Phytochemical reinvestigation of labdane-type diterpenes and their cytotoxicity from the rhizomes of Hedychium coronarium

A comprehensive reinvestigation of chemical constituents from the rhizomes of Hedychium coronarium resulted in the isolation of one new labdane-type diterpene, together with eight known compounds. Their structures were established by spectroscopic methods. Some of the isolated compounds showed significant cytotoxicity with IC₅₀ values lower than 4 μg ml^?1.     

Sesquiterpenoids and diarylheptanoids from Nidus vespae and their inhibitory effects on nitric oxide production

Two coriamyrtin-type sesquiterpenes, fengfangin A (1) and tutin (2), and six diarylheptanoids, namely alnusone (3), centrolobol (4), muricarpone B (5), 1-(3,4-dihydroxyphenyl)-7-(4-hydroxyphenyl)heptan-3-one (6), (3S)-1-(3,4-dihydroxyphenyl)-7-(4-hydroxyphenyl)heptan-3-ol (7), and (3S)-1-(4-hydroxyphenyl)-7-(3,4-dihydroxyphenyl)heptan-3-ol (8), were isolated from the 95% EtOH extract of nidus vespae, the nest of Polistes species. Their structures were identified by spectroscopic methods. Compounds 1 and 8 are new products. The absolute configuration of 1 was determined by single-crystal X-ray diffraction analysis using Flack parameter. The biological tests showed that compounds 5, 6, and 8 could inhibit nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells with IC(50) values in the range of 13-17 μM, whereas the sesquiterpenes were inactive in this assay (>25 μM). In addition, the ecological significance of the presence of neurotoxic sesquiterpene lactones in nidus vespae is briefly discussed.     

New guaiane sesquiterpenes from Artemisia rupestris and their inhibitory effects on nitric oxide production

Phytochemical investigation of the ethanol extract of the aerial parts of Artemisia rupestris resulted in the isolation of three new guaiane sesquiterpenes, (1R,7R,10S)-1-hydroxy-3-oxoguaia-4,11(13)-dien-12-oic acid (1), (1R,7R,10S)-10-hydroxy-3-oxoguaia-4,11(13)-dien-12-oic acid (2), pechueloic acid 12-O-β-d-glucopyranoside (3), together with 12 known compounds (4–15). The structures of these new compounds were established on the basis of extensive spectroscopic analysis and electronic circular dichroism (ECD) calculation. All isolates were evaluated for their in vitro inhibitory effects on nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages cells, and the structure–activity relationships were also discussed.     

Chemical constituents from the fruit of Gardenia jasminoides and their inhibitory effects on nitric oxide production

Three new iridoid glycosides, 6″-O-trans-caffeoylgenipin gentiobioside (1), genipin 1-O-β-d-apiofuranosyl (1→6)-β-d-glucopyranoside (2), genipin 1-O-α-d-xylopyranosyl (1→6)-β-d-glucopyranoside (3), three new monocyclic monoterpenoids, jasminoside R (4), jasminoside S (5), jasminoside T (6), together with nine known iridoid glycosides (7–15) and three crocetin glycosides (16–18), were isolated from the fruit of Gardenia jasminoides. Their chemical structures were established mainly by 1D and 2D NMR techniques and mass spectrometry. Inhibitory effects of the isolated compounds on nitric oxide production in lipopolysaccaride-activated macrophages were evaluated. Compounds 8 and 18 showed strong inhibitory activity on NO production with IC₅₀ values of 11.14 ± 0.67 and 5.99 ± 0.54 μM, respectively.     

