Rumex japonicus Houtt. Protects Dopaminergic Neurons by Regulating Mitochondrial Function and Gut–Brain Axis in In Vitro and In Vivo Models of Parkinson’s Disease

Parkinson’s disease (PD) is the second most common neurodegenerative disease worldwide. Rumex japonicus Houtt. (RJ) has been used to treat gastrointestinal and inflammatory diseases in East Asia. However, it is unknown whether RJ can prevent PD. We investigated the neuroprotective effects of RJ in cellular and animal PD models, focused on mitochondrial function and the gut–brain axis. SH-SY5Y cells were treated with RJ (0.01 mg/mL) for 24 h, after which they were treated with the 1-methyl-4-phenylpyridinium ion (MPP+). MPP+-induced apoptosis increased mitochondrial reactive oxygen species and decreased ATP, PINK1, and DJ-1, which were inhibited by RJ. Ten-week-old C57BL/6N male mice were treated with 30 mg/kg of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) for 5 days and orally administered 50 or 100 mg/kg of RJ for 14 days. RJ alleviated MPTP-induced behavioral impairment, dopaminergic neuronal death, and mitochondrial dysfunction in the substantia nigra (SN) and suppressed the MPTP-induced increase in lipopolysaccharide, interleukin-1β, tumor necrosis factor-α, α-synuclein, and apoptotic factors in the SN and colon. Moreover, RJ inhibited the MPTP-mediated disruption of the tight junction barrier in the colon and blood–brain barrier of mice. Therefore, RJ alleviates MPTP-induced inflammation and dopaminergic neuronal death by maintaining mitochondrial function and tight junctions in the brain and colon.

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

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.