Identification and anti-inflammatory activity of chemical constituents and a pair of new monoterpenoid enantiomers from the fruits of Litsea cubeba
Eighteen compounds were isolated from the methanol extract of the fruits of Litsea cubeba by silica gel,ODS,Sephadex LH-20 column chromatography,semi-preparative RP-HPLC,chiral HPLC and recrystallization.Their structures were elucidated by spectroscopic analyses and by comparison with reported spectroscopic data and physicochemical properties,and the absolute configurations of the enantiomers were established by experimental and calculated electronic circular dichroism spectra.These compounds were identified as(+)-(R)-4-hydroxypiperi-tenone(1a),(-)-(S)-4-hydroxypiperitenone(1b),(3S,4S,6R)-3,6-dihydroxy-1-menthene(2),(4S,5R)-4-hydroxy-5-isopropyl-2-methylcyclohex-2-en-1-one(3),(R)-6-hydroxy-3-(2-hydroxypropan-2-yl)-6-methylcyclohex-2-enone(4),(4S,6R)-4-hydroxy-6-isopropyl-3-methylcyclohex-2-enone(5),(1R,3S,4R)-3-hydroxy isopulegol(6),subamone(7),(6S)-3,7-dimethyl-7-hydroxy-2(Z)-octen-6-olide(8),(6S)-6,7-dihydroxy-3,7-dimethyloct-2(Z)-enoate(9),holostylactone(10),sesamin(11),dimethylmatairesinol(12),p-hydroxybenzoylcarbinol(13),syringaldehyde(14),p-hydroxybenzaldehyde(15),4-hydroxy-3-methoxybenzaldehyde(16),5,4'-dihydroxy-7-methoxyflavone(17).Among them,compounds 1a and 1b were a pair of new monoterpenoid enantiomers,8 and 9 were new natural products,2-7,10,11 and 17 were isolated from Litsea genus for the first time.The in vitro anti-inflammatory effects of compounds 1-17 were evaluated using lipopolysaccharide-stimulated RAW264.7 cells,the results showed that compound 14 exhibited significant anti-inflammatory activity with NO inhibitory rate of 66.27％at a concentration of 40 µmol·L1.
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