Picrachinentins A-F, 14-Membered Cyclopeptide Alkaloid-Type Burpitides with Uncommon N-Terminal Modifications from Picrasma chinensis and Their Neuroprotective Activity.

Picrachinentins A-F (1-6, respectively), six novel cyclopeptide alkaloid-type burpitides (CPABs), were isolated and fully elucidated from the EtOH extract of the stems and leaves of Picrasma chinensis. Structurally, compounds 1-6 have a 14-membered paracyclophane ring system that was closed through an ether bond between the ß-hydroxy amino acid and tyrosine and modified with a 4,5-methylenedioxybenzoyloxy (MDBz, 3 and 5) or hexanoyl (Hexa, 1, 2, 4, and 6) group at the N-terminus. Interestingly, this is the first report on the isolation and characterization of CPABs from plants of the Simaroubaceae family. In addition, all compounds showed a neuroprotective effect against H2O2-damaged SH-SY5Y cells. Compound 1 was further investigated for its neuroprotective activities using a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson's disease animal model, and it dramatically improved MPTP-impaired motor behavioral performance. Biochemical analysis revealed compound 1 restored the tyrosine hydroxylase expression in the striatum of the MPTP-damaged mouse brain, which demonstrates its protective effect on dopaminergic neurons.

Triterpenoids and triterpenoid saponins from Vitex negundo and their anti-inflammatory activities.

Seven undescribed polyoxygenated ursane-type triterpenoids (vitnegundins A-G), three undescribed triterpenoid saponins (vitnegundins H-J), and 17 known ones were isolated from an EtOH extract of the aerial parts of Vitex negundo L. The structures of the undescribed compounds were established by extensive spectroscopic analysis. The absolute configurations of vitnegundins A, B, and E were determined by single-crystal X-ray diffraction data. Vitnegundins B-D are pentacyclic triterpenoids possessing rare cis-fused C/D rings and vitnegundins C-H represent undescribed ursane-type triterpenoids with 12,19-epoxy moiety. In the biological activity assay, vitnegundin A, vitnegundin E, and swinhoeic acid displayed inhibitory effects against LPS-induced NO release in BV-2 microglial cells, with IC50 values of 11.8, 44.2, and 19.6 µM, respectively.

New sesquiterpenoids with neuroprotective effects in vitro and in vivo from the Picrasma chinensis.

Three undescribed sesquiterpenes, designed as pichinenoid A-C (1-3), along with nine known ones (4-12) were isolated from the stems and leaves of Picrasma chinensis. The new isolates including their absolute configurations were elucidated based on extensive spectroscopic methods, single crystal X-ray diffraction, and electronic circular dichroism (ECD) experiments, as well as comparison with literature data. Structurally, compounds 1 and 2 are descending sesquiterpenes, while pichinenoid C (3) is a rare sesquiterpene bearing a 2-methylenebut-3-enoic acid moiety at the C-6 side chain. All the isolated compounds were tested for their neuroprotective effects against the H2O2-induced damage on human neuroblastoma SH-SY5Y cells, and most of them showed moderate neuroprotective activity. Especially, compounds 1, 3-5, and 7 showed a potent neuroprotective effect at 25 or 50 µM. Moreover, the neuroprotective effects of compounds 1 and 4 were tested on a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson's disease (PD) mouse model. Results of western blot and immunofluorescence indicated that compound 4 significantly counteract the toxicity of MPTP, and reversed the expression of tyrosine hydroxylase (TH) in substantia nigra (SN) and striatum (ST) of the mouse brain. Interestingly, western blot data suggested compound 4 also enhanced B-cell lymphoma-2 (Bcl-2) and heme oxygenase 1 (HO-1) expressions in the brain tissues from MPTP damaged mouse.

Clerodane diterpenoids with in-vitro anti-neuroinflammatory activity from the tuberous root of Tinospora sagittata (Menispermaceae).

