RESUMEN
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.
RESUMEN
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.
RESUMEN
The poor stability of the ligustilide (LIG) makes its quantitation in Angelica sinensis (AS) difficult. This study establishes a chemical conversion method for the determination of ligustilide content in AS and proposes a national pharmacopoeia standard. Mechanical agitation and sonication of a powdered AS extract in a methanol/cyprolamine mixture facilitated the stabilization and transformation of ligustilide. Using an external reference HPLC-DAD method, the cyclopropyl-ligustilide (LIGc) content in the mixture could be determined. The content of ligustilide was greater than 1.0% based on 144 AS specimens including 68 obtained from the originally planted areas of Qinghai and Gansu Province; 55 specimens were obtained from Minxian and Weiyuan County medicine markets, and 21 specimens for which the storage period reached or exceeded 1.5 years. According to the Hong Kong Chinese materis medica standards, the content of ligustilide in AS should not be lower than 0.6%. The developed method could also be applied to the quality control of other Chinese medicinal materials (such as Ligusticum chuanxiong) or Chinese patent medicines in which ligustilide is the main component.