Phytochemical Profiling and In Vitro Antioxidant Activity of Hibiscus sabdariffa Calyces Collected from Different Agro-Ecological Zones in Nigeria

Hibiscus sabdariffa, locally known as zobo, is cultivated extensively across multiple agro-ecological zones in Nigeria and consumed as a beverage and traditional remedy for hypertension, dyslipidaemia, and oxidative stress-related conditions. The phytochemical composition of this plant may vary significantly based on growing conditions and geographical origin. This study comparatively profiles the phytochemical constituents and in vitro antioxidant activity of H. sabdariffa calyces sourced from Zamfara (North West), Plateau (North Central), and Ogun (South West) States. Standard phytochemical screening and high-performance thin layer chromatography (HPTLC) were used for constituent identification. Antioxidant activity was evaluated using DPPH, ABTS, and FRAP assays. Total phenolic and flavonoid content were quantified by the Folin-Ciocalteu and aluminium chloride methods, respectively. All three samples contained anthocyanins, flavonoids, polyphenols, and organic acids; however, significant inter-zonal variation was observed. Samples from Zamfara recorded the highest anthocyanin content, while Plateau samples showed superior DPPH radical scavenging activity. These findings indicate that geographical origin significantly influences the phytochemical profile and antioxidant potency of H. sabdariffa, with implications for standardisation in herbal product development. Keywords: Hibiscus sabdariffa, antioxidant, phytochemical profiling, agro-ecological zones, DPPH