Optimization of Solvent Extraction for Phenolic, Flavonoid, and Elemental Profiling of Nerium oleander, Bulbine frutescens, and Cotyledon orbiculata: Implications for Phytomedicinal Applications

Medicinal plants are important sources of bioactive phytochemicals and essential mineral elements with therapeutic potential. This study investigated the effects of extraction solvent polarity on the total phenolic content (TPC), total flavonoid content (TFC), and elemental composition of Nerium oleander, Bulbine frutescens, and Cotyledon orbiculata. Phenolic and flavonoid contents were determined spectrophotometrically, while elemental nutrients in N. oleander extracts were analyzed using inductively coupled plasma-optical emission spectroscopy. N. oleander exhibited the highest phenolic and flavonoid contents among the three species. Dichloromethane extracts yielded the highest TPC (6.936 ± 0.613 mg GAE/100 mg), whereas hexane extracts produced the highest TFC (8.793 ± 0.020 mg QE/100 mg). Extraction solvent significantly affected phenolic recovery (p < 0.05), with a significant interaction between solvent and plant species. Essential macroelements (Ca, Mg, Na and K) and micronutrients (Al, Mn, Zn and Fe) were detected, while Cr, Cu, Ni and Pb were absent or below detectable limits. These findings demonstrate the importance of solvent selection and highlight N. oleander as a promising source of phytochemicals and mineral nutrients for phytomedicinal and nutraceutical applications.