Juncaceae is a relatively small plant family with approximately 500 plant species worldwide. It can be divided into seven genera of which Juncus L. is the largest and by far the most important one from phytochemical and pharmacological points of view. Various Juncus species are used in the traditional Chinese medicine for the treatment of numerous disorders (e.g. fidgetiness, insomnia, painful urination, pharyngitis, and aphtha). Medulla Junci, the dried stem pith of J. effusus, is official in the Pharmacopoeia of the People’s Republic of China (2005).
Juncaceae species accumulate different secondary metabolites, e.g. phenanthrenes, flavonoids, triterpenes, steroids, coumarins and phenolic acid derivatives. According to the literature data, the major bioactive components of Juncaceae species are phenanthrenes. Almost 20% of currently known natural phenanthrenes were described from Juncus species.
In continuation of our work dealing with the isolation of biologically active secondary metabolites from Juncaceae species, Juncus atratus was investigated. The dried plant material was extracted with methanol. After evaporation, it was subjected to solvent–solvent partition with n-hexane, CH2Cl2 and ethyl acetate. The CH2Cl2 fraction was chromatographed by a combination of different methods, including CC, VLC, gel filtration, preparative TLC, and HPLC. The structure elucidation of the compounds was carried out by extensive NMR spectroscopic analysis, and HRMS experiments.
The results allowed the identification of five phenanthrenes [1 phenanthrene (dehydroeffusol), and 4 dihydrophenanthrenes (juncatrins A and B, effusol, and juncuenin B)], two flavonoids (apigenin and luteolin), one diterpene (phytol), and a fatty acid. Juncatrins A and B are new natural products, substituted by an acetyl and an acetylene group, respectively, instead of a vinyl group. This was the first time that a phenanthrene with acetylene moiety was isolated from natural source. All compounds were isolated for the first time from J. atratus.
Acknowledgement: This work was supported by the GINOP-2.3.2-15-2016-00012.