The aim of this experiment is to intensively study the chemical constituents,especially organic acids from a medicinal plant Portulaca oleracea L.,and screen their anti-inflammatory activity.Twenty compounds (Fig.1) were isolated and identified based on spectroscopic methods,as succinic acid (1),mono-methyl succinate (2),L-malic acid (3),L-1-methyl malate (4),L-4-methylmalate (5),L-dimethyl malate (6),L-6-ethyl citrate (7),L-1-methyl citrate (8),L-1,5-dimethyl citrate (9),4-hydroxy-5-methylfuran-3-carboxylic acid (10),5-hydroxymethyl-furoic acid (11),stearic acid (12),L-pyroglutamic acid (13),cyclo-(tyrosine-leucine) (14),L-leucine (15),(-)-dehydrovomifoliol (16),(-)-epiloliolide (17),3,4-dihydroxyphenylethanol (18),succinimide (19),and uracil (20).Among them,fourteen compounds (2,4-8,10,11,13-18) were firstly isolated from P.oleracea.Compound 18 (12.5 μM) exhibited potent anti-inflammatory effect in lipopolysaccharide (LPS)-induced macrophage cells (RAW264.7) by reducing NO production.