Highly methoxylated neolignans from the endangered plant Yulania cylindrica and their chemotaxonomic significance

Abstract

Three previously undescribed highly methoxylated neolignans, cylindrienones A‒C (1–3, resp.), together with five related known neolignans (4–8) were isolated from the twigs and leaves of the ornamental and medicinal plant Yulania cylindrica, a ‘vulnerable’ species endemic to China. The new structures were established by spectroscopic methods including HRESIMS, 2D-NMR, and electronic circular dichroism (ECD). The known ones were identified by comparing their observed and reported physicochemical properties and spectroscopic data. Compounds 1 and 2 are (C8–C3')-neolignan derivatives possessing a unique cyclohexadienone unit, while compound 3 is a rearranged neolignan containing a rare tricycle [4.2.0.02,8]octane moiety. Compounds 1–8 were isolated from Y. cylindrica for the first time. Compounds 4 and 7 were even firstly found from the family Magnoliaceae. The chemotaxonomic significance of the isolated methoxylated neolignans was briefly discussed.