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Viburnum macrocephalum f. keteleeri, not well explored in the pharmaceutical field, is a tall deciduous shrub and commonly used as folk medicines for the treatment of type 2 diabetes (T2D). In this study, the dried branches of V. macrocephalum f. keteleeri were extracted with 95% ethanol and the extract was fractionated on the basis of polarity with ethyl acetate and n-butanol. Among the different fractions, the ethyl acetate fraction exhibited the highest α-glucosidase inhibitory activity, and its bioassay-guided fractionation led to the isolation and identification of six compounds including a new 8-O-4′-neolignan glycoside (1), categorized as a rare 7-deoxy skeleton, three previously undescribed phenolic glycosides (2–4), together with two known secondary metabolites (5, 6), which were found for the first time in Viburnum. Noticeably, compound 1 had almost the same intestinal α-glucosidase inhibitory activity as the positive control acarbose.

A novel norneolignan glycoside (1), categorized as an unusual 7-noraryl-4′,7-epoxy-8,5′-neolignan glycoside, four new phenolic glycosides (2–5), and a known neolignan glycoside (6) have been isolated from the ethanolic extract of the stems of Viburnum fordiae Hance. Dried stems of V. fordiae were extracted with 95% ethanol, and the concentrated extract was portioned successively with petroleum ether, ethyl acetate and n-butanol. The n-butanol portion was subjected to the macroporous resin HPD-100, silica gel, octadecyl SiO2, MCI gel and Sephadex LH-20 columns to obtain six compounds. Their structures including absolute configurations were determined by spectroscopic data [1H and 13C nuclear magnetic resonance (NMR), total correlation spectroscopy (TOCSY), heteronuclear single quantum coherence (HSQC), heteronuclear multiple-bond correlation (HMBC) and optical rotatory dispersion (ORD)] and chemical methods.