Two new alkaloids from Portulaca oleracea L. and their bioactivities

Two new indole alkaloids, identified as (E)-1-(5,6-dihydroxy-1H-indol-1-yl)-3-(4-hydroxyphenyl)prop-2-en-1-one, named oleraindole A (1), and (E)-1-(5,6-dihydroxy-1H-indol-1-yl)-3-(4-hydroxy-3-methoxyphenyl)prop-2-en-1-one, named oleraindole B (2), together with five known indole alkaloids, (-)-neoechinulin A (3), neoechinulin D (4), isoechinulin A (5), MT-6 (6) and echinulin (7) were isolated from the aqueous extract of Portulaca oleracea L. for the first time, using various chromatographic techniques. The structures of seven alkaloids were elucidated by the 1D and 2D NMR and HR-ESI-TOF-MS spectroscopic methods. Oleraindole A (1) and oleraindole B (2) exhibited a relatively high anticholinesterase activity with IC₅₀ values of 55.12 ± 0.20 μΜ and 46.76 ± 0.08 μM, and antioxidant activities with the IC₅₀ values of 16.20 ± 0.11 μM and 13.88 ± 0.06 μM among seven alkaloids.