Effects of the removal of pigment on the anti-oxidant property of methanolic extract of Hibiscus Sabdarifa Calyx

Abstract

Hibiscus sabdariffa is a widely consumed medicinal plant known for its rich phytochemical content and antioxidant potential. This study evaluated the antioxidant properties of its calyx extracted with methanol using spectrophotometric and biochemical assays. Given the global interest in natural antioxidants for therapeutic and food preservation purposes, this study provides insight into the efficacy of H. sabdariffa as a viable source. The methanolic extracts were subjected to UV-Visible spectroscopic analysis and antioxidant activity assays: DPPH radical scavenging, Ferric Reducing Antioxidant Power (FRAP), and Inhibition of Lipid Peroxidation (ILP) were conducted at the concentration (µg/ml) of 500, 250, 125 and 62.5 respectively across the three samples A, B and C (pigmented, de-pigmented and desorbed) to evaluate comparative efficiency. The UV spectrum revealed maximum absorbance at 550 nm, for sample A (3.000), sample B (0.312) and sample C (4.472) indicating the presence of phenolic compounds in varying degrees. DPPH assay showed that the desorbed sample exhibited the highest free radical scavenging activity at 76.9±0.2 (µg/ml), 67.04±0.1 (µg/ml), 48.22±0.29 (µg/ml) and 32.85±0.05 (µg/ml), while the de-pigmented sample had the lowest at 68.24±0.22 (µg/ml), 55.72±0.03 (µg/ml), 25.63±26.9 (µg/ml) and 14.02±0.7 (µg/ml). This trend is similar with FRAP assay, desorbed sample was found to be strongest (91.59±0.03 (µg/ml), 86.9±0.1 (µg/ml), 76.8±0.03 (µg/ml) and 59.92±0.09 (µg/ml) and de-pigmented sample being the weakest (80.6±0.02 (µg/ml), 75.58±0.03 (µg/ml), 60.55±0.09 (µg/ml) and 36.59±0.03 (µg/ml)). The results’ trend was also similar with ILP assay; the desorbed pigment provided a higher inhibition of lipid peroxidation (69.41±0.2 (µg/ml), 58.63±0.07 (µg/ml), 43.63±0.29 (µg/ml) and 29.07±0.44 (µg/ml)) compared to the original and de-pigmented samples. In conclusion, antioxidant activity may be correlated with pigment concentration. These findings suggested that H. sabdariffa pigment extracted with methanol possesses potent antioxidant capacity suitable for nutraceutical applications.