Diverse neolignans and lignans from an aqueous extract of the Angelica sinensis root head.

Neolignans and lignans with diverse new chemical structures, including eleven pairs of separated chiral enantiomers [(+)-/(-)-1-(+)-/(-)-5, (+)-/(-)-8, (+)-/(-)-10, and (+)-/(-)-12-(+)-/(-)-15], two achiral compounds (6 and 9), and an unseparated racemate [(±)-11], together with a new natural product (7) and 21 known derivatives, were isolated from an aqueous extract of the Angelica sinensis root head (guitou). Among the chiral isolates, (+)-/(-)-13 and (+)-/(-)-15 were scalemic pairs with enantiomeric ratios of around 3:1 and 1.5:1, respectively, while others were enantiomeric equivalent pairs. This indicates that the diverse neolignans in A. sinensis are biosynthesized via different pathways with varying degrees of stereo-controlled manners.

Minor alkaloids from an aqueous extract of the hook-bearing stem of Uncaria rhynchophylla.

Seven new monoterpene alkaloids (1-7), along with 18 known analogues, were isolated from an aqueous decoction of the hook-bearing stems of Uncaria rhynchophylla (Gou-teng). Their structures were determined by spectroscopic data analysis and electronic circular dichroism (ECD) calculations. Compound 1 is the first monoterpene 22-norindoloquinolizidine alkaloid with a ketene unit, while 2 and 3 are unusual indoloquinolizidine alkaloids having an oxazinane ring.[Formula: see text].

Minor triterpenes from an aqueous extract of the hook-bearing stem of Uncaria rhynchophylla.

Six new triterpenes, uncarinic acids KP (1-6), along with 24 known analogues, were isolated as minor constituents of an aqueous decoction of the hook-bearing stems of Uncaria rhynchophylla (Gou-teng). By comprehensive spectroscopic data analysis, their structures were elucidated as derivatives of olean-12-en-28-oic acid and urs-12-en-28-oic acid with different oxidized forms at C-3, C-6, and/or C-23, respectively. Cell-based preliminary bioassay showed that the (E)-/(Z)-coumaroyloxy and (E)-/(Z)-feruloyloxy units at C-27 of olean-12-en-28-oic acid and urs-12-en-28-oic acid played roles in their bioactivities.[Formula: see text].

Denudatine-type diterpenoid alkaloids from an aqueous extract of the lateral root of Aconitum carmichaelii.

Five new denudatine-type diterpenoid alkaloids (1-5), along with the known analogue aconicarmine (6), were isolated from an aqueous decoction of the lateral roots of Aconitum carmichaelii (fu-zi). Their structures were determined by spectroscopic data analysis and electronic circular dichroism (ECD) calculations. Compound 5 is the first denudatine-type diterpenoid alcohol iminium alkaloid, which could be partially transformed into the aza acetal form in pyridine-d5. Compound 5 inhibited mice writhing in an acetic acid-induced writhing assay.

Diglycosidic indole alkaloid derivatives from an aqueous extract of Isatis indigotica roots.

Six new indole alkaloid diglycosides named isatigotindolediosides A-F (1-6), along with three known analogs (7-9), were isolated from an aqueous extract of the Isatis indigotica roots (ban lan gen). Their structures including the absolute configurations were determined by comprehensive spectroscopic data analysis, combined with enzyme or acid hydrolysis, and comparison of experimental circular dichroism (CD) and calculated electronic circular dichroism (ECD) spectra. In the preliminary assays, compounds 3, 5, and 8 showed antiviral activity against Coxsackie virus B3.

20C, a bibenzyl compound isolated from Gastrodia elata, protects PC12 cells against rotenone-induced apoptosis via activation of the Nrf2/ARE/HO-1 signaling pathway.