Steroidal constituents from the leaves of Hosta longipes and their inhibitory effects on nitric oxide production

Hosta longipes (FR. et SAV.) MATSUMURA (Liliaceae) is an edible vegetable in Korea. This study was conducted with the aim of evaluating the potential of H. longipes as a functional food for the treatment of neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease. In this respect, the study resulted in the identification of three new steroidal compounds, longipenane (1), longipenane 26-O-β-d-glucopyranoside (2) and neogitogenin 3-O-α-l-rhamnopyranosyl-(1→2)-O-[β-d-glucopyranosyl-(1→4)]-β-d-galactopyranoside (3), along with two known steroidal saponins (4 and 5). The identification and structural elucidation of these compounds were based on 1D and 2D NMR measurements, high-resolution FAB mass spectroscopy (HR-FAB-MS), and chemical methods. A proinflammatory mediator, nitric oxide (NO), in murine microglial BV-2 cells was used to assess the anti-neuroinflammatory effect of the isolated compounds from H. longipes. Among them, compounds 4 and 5 showed strong inhibitory effects on NO production without high cell toxicity in lipopolysaccharide-activated BV-2 cells (IC₅₀ = 17.66 and 13.16 μM, respectively).     

Complex inhibitory effects of nitric oxide on autophagy

Autophagy, a major degradation process for long-lived and aggregate-prone proteins, affects various human processes, such as development, immunity, cancer, and neurodegeneration. Several autophagy regulators have been identified in recent years. Here we show that nitric oxide (NO), a potent cellular messenger, inhibits autophagosome synthesis via a number of mechanisms. NO impairs autophagy by inhibiting the activity of S-nitrosylation substrates, JNK1 and IKKβ. Inhibition of JNK1 by NO reduces Bcl-2 phosphorylation and increases the Bcl-2-Beclin 1 interaction, thereby disrupting hVps34/Beclin 1 complex formation. Additionally, NO inhibits IKKβ and reduces AMPK phosphorylation, leading to mTORC1 activation via TSC2. Overexpression of nNOS, iNOS, or eNOS impairs autophagosome formation primarily via the JNK1-Bcl-2 pathway. Conversely, NOS inhibition enhances the clearance of autophagic substrates and reduces neurodegeneration in models of Huntington's disease. Our data suggest that nitrosative stress-mediated protein aggregation in neurodegenerative diseases may be, in part, due to autophagy inhibition.     

Withanolides from Physalis peruviana showing nitric oxide inhibitory effects and affinities with iNOS

A phytochemical study to obtain new nitric oxide (NO) inhibitors resulted in the isolation of five new withanolides from the whole plants of Physalis peruviana. The structures were determined on the basis of extensive NMR spectroscopic data analysis as well as the time-dependent density functional theory (TDDFT) electronic circular dichroism (ECD) calculations. The NO inhibitory effects were examined by inhibiting NO release in lipopolysaccharide-stimulated murine microglial BV-2 cells. Molecular docking studies showed the strong interactions of bioactive compounds with the inducible nitric oxide synthase (iNOS) protein, revealing the potential mechanism of NO inhibition of bioactive compounds.     

Chemical constituents of the rhizomes of Hedychium coronarium and their inhibitory effect on the pro-inflammatory cytokines production LPS-stimulated in bone marrow-derived dendritic cells

The rhizomes of Hedychium coronarium have been used for the treatment of inflammation, skin diseases, headache, and sharp pain due to rheumatism in traditional medicine. From this plant, three new labdane-type diterpenes 1–3, named coronarins G–I as well as seven known 4–10, coronarin D, coronarin D methyl ether, hedyforrestin C, (E)-nerolidol, β-sitosterol, daucosterol, and stigmasterol were isolated. Their chemical structures were elucidated by mass, 1D- and 2D-nuclear magnetic resonance spectroscopy. They were evaluated for inhibitory effects on lipopolysaccharide-stimulated production of pro-inflammatory cytokines in bone marrow-derived dendritic cells. Among of them, compounds 1, 2, and 6 were significant inhibitors of LPS-stimulated TNF-α, IL-6, and IL-12 p40 productions with IC₅₀ ranging from 0.19 ± 0.11 to 10.38 ± 2.34 μM. The remains of compounds showed inactivity or due to cytotoxicity. These results warrant further studies concerning the potential anti-inflammatory benefits of labdane-type diterpenes from H. coronarium.     

