| The chemical constituents of the leaves of Rhododendron dauricum L.and their biological activities were investigated in this study.R.dauricum is a semievergreen shrub species belonging to the genus Rhododendron(family Ericaceae),widely distributed in regions of northeast China,north Mongolia,Korean Peninsula,Japan and Russia.As a traditional Chinese medicine,R.dauricum mainly used to treat acute and chronic bronchitis,asthma and cough.Previous studies have verified that R.dauricum are enriched with a large number of active components,which exhibited diverse biological activities,including anti-oxidant,anti-tumour,anti-inflammatory,and anti-bacterial activity.In order to search for more structurally unique active components from this plant,various column chromatography methods were used in this study to separate and purify compounds from the ethanol extract of R.dauricum.Seventy-nine compounds(1-79)were isolated and identified on the basis of spectral data and by comparisons of spectroscopic data with reported values in the literatures,including two new flavonoids quercetin 3-O-?-D-(6"-p-methoxybenzoyl)-galactopyranoside(9),(2S)-6,8-dimethyl-5,7,3',4'-tetrahydroxyflavanone 4'-O-?-D-glucopyranoside(12),two new grifolin derivatives rhododentin A(31),daurichromene E(32),one new triterpenoid 20-taraxastene-22?-methoxy-3?-ol(38),other compounds,avicularin(1),quercetin 3-O-?-D-galactopyranoside(2)kaempferol-3-O-arabinofuranoside(3),quercetin 3-O-?-L-(2"-O-acetyl)arabinofuranoside(4),betmidin(5),quercetin(6),kaempferol-3-O-?-D-glucopranoside(7),isorhamnetin 3-O-?-D-glucopyranoside(8),taxifolin 3-O-?-D-glucopyranoside(10),trans-taxifolin 3-O-?-L-arabinopyranoside(11),myrciacitrin III(13),matteucinol(14),8-demethylfarrerol(15),cyrtominetin(16),(+)-catechin(17),myrciaphenone(18),arbutin(19),rodiolinozide(20),phloracetophenone 2-O-?-D-mannopyranosyloxy(21),tachioside(22),isotachioside(23),4-hydroxyphenyl-?-D-glucopyranosyl-(1?2)-?-D-glucopyranoside(24),4-(4-hydroxy-3-methoxyphenyl)-2-butanone(25),(+)-rhodolatouchol(26),benzyl 2-O-?-D-glucopyranosyl-2,6-dihydroxybenzoate(27),confluentin(28),cannabichromeorcin(29),grifolin(30),daurichromene A(33),daurichromene B(34),5-hydroxy-2-methyl-2-(4-methyl-3-penten-1-yl)-2H-1-benzopran-7-pentanol(35),albatrellutin(36),(2R,3R)-2H-1-benzopyran-3,5-diol,2-[(3E)-4,8-dimethyl-3,7-nonadien-1-yl]-3,4-dihydro-2,7-dimethyl(37),asiatic acid(38),ursolic acid(40),2?,3?,19?,23-tetrahydroxyurs-12-en-28-oic acid(41),2a,3a,19a,23-tetrahydroxyurs-12-en-28-oic acid(42),uvaol(43),2?,3?,24-trihydroxyurs-12-en-28-oic acid(44),(2a,3?)-urs-12-ene-2,3-diol(45),?-amyrin(46),2?-hydroxyursolic acid(47),erythrodiol(48),3-epifriedelinol(49),lupeol(50),cassipourol(51),grayanotoxin I(52),(-)-clovane-2,9-diol(53),(2S,5S)-1-oxaspiro[4.5]deca-3,6-dien,6-(hydroxymethyl)-2,10,10-trimethyl-8-one(54),icariside B2(55),blumenol A(56),a mixture of(6S,9R)-roseoside(57)and(6S,9S)-roseoside(58),(6R,9R)-3-oxo-?-ionol-?-D-glucoside(59),?-sitosterol-3-O-(6'-O-13"-octadecenoyl)-?-D-glucoside(60),daucosterol(61),?-sitosterol(62),24-methylenepollinastanol(63),methyl-(6-O-p-hydroxybenzoyl)-?-D-glucopyranoside(64),(Z)-3-hexenyl?-D-glucopyranoside(65),butyl-?-D-fructofuranoside(66),butyl-?-D-fructofuranoside(67),methyl-?-D-fructofuranoside(68),methyl-?-D-fructofuranoside(69),methyl 1,3-O-(1-methylethylidene)-?-D-fructofuranoside(70),feruloylquinic acid(71),butyl-4-O-comaroylquinate(72),benzyl-?-D-glucopranoside(73),phenylethyl-O-?-D-glucopyranoside(74),noreugenin(75),skimmin(76),pinoresinol-4-O-?-D-glucopyranoside(77),(7R,8S)-dihydrodehydrodiconiferylalcohol 4-O-?-D-glucopyranoside(78),streptokordin(79).Among them,thirty-seven compounds(4,5,9,12,13,16,20,21,24,27,31,32,35-38,44,45,51,53,54,57-59,63-70,72,74,76,78,and 79)were found in family Ericaceae for the first time,one compound(56)has not been reported in any species of the genus Rhododendron,and eighteen compounds(7,8,14,18,22,23,25,26,29,41,42,47,49,55,71,73,75,and 77)were first isolated from R.dauricum.According to the different types of compounds purified from R.dauricum,the flavonoids,phenols,grifolin derivatives and megastigmanes were evaluated for their anti-inflammatory activity,the anti-complementary activity of 14 flavonoids and the anti-tumour activity of 13 triterpenoids were also determined.First,favonoids(1-17),phenols(18-28),grifolin derivatives(29-37)and megastigmanes(55-59)were selected to evaluate their cell viability and inhibition of TNF-? production in LPS-induced RAW 264.7 cells.Compounds 3,4,6,7,10-13,15,23-26,29-30,32-34,36,37 and 55-58 showed inhibitory activity against TNF-? production,among them,compounds 4,11,24 and 32 exhibited notable inhibitory effects against TNF-? production with IC50 values of 46.24 ± 1.2,49.61 ± 2.3,34.50 ± 1.8,and 48.12± 3.2 ?M,respectively.Then,fourteen flavonoids(1-12,14 and 15)were also evaluated for their anti-complementary activity and all the tested flavonoids exhibited anti-complementary effects with CH50 values ranging from 0.14 to 2.25 mM.In particular,compounds 2,4,9 and 15 showed the highest anti-complementary activity with CH50 values of 0.14±0.01,0.22±0.11,0.31±0.18,and 0.28±0.08 mM,respectively.In a mechanistic study,quercetin 3-O-?-D-galactopyranoside(2)interacted with C2,C4 and C5 components,quercetin 3-O-?-D-(6"-p-methoxybenzoyl)-galactopyranoside(9)acted on C1q,C2,C3 and C5 components,and 8-demethylfarrerol(15)interacted with C2,C4,C5 and C9 components.Additionally,the isolated triterpenoids(38-50)from the leaves of R.dauricum were tested for their cytotoxic activity against A549,HeLa,and SK-Hepl cancer cell lines.The results showed that compounds 38 and 46 could inhibit the growth of three different human cancer cells and compound 38 showed better cytotoxic against A549,HeLa,and SK-Hepl cells than the other tested compounds with IC50 values of 34.04±1.01,64.04±1.75,and 44.04±0.05 ?M,respectively.The research revealed that there are several compounds obtained from the R.dauricum have anti-inflammatory,anti-complementary,and anti-tumour activity,which provided a scientific basis for the further development and utilization of R.dauricum. |
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