Integrated Green Microwave Extraction and Hydrophobic Resin-Based Enrichment of Mitragynine from Mitragyna speciosa

Abstract

Kratom (Mitragyna speciosa Korth.) has emerged as a promising botanical source of bioactive indole alkaloids, most notably mitragynine, which exerts analgesic activity through partial agonism at μ-opioid receptors. Advancing its pharmacological and clinical potential requires extraction and purification strategies that are efficient, safe, and environmentally responsible, as many conventional methods rely on toxic solvents and produce impure extracts. This study developed an integrated green extraction platform to obtain mitragynine-enriched extracts from kratom leaves with high efficiency and sustainability. Microwave-assisted extraction (MAE), selected for its solvent-saving and energy-efficient performance, produced an ethanolic crude extract with a yield of 28.6% and a mitragynine content of 6.54 ± 0.28% w/w. Initial purification using the low-cost hydrophobic resin SEPLITE^® LXA1180 resulted in co-elution of plastid pigments, prompting optimization of both the extraction solvent and elution system. Incorporating 35% glycerin in ethanol effectively suppressed chlorophyll solubilization, while subsequent fractionation using stepwise elution (40%, 50%, and 80% ethanol) markedly reduced polar impurities. The optimized protocol yielded a purified fraction (B2) with a substantially increased mitragynine concentration of 32.41 ± 1.18% w/w. Overall, this integrated MAE–hydrophobic resin approach enhances mitragynine purity while adhering to green-extraction principles through the use of safer solvents and minimized waste. The method provides a practical, scalable, and sustainable framework for preparing standardized mitragynine-rich extracts, supporting future development of kratom-derived analgesic candidates.