Effect of Different Solvents on Phytochemicals of Rinorea oblongifolia Leaves and Stems

Background and Objective: Medicinal plants are widely used due to their bioactive phytochemicals, which possess antioxidant and therapeutic properties. Rinorea oblongifolia, though less studied, is used in traditional medicine. This study evaluated the influence of solvent polarity on the phytochemical composition and antioxidant activity of its leaves and stems, aiming to identify the most effective solvents and plant parts for extracting bioactive compounds. Materials and Methods: Leaves and stems of R. oblongifolia were extracted using methanol, ethyl acetate, n-hexane, hot water, and cold water. Qualitative and quantitative phytochemical screenings were conducted, and antioxidant activity was evaluated using DPPH, FRAP, nitric oxide, and ABTS assays. Total phenol and flavonoid contents were measured spectrophotometrically. Pearson correlation was used to assess the relationship between phytochemical content and antioxidant activity (p>0.05). Results: Flavonoids, saponins, steroids, phenols, terpenoids, and cardiac glycosides were present in most extracts, with more diversity in leaves. Alkaloids were detected only in the cold-water leaf extract; anthraquinones and phlobatannins were absent. The hot water leaf extract showed the highest phenolic (5.10±1.03 mg GAE/g) and flavonoid content (4.89±0.65 mg QE/g). It also had the strongest DPPH activity (78.54%) compared to the lowest in the n-hexane stem extract (23.47%). Leaf extracts, especially with hot water and methanol, consistently outperformed stem extracts across all assays. A strong correlation (r>0.85) was observed between phenolic/flavonoid content and antioxidant activity. Conclusion: Solvent type and plant part significantly affect phytochemical extraction and antioxidant activity in R. oblongifolia. Leaves, particularly with hot water or methanol extraction, are the richest source of antioxidants. These findings support its traditional use and suggest potential for developing natural antioxidant formulations. Further studies on antimicrobial activity and safety are recommended.