| Lychee(Litchi chinensis Sonn.),the only species of the genus Litchi in the Sapindaceae family,is widely cultivated in tropical and subtropical regions,such as Southeast Asia,and in our country is mainly distributed in southern provinces such as Fu Jian.The fruit of lychee is a delicious fruit with aromatic and musky flavor and has a rich nutritional value,while the litchi seed is largely discarded as a waste.Meanwhile,lychee seed is also a traditional Chinese medicine,which can be used to relieve the painful of epigastric and testicular swelling.In this paper,the anti-neuroinflammatory constituents of dichloromethane layer from 75% ethanol extract of lychee seed were investigated.Comprehensive application of various chromatographic separation methods resulted in a total of 61 pure compounds.The chemical structures of these isolated compounds were elucidated based on the physicochemical properties and spectroscopic techniques,which were identified as follows:(1)Jasmonates:(1R,2R,2’E)-2-(5’-ethoxy-5’-oxo-2’-penten-1-yl)-3-oxo-cyclopentaneacetic acid methyl ester(1*),(1R,2R,2’E)-2-(5’-methoxy-5’-oxo-2’-penten-1-yl)-3-oxo-cyclopentane-acetic acid ethyl ester(2*),(1R,2R,2’E)-2-(5’-methoxy-5’-oxo-2’-penten-1-yl)-3-oxocyclopentaneacetic acid methyl ester(3),(1R,2R,2’Z)-2-(5’-hydroxy-pent-2’-enyl)-3-oxo-cyclopentaneacetic acid(4),methyl(1R,2R,2’Z)-2-(5’-hydroxy-2’-enyl)-3-oxo-cyclopentane acetate(5),(1R,2R,2’E)-2-[5’-(hydroxy)-2’-penten-1-yl]-3-oxocyclopentaneacetic acid methyl ester(6*),methyl 2-((1R,2R)-2-((E)-5’-phenylacetoxypent-2-en-1-yl)-3-oxocyclo-pentyl)acetate(7*),2-(2’-trans-pentenyl-5’-hydroxy)-3-methyl-2-cyclo-penten-1-one(8*).(2)Terpenoids:(+)-dehydrovomifoliol(9),4,5-dihydroblumenol A(10),(S)-(+)-trans-abscisic acid(11),(S)-(+)-cis-abscisic acid(12),(S)-(-)-phaseic acid(13),(3S,5R,6S,9R)-megastigman-3,9-diol(14),boscialin(15),grasshopper ketone(16),(-)-loliolide(17),pterodontriol(18),junipediol(19),(-)-4α,10β-aromadendranediol(20),(-)-4β,10β-aromadendranediol(21),caryolane-1β,9α-diol(22).(3)Coumarins:6,7-dimethoxycoumarin(23),scopoletin(24),umbelliferone(25),isofraxidin(26),fraxidin(27),8-(7’,8’,9’-propanetriol-4’-methoxy-3’-Ophenylpropanoid)-7-hydroxy-6 methoxycoumarin(28).(4)Lignans: 3,3’-bis[3,4-dihydro-4-hydroxy-6-methoxy-2H-1-benzopyran](29),(+)-epipinoresinol(30),ligballinol(31),salicifoliol(32),(+)-isolariciresinol(33).(5)Flavonoids : 5,7-dihydroxy-2-methylchromone(34),5,7-dihydroxychromanone(35),pinocembrin(36),naringenin(37),davidigenin(38).(6)Alkaloids:cyclo-(S-Pro-S-Ile)(39),cyclo-(S-Pro-R-Leu)(40),cyclo-(S-Phe-S-Val)(41),cyclo-(S-Leu-S-Val)(42),1H-indole-3-carbaldehyde(43),argaminolic A(44).(7)Phenolic acids:p-hydroxybenzaldehyde(45),4-hydroxyacetophenone(46),benzoic acid(47),3-methoxy-4-hydroxybenzoic acid(48),trans-cinnamic acid(49),ferulic acid(50),4-hydroxy cinnamic acid(51),ethyl 3,4-dihydroxybenzoate(52),protocatechuic acid methyl ester(53),2-(4-hydroxyphenyl)ethanol(54),1-phenyl-1,2-ethanediol(55),phenylacetamide(56),methyl 3-(4-hydroxyphenyl)propionate(57).(8)Other classes : 9,12,15-octadecatrienoic acid(58),2-hydroxy-3-methyl-4H-pyran-4-one(59),5-hydroxy-4-phenyl-5H-furan-2-one(60)phenylethanol-8-O-β-D-glucoside(61).Among the 61 purified compounds,there were eight jasmonates(1-8),fourteen terpenoids(9-22),six coumarins(23-28),five lignans(29-33),five flavonoids(34-38),six alkaloids(39-44),thirteen phenolic acids(45-57),and four others(58-61).Among them,compounds 1,2 and 6-8 were five new compounds.Meanwhile,some of the isolated compounds were evaluated for the anti-neuroinflammatory activities in vitro.Compared with minocycline(22.89 ± 7.42 μmol/L),compounds 1,11 and 20 showed obvious inhibitory effect on NO release in LPS-induced BV-2 cells.Furtherly,Western blot,q RT PCR and immunofluorescence staining were used to investigate the anti-neuroinflammatory mechanism of compounds 1,2 and 20 at protein and m RNA levels.This study provides a chemical basis for the further development and utilization of lychee seed. |
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