient, led to the isolation of pure faradiol. The structure of the isolated compound was confirmed by NMR experiments. The yield of the extraction procedure was 0,25%, which resulted in the isolation of 1.5 g pure faradiol from 600 g plant material.