Acylated iridoid glycosides with hyaluronidase inhibitory activity from the rhizomes of Picrorhiza kurroa Royle ex Benth.

Seven new acylated iridoid glycosides, picrorhizaosides A-G (1-7), were isolated from the methanol extract of the rhizomes of Picrorhiza kurroa Royle ex Benth. (Plantaginaceae), in addition to six known iridoid glycosides (8-13). The structures of these new iridoids, including their stereochemistry, were determined based on chemical and physicochemical evidence derived from NMR and MS analysis. Of the isolates, picrorhizaosides D (4, IC₅₀ = 43.4 μM) and E (5, 35.8 μM); picrosides I (8, 60.7 μM), II (9, 22.3 μM), and IV (11, 59.2 μM); and minecoside (13, 57.2 μM), exhibited a similar or stronger hyaluronidase inhibitory activity than those of the antiallergic medicines disodium cromoglycate (64.8 μM), ketotifen fumarate (76.5 μM), and tranilast (227 μM).