New Amides and Phenylpropanoid Glucosides from the Fruits of Piper retrofractum

ABSTRACT: Two new amides (E)-N-cinnamoyl-2-methoxypiperidine (1) and (R)-1-(2-oxopyrrolidin-3-yl)-5,6-dihydropyridin-2(1H)-one (2), four new amide glucosides, retrofractosides A–D (3–6), and two new phenylpropanoid glucosides, retrofractosides E (7) and F (8), together with 24 known compounds (9–32) were isolated from the fruits of Piper retrofractum. The chemical structures of these new compounds were elucidated based on extensive spectroscopic analysis. All of these isolates (1–32) were evaluated for inhibitory activity against mouse platelet aggregation induced by the peptide AYPGKF-NH(2). (E)-N-(Tetrahydro-2H-pyran-2-yl)cinnamamide (9) showed a weak inhibitory effect, with an inhibition ratio of 52.0% at a concentration of 150 μM. GRAPHICAL ABSTRACT: [Image: see text] ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s13659-019-0208-z) contains supplementary material, which is available to authorized users.