Linaburiosides A-D, acylated iridoid glucosides from Linaria buriatica

Four previously undescribed acylated iridoid glucosides, linaburiosides A‒D, one undescribed iridoid, 7-deoxyiridolactonic acid, and one known acylated iridoid glucoside, iridolinarin C, were isolated from the aerial parts of a Mongolian traditional herbal medicine, Linaria buriatica. Linaburiosides A‒D had an acyl moiety corresponding to 7-deoxyiridolactonic acid. Detailed spectroscopic analyses of linaburiosides A‒D and 7-deoxyiridolactonic acid led to the assignment of their structures. The absolute configuration of 7-deoxyiridolactonic acid was elucidated by application of the PGME method; those of linaburiosides A‒D were assigned on the basis of chemical conversions, as well as application of the modified Mosher's method. The absolute configuration of iridolinarin C was also elucidated in this study. Anti-inflammatory and antiproliferative activities of isolated compounds and their derivatives were evaluated.