AIM: Our preliminary study shows that a bibenzyl compound isolated from Gastrodia elata, 2-[4-hydroxy-3-(4-hydroxybenzyl)benzyl]-4-(4-hydroxybenzyl)phenol (designated 20C), protects PC12 cells against H2O2-induced injury. In this study we investigated whether 20C exerted neuroprotective action in a cell model of Parkinson's disease. METHODS: A cell model of Parkinson's disease was established in PC12 cells by exposure to rotenone (4 µmol/L) for 48 h. Cell viability and apoptosis were assessed, and intracellular ROS level and the mitochondrial membrane potential (MMP) were detected. The expression of apoptosis-related proteins Bax, Bcl-2, cytochrome c, cleaved caspase-3, and oxidative stress-related proteins Nrf2, HO-1 and NQO1 were examined using Western blotting. The mRNA levels of HO-1 and NQO1 were determined with RT-PCR. The nuclear translocation of Nrf2 was observed with immunofluorescence staining. RESULTS: Treatment with rotenone significantly increased the number of apoptotic cells, accompanied by marked increases in the Bax/Bcl-2 ratio, cytochrome c release and caspase-3 activation. Rotenone also increased ROS accumulation, reduced MMP, and increased the nuclear translocation of Nrf2 as well as the mRNA and protein levels of the Nrf2 downstream target genes HO-1 and NQO1 in PC12 cells. Co-treatment with 20C (0.01-1 µmol/L) dose-dependently attenuated rotenone-induced apoptosis and oxidative stress in PC12 cells. Nrf2 knockdown by siRNA partially reversed the protective effects of 20C in rotenone-treated PC12 cells. CONCLUSION: The bibenzyl compound 20C protects PC12 cells from rotenone-induced apoptosis, at least in part, via activation of the Nrf2/ARE/HO-1 signaling pathway.

Bibenzyl compound 20c protects against endoplasmic reticulum stress in tunicamycin-treated PC12 cells in vitro.

AIM: Accumulation of α-synuclein (α-syn) in the brain is a characteristic of Parkinson's disease (PD). In this study, we investigated whether treatment with tunicamycin, an endoplasmic reticulum (ER) stress inducer, led to the accumulation of α-syn in PC12 cells, and where α-syn protein was accumulated, and finally, whether bibenzyl compound 20c, a novel compound isolated from Gastrodia elata (Tian ma), could alleviate the accumulation of α-syn and ER stress activation in tunicamycin-treated PC12 cells. METHODS: PC12 cells were treated with tunicamycin for different time (6 h, 12 h, 24 h, 48 h). Cell viability was determined by a MTT assay. Subcellular fractions of ER and mitochondria were extracted with the Tissue Endoplasmic reticulum Isolation Kit. The levels of α-syn protein and ER-stress-associated downstream chaperones were detected using Western blots and immunofluorescence. RESULTS: Treatment of PC12 cells with tunicamycin (0.5-10 µg/mL) dose-dependently increased the accumulation of α-syn monomer (19 kDa) and oligomer (55 kDa), and decreased the cell viability. Accumulation of the two forms of α-syn was observed in both the ER and mitochondria with increasing treatment time. Co-treatment with 20c (10-5 mol/L) significantly increased the viability of tunicamycin-treated cells, reduced the level of α-syn protein and suppressed ER stress activation in the cells, evidenced by the reductions in phosphorylation of eIF2α and expression of spliced ATF6 and XBP1. CONCLUSION: Tunicamycin treatment caused accumulation of α-syn monomer and oligomer in PC12 cells. Bibenzyl compound 20c reduces the accumulation of α-syn and inhibits the activation of ER stress, which protected PC12 cells against the toxicity induced by tunicamycin.

[Lignanoids from an aqueous extract of the roots of Codonopsis pilosula].

Sixteen lignanoids were isolated from an aqueous extract of the commonly used Chinese traditional medicine Dangshen, the dried roots of Codonopsis pilosula, by using a combination of various chromatographic techniques, including silica gel, macroporous adsorbent resin, MCI resin, sephadex LH-20, and reversed phase semi-preparative HPLC. On the basis of spectral data analysis, their structures were elucidated and identified as（-）-（7R,7'R,8R,8'S）-4,4'-dihydroxy-3,3',5,5',7-pentamethoxy-2,7'-cyclolignane（1）,（-）-（7R,8S）- dihydrodehydrodiconiferyl alcohol 4-O-ß-D-glucopyranosyl-（1'''→2''）-ß-D-glucopyranoside（2）,（-）-（7R,8S）- dihydrodehydrodiconiferyl alcohol（3）,（+）-（7S,8R）-dehydrodiconiferyl alcohol（4）,（+）-balanophonin（5）,（+）- demethoxypinoresinol（6）,（+）-pinoresinol（7）,（+）-epipinoresinol（8）,（-）-syringaresinol（9）,（-）-medioresinol（10）,（-）-lariciresinol（11）,（-）-secoisolariciresinol（12）,（-）-ent-isolariciresinol（13）,（+）-（7S,8S）-3-methoxy-3',7- expoxy-8,4'-neolignan-4,9,9'-triol（14）,（+）-（7S,8R）-3',4-dihydroxy-3-methoxy-8,4'-neolignan（15）, and（-）-（7R,8R）-3',4-dihydroxy-3-methoxy-8,4'-neolignan（16）. All these compounds were isolated from C. pilosula for the first time, while compound 1 is a new natural product of 2,7'-cyclolignan and 2 is a new 4',7-epoxy- 8,3'-neolignan diglucoside. Compound 12 showed activity against Fe(2+)-cysteine induced rat liver microsomal lipid peroxidation with an inhibition ratio of（63.4 ± 8.3） % at 1×10(-5) mol·L(-1).

