Diastereomers of lithospermic acid and lithospermic acid B from Monarda fistulosa and Lithospermum erythrorhizon.

Abstract Monardic acids A ( 1 ) and B ( 2 ), which are (7 R ,8 R ) diastereomers of lithospermic acid (LA) and lithospermic acid B, respectively, were isolated from Monarda fistulosa . A (7 S ,8 R ) isomer ( 3 ) of LA was also isolated from this plant, and a (7 R ,8 S ) isomer ( 7 ) of LA was obtained from Lithospermum erythrorhizon . The absolute configuration of 1 was confirmed by analysis of its hydrolysates, 7-epiblechnic acid and 2 R -3-(3,4-dihydroxyphenyl)-2-hydroxypropanoic acid. The configuration in the dihydrobenzofuran moieties of 2 , 3 , and 7 was extrapolated by using the phenylglycine methyl ester method and a Cotton effect at approximately 250–260 nm in their electronic circular dichroism spectra. Diastereomers ( 1 – 3 and 7 ) displayed moderate hyaluronidase inhibitory and histamine release inhibitory activities.