Antioxidant property, anti-inflammatory and analgesic effects of aqueous extracts of two onion bulbs varieties (Allium cepa L.)

Abstract

Background

oxidative stress and inflammation remain the main health problems often linked to degenerative diseases. The aim of this study was to evaluate antioxidant, analgesic and anti-inflammatory properties of onion growth in Cameroon.

Methods

Aqueous extracts were produced from two varieties of onion (Violet of galmi; Goudami) and were quantified for their polyphenols content. Concentrations of extracts (0.1, 0.5, 1, 1.5 mg/mL) were also prepared, their in vitro antioxidant properties evaluated by using standard methods. Anti-inflammatory effect of onion extracts was assessed by applying carrageenan sub plantar test to Wistar rats, but acetic acid test was used to study analgesic effect.

Results

The polyphenols content and antioxidant activities of onion extracts changed significantly (p < 0.05) with variety and increased (p < 0.05) with concentration. Total phenolic (range 58.03–67.43%), Total Reducing power (range 0.27–0.94%), DPPH radical scavenging (range 37.33–202.08%) were higher in Violet of galmi extracts, while Ferrous ion chelating power (range 23.15–97.42%) was higher in Goudami extract. The two varieties of onion extracts reduce (p < 0.05) rat paw edema in a dose dependent manner compared with negative control group. Violet of Galmi variety (1.5 mg/kg) reaches 100% of inhibition after 2 h whereas the Goudami variety (1.5 mg/kg) reaches 100% of inhibition after 3 h. In terms of analgesic activity, aqueous extract of the two varieties of onion exhibited analgesic effect characterized by reduction in writhes. Analgesic activity increased significantly (p < 0.05) with concentration of onion but Violet of galmi extracts has also shown more efficacy than Goudami extracts.

Conclusion

The present findings suggest that aqueous extract of violet of galmi and Goudami bulb onions have antioxidant activity and protective effects against inflammation and pain.