Chemical Constituents From Portulaca Oleracea L. And Their Bioactivities

Portulaca oleracea L.is an annual succulent herb in the Portulacaceae family,which is used as a medicinal and edible plant in more than 40 countries in Asia,Africa,Europe,South America and North America.According to Chinese Pharmacopoeia,P.oleracea is cold in nature and acidic in taste,with the functions of clearing heat and detoxifying,hemostasis and cooling blood,and relieving dysentery,it is clinically used to treat heat toxic dysentery,carbuncles,boils,eczema,erysipelas,snake and insect bites,hematochezia,hemorrhoids and bleeding.Modern pharmacological studies showed that P.oleracea has a wide range of functions including antibacterial,anti-inflammatory,analgesic,antioxidant,anti-aging,antiasthma,hypoglycemic,hypolipidemic and immune enhancement activities.P.oleracea contains several types of chemical constituents such as alkaloids,organic acids,flavonoids,lignans,terpenes and polysaccharides.Our research group has previously found that P.oleracea contains many catecholamine derivatives which are positive when reacted with ferric chloride or ninhydrin,and their structural diversities need to be discovered.In addition,the relation between constituents and bioactivity of P.oleracea is not so clear,and active substances still need to be intensively studied.In this paper,56 compounds were isolated from n-butanol fraction of water extract as well as 60%ethanol extract of P.oleracea,through purification by silica gel,polyamide,Sephadex LH-20 column chromatography and semi-preparative HPLC and their structures were elucidated based on MS,NMR and CD data analysis.Among them,27 compounds were alkaloids,including 3-methoxy-4-hydroxy phenylethyl amine(1),6-hydroxy-7-methy 1-3,4dihydroisoquinolin-1(2H)-one(2),6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline(3),(R)-(+)salsolinol(4),(S)-(-)-6,7-dihydroxy-1,2-dimethyl-1,2,3,4-tetrahydroisoquinoline(5),(R)-(-)6,7-dihydroxy-1-(3,4-dihydroxyphenyl)-1,2,3,4-tetrahydroisoquinoline(6),oleracein E(7),(R)-(-)-6,7-dihydroxy-1-(methyl n-octanoate)-1,2,3,4-tetrahydroisoquinoline(8),1H-indole3-carbaldehyde(9),1H-indole-3-carboxylic acid(10),1-amino-1H-indole-3-carboxylic acid(11),ethyl indolyl-3-glyoxylate(12),oleracein A(13),oleracein B(14),1H-pyrrole-2,3dicarboxylic acid(15),urea(16),uracil(17),thymine(18),cytosine(19),adenine(20),xanthine(21),hypoxanthine(22),allantion(23),cytidine(24),adenosine(25),inosine(enol-type)(26),inosine(keto-type)(27);two were amino acids,L-(-)-phenylalanine(28)and L-(+)-cysteine(29);17 were phenolic compounds,including 6,7-dihydroxycoumarin(30),catechol(31),protocatechuyl aldehyde(32),protocatechuic acid(33),vanillin(34),vanillic acid(35),4hydroxy-3,5-dimethoxybenzaldehyde(36),syringic acid(37),p-hydroxy benzoic acid(38),phydroxy acetophenone(39),salicylic acid(40),trans-ferulic acid(41),trns-ferulamide(42),trans-caffeic acid(43),trans-p-coumaric acid(44),cis-p-coumaric acid(45);one was halogenated compound,i.e.,2,4-dichlorobenzoic acid(46);8 were fatty acids,including methyl(9E,11E)-13-oxooctadeca-9,11-dienoate(47),methyl(7E,9E)-11-oxooctadeca-7,9-dienoate(48),methyl linolenate(49),ethyl linolenate(50),methyl linoleate(51),ethyl linoleate(52),methyl oleate(53),methyl palmitate(54);two were sterols including β-sitosterol(55)and βdaucosterol(56).Among these constituents,ten compounds(1-8,13,14)were catecholamine derivatives,3 compounds(2,8,48)were new,including two new catecholamine derivatives,2 compounds(11,47)were new natural products,and 22 compounds were isolated from P.oleracea for the first time(1,5,6,10,12,15,16,18,19,21,22,24,26,27,45,46,49,50,51,52,53,54).The anti-inflammatory and antioxidant activities of above 56 compounds were preliminarily screened,using LPS-induced murine RAW 264.7 macrophage inflammatory model and in vitro DPPH radical-scavenging assay,respectively.The results showed that compounds 7,8,12,13,14,20,21,23,25,30,32,34,46,47-52,55 and 56 had potent or moderate anti-inflammatory activities,as indicated by significant inhibition of nitric oxide production in LPS-induced RAW 264.7 macrophages in a dose-dependent manner,with ECso values ranging from 4.25 to 69.75 μM.Compounds 2,3,6,7,8,13,14,30,32,33,37,41,42 and 43 exhibited DPPH radical scavenging activities,with EC50 values ranging from 6.68 to 64.04 μM,some of which equivalent to or potent than that of natural antioxidant vitamin C.