Phytochemical composition and pharmacological evaluation of different extracts of Oenothera rosea L´Hér. ex Ait (Onagraceae) aerial part

Oenothera genus consists of 145 herbs species which has been used for the treatment of skin diseases, diabetes mellitus, renal and liver problems, and as anti-diarrheic and anti-inflammatory drugs, among others. A great variety of chemical compounds have been reported from Oenothera genus among them tannins, flavonoids, steroids, carbohydrates and lipids. This study was focused on investigating the effect of different extracts of Oenothera rosea L´ Hér. ex Ait aerial part (from water ethanol, methanol, ethyl acetate, chloroform and hexane) on total flavonoid and phenolic compounds content; as well as the evaluation of their antioxidant, analgesic and anti-inflammatory activities. Antioxidant activity was performed considering the ability of the extracts to scavenge DPPH• free radicals, while analgesic and anti-inflammatory activities of most potent extracts were evaluated by acetic acid writhing reflex, hot plate and cotton pellet-induced granuloma formation models, respectively. Methanol, ethanol and ethyl acetate extracts showed a high phenolic compounds content, being ethanol the best solvent for extraction of flavonoids (28.84 ± 0.46 mg flavonoids/g extract). The highest antioxidant activity was observed with methanol, hexane and ethyl acetate extracts (89.51 ± 0.38, 89.42 ± 0.42 and 89.05 ± 0.34%, respectively). Ethanol and ethyl acetate extracts showed analgesic activity with inhibition percentages of the evaluated parameters of more than 50%. Ethyl acetate extract down-regulated chronic inflammation without inducing gastrointestinal damage. These findings provide scientific evidence of O. rosea folkloric use and highlight their importance as a possible natural treatment for several diseases.