Seven new 3,4-dihydro-furanocoumarin derivatives from Angelica dahurica

OBJECTIVE: To study the chemical constituents of the roots of Angelica dahurica, a well-known Chinese herbal medicine named Baizhi in Chinese. METHODS: Compounds were separated by various chromatographies, and the structures of new compounds were elucidated based on the analysis of their spectroscopic and spectrometric data (1D, 2D NMR, HRESI MS, IR, and UV). The absolute configurations of new compounds were determined by the calculated electronic circular dichroism and chemical derivatization. The inhibitory activities of all isolates against nitric oxide (NO) production were evaluated using lipopolysaccharide-activated RAW 264.7 macrophage cells. RESULTS: Seven new 3,4-dihydro-furanocoumarin derivatives (1a/1b, 2a/2b, 3a/3b, 4) together with a known furanocoumarin (5) were isolated from the roots of A. dahurica. The new compounds included three pairs of enantiomers, (4S, 2′′R)-angelicadin A (1a)/(4R, 2′′S)-angelicadin A (1b), (4S, 2′′S)-angelicadin A (2a)/(4R, 2′′R)-angelicadin A (2b), and (4S, 2′′S)-secoangelicadin A (3a)/(4R, 2′′R)-secoangelicadin A (3b), together with (4R, 2′′R)-secoangelicadin A methyl ester (4). The known xanthotoxol (5) inhibited the NO production with the half-maximal inhibitory concentration (IC(50)) value of (32.8 ± 0.8) µmol/L, but all the new compounds showed no inhibitory activities at the concentration of 100 µmol/L. CONCLUSION: This is the first report of the discovery of 3,4-dihydro-furanocoumarins from A. dahurica. The results are not only meaningful for the understanding of the chemical constituents of A. dahurica, but also enrich the reservoir of natural products.