Phytochemical Composition, Antioxidant Activities and FTIR Analysis of the Leaves of Rosa abyssinica Lindley and Justicia schimperiana (Hochst. ex Nees) T. Anders

Objective The current study's objective was to evaluate the antioxidant activity and the phytochemical composition of the leaves of Rosa abyssinica and Justicia schimperiana . Methods The crude extracts (80% methanol) and solvent fractions (aqueous, ethyl acetate and n-hexane) were prepared utilizing cold maceration and solvent fraction methods, respectively. The total alkaloid content (TAC) was quantified for the dried leaf powders. The total phenolic (TPC) and flavonoid (TFC) contents of the crude extracts were also assessed. The antioxidant activity of the crude extracts and solvent fractions was assessed by 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and ferric reducing antioxidant power (FRAP) assays. Analysis using fourier transform infrared (FTIR) spectroscopy was also carried out. Results The leaves of R. abyssinica exhibited a higher TAC (8.89%). Both TPC (11.58 ± 0.35 mg GAE/g of extract) and TFC (13.11 ± 0.97 mg QT/g of extract) were observed to be higher in the crude extract of R. abyssinica. Among all tested extracts, R. abyssinica 's n-hexane fraction (RANF) showed the highest activity specifically in DPPH (IC 50  = 0.24 ± 0.01 mg/ml) and ABTS (IC 50  = 0.15 ± 0.03 mg/ml) radical scavenging activity. The aqueous fraction (RAAF) exhibited the strongest activity in FRAP assay (6.49 ± 0.21 mg AA/g of extract). From the Fourier transform infrared (FTIR) spectroscopic analysis, C-H, C = O, O-H and C-O functional groups were identified in the crude extracts of both plants. Conclusion These findings provide a basis for future investigation aimed at identifying bioactive compounds and exploring their potential therapeutic applications.