Conjugation of l-NAME to prenyloxycinnamic acids improves its inhibitory effects on nitric oxide production

A series of 10 compounds resulting from the conjugation of O-prenylated naturally occurring benzoic and cinnamic acids to l-NAME were synthesized and tested together with the corresponding unprenylated parent molecule as anti-inflammatory agents for their inhibitory effects on NO production in LPS-stimulated RAW 264.7 macrophages. Results indicated that the coupling between O-geranyl and O-isopentenylcinnamic acids and l-NAME led to products with an enhanced activity when compared to the parent compounds.     

Diarylheptanoids from Curcuma kwangsiensis and their inhibitory activity on nitric oxide production in lipopolysaccharide-activated macrophages

Eleven diarylheptanoids (1-11) were isolated from rhizomes of Curcuma kwangsiensis, together with seven known compounds. Their structures were elucidated by 1D and 2D NMR, circular dichroism (CD), and accurate mass measurements. Inhibitory effects of the isolated compounds on nitric oxide production in lipopolysaccaride-activated macrophages were evaluated. Compounds 1, 2, and 3 showed strong inhibitory activity on NO production with IC(50) values of 3.13, 2.81 and 2.41 μM, respectively.     

Sera from patients with sepsis induce nitric oxide production in vascular smooth muscle cells

BACKGROUND: Nitric oxide (NO) is an important physiological mediator of vascular tone and is involved in pathophysiology of septic shock. Although plasma nitrite is a stable end product of NO oxidation derived from endogenous NO, the plasma nitrite level is also easily affected by the intake of various foods, bacterial products and renal functional status. AIMS: We propose an excellent alternative assay technique for measuring endogenous NO production. METHODS: We measured the nitrite level in cultured vascular smooth muscle cells (SMC) treated with serum obtained from patients with sepsis (4 patients), by means of a chemiluminescence detector. RESULTS: The nitrite concentrations in such cells were significantly higher as compared to those in the cells treated with normal serum. Moreover, the increased nitrite levels in the SMC treated with the sera obtained from patients with sepsis were completely inhibited by L-nitroarginine (1 mmol/L), a nitric oxide synthase inhibitor. CONCLUSION: These data suggest that this assay method enable us to know the ability of endogenous NO production in each patient.     

Labdane-type diterpenes: thermal effects on phospholipid bilayers, incorporation into liposomes and biological activity

Labd-13(E)-ene-8alpha,15-diol (1) and its derivative labd-13(E)-ene-8alpha-ol-15-yl-acetate (2) are water insoluble biological active molecules and their structures were elucidated using NMR and X-ray techniques. Differential scanning calorimetry (DSC) was applied to study the thermal effects of 1 and 2 on DPPC bilayers. Liposomes composed of egg phosphatidylcholine/dipalmytoylphosphatidylglycerol (9:0.1 molar ratio) were prepared by the thin-film hydration method and were used for incorporating 1 and 2. Free and liposomal 1 and 2 were tested for their activity against human cancer cell lines using the sulphorhodamine B assay. The effect of 1 and 2 on DPPC bilayers caused abolition of the pre-transition temperature, lowering of the main phase transition and reduction of the transition enthalpy only in the presence of cholesterol. The liposomes that have been designed and developed offer high incorporation efficiency; 62.4% (0.369 drug/lipid molar ratio) and 99.7% (0.661 drug/lipid molar ratio) for 1 and 2, respectively. Liposomal 2 showed growth-inhibiting activity against the majority of the tested cell lines.     

Syntheses of 1,2,3-triazolyl salicylamides with inhibitory activity on lipopolysaccharide-induced nitric oxide production

A 28-membered 1,2,3-triazolyl salicylamide library was synthesized via a Cu(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition and evaluated for their abilities to inhibit NO production in LPS-activated RAW264.7 macrophage cells. Among 28 analogues, 29g showed a significant inhibitory activity (IC₅₀ = 12.8 μM). The inhibitory effects of 29g on LPS-mediated NO production in macrophage cells appeared to be associated with the suppression of iNOS expression.     

