Title
Photosensitizing anthraquinones from Heterophyllaea lycioides (Rubiaceae)
Author
Jesica A. Dimmer, Susana C. Núñez Montoya, Caterine S. Mendoza, José L. Cabrera
Year
2017
Journal
Phytochemistry
Abstract
Seven anthraquinones were isolated from aerial parts of Heterophyllaea lycioides (Rusby) Sandwith (Rubiaceae), including three derivatives that have not been described before: a hetero-bianthraquinone identified as (R)-2-hydroxymethyl-2′methyl-1,1′,6,6′-tetrahydroxy-5,5′ bianthraquinone (lycionine), and two mono-chlorinated derivatives related to soranjidiol. One of them is a homo-bianthraquinone: (R)-7-chloro-2,2′-dimethyl-1,1′,6,6′-tetrahydroxy-5,5′ bianthraquinone (7-chlorobisoranjidiol), whereas the second halogenated derivative corresponds to a monomeric structure: 5-chloro-1,6-dihydroxy-2-methyl anthraquinone (5-chlorosoranjidiol). The four known compounds were already isolated from another species of this genus, H. pustulata, and they were identified as 5,5′-bisoranjidiol, soranjidiol, pustuline and heterophylline. Structural elucidation was performed by means of an extensive spectroscopic analysis, including 1D and 2D NMR data as well as by HRMS analysis. Chemical structures of 7-chlorobisoranjidiol and 5-chlorosoranjidiol were confirmed by their synthesis from 5,5′-bisoranjidiol and soranjidiol, respectively. Type I photosensitizing properties (superoxide anion radical generation, O2radical dot−) were assessed by using the nitroblue tetrazolium assay. When lycionine and chlorinated derivatives were irradiated, they enhanced the O2radical dot−production with respect to the control; 7-chlorobisoranjidiol stood out by generating an increase of 20%, whereas the other anthraquinones only produced a slight increase of 7%.
Instrument
J-810
Keywords
Circular dichroism, Absolute configuration, Pharmaceutical