Optimization of ionic liquid-microwave assisted extraction method of Mahkota Dewa (Phaleria macrocarpa (Scheff.) Boerl.) fruit pulp

Mahkota dewa fruit pulp (Phaleria macrocarpa, PMp) is often used as a medicinal raw material in Indonesia. The texture of the P. macrocarpa fruit is hard due to high lignin and cellulose contents and it often inhibits an extraction process of secondary metabolism. This study is conducted to get optimum extraction condition by using the ionic liquid-microwave assisted extraction (IL-MAE) method, assessing the effect of pretreatment with urea and the antioxidant activity of PMp. Solvent [BMIM]BF₄ has been chosen for extraction by varying three parameters: solvent concentration, extraction time, and solvent–sample ratio. The optimum condition was determined based on total phenolic content (TPC; milligram equivalent to quercetin as reference), antioxidant activity assay has been carried out using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) method, and selectivity to extract polar compound was carried out using High-Performance Liquid Chromatography (HPLC) method. The optimum extraction condition has been achieved at run 11 with the condition: 10% microwave power, using [BMIM]BF₄ (2.5 M) as a solvent, using 0.01 M KH₂PO₄ as a salt solution, 2.5 minutes extraction time, solvent: sample ratio (17.5: 1), resulting TPC value of 191.72 ± 1.27 mgGAE/g powder, and DPPH radical-scavenging activity of 12.1 ± 0.003%. The IL-MAE method can extract the marker of phenolic compounds (quercetin, mahkoside, benzophenone, and mangiferin) and showed selectivity in extracting polar compound than conventional methods. Pretreatment using 8% urea for 12 hours produced no significant difference in TPC values from the IL-MAE method at optimum conditions. The IL-MAE method gives the highest TPC and superior antioxidant activity in PMp extraction.