C14-polyacetylene glucosides from Codonopsis pilosula.

Seven new C14-polyacetylene glucosides codonopilodiynosides A-G (1-7) were isolated from an aqueous extract of the Codonopsis pilosula roots. Their structures were determined by spectroscopic and chemical methods as (-)-(5S,6E,12E)-tetradeca-6,12-dien-8,10-diyn-1,5,14-triol 5-O-ß-D-glucopyranoside (1), (-)-(5S,6E,12E)-tetradeca-6,12-dien-8,10-diyn-1,5,14-triol 5-O-ß-D-glucopyranosyl-(1″ → 2')-ß-D-glucopyranoside (2), (-)-(5S,6E,12E)-tetradeca-6,12-dien-8,10-diyn-1,5,14-triol 5,14-di-O-ß-D-glucopyranoside (3), (-)-(5S,6E)-tetradeca-6-en-8,10-diyn-1,5,14-triol 5-O-ß-D-glucopyranoside (4), (-)-(5S,6E,12E)-tetradeca-6,12-dien-8,10-diyn-1,5-diol 5-O-ß-D-glucopyranosyl-(1″ → 2')-ß-D-glucopyranoside (5), (-)-(6S,4E,12E)-tetradeca-4,12-dien-8,10-diyn-1,6-diol 6-O-ß-D-glucopyranosyl-(1″ → 2')-ß-D-glucopyranoside (6), and (-)-(5S,6E)-tetradeca-6-en-1,5-epoxy-8,10-diyn-14-ol 14-O-ß-D-glucopyranosyl-(1″ → 2')-ß-D-glucopyranoside (7), respectively. The absolute configurations of 1-7 were assigned by enzymatic hydrolysis followed by isolation of glucose and aglycones (1a and 4a-7a), and subsequent comparison of specific rotation, TLC, and (1)H NMR data of the glucose with an authentic sugar sample and application of modified Mosher's method based on the MPA determination rule of Δδ(RS) values for 1a and 4a, and Δδ(S) values for 6a. The configuration of 7 was assigned by electronic circular dichroism calculations based on the quantum-mechanical time-dependent density functional theory.

4-Hydroxybenzyl-substituted glutathione derivatives from Gastrodia elata.

Seven new 4-hydroxybenzyl-substituted glutathione derivatives (2-8), together with a known analogue (1), were isolated from the aqueous extract of Gastrodia elata Blume rhizomes. Their structures were determined by using spectroscopic and chemical methods. The absolute configurations of 1-8 were assigned by using Marfey's method, combined with comparing the NMR and CD spectroscopic data of sulfoxide moieties in 3-6 with those of S-(4-hydroxybenzyl)cysteine sulfoxide stereoisomers (9-12) synthesized as authentic samples. The configurations of 9-12 were confirmed by electronic CD calculations based on the quantum-mechanical time-dependent density functional theory. Furthermore, the structures of 1, 3, 5, 7, and 8 were verified by synthesis. Compound 3 was active against serum deprivation-induced PC12 cell damage and synthetic 9-14 exhibited activity against Fe(2+)-cysteine induced rat liver microsomal lipid peroxidation.

[Glycosides from Machilus wangchiana].

