Comparative Extraction, Preliminary Phytochemical Screening, and Antioxidant Activity of Mirabilis jalapa L. Tuberous Roots Found in Sri Lanka

Mirabilis jalapa, or the Four O’clock plant, is an ornamental plant that has medicinal value due to its various phytochemical compositions. This study aims to examine the M. jalapa roots for their phytochemical spectrum and determine their in vitro antioxidant capacity. The plant was collected and authenticated, and then maceration, sonication, and Soxhlet extraction techniques were employed for aqueous, methanol, dichloromethane (DCM), and hexane extracts. Thin-layer chromatography (TLC) coupled with spray reagents was used to screen bioactives. Total Phenolic Content (TPC), DPPH (2,2-diphenyl-1-picrylhydrazyl), and ABTS (2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid)) radical-scavenging activity assays were performed to investigate the antioxidant potential. TLC screening revealed that maceration and Soxhlet extraction separated most compounds. The TPC values of methanol and aqueous macerates were the highest among all extracts. In the DPPH scavenging assay, these extracts showed a significantly higher activity, with IC50 values (half-maximal inhibitory concentration) below the lowest concentration tested (<0.03125 mg/mL). The ABTS assay identified the same two extracts as the most active, but scavenging remained below 50% (maximum 43.30% at 1 mg/mL); therefore, IC50 could not be determined. Overall, methanol and aqueous extracts of M. jalapa roots showed significantly higher antioxidant activity, perhaps due to their variety of bioactive compounds that justified their incorporation in traditional medicine.