Plants belonging to the genus Euphorbia are known to possess considerable chemical, medicinal, and economic importance [1]. Terpenes, including diterpenes and triterpenes, steroids, cerebrosides, glycerols, and phenolic compounds are characteristic constituents of Euphorbia species [2]. In the course of our work focusing on the isolation of special metabolites from various Euphorbia species, the chemical composition of Euphorbia gossypina var. coccinea Pax. (Euphorbiaceae) was thoroughly investigated [3]. The aim of our work was the identification of the special metabolites of the plant. This plant is a perennial, much-branched, succulent, herbaceous, evergreen shrub native to Kenya and Tanzania. Preparations of E. gossypina have long been used in traditional medicine for the treatment of swollen legs and general body pain. Moreover, it is applied as eye drops in the treatment of conjunctivitis and warts [4]. The diluted latex of small twigs is taken to treat laryngitis [5]. In Somalia, the latex is applied to treat mange in livestock [6]. There is no literature data on the phytochemistry and pharmacology of E. gossypina var. coccinea.
Herein, we report the isolation and structure elucidation of fourteen compounds, among them being eight new polyoxypregnane ester derivatives (euphogossypins A–H, 1–8), two new lignans (gossypilignans A and B, 9 and 10), and four known compounds, including the pregnane 12-O-benzoyldeacylmetaplexigenin (11), the lignan 9α-hydroxypinoresinol (12), and the flavonoids naringenin (13) and querctirin (14) from E. gossypina var. coccinea.
Pregnane glycosides are C21 steroidal natural compounds, in which the pregnane part is attached to different sugars. These compounds demonstrate a fair degree of diversity in their aglycone part with different numbers and types of sugar units being attached to the aglycone at position C-3 [7]. The sugar part of these compounds can be a mono- or disaccharide, or an oligosaccharide chain arranged mainly linearly to the pregnane skeleton through an acetal linkage. The characteristic monosaccharides of pregnane glycosides are d-glucose, l-rhamnose, d-cymarose, d-oleandrose, d-allose, and d-digitoxose. The occurrence of pregnane glyosides is characteristic of the Asclepiadaceae, Apocynaceae, Malpighiaceae, Ranunculaceae, and Zygophyllaceae families [8]. Pregnane glycosides are reported to possess noteworthy pharmacological properties, such as immunosuppressant, cytotoxic, antidepressant, anti-inflammatory, antioxidant, antibacterial, antifungal, and antiproliferative activities [8]. Therefore, the isolated compounds were tested for their antiproliferative activity against the HeLa cell line using the MTT assay.