Twenty-six clerodane diterpenoids have been isolated from T. sagittata, a plant species of traditional Chinese medicine Radix Tinosporae, also named as "Jin Guo Lan". Among them, there are eight previously undescribed clerodane diterpenoids (tinotanoids A-H: 1-8), and 18 known diterpenoids (9-26). The absolute configurations of compounds 1, 2, 5, 8, 13, 17 and 20 were determined by single-crystal X-ray diffraction. Compound 1 is the first example of rotameric clerodane diterpenoid with a γ-lactone ring which is constructed between C-11 and C-17; meanwhile, compounds 3 and 4 are two pairs of inseparable epimers. Compounds 2, 12 and 17 demonstrated excellent inhibitory activity on NO production against LPS-stimulated BV-2 cells with IC50 values of 9.56 ± 0.69, 9.11 ± 0.53 and 11.12 ± 0.70 µM, respectively. These activities were significantly higher than that of the positive control minocycline (IC50 = 23.57 ± 0.92 µM). Moreover, compounds 2, 12 and 17 dramatically reduced the LPS-induced upregulation of iNOS and COX-2 expression. Compounds 2 and 12 significantly inhibited the levels of pro-inflammatory cytokines TNF-α, IL-1ß and IL-6 that were increased by LPS stimulation.

Structurally diverse stilbenes from Gnetum parvifolium and their anti-neuroinflammatory activities.

Phytochemical investigation on the aerial parts of Gnetum parvifolium led to the isolation of 15 new and eight known structurally diverse stilbenes. The isolated compounds comprised (E)- or (Z)-stilbene (1-6, 15-20), dihydrostilbene (21), phenylbenzofuran (7, 8, 22), benzylated stilbene (9-11), benzylated stilbene dimer (12), and nitrogen-containing stilbene (13a, 13b, 14) types. The structures of the new compounds (1-12, 13a, 13b, 14) were established through spectroscopic analyses and experimental and calculated ECD data. Compound 12 is the first stilbene dimer connected through a benzyl group. In the anti-neuroinflammatory activity assay, compounds 4, 5, 9-11, 13b, and 16-21 displayed significant inhibitory effects against LPS-induced NO release in BV-2 microglial cells, with IC50 values of 0.35-16.1 µM. Compound 10 had the most potent activity (IC50 = 0.35 µM), and the further research indicated that it could decrease the mRNA levels of iNOS, IL-1ß, IL-6, and TNF-α in a dose-dependent manner.

Tinopanoids K-T, clerodane diterpenoids with anti-inflammatory activity from Tinospora crispa.

A total of 17 structurally diverse clerodane diterpenoids, including ten undescribed clerodane diterpenoids (tinopanoids K-T, 1-10) and seven known compounds (11-17), were isolated from the vines and leaves of Tinospora crispa. Compound 3 has not only bear the dominant substituents of γ-hydroxy-α, ß-unsaturated-γ-lactone with anti-inflammatory activity, but also a ternary epoxy structure at C-3/C-4. The planar structures and relative configurations of the clerodane diterpenoids were elucidated by spectroscopic data interpretation. The absolute configurations of compounds 1, 4, 8 and 13 were determined by single-crystal X-ray crystallographic, while that of compound 3 was determined using computed ECD data and single crystal X-ray diffraction of related p-bromobenzoate ester (3a). Subsequently, all compounds were evaluated for their inhibitory effect on nitric oxide (NO) production of LPS-activated BV-2 cells, and compounds 3 and 8 exhibited better NO inhibitory potency, with IC50 values of 5.6 and 13.8 µM than the positive control minocycline (Mino, IC50 = 22.9 µM). The corresponding results of western blot analysis and qRT-PCR revealed that compound 3 can significantly inhibit the inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) protein expressions, mRNA levels of pro-inflammatory cytokins of tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6) and interleukin 1ß (IL-1ß). The underlying mechanism by which compound 3 exerted anti-neuroinflammatory effects was investigated by western blot and immunofluorescence assay, which suggested compound 3 inhibited LPS induced neuroinflammation via the suppression of toll-like receptor 4 (TLR4) dependent Signal Transducer and Activator of Transcription 3 (Stat3) and mitogen-activated protein kinase (MAPK) signaling pathways, and the activation of Heme Oxygenase-1 (HO-1) mediated signals.

New polychlorinated bibenzyls from Rhododendron minutiflorum.

