A novel skeleton alkaloid was obtained from Portulaca oleracea L., which was identified as 10,11-dihydroxybenzo[5′,6′] pentaleno[1′,2′:3,4]pyrrolo[2,1-b]oxazol-7(11bH)-one, named oleracone M, and its structure was determined using UHPLC-ESI-QTOF/MS, 1D NMR and 2D NMR spectroscopy, and circular dichroism. Then the bioactivities of the compound were investigated including the anti-inflammatory, anti-acetylcholinesterase and antioxidant activities. The results showed that the novel skeleton alkaloid exhibited the potent effect on inhibiting the secretion of IL-1β at 10 μM, anticholinesterase activity with IC50 value of 49.58 μM, and antioxidant activity with IC50 value of 66.43 μM. © 2023