ABSTRACT
Ten dimeric phthalide racemates (1-10) were isolated from an aqueous extract of the Angelica sinensis root head (Guitou) by separation techniques of column chromatography over macroporous adsorbent resin, MCI resin, silica gel, and Sephadex LH-20, together with preparative thin-layer chromatography and reversed phase HPLC. The racemates were further separated into (+)-/(-)-1-(+)-/(-)-10 with chiral HPLC. Their structures including absolute configurations were elucidated by comprehensive analysis of spectroscopic data, combined with electronic circular dichroism (ECD) and NMR calculations as well as single crystal X-ray diffractions. Compounds (+)-/(-)-1-(+)-/(-)-10 are either new structure or new natural product, named (+)-/(-)-angelidipthalidic acids A-H [(+)-/(-)-1-(+)-/(-)-8] and (+)-/(-)-angelidipthalidols A and B [(+)-/(-)-9 and (+)-/(-)-10], respectively. Meanwhile, dimeric phthalide mono- and bis-lactone derivatives with 3.3′a,8.6′- and 3.6′,8.3′a-coupling patterns as well as determination of their relative configurations are discussed.
ABSTRACT
Eleven monoterpenes including seven new chemical structures or new natural products covering two pairs of scalemic enantiomers, together with four known analogues, were isolated from an aqueous extract of the Angelica sinensis root head (Guitou) by separation techniques of column chromatography over macroporous adsorbent resin, MCI resin, silica gel, Sephadex LH-20, and Toyopearl HW-40C, together with preparative thin-layer chromatography as well as reversed phase and chiral HPLC. Their structures were determined by spectroscopic data analysis, combined with theoretic calculation of electronic circular dichroism (ECD) spectra and single crystal X-ray diffraction. The new structures or new natural products named (+)-/(-)-angelinones A and B [(+)-/(-)-1 and (+)-/(-)-2], angelinones C and D (3 and 4), and angelinol A (5), respectively, while the known analogues were 6β,9-dihydroxy-(+)-α-pinene (6), 1,1,5-trimethyl-2-hydroxymethyl-cyclohexa-2,5-dien-4-one (7), jasminol E (8), and (+)-trans-sobrerol (9). All the isolates were reported in this plant for the first time, except for the previously reported 6 from an ethanol extract of the aerial parts of A. sinensis, of which the structure was confirmed by X-ray crystallography in this study.