Abstract
Litsea cubeba, an important medicinal plant, is widely used as a traditional Chinese medicine and spice. Using cytotoxicity-guided fractionation, nine new lignans 1–9 and ten known analogues 10–19 were obtained from the EtOH extract of the twigs of L. cubeba. Their structures were assigned by extensive 1D- and 2D-NMR experiments, and the absolute configurations were resolved by specific rotation and a combination of experimental and theoretically calculated electronic circular dichroism (ECD) spectra. In the cytotoxicity assay, 7′,9-epoxylignans with feruloyl or cinnamoyl groups (compounds 7–9, 13 and 14) were selectively cytotoxic against NCI-H1650 cell line, while the dibenzylbutyrolactone lignans 17–19 exerted cytotoxicities against HCT-116 and A2780 cell lines. The results highlighted the structure-activity relationship importance of a feruloyl or a cinnamoyl moiety at C-9′ or/and C-7 ketone in 7′,9-epoxylignans. Furthermore, compound 11 was moderate active toward protein tyrosine phosphatase 1B (PTP1B) with an IC50 value of 13.5 μM, and compounds 4–6, 11 and 12 displayed inhibitory activity against LPS-induced NO production in RAW264.7 macrophages, with IC50 values of 46.8, 50.1, 58.6, 47.5, and 66.5 μM, respectively.
Highlights
Plants from the Litsea species (Lauraceae) are widely distributed in tropical or subtropical areas.Litsea cubeba, mainly grown in the east and south of China, is broadly used as a traditional Chinese medicine and spice
Detailed are the isolation, structural elucidation, TLC, and preparative HPLC led to the discovery of nine new lignans 1–9 and the ten known ones 10
Only 70,9-epoxylignans with feruloyl or cinnamoyl group were selectively cytotoxic against NCI-H1650 cell line, with IC50 values of less than 20 μM. These results suggested the presence of a feruloyl or a cinnamoyl moiety at C-90 in 70,9-epoxylignans is essential for cytotoxicity against NCI-H1650 cell line
Summary
Mainly grown in the east and south of China, is broadly used as a traditional Chinese medicine and spice. Previous phytochemical investigation of the fruits and roots of L. cubeba have reported the discovery of aporphine-type alkaloids, lignans, and phenolic constituents [5,6,7,8,9,10,11]. Aporphine-type alkaloids and lignans were considered as the major active principles of Molecules 2019, 24, 306; doi:10.3390/molecules24020306 www.mdpi.com/journal/molecules study on L. cubeba twigs by our group led to the characterization of 36 aromatic glycosides from the the water-soluble fraction of an ethanolic extract. We have investigated the constituents of the EtOAc-soluble fraction of the ethanolic extract of L. cubeba twigs
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