Four New Monoterpenoid Glycosides from the Flower Buds of Magnolia biondii

Four new monoterpenoid glycosides 1–4, named magnoliaterpenoid A–D, were isolated from a 50% aqueous acetone extract of flower buds of Magnolia biondii, along with one known compound, (1′R,3′S,5′R,8′S,2Z,4E)-dihydrophaseic acid 3-O-β-d-glucopyranoside (5). Their structures and relative configuration were identified by extensive spectroscopic analysis (IR, UV, MS, 1D and 2D NMR). The aglycones of these four new compounds possess seven-membered rings systems, which are very rare. A plausible biosynthetic route for the four new compounds was proposed via the biogenetic isoprene rule. Compounds 1, 2, 3, and 4 showed no antimicrobial activity at the concentration range of 1.95–250 µg/mL.