Dimeric phthalides from an aqueous extract of the Angelica sinensis root head

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.