Ten glycosidic compounds were isolated from an ethanol extract of Machilus wangchiana by a combination of various chromatographic techniques including column chromatography over silica gel and Sephadex LH-20 and reversed-phase flash chromatography and HPLC. Their structures were identified by spectroscopic data analysis (IR, MS, and NMR) as icariside B1 (1), boscialin-3-O-ß-D-glucopyranoside (2), pisumionoside (3), isolariciresinol-9'-O-ß-D-xylopyranoside (4), 5'-methoxyisolariciresinol-9'-O-ß-D-xylopyranoside (5), lyoniresinol-9'-O-ß-D-xylopyranoside (6), (E) -4-hydroxyphenylprop-7-ene 4-O-ß-D-glucopyranoside (7), (E) - 4-hydroxy-3-methoxyphenylprop-7-ene 4-O-α-L-rhamnopyranosyl-(1 --> 6) -ß-D-glucopyranoside (8), 4-hydroxy-3-methoxyphenylprop-8-ene 4-O-ß-D-xylopyraosyl-(1 --> 6) -ß-D-glucopyranoside (9), and 4-hydroxy-3,5-dimethoxyphenylprop-8-ene 4-O-α-L-rhamnpyranosyl-(1 --> 6)-ß-D- glucopyranoside (10), respectively.

Aromatic acid derivatives from the lateral roots of Aconitum carmichaelii.

Seven new aromatic acid derivatives (1-7), together with five known analogs, were isolated from the lateral roots of Aconitum carmichaelii. Structures of the new compounds were determined by spectroscopic and chemical methods as 4-methyl ( - )-(R)-hydroxyeucomate (1), 4-butyl ( - )-(R)-hydroxyeucomate (2), 4-butyl-1-methyl (+)-(R)-2-O-(4'-hydroxy-3'-methoxybenzoyl)malate (3), 1-butyl-4-methyl (+)-(R)-2-O-(4'-hydroxy-3'-methoxybenzoyl)malate (4), dimethyl (+)-(R)-2-O-(4'-hydroxy-3'-methoxybenzoyl)malate (5), dimethyl (+)-(R)-2-O-(4'-hydroxybenzoyl)malate (6), and methyl ( ± )-3-(4'-hydroxy-3'-methoxyphenyl)-3-sulfopropionate (7), respectively. Compounds 1 and 2 are 2-benzylmalates (eucomate derivatives), 3-6 belong to 2-O-benzoylmalates, and 7 is a rare phenylpropionate containing a sulfonic acid group. The absolute configurations of eucomate derivatives were confirmed by X-ray crystallographic analysis of 4-methyl eucomate (11).

Glycosides from the bark of Machilus robusta.

Six new glycosidic constituents (1-6), together with 10 known analogs, have been isolated from the bark of Machilus robusta. Structures of the new compounds, including the absolute configurations, were determined by spectroscopic and chemical methods as ( - )-nectandrin B-ß-d-glucopyranoside (1), ( - )-(7R,7'R,8S,8'R)-4,4'-dihydroxy-3,3'-dimethoxy-7,7'-epoxylignan-4-O-ß-d-glucopyranoside (2), ( - )-(7R,7'R,8S,8'R)-4,4'-dihydroxy-3,3'-dimethoxy-7,7'-epoxylignan-4'-O-ß-d-glucopyranoside (3), ( - )-(8S,8'R)-4,4'-dihydroxy-3,3',5'-trimethoxylignan-4'-O-ß-d-glucopyranoside (4), ( - )-(7R,8R)-syringylglycerol-8-O-ß-d-glucopyranoside (5), and ( - )-3-hydroxy-2-methyl-4-pyrone-3-O-ß-d-xylopyranosyl-(1 â†’ 6)-O-ß-d-glucopyranoside (6), respectively.

Aromatic glycosides from the flower buds of Lonicera japonica.

Six new glycosides (1-6) have been isolated from the flower buds of Lonicera japonica. Their structures including the absolute configurations were determined by spectroscopic and chemical methods as ( - )-2-hydroxy-5-methoxybenzoic acid 2-O-ß-d-(6-O-benzoyl)-glucopyranoside (1), ( - )-4-hydroxy-3,5-dimethoxybenzoic acid 4-O-ß-d-(6-O-benzoyl)-glucopyranoside (2), ( - )-(E)-3,5-dimethoxyphenylpropenoic acid 4-O-ß-d-(6-O-benzoyl)-glucopyranoside (3), ( - )-(7S,8R)-(4-hydroxyphenylglycerol 9-O-ß-d-[6-O-(E)-4-hydroxy-3,5-dimethoxyphenylpropenoyl]-glucopyranoside (4), ( - )-(7S,8R)-(4-hydroxy-3-methoxyphenylglycerol 9-O-ß-d-[6-O-(E)-4-hydroxy-3,5-dimethoxyphenylpropenoyl]-glucopyranoside (5), and ( - )-4-hydroxy-3-methoxyphenol ß-d-{6-O-[4-O-(7S,8R)-(4-hydroxy-3-methoxyphenylglycerol-8-yl)-3-methoxybenzoyl]}-glucopyranoside (6), respectively.

