A New Tricyclic Alkaloid from Portulaca oleracea L.

A new tricyclic alkaloid named portulacatone (1), i.e., 5,6-dihydro-8,9-dihydroxy-11H-pyrrolo[2,1-b][3]benzazepin-11-one, together with eight known compounds, methyl 4-hydroxyphenylacetate (2), p-hydroxybenzaldehyde (3), vanillin (4), protocatechualdehyde (5), p-hydroxybenzoic acid (6), iseluxine (7), oleracein E (8), and (+)-(R)-feruloyl malate (9) were isolated from aerial parts of Portulaca oleracea L. Their structures were elucidated based on spectroscopic analyses. Among them, compounds 1-7 and 9 were isolated from this medicinal plant for the first time. Compounds 1 and 7 showed dose-dependent scavenging activities against DPPH (2,2-diphenyl-1-picryl-hydrazyl) free radical, with EC50 values of 14.36M and 9.98M, respectively, more potent than the natural antioxidant vitamin C (EC50 20.72M).