Five new polychlorinated bibenzyls (1-5) along with 3 known compounds (6-8) were isolated from the stems and leaves of Rhododendron minutiflorum. The chemical structures of all the isolates were determined by spectroscopic methods, and compounds 1 and 2 were further verified by single-crystal X-ray diffraction analyses. Compounds 1-5 were halogenated compounds which bear three to five chlorine atoms in their chemical structures. Biologically, compounds 2, 5 and 6 showed varying degrees of toxicity toward the Asian citrus psyllid (Diaphorina citri) with LD50 values 27.15, 17.02 and 16.20 mg/L, respectively. These values were comparable to the positive control matrine (LD50 = 11.86 mg/L), which were calculated using observations on day 6. Meanwhile, compound 4 had α-glucosidase inhibitory activity with IC50 value of 17.87 ± 0.74 µM.

Terpenoids with α-glucosidase inhibitory activity from Rhododendron minutiflorum Hu.

Five undescribed triterpenoids, two unusual omphalane-type sesquiterpenoids together with twenty-five known compounds were isolated from the leaves and stems of Rhododendron minutiflorum Hu. The absolute configurations of 1-3 and 6 were established by single-crystal X-ray diffraction analysis and electronic circular dichroism (ECD). Compounds 6-7 feature the rare omphalane-type sesquiterpene skeleton and are verified by single-crystal X-ray diffraction analysis for the first time. In the biological activity assay, most of the triterpenoids have different degrees of inhibitory effects on α-glucosidase, with IC50 values ranging from 6.97 to 229.3 µM (the positive control drug acarbose has an IC50 value of 3.07 × 10-3 µM). Structure and activity relationship (SAR) study reveals that the oxidation degrees of C-3, C-8, or C-11 to C-13 of the ursane-type triterpenoid influence the inhibitory activity dramatically.

New enantiomeric lignans and new meroterpenoids with nitric oxide release inhibitory activity from Piper puberulum.

Six new lignans with various type of linkage between two C6-C3 fragments (1a, 1b, 2a, 2b, 3, 4), two new meroterpenoids (5, 6) and 24 known compounds (7-30) were isolated from an EtOH extract of the stems and leaves of Piper puberulum. The absolute configurations of enantiomers 1a and 1b were determined by single-crystal X-ray diffraction analysis, 2a and 2b were determined by comparing their calculated and experimental ECD spectra. Biogenetically, all the new lignans may come from the polymerization of two molecules of hydroxychavicol (30). In the anti-neuroinflammation activity assay, the IC50 values of fifteen compounds were lower than those of the positive control minocycline, and compound 1a showed good activity, but its enantiomer 1b showed no activity. Compound 1a have notable anti-neuroinflammatory activity, and can significantly decrease mRNA levels of proinflammatory cytokines (IL-1ß, IL-6, TNF-α) in a dose-dependent manner.

Chebulic acid derivatives from Balakata baccata and their antineuroinflammatory and antioxidant activities.

Sixteen chebulic acid derivatives, including nine new (1-9) and seven known (10-16) ones, were isolated from an ethanol extract of the branches and leaves of Balakata baccata. The structures of the new compounds were elucidated by their UV, IR, HRESIMS, NMR, electronic circular dichroism (ECD) and single-crystal X-ray diffraction data. The effects of all the isolates on antineuroinflammatory and antioxidant activities were evaluated. Compared with the positive control minocycline (IC50 = 1.21 ± 0.71 µM), compounds 1-16 with IC50 values being greater than 50 µM, displayed almost no effects on the inhibition of NO production in LPS-induced BV-2 microglial cells, however, the results of antioxidant activity for compounds 1-16 showed significant DPPH-radical scavenging abilities with EC50 value ranging from 3.98 to 14.24 µM, while the EC50 value of positive control vitamin C was 14.31 µM. At last, the results of PCR (qRT-PCR) analysis showed that compound 1 could enhance the expression of antioxidases (HO-1, GCLC, and NQO1) at the mRNA levels.

New Tyramine- and Aporphine-Type Alkamides with NO Release Inhibitory Activities from Piper puberulum.

