European Journal of Medicinal Plants

Aim: In this work, the antioxidant activity of organic and aqueous extracts of seed of Coula edulis Baill. was evaluated.

Study Design: Seeds of Coula edulis were collected, authenticated and extracted with acetone, ethanol and water respectively. The resulting extracts were used for antioxidant assay.

Place and Duration of Study: This work was done at the Department of Chemistry, University of Uyo between November 2015 and July 2016.

Methodology: Air-dried seeds of Coula edulis (800 g) were pulverized and macerated with 2.5 L of acetone, ethanol and water separately for 24 hrs at room temperature and then filtered. The acetone and ethanol filtrates were concentrated in vacuo, while the aqueous extract was freeze-dried to obtain the crude acetone (AcE), ethanol (EtE) and aqueous (AqE) extracts respectively. Content of total phenolics, flavonoids and vitamin C in the extracts were determined. Also, the DPPH and ABTS scavenging activity as well as the metal chelating and reducing power of the extracts were also evaluated.

Results: Our results indicated that Coula edulis seed is a rich source of total phenolics, flavonoids and vitamin C. Amongst the tested extracts, the acetone extract contained the highest amount of total phenolics (28.3 mgGAE/g), could chelate Fe²⁺ ions more effectively (IC₅₀ = 46.2 μg/mL) and showed the best DPPH radical scavenging ability (IC₅₀ = 19.2 μg/mL). The aqueous extract was the richest in flavonoids and vitamin C. Also, it showed the best reducing power and ABTS radical scavenging abilities with an IC₅₀ of 25.2 μg/mL.

Conclusion: Coula edulis seed is a good source of natural antioxidants that can be exploited in food and therapeutic applications.