[Lignans from Machilus robusta].

Eighteen lignans were isolated from an ethanol extract of Machilus robusta by a combination of various chromatographic techniques including column chromatography over silica gel, Sephadex LH-20 and reversed-phase HPLC. Their structures were identified by spectroscopic data analysis as isolariciresinol-9'-O-beta-D-xylopyranoside (1), (+)-5'-methoxy-isolariciresinol-9'-O-beta-D-xylopyranoside(2), lyoniresinol-9'-O-beta-D-xylopyranoside(3), (+)-(8S, 8'S) -4, 4'-dihydroxy-3, 3', 5, 5'-tetramethoxylignan-9, 9'-diol 9-O-beta-D-xylopyranoside (ssioriside, 4), lyoniresinol (5), meso-dihydroguaiaretic acid (6), (+)-(8S, 8'R)-3', 4, 4'-trihydroxy-3'-methoxylignan (7), (8S, 8'R)-4'-hydroxy-3, 3', 4-trimethoxylignan (meso-monomethyl dihydroguaiaretic acid, 8), (+)-guaiacin (9), isoguaiacin (10), (-)-(7'R, 8R, 8'R)-4, 4'-dihydroxy-3, 3', 5-trimethoxy-2, 7'-cyclolignan (11), henricine B (12), (-)-(7S, 7'S, 8R, 8'R)-4, 4'-dihydroxy-3, 3', 5, 5'-tetramethoxy-7, 7'-epoxylignan-9, 9'-dio] (7S, 7'S, 8R, 8'R-icariol A2, 13), (+)-(7R, 8R, 7'E)-4-hydroxy-3, 5'-dimethoxy-7, 4'-epoxy-8, 3'-neolignan-7'-ene (licarin A, 14), nectandrin B (15), machilin-I (16), (-)-pinoresinol (17), and (-)-syringaresinol (18). All compounds were isolated from this plant for the first time. In the preliminary assay, compound 17 showed inhibitory activity against NO secretion of mouse peritoneal macrophages with an inhibition rate of 72.2% at 10 micromol x L(-1).

[Chemical consitituents from root of Isatis indigotica].

Thirty-three compounds were isolated from the root decoction of Isatis indigotica by using a combination of various chromatographic techniques including silica gel, macroporous adsorbent resin, Sephadex LH-20, and reversed-phase HPLC. Their structures were elucidated by spectroscopic data as (+)-dehydrovomifoliol (1), (S)-(+)-abscisic acid (2), vomifoliol (3), cyclo (L-Phe-L-Leu) (4), cyclo(L-Phe-L-Tyr) (5), cyclo(L-Tyr-L-Leu) (6), cyclo(L-Pro-L-Tyr) (7), evofolin B (8), (+)-syringaresinol (9), (-)-(7R,7'R,8S,8'S)-4,4'-dihydroxy-3-methoxy-7,9';7',9-diepoxy-lignan (10), (-)-medioresinol (11), (+) -(7R,7'R,8S,8'S) -neo-olivil (12), (-) -5-methoxyisolariciresinol (13), 1,3-dihydro-2H-indol-2-one (14), isalexin (15), dihydroneoascorbigen (16), indican (17), (-) -(S) -cyanomethyl-3-hydroxyoxindole (18), isoformononetein (19), calycosin (20), stigamast-5-ene-3beta-ol-7-one (21), acetovanillone (22), 3, 5-dimethoxy-4-hydroxyacetophenone (23), dihydroconiferyl alcohol (24), dihyroferulic acid (25), 3-hydroxy-1-(4-hydroxyphenyl) propan-1-one (26), beta-hydroxypropiovanillone (27), 4-aminobenzoic acid (28), 3-(4-hydroxyphenyl) propan-1-ol (29), 4-(2-hydroxyethyl) phenol (30), 2-methoxy-4-vinylphenol (31), pyrocatechol (32), and 4-pentenamide (33). These compounds were isolated from the root of I. indigotica for the first time. In preliminary in vitro assays, compound 19 showed activity against the influenza virus A/Hanfang/359/95 (H3N2), the herpes simplex virus 1 (HSV-1), and Coxsackie virus B3 (Cox-B3), with IC50 values of 2.06, 6.84, and 8.70 micromol x L(-1), respectively, but other compounds were in-active at a concentration of 1.0 x 10 x (-5) mol x L(-1).

