A New Anthraquinone From the Roots of Senna Obtusifolia

Background Senna obtusifolia is a widely used medicinal plant rich in anthraquinones, yet the chemical constituents of its roots remain insufficiently characterized compared with its seeds and aerial parts. To expand the phytochemical understanding of this species, the ethyl acetate extract of naturally grown roots was investigated. Methods The EtOAc extract of S. obtusifolia roots was subjected to repeated chromatographic separation, and the structures of the isolated compounds were elucidated using NMR and MS techniques. Results One new anthraquinone, 6-dehydroxy-9- O -methylviocristin ( 1 ), together with 13 known anthraquinones ( 2 – 14 ) and two known diterpenoids ( 15 and 16 ), was isolated. Compound 1 possesses a 2-methyl-1,4-anthracenedione skeleton and is characterized by O -methylation at C-8 and C-9, representing a structurally plausible O -methylated derivative of related anthraquinones previously reported from S. tora . Conclusions This study provides the systematic characterization of anthraquinones from the roots of S. obtusifolia , revealing distinct oxidation and methylation patterns compared with aerial organs. These findings contribute to the chemotaxonomic understanding of the Senna genus and offer new insights into the biosynthetic diversity of root-derived anthraquinones.