Isolation of Momilactones A and B from Rice Husk Using High-Speed Countercurrent Chromatography

Momilactones, allelochemicals from rice plants, exhibit diverse effects, including functioning as crop-friendly pesticides, and possessing antifungal and anticancer properties. The present study aimed to optimize the isolation of momilactones A (MA) and B (MB) using high-speed countercurrent chromatography (HSCCC), prioritizing the minimization of organic solvent waste and utilizing discarded rice husk. By employing techniques such as solvent reuse and HSCCC, we successfully isolated the highly purified fractions of MA and MB (>95% purity, as verified by HPLC) from rice husk. The optimized two-phase solvent system ( n-hexane/ethyl acetate/methanol/water, 7/3/5/5, v/v/v/v ) was specifically chosen for its efficiency in HSCCC, applied to extracts from 2 kg of rice husk. The separation was performed using the lower mobile phase of the two-phase solvent system at a flow rate of 1.0 mL/min after rotating the multilayer coiled column at the revolution speed of 1000 rpm. The retention of the stationary phase was observed to be 77%. The purity of isolated MA (3.0 mg) and MB (2.0 mg) was determined to be 99.0% and 98.2% via LC-UV chromatogram, respectively. Significantly, the organic solvents used in the extraction and HSCCC processes were redistilled and recycled, leading to an over 80% reduction in solvent consumption. This study demonstrates the feasibility of a sustainable, economical, and effective chromatographic method for isolating allelochemicals from waste plant materials.