Absolute stereostructures of polypodane- and octanordammarane-type triterpenes with nitric oxide production inhibitory activity from guggul-gum resins

The methanolic extract from guggul-gum resin, the resin of Balsamodendron mukul, was found to inhibit nitric oxide production in lipopolysaccharide-activated mouse peritoneal macrophages (IC(50) = 13 microg/mL). From the methanolic extract, three new polypodane-type triterpenes, myrrhanol B and myrrhanones B and A acetate, and a new octanordammarane-type triterpene, epimansumbinol, were isolated together with 17 known compounds including progesterone and the related steroids. The absolute stereostructures of new triterpenes were elucidated on the basis of chemical and physicochemical evidence. The several constituents showed inhibitory effects on nitric oxide production and induction of inducible nitric oxide synthase.     

neo-Clerodane diterpenes from Ajuga ciliata and their inhibitory activities on LPS-induced NO production

Two new neo-clerodane diterpenes, (12S)-6α-acetoxy-4α,18-epoxy-12-hydroxy-19-tigloyloxy-neo-clerod-13-en-15,16-olide (1) and 6α,18-diacetoxy-4α-hydroxy-19-tigloyloxy-neo-clerod-13-en-15,16-olide (2), along with three known analogs (3–5) have been isolated from the whole plants of Ajuga ciliata Bunge. Their structures were elucidated on the basis of spectroscopic data analyses (IR, ESI-MS, HR-ESI-MS, HMQC, HMBC, COSY, and NOESY). The inhibitory activities on LPS-induced NO production of these diterpenes were evaluated and compounds 1 and 5 showed inhibitory effects.     

Diterpenoids and a Diarylheptanoid from Hedychium coronarium with Significant Anti‐Angiogenic and Cytotoxic Activities

Two new labdane diterpenoids, namely hedycoronals A and B ( 1 and 2 , resp.), were isolated from the rhizomes of Hedychium coronarium, together with eight known diterpenoids, 4 – 11 , and a known diarylheptanoid, 3 . The structures of 1 and 2 were established by detailed interpretation of their 1D‐ and 2D‐NMR spectra and HR‐ESI‐MS data. Inhibitory activities against human umbilical vein endothelial cells (HUMECs) proliferation and cytotoxic activities against four cancer cell lines were assessed for all the isolates. Most of these metabolites showed moderate or potent cytotoxic activities against four cancer cell lines. Moreover, compounds 3 and 8 exhibited promising inhibitory activities against HUMECs with the IC₅₀ values of 6.4 to 3.3 μM .     

Analysis of the effects of nitric oxide and oxygen on nitric oxide production by macrophages

The interactions between NO and O(2) in activated macrophages were analysed by incorporating previous cell culture and enzyme kinetic results into a novel reaction-diffusion model for plate cultures. The kinetic factors considered were: (i) the effect of O(2) on NO production by inducible NO synthase (iNOS); (ii) the effect of NO on NO synthesis by iNOS; (iii) the effect of NO on respiratory and other O(2) consumption; and (iv) the effects of NO and O(2) on NO consumption by a possible NO dioxygenase (NOD). Published data obtained by varying the liquid depth in macrophage cultures provided a revealing test of the model, because varying the depth should perturb both the O(2) and the NO concentrations at the level of the cells. The model predicted that the rate of NO(2)(-) production should be nearly constant, and that the net rate of NO production should decline sharply with increases in liquid depth, in excellent agreement with the experimental findings. In further agreement with available results for macrophage cultures, the model predicted that net NO synthesis should be more sensitive to liquid depth than to the O(2) concentration in the headspace. The main reason for the decrease in NO production with increasing liquid depth was the modulation of NO synthesis by NO, with O(2) availability playing only a minor role. The model suggests that it is the ability of iNOS to consume NO, as well as to synthesize it, that creates very sensitive feedback control, setting an upper bound on the NO concentration of approximately 1 microM. The effect of NO consumption by other possible pathways (e.g., NOD) would be similar to that of iNOS, in that it would help limit net NO production. The O(2) utilized during enzymatic NO consumption is predicted to make the O(2) demands of activated macrophages much larger than those of unactivated ones (where iNOS is absent); this remains to be tested experimentally.