Efficiency and selectivity of triterpene acid extraction from decoctions and tinctures prepared from apple peels

Background: This study assessed the extraction efficiency of ursolic (UA) and oleanolic acids (OA), as well as the total phenols in aqueous and hydroethanolic extracts of dry apple peels at room temperature. Materials and Methods: After running preliminary assays on decoctions and tinctures (ethanol: water 7:3 v/v), the extracts from dried apple (cv. Fuji) peels were obtained by static maceration over varied intervals (2 to 180 days). The UA and OA content in the extracts was quantified by High Performance Liquid Chromatography with Diode Array Detection (HPLC-DAD) with a reversed phase column and isocratic elution (CH ₃ CN/H ₂ O/H ₃ PO ₄ ) against calibration curves (R ² > 0.9995). The total phenol content in the extracts was evaluated spectrophotometrically at 760 nm using the Folin-Ciocalteau method referencing gallic acid. Results: UA and OA in the hydroethanolic extracts ranged from 3.63-6.12 mg/g and 2.12-3.30 mg/g, corresponding to 1.72-3.07 and 1.00-1.66 mg/g in the raw material, respectively. Higher values of triterpene acid content corresponded to maceration periods of 10 or 30 days. The residual phenol and polyphenol content ranged from 6.97 to 11.6 mg/g. The UA and OA yields, as well as the total phenol content, versus the maceration time were plotted in Control Charts within confidence intervals (95%) and were unaffected during the assayed period. Conclusion: Apple peel tinctures from 10% solids obtained at room temperature exhibited the highest content of triterpene acids when employing a maceration period of 10 to 30 days. Extracts prepared using this procedure contained an average of 7.33 mg/g of total triterpene acids and 10.6 mg/g phenolic compounds. These results establish supporting data for apple peel tinctures and their derived phytopharmaceuticals that are standardized on the ursolic-oleanolic acid content.