Chiral LC-MS-guided isolation of angular-type pyranocoumarins from Peucedani Radix

This study utilized a chiral liquid chromatography-mass spectrometry (LC-MS)-guided isolation strategy to accurately capture angular-type pyranocoumarins (APs) in Peucedani Radix (Chinese name: Qianhu). Sixteen APs were successfully purified from the ethyl acetate extract of Peucedani Radix through deploying various techniques such as silica gel, ODS, Sephadex LH-20, and achiral (chiral) semi-preparative liquid chromatography. After extensive structural measurements, such as ¹H and ¹³C NMR spectroscopy, their structures were identified as (3′S)-3′-(2-methyl-butyroyl)-4′-oxo-3′, 4′-dihydroseselin (1A), (3′R)-3′-(2-methyl-butyroyl)-4′-oxo-3′, 4′-dihydroseselin (1B), (3′S)-3′-isovaleryl-4′-oxo-lomatin (2A), (3′R)-3′-isovaleryl-4′-oxo-lomatin (2B), (3′S)-3′-angeloyloxy-4′-oxo-3′, 4′-dihydroseselin (3A), (3′R)-3′-angeloyloxy-4′-oxo-3′, 4′-dihydroseselin (3B), (3′S, 4′S)-praeruptorin B (4A), (3′R, 4′R)-praeruptorin B (4B), (3′S, 4′S)-praeruptorin E (5A), (3′R, 4′R)-praeruptorin E (5B), 3′-isovaleryl-4′-angeloyl-cis-khellactone (6), 3′-angeloyl-4′-(2-methyl-butyroyl)-cis-khellactone (7), (3′S, 4′S)-praeruptorin A (8A), (3′R, 4′R)-praeruptorin A (8B), (3′S, 4′S)-khellactone (9A), and (3′R, 4′R)-khellactone (9B), respectively. Thereof, compounds 1A and 1B were new compounds, while compound 2A represents a new configuration for a known planar structure. Compounds 2A and 2B were isolated for the first time from Peucedani Radix. Above all, chiral LC-MS-guided isolation strategy is advantageous at rapid capturing new compounds from herbal medicines, providing an effective means for the separation of novel structures, especially new enantiomers.