Evaluation of Antioxidant Activity and Phenolic Content of Hibiscus sabdariffa Calyces from Jigawa State

Hibiscus sabdariffa, commonly known as zobo or roselle, is widely cultivated in North West Nigeria and used to prepare a popular traditional beverage. The antioxidant properties of its calyces are of growing scientific and commercial interest. This study evaluates the total phenolic content, total flavonoid content, and antioxidant activity of aqueous and ethanolic extracts of Hibiscus sabdariffa calyces obtained from farmers in Jigawa State. Total phenolic content was determined by the Folin-Ciocalteu method using gallic acid as a reference standard. Total flavonoid content was assessed by the aluminium chloride colorimetric method using quercetin as a standard. Antioxidant activity was evaluated by DPPH radical scavenging assay, ABTS assay, and ferric reducing antioxidant power assay. Ascorbic acid was used as a positive control in radical scavenging tests. Results indicate that the ethanolic extract contained significantly higher total phenolic content (248 milligrams gallic acid equivalent per gram) and total flavonoid content than the aqueous extract. Correspondingly, the ethanolic extract exhibited superior DPPH radical scavenging activity with an IC50 of 0.31 milligrams per millilitre, compared to 0.62 milligrams per millilitre for the aqueous extract. The findings confirm the high antioxidant potential of Hibiscus sabdariffa from Jigawa State and support further investigation of its application in functional food and nutraceutical formulation. Keywords: Hibiscus sabdariffa, antioxidant activity, phenolic content, Jigawa State, DPPH assay