Effect of phenolic compounds from Oenothera rosea on the kaolin-carrageenan induced arthritis model in mice.

Oenothera rosea (Onagraceae), commonly known as "hierba del golpe" in Mexico, is an herbaceous plant widely used in Mexican traditional medicine for the treatment of pain and inflammation.The aim of this study was to assess the effect of extracts and compounds isolated from O. rosea in kaolin-carrageenan induced arthritis.Hydroalcoholic extract from aerial parts of O. rosea was obtained and chemically separated in order to obtain OrEA and isolated compounds using column chromatography, HPLC, UPLC and NMR analysis. O. rosea extract and derivatives were tested on the kaolin/carrageenan (K/C) induced arthritis model on ICR mice. Knee inflammation and paw withdrawal threshold were assessed following intraarticular administration of kaolin and carrageenan (4% and 2%, respectively) and subsequent oral administration of O. rosea. TNF-α, IL-1β, IL-6 and IL-10 levels from synovial capsule were measured using ELISA kits. NF-κB activity was also measured using the RAWBlue™ cell line. Finally, spleen and lungs were dissected to investigate body index.

Oral administration of the O. rosea ethyl acetate fraction (25 and 100 mg/kg) and isolated compounds (2 mg/kg) reduced the edema induced by kaolin/carrageenan, similar to the effect of methotrexate (1 mg/kg). Hyperalgesia but not allodynia was observed during this experiment. O. rosea derivatives reduced this behavior. The quantification of cytokines showed a reduction in TNF-α, IL-1β and IL-6, as well as an increase of IL-10. NF-κB production was also reduced by administering O. rosea derivatives. Chemical analysis of O. rosea derivatives showed that the major compounds present in the ethyl acetate fraction were phenolic compounds. Gallic acid, quercetin glucoside and quercetin rhamnoside were separated and identified by UPLC-UV-MS, and myricetin glycoside and tamarixetin glucoside using ¹H and ¹³C NMR.

O. rosea produces different phenolic compounds capable of reducing the inflammation and secondary mechanical hyperalgesia produced by K/C administration. They also reduced proinflammatory cytokines and increased anti-inflammatory cytokines. Finally, NF-κB modulation was reduced by the administration of O. rosea. Therefore, O. rosea could be considered of interest in inflammatory and painful diseases.