Structural Determination of a New Cycloartane Glycoside from Asplenium ruprechtii

We characterized a new cycloartane glycoside, herein known as aspleniumside F (1), along with five known compounds as kaempferol-3-O-[(6-O-(E)-feruloyl)-β-D-glucopyranosyl]-(1→2)-β-D-galacopyranoside (2), quercetin-3-O-[(6-O-(E)-feruloyl)-β-D-glucopyranosyl]-(1→2)-β-D-glucopyranoside (3), kaempferol-3-O-[(6-O-(E)-caffeoyl)-β-D-glucopyranosyl]-(1→2)-β-D-glucopyranoside (4), kaempferol-3-O-[(6-O-(E)-caffeoyl)-β-D-glucopyranosyl]-(1→2)-β-D-glucopyranosyl-7-O-β-D-glucopyranoside (5), and kaempferol-3-O-[(6-O-p-coumaroyl)-β-D-glucopyranosyl]-(1→2)-β-D-glucopyranosyl-7-O-β-D-glucopyranoside (6), from Asplenium ruprechtii Sa. Kurata, a folk medicine widely used to treat Thromboangiitis obliterans in China, Japan, and Korea. Based on spectroscopic, mainly 1D-, 2D-NMR and (+)-HR-ESI-MS, analyses as well as through comparisons with previous reports, its chemical structure was determined as 3β,24,30-tri-β-D-glucopyranosyl-23,25-dihydroxycycloartane (= (23R,24R)-3β,24-bis-(β-D-glucopyranosyloxy)-23,25-dihydroxy-9β-9,19-cyclolanostan-29-yl β-D-glucopyranoside). According to the ¹ H coupling constant of anomeric protons and co-TLC of the acid hydrolysate with D-glucose, all three glycoside groups in 1 were revealed as β-D-glucopyranosyl. Furthermore, SOD-like antioxidant activity evaluation via IC₅₀ of 12.43, 6.78, 9.12, 6.94 and 4.85 μM revealed that compounds 2-6 had bioactivity.