Three new tyramine-type alkamides (1-3), three new natural products (4-6), five new N-acylated/formylated aporphine alkamides with different ratios of rotational isomers (7-11), and 20 known alkamides (12-31) were isolated from an EtOH extract of the stems and leaves of Piper puberulum. The absolute configurations of compounds 7, 8, and 10 were determined by single-crystal X-ray diffraction analysis. In the biological activity assay, compounds 3, 5, and 10-23 displayed inhibitory effects against lipopolysaccharide-induced NO release in BV-2 microglial cells, exhibiting IC50 values of 0.93-45 µM.

Piperhancins A and B, Two Pairs of Antineuroinflammatory Cycloneolignane Enantiomers from Piper hancei.

Two pairs of cycloneolignane enantiomers, piperhancins A and B (1 and 2, respectively), along with two enantiomeric pairs of biosynthetic related neolignanes, hancinone C (3) and piperhancin C (4), were isolated from the stems of Piper hancei. Compound 1 is an unprecedented 1',2:1,2'-dicyclo-8,3'-neolignane. Their structures and absolute configurations were elucidated by spectroscopic analyses, X-ray diffraction, and electronic circular dichroism calculations. Among all of the isolates, compounds (+)-1, (-)-1, (+)-2, (-)-2, and (+)-3 could significantly inhibit the production of nitric oxide secreted by lipopolysaccharide (LPS)-induced neuroinflammation in BV-2 microglial cells, with IC50 values of 1.1-26.3 µM. In addition, compound (-)-1 could decrease the mRNA levels of iNOS, IL-6, and TNF-α induced by LPS in BV-2 microglial cells.

Flavonol glycosides and phenylpropanoid glycosides with inhibitory effects on microglial nitric oxide production from Neoshirakia japonica.

Five new flavonol glycosides (1-5), one new phenylpropanoid glycoside (6), and nine known glycosides (7-15) were isolated from the stems and leaves of Neoshirakia japonica. The structures of the new compounds were determined by detailed analysis of spectroscopic data (HRESIMS, 1D and 2D NMR) and acid hydrolysis experiment. The antineuroinflammatory effects of all the isolates were evaluated by inhibiting NO production against LPS-induced BV-2 microglial cells. Compounds 1, 8, and 9 showed more potent inhibitory activities with IC50 values of 2.7, 5.5, and 4.1 µM, respectively, than that of the positive control minocycline (IC50 = 15.6 µM), while compounds 7 (IC50 = 17.0 µM) and 10 (IC50 = 24.3 µM) also displayed inhibitory activities to a certain degree.

Diterpenoids and triterpenoids from Triadica rotundifolia and their effects on microglial nitric oxide production.

Four new diterpenoids (1-4), three new triterpenoids (12-14), and seven known diterpenoids (5-11) were obtained from an aqueous EtOH extract of the aerial parts of Triadica rotundifolia. The structures of new compounds were determined by spectroscopic techniques. Their absolute configurations were verified via single-crystal X-ray diffraction data, Mo2(OAc)4 induced electronic circular dichroism (ECD), and ECD calculations. The antineuroinflammatory effects of the isolates were assessed by inhibiting NO production in LPS-induced BV-2 microglial cells. Compared with the positive control minocycline (IC50 = 16.1 µM), compounds 3, 8, 11 showed moderate inhibitory activities with IC50 values of 35.9, 17.0, 31.5 µM, respectively.

Isolation, Absolute Configuration, and Biological Activities of Chebulic Acid and Brevifolincarboxylic Acid Derivatives from Euphorbia hirta.

Twenty new chebulic acid and brevifolincarboxylic acid derivatives, including eight optically pure or achiral compounds (1-7 and 14) and six pairs of enantiomers (8a/8b-13a/13b), along with nine known analogues (15-23), were isolated from an EtOH extract of the aerial parts of Euphorbia hirta. The absolute configurations of the new compounds were assigned based on single-crystal X-ray diffraction analysis and comparison of the experimental and calculated ECD data. Racemic or scalemic mixtures of 8-13 were isolated, and their enantiomers were analyzed by chiral-phase HPLC-ECD measurements. Compound 12 possesses an unprecedented 2H-cyclopenta[de]chromene-2,5(4H)-dione scaffold. Compounds 12, 20, and 23 displayed moderate inhibitory effects against lipopolysaccharide-induced nitric oxide production in BV-2 microglial cells, while all the isolates exhibited significant DPPH radical scavenging activities with EC50 values of 2.2-15.8 µM.

