A polyamide column chromatography method using an aqueous ammonia mobile phase was developed for large-scale accumulation of water-soluble indoline amide glucosides from a medicinal plant, Portulaca oleracea. Ten new [oleraceins H, I, K, L, N, O, P, Q, R, S (1-10)] and four known [oleraceins A-D (11-14)] indoline amide glucosides were further purified and structurally characterized by various chromatographic and spectroscopic methods. The DPPH radical scavenging activities of oleraceins K (5) and L (6), with EC50 values of 15.30 and 16.13 μM, respectively, were twice that of a natural antioxidant, vitamin C; the EC50 values of the 12 other indoline amides, which ranged from 29.05 to 43.52 μM, were similar to that of vitamin C. Structure-activity relationships indicated that the DPPH radical scavenging activities of these indoline amides correlate with the numbers and positions of the phenolic hydroxy groups.

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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 14.36 μM and 9.98 μM, respectively, more potent than the natural antioxidant vitamin C (EC50 20.72 μM).