[Chemical constituents from flower buds of Lonicera japonica].

Eighteen compounds were isolated by a combination of various chromatographic techniques including column chromatography over macroporous resin, MCI gel, silica gel, and sephadex LH-20 and reversed-phase HPLC. Their structures were elucidated by spectroscopic data analysis as adinoside A (1), stryspinoside (2), benzyl alcohol beta-glucopyranoside (3), benzyl 2-o-beta-D-glucopyranosyl-2,6-dihydroxybenzoate (4) , gentisic acid 2-O-beta-D-glucopyranoside (5), eugenyl beta-D-glucopyranoside (6) , eugenyl-P-xylopyranosyl-(1-->6)-beta-glucopyranoside (7), (-)-lyoniresinol 9-O-fP-D-glucopyranoside (8) , (+)-lyoniresinol 9-O-beta-D-glucopyranoside (9) , apigenin-7-O-L-rhamnopyranoside (10), luteolin-3 '-O-L-rhamnoside (11) , ursolic acid (12) , beta-sitosteryl-3beta-glucopyranoside-6'-O-palmitate (13), abscisic acid (14), guanosine (15), 5-methyluracil (16), trans-cinnamic acid (17), and 4-hydroxybenzaldehyde(18). These compounds were obtained from this plant for the first time.

Phenylpropene diglycosides from the bark of Machilus wangchiana.

Five new phenylpropene diglycosides (1-5), together with three known analogs, have been isolated from an ethanol extract of the bark of Machilus wangchiana. Their structures were determined by spectroscopic and chemical methods. In the preliminary assay, compounds 2 and 5-8 reduced dl-galactosamine (GalN)-induced hepatocyte (WB-F344 cells) damage with 37-41% inhibitions at 10 µM.

Anthraquinones from the roots of Knoxia valerianoides.

Five new 9,10-anthraquinones (1-5) were isolated from an ethanol extract of the roots of Knoxia valerianoides. Their structures including absolute configuration of 1 were determined by spectroscopic analysis. Compounds 4 and 5 showed moderate activity against nitrogen oxide production in macrophages induced by lipopolysaccharide, at 10(- 5) M, with inhibition ratios of 50.4 ± 3.6 and 41.7 ± 2.1%, respectively.

A bibenzyl compound 20C protects rats against 6-OHDA-induced damage by regulating adaptive immunity associated molecules.

Parkinson's disease (PD) is a neurodegenerative disease with complicated pathogenesis. A novel bibenzyl compound 2-[4-hydroxy-3-(4-hydroxyphenyl)benzyl]-4-(4-hydroxyphenyl)phenol (20C) has been shown to have some neuroprotective effects, and its mechanism still needs further research. In this study, we used a 6-hydroxydopamine (6-OHDA)-induced PD rat model to evaluate the protective effect of 20C. Our study found that 20C could improve behavioral defects in 6-OHDA-lesion rats, decrease neuroinflammation and protect their DA neurons. It could inhibit the activity of inducible nitric oxide synthase (iNOS) induced by 6-OHDA, and lead to a decrease in the expression of nitrated-α-synuclein. When exposed to AMT-an inhibitor of iNOS, the nitrated-α-synuclein in PC12 decreased, and 20C demonstrated the same function on nitrated-α-synuclein as AMT. Besides, we also found that nitrated-α-synuclein was displayed in microglia. And 20C could decrease the expression of antigen-presenting molecule major histocompatibility complex I (MHC I) in dopamine (DA) neurons and MHC II in microglia induced by 6-OHDA. So, these imply that nitrated-α-synuclein might act as an endogenous antigen activating adaptive immunity, and the neuroprotection of 20C might be associated with inhibiting the activity of iNOS, decreasing the expression of the antigen molecule nitrated-α-synuclein and the antigen presenting molecule MHC. Our results indicated that inhibiting iNOS might be an effective strategy to protect neurons from oxidative stress.