Study on the Chemical Structures and Free Radical Scavenging Ability of Anthraquinones and Its c-Glycosides from Rumexjaponicus Houtt.

Abstract

Rumex japonicus Houtt. (RJH) is a kind of Traditional Chinese Medicine (TCM) widely used in the treatment of serious skin diseases such as psoriasis. To further explore its bioactive components, the five-year root of RJH was used, the nuclear magnetic resonance (NMR) technique was employed with DMSO-d6 solvent for chemical structures, the scavenging capacity of the free radicals (DPPH, alkyl, –OH, and ˙O−2) was evaluated by electron spin resonance (ESR) method. In the results, seven compounds that were wholly characterized as anthraquinones (1 and 2), its c-glycosides (4–7), and flavonoid glycoside (3) especially for the hydrogen atoms from –OH groups located at phenol rings and glucose moieties. The compound 4 and 5 showed the significant bioac-tivity with the IC50 values (DPPH: 23.34 and 23.25 μM; alkyl: 20.27 and 20.15 μM; –OH: 26.03 and 25.50 μM; and ˙O−2: 14.69 and 14.68 μM, respectively). In conclusion, the DMSO-d6 solvent could make active protons be expressed clearly for accurate assignments. The compounds 4 and 5 could be suggested to be applied for potential candidates for related drugs.