Anti-inflammatory activity of isobutylamides from zanthoxylum nitidum var. tomentosum.

Inflammation is a very common and important basic pathological process. There is still a great need for the isolation of effective anti-inflammatory agents from plants. In this paper, five new isobutylamides, zanthoxylumamides E-I (1-5), and four known isobutylamides (6-9) were isolated from Zanthoxylum nitidum var. tomentosum (Rutaceae). Chiral resolution of seven racemic isobutylamides (1-4 and 6-8) was successfully performed, and the absolute configurations of two stereoisomers of 1-4 were validated by ECD and NMR. The obtained isobutylamides were evaluated in vitro anti-inflammatory activity with the lipopolysaccharide (LPS)-stimulated production of nitric oxide (NO) in murine macrophage RAW264.7 cells. Compound 8 exhibited significant inhibition of LPS-induced NO production. The underlying molecular mechanisms of the anti-inflammatory activity of 8 revealed that it suppressed the NO production through the modulation of myeloid differentiation factor 88 (MyD88) and interferon regulatory factor 3 (IRF3) signaling pathways.

Sesquiterpenes and diterpenes from Euphorbia thymifolia.

One new pseudoguaianolide (1), one new megastigmane (6), and one new ent-abietane diterpene (9), together with seven known compounds (2-5, 7, 8, and 10) were isolated from the aerial parts of Euphorbia thymifolia. The structures of the new compounds and their relative configurations were determined by spectroscopic data analysis. The absolute configurations of compounds 1, 6, and 9 were determined by single-crystal X-ray crystallographic analysis, modified Mosher's method and calculated ECD experiment, respectively. All compounds were tested for their inhibitory effects against LPS-induced NO production in BV-2 microglial cells, and pseudoguaianolides (1-5) showed significant activity with IC50 values of 0.41-15.32 µM.

Sesquiterpenoid Compounds from Curcuma kwangsiensis.

Two previously undescribed guaiane-type sesquiterpenes (1 and 2), a pair of new salvialane-type sesquiterpenes (3a and 3b), together with 11 known compounds were isolated and purified from the rhizomes of Curcuma kwangsiensis. Their structures were elucidated by the extensive spectroscopic data (1D- and 2D-NMR) analysis. All the isolated compounds were assessed for their anti-neuroinflammatory activity by inhibiting the nitric oxide (NO) production in lipopolysaccharide (LPS)-activated murine BV-2 microglial cells in vitro assay, and the isolates 3 and 11 showed anti-neuroinflammatory activity with IC50 values of 1.85 and 20.05 µm, respectively.

Coumarinolignoids and lignanoids from the stems and leaves of Sapium discolor.

Two new coumarinolignoids, sapiumins D (1) and E (2), a new lignanoid, lariciresinol 9'-benzoate (3), together with six known coumarinolignoids (4-9) and eight known lignanoids (10-17), were isolated from the stems and leaves of Sapium discolor. The structures of the isolated compounds were elucidated by extensive spectroscopic methods, including NMR, MS, and single crystal X-ray diffraction experiments. Compounds 5, 10, 11, and 13 significantly inhibited nitric oxide production in lipopolysaccharide-induced BV-2 microglial cells, with IC50 values in the range of 2.13-11.37 µM.

New terpenoid and phenylpropanoid glycosides from Tinospora sinensis.

Two new cadinane sesquiterpene glucosides (1, 2), two new phenylpropanoid glycosides (3, 4), and two new diterpenoid glucosides (5, 6), as well as 6 known compounds were isolated from the stems of Tinospora sinensis. The structures of these compounds were elucidated by extensive spectroscopic analysis and chemical methods. The absolute configuration of compound 1 was determined by timedependent density functional theory (TDDFT) electronic circular dichroism (ECD) calculations and in situ dimolybdenum CD method. All the isolated compounds except for compounds 7, 11 and 12 were evaluated for their anti-neuroinflammatory effect by inhibiting the nitric oxide (NO) production in lipopolysaccharide (LPS)-activated murine BV-2 microglial cells, and compound 4 showed anti-neuroinflammatory activity with IC50 values 42.90 µM in vitro assay.