Preparative Separation of Three Monoterpenes from Perilla frutescens var. crispa Using Centrifugal Partition Chromatography

Three monoterpenes, namely, 9-hydroxy isoegomaketone (1), isoegomaketone (2), and perilla ketone (3), were successfully separated from the supercritical carbon dioxide (SC-CO₂) extract of the leaves of Perilla frutescens var. crispa (cv. Antisperill; Lamiaceae) by centrifugal partition chromatography (CPC). To obtain large quantities of these materials required for studies on their mechanism of action and in vivo effectiveness in inflammation, we used CPC because of its high loading capacity and reproducibility to purify the three compounds. Compound 1 (2.60 mg, 96.7% purity at 254 nm) was purified from 500 mg of the SC-CO₂ extract of P. frutescens var. crispa (cv. Antisperill), using a two-phase solvent system comprising n-hexane/ethyl acetate/ethanol/water (5:5:5:5 v/v) in a descending mode. As compounds 2 (56.1 mg, 97.6% purity at 254 nm) and 3 (78.6 mg, 96.1% purity at 254 nm) are highly volatile and difficult to recover from an aqueous mobile phase after purification during the drying process, they were obtained from the same amount of the processed extract in an ascending mode using the upper organic phase as the mobile phase (n-hexane/ethyl acetate/ethanol/water, 8:2:8:2 v/v). The structures of compounds 1-3 were confirmed by ¹H- and ¹³C-NMR analysis. Thus, based on our findings, we recommend centrifugal partition chromatography as a powerful technique for purifying the active principal compounds 1 and 2 from the leaves of P. frutescens var. crispa.