8,4′-Oxyneolignane glucosides from an aqueous extract of “ban lan gen” (Isatis indigotica root) and their absolute configurations

Abstract

Three pairs of glycosidic 8,4′-oxyneolignane diastereoisomers, named isatioxyneolignosides A−F (1–6), were isolated from an aqueous extract of Isatis indigotica roots. Their structures and absolute configurations were elucidated by comprehensive spectroscopic data analysis and enzyme hydrolysis. The validity of ΔδC8-C7 values to distinguish threo and erythro aryl glycerol units and Cotton effects at 235±5 nm to determine absolute configurations at C-8 in 1–6 and their aglycones (1a–6a) are discussed.

Keywords

• Cruciferae
• Isatis indigotica
• Isatioxyneolignosides A−F
• 8,4′-Oxyneolignane
• Threo/erythro Isomers
• ΔδC8-C7 value
• Absolute configuration
• Cotton effect