The Medicinal Moroccan Plant Cladanthus arabicus as a Prominent Source of Sesquiterpenes Cladantholide and Sintenin

The yellow-flowering plant Cladanthus arabicus (L.) Cass., commonly called Arabian Cladanthus or palm springs daisy, is typical of the West Mediterranean region and is particularly abundant in Morocco. The plant is used in traditional Moroccan medicine for the treatment of diabetes and other ailments. Over the past 20 years, this abundant wild plant has been neglected from a phytochemical viewpoint. For the first time, the present review provides a survey of the pharmacological properties reported from extracts of C. arabicus and from essential oils derived from the aerial parts, mainly antimicrobial, antioxidant, and anti-inflammatory properties. The main bioactive natural products are discussed, with a focus on two rare sesquiterpenes of major interest, which are abundant in the stems and leaves: the 6,12-guaianolide cladantholide and the germacranolide sintenin. These sesquiterpene lactones and their analogues are presented to highlight their properties, extraction or total synthesis, and their therapeutic benefits. They both represent convenient biosourced precursors for the synthesis of derivatives. Sintenin may be used as a starting material for the design of hemi-synthetic germacradienolide-type costunolide or parthenolide derivatives. The 6,12-guaianolide scaffold of cladantholide offers opportunities to design novel arglabin derivatives. The therapeutic potential of the neglected and under-utilized plant Cladanthus arabicus and its original phytochemicals shall be explored further.