Secondary Metabolites from the Barks of Eucommia ulmoides and Their Bioactivities

Eucommia ulmoides Oliv., exhibiting diverse bioactivities including antimicrobial, antioxidant, neuroprotective, anti-tumor and anti-inflammatory properties, has long been known as an active ingredient commonly used in antihypertensive herbal prescriptions in China. The 95% ethanol extract of the barks of E. ulmoides showed antimicrobial and antioxidant activities and then was isolated by bioactivity-guided fractionation to obtain a new cinnamyl glucoside, 1-O-trans-cinnamoyl-β-D-apiofuranosyl-(1→6)-β-D-glucopyranose (1), together with twenty known secondary metabolites (2–21). And their structures were identified by extensive spectroscopic analyses, including 1D and 2D NMR, UV, IR and HRESIMS, and chemical methods. All secondary metabolites were evaluated for their antimicrobial and antioxidant activities in vitro. Compounds 7, 8, 11, and 21 exhibited moderately antimicrobial activity. In the antioxidant activity assay, compounds 3, 7, 11, and 14 showed intense activity in ferric reducing antioxidant power (FRAP) with the values of 9.82 mmol/g, 19.25 mmol/g, 14.52 mmol/g, and 12.58 mmol/g in comparison to Trolox (9.02 mmol/g). And compounds 2, 11, and 14–16 showed more potent activity with IC50 values ranging from 18.34 to 24.36 M than Trolox (26.35 M) in ABTS+• scavenging assay.