Phenolic Constituents Isolated from the Twigs of Cinnamomum cassia and Their Potential Neuroprotective Effects

Seven new α,β-diphenyl-γ-butyrolactones ( 1 – 7 ), three new lignans ( 8 – 10 ), five new neolignans ( 11 – 15 ), two new 1,3-biphenylpropanoids ( 16 and 17 ), and a new flavonol galactoside-lignan ester ( 18 ), together with 43 known compounds ( 19 – 61 ), were isolated from the twigs of Cinnamomum cassia . Their structures were elucidated by spectroscopic data analysis as well as chemical methods. The α,β-diphenyl-γ-butyrolactones are a class of unique natural compounds that have only been isolated from C. cassia . Compounds 11 and 12 are rare examples of neolignans possessing a 1,2-dioxetane moiety. Compound 13 is a new oxyneolignan possessing a unique C-9–O–C-9′ linkage between the benzopyran and cinnamyl alcohol moieties. Compound 15 is the first example of a natural neolignan possessing a 2-styryl-3-phenyltetrahydrofuran skeleton. The isolated compounds were evaluated for their neuroprotective activities against tunicamycin-induced cytotoxicity in SH-SY5Y cells. Compounds 3, 5, 10, 11, 12, 20, 36, and 56 showed statistically significant neuroprotective activity with EC 50 values ranging between 21 and 75 μM.