Comparative Phytochemical Profiling and Anti-Lipid-Peroxidative Activity of Justicia secunda Vahl Leaf Extract and Solvent Fractions

Abstract

Background: Justicia secunda Vahl is a medicinal plant rich in antioxidant phytochemicals. This study evaluated the phytochemical profiles and in vitro anti-lipid-peroxidative activities of its crude ethanol extract and solvent fractions. Materials and Methods: Extraction was performed with 70% ethanol, and the crude extract was fractionated using water, methanol, ethyl acetate, and n-hexane. Chemical constituents were characterised by gas chromatography–mass spectrometry (GC–MS). Identified compounds were classified according to major chemical groups, and their relative abundances were calculated. Lipid peroxidation was evaluated using an iron-induced liver homogenate model by measuring malondialdehyde (MDA) formation using the thiobarbituric acid-reactive substances assay. Samples were tested at graded concentrations, and IC₅₀ values were estimated by regression analysis using butylated hydroxytoluene (BHT) as the reference antioxidant. Results: Marked solvent-dependent differences occurred in phytochemical composition. Phenolic compounds accounted for 14.82%, 18.08%, 19.80% and 6.90% of the aqueous, methanol, ethyl acetate, and n-hexane fractions, respectively, while terpenes predominated in the n-hexane fraction (51.84%). The aqueous, methanol, ethyl acetate and n-hexane fractions exhibited MDA inhibition of 43.35%, 33.27%, 44.41% and 51.84%, respectively, with the n-hexane fraction showing the highest inhibitory activity and an extrapolated IC₅₀ of −16.19 mg/mL, compared with 0.22 mg/mL for BHT. Discussion and Conclusion: The differential antioxidant activity observed among the fractions corresponds with their distinct phytochemical profiles. The strong activity of the n-hexane fraction despite its lower phenolic abundance suggests an important contribution from lipophilic constituents, particularly terpenoids. Overall, solvent fractionation significantly influenced the phytochemical composition and anti-lipid-peroxidative activity of J. secunda. The n-hexane fraction warrants further bioassay-guided investigation to identify compounds responsible for its activity.