Water Soluble Organic Acids And Isoquinoline Alkaloids From Portulaca Oleracea And Their Bioactivities

Portulaca oleracea L.,an herbaceous succulent annual plant belonging to genus Portulaca in Portulacaceae family,is a medicinal and edible plant.P.oleracea is recorded in Chinese Pharmacopoeia to have heat-clearing,detoxifying,dispelling heat from blood,stopping bleeding,and stopping dysentery effect.Modern pharmacological research showed that P.oleracea exhibited a wide range of pharmacological activities,including antibacterial,antioxidant,anti-aging,anti-hypoxia,anti-diabetes,hypolipidemic,anti-dementia,anti-depression,relaxing bronchial smooth muscle,anti-inflammatory and anti-asthma effect.There are many types of chemical constituents present in P.oleracea,including organic acids,polysaccharides,flavonoids,coumarins,terpenoids,steroids and alkaloids.However,its bioactive compounds remain unclear and need to be further studied.Water-soluble organic acids and alkaloids are two main components of P.oleracea.In the present study,we aimed to intensively study the chemical constituents of water soluble organic acids and isoquinoline alkaloids from P.oleracea,and screen their anti-inflammatory,quinone reductase(QR)inductive activity and β2-adrenergic receptor(β2-AR)agonist activity.A total of 38 compounds 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-methyl malate(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-dihydroxyphenyl-ethanol(18),succinimide(19),uracil(20),citric acid(21),methyl 5-hydroxy-4-oxo-4H-pyran-2-carboxylate(22),L-isoleucine(23),L-phenylalanine(24),dopamine(25),2-sulfonic acid dopamine(26),(S)-(-)-(6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline)-propanoic acid ethyl ester(27),oleracein E(28),6,7-dihydroxy-1-methyl-3,4-dihydroisoquinoline(29),6,7-dihydroxy-3,4-dihydro-isoquinoline(30),(S)-(-)-salsoinol(31),(R)-(+)-1-isobutyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline(32),1-(5-(hydroxymethyl)-furan-2-yl)-3,4-dihydroiso-quinoline-6,7-diol(33),1-(furan-2-yl)-3,4-dihy droisoquinoline-6,7-diol(34),2-(furan-2-yl-methyl)-6,7-dihydroxy-3,4-dihydroisoquinoline-2-ium(35),(R)-(+)-1-benzyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquino line(36),L-tyrosine(37)and adenine(38).Among them,compounds 33-35 were new isoquinoline alkaloids,27 compounds(2,4-8,10,11,13,15-18,22,25-27,29-37)were isolated from P.oleracea for the first time.Compound 16(6.25 μM)and compound 18(12.5 μM)increased QR activity by 16%and 29%respectively in Hepa lclc7 cells.Compounds 1-15,17,19-21 showed no QR activity.Compounds 18,25-36 exhibited potent anti-inflammatory effect in lipopolysaccharide(LPS)-induced macrophage cells(RAW264.7)by reducing NO production.Compounds 18,25,27,28,31,34 showed strong anti-inflammatory activity with the EC50 value of 45.42 μM,17.96 μM,36.33μM,35.36 μM,58.71 μM,18.12 μM respectively.Compounds 1-17,19-21 showed no anti-inflammatory.Compounds 25-36 showed β2-AR agonist activity.Among them,compounds 34 and 36 showed strong β2-AR agonist activity with the EC50 value of 5.125 μM and 87.86 nM respectively.Above results indicated that the new isoquinoline alkaloid 34 showed potent anti-inflammatory and P2-AR agonist dual function,its pharmacological action and structure-activity relationship need to be further studied.