Chiral resolution and bioactivity of enantiomeric benzofuran neolignans from the fruit of Rubus ideaus L.

Rubus ideaus L., a member of the Rosaceae family, is popular for its distinctive flavor and attractive red color. In order to explore the functional factors possibly presented in the fruit, seven new benzofuran neolignans (1a/1b-3a/3b and 4b), together with one known neolignan 4a, were isolated from the fruit of R. ideaus. Compounds 1a/1b-4a/4b as four pairs of enantiomers were separated on a chiral chromatographic column. Their structures including absolute configurations were elucidated by extensive spectroscopic data analyses, including UV, IR, HRESIMS, NMR, and comparing their experimental electronic circular dichroism (ECD) spectra with calculated ECD spectra. Additionally, all these enantiomeric compounds were evaluated for their antioxidant, neuroprotective, and anti-Aβ aggregation activities.