Synthesis of new heterocyclic lupeol derivatives as nitric oxide and pro-inflammatory cytokine inhibitors

A series of heterocyclic derivatives including indoles, pyrazines along with oximes and esters were synthesized from lupeol and evaluated for anti-inflammatory activity through inhibition of lipopolysaccharide (LPS) induced nitric oxide (NO) production in RAW 264.7 and J774A.1 cells. All the synthesized molecules of lupeol were found to be more active in inhibiting NO production with an IC₅₀ of 18.4–48.7 μM in both the cell lines when compared to the specific nitric oxide synthase (NOS) inhibitor, L-NAME (IC₅₀ = 69.21 and 73.18 μM on RAW 264.7 and J774A.1 cells, respectively). The halogen substitution at phenyl ring of indole moiety leads to potent inhibition of NO production with half maximal concentration ranging from 18.4 to 41.7 μM. Furthermore, alkyl (11, 12) and p-bromo/iodo (15, 16) substituted compounds at a concentration of 20 μg/mL exhibited mild inhibition (29–42%) of LPS-induced tumor necrosis factor alpha (TNF-α) and weak inhibition (10–22%) towards interleukin 1-beta (IL-1β) production in both the cell lines. All the derivatives were found to be non-cytotoxic when tested at their IC₅₀ (μM). These findings suggest that the derivatives of lupeol could be a lead to potent inhibitors of NO.     

Xanthine oxidase inhibitory terpenoids of Amentotaxus formosana protect cisplatin-induced cell death by reducing reactive oxygen species (ROS) in normal human urothelial and bladder cancer cells

The diterpenoids (+)-ferruginol (1), ent-kaur-16-en-15-one (2), ent-8(14),15-sandaracopimaradiene-2α,18-diol (3), 8(14),15-sandaracopimaradiene-2α,18,19-triol (4), and (+)-sugiol (5) and the triterpenoids 3β-methoxycycloartan-24(24¹)-ene (6), 3β,23β-dimethoxycycloartan-24(24¹)-ene (7), 3β,23β-dimethoxy-5α-lanosta-24(24¹)-ene (8), and 23(S)-23-methoxy-24-methylenelanosta-8-en-3-one (9), isolated from Amentotaxus formosana, showed inhibitory effects on xanthine oxidase (XO). Of the compounds tested, compound 5 was a potent inhibitor of XO activity, with an IC₅₀ value of 6.8 ± 0.4 μM, while displaying weak ABTS radical cation scavenging activity. Treatment of the bladder cancer cell line, NTUB1, with 3–10 μM of compound 5 and 10 μM cisplatin, and immortalized normal human urothelial cell line, SV-HUC1, with 0.3–1 μM and 10–50 μM of compound 5 and 10 μM cisplatin, respectively, resulted in increased viability of cells compared with cytotoxicity induced by cisplatin. Treatment of NTUB1 with 20 μM cisplatin and 10 or 30 μM of compound 5 resulted in decreased ROS production compared with ROS production induced by cisplatin. These results indicate that 10 or 30 μM of compound 5 in NTUB1 cells may mediate through the suppression of XO activity and reduction of reactive oxygen species (ROS) induced by compound 5 cotreated with 20 μM cisplatin and protection of subsequent cell death.     

Synthesis and biological evaluation of 3′,4′,5′-trimethoxychalcone analogues as inhibitors of nitric oxide production and tumor cell proliferation

A series of 23 3′,4′,5′-trimethoxychalcone analogues was synthesized and their inhibitory effects on nitric oxide (NO) production in LPS/IFN-γ-treated macrophages, and tumor cell proliferation has been investigated. 4-Hydroxy-3,3′,4′,5′-tetramethoxychalcone (7), 3,4-dihydroxy-3′,4′,5′-trimethoxychalcone (11), 3-hydroxy-3′,4,4′,5′-tetramethoxychalcone (14), and 3,3′,4′,5′-tetramethoxychalcone (15) were the most potent growth inhibitory agents on NO production, with an IC₅₀ value of 0.3, 1.5, 1.3 and 0.3 μM, respectively. The tumor cells proliferation assay results revealed that several compounds exhibited potent inhibition activity against different cancer cell lines. The chalcone 15 was the most potent anti-proliferative compound in the series with IC₅₀ values of 1.8 and 2.2 μM toward liver cancer Hep G2 and colon cancer Colon 205 cell lines, respectively. 2,3,3′,4′,5′-Pentamethoxychalcone (1), 3,3′,4,4′,5,5′-hexamethoxychalcone (3), 2,3′,4,4′,5,5′-hexamethoxychalcone (5), 2-hydroxy-3,3′,4′,5′-tetramethoxychalcone (10), 11 and 14 showed significant anti-proliferation actions in Hep G2 and Colon 205 cells with an IC₅₀ values ranging between 10 and 20 μM. Among the tested agents, compound 7 showed selective NO production inhibition (IC₅₀ = 0.3 μM), while has no effect on tumor cell proliferation (IC₅₀ >100 μM). 3,3′,4,4′,5′-Pentamethoxychalcone (2) showed selective anti-proliferation effect in Hep G2 cells, in addition to its potent NO inhibition, however has no such response in Colon 205 cells. In contrast, 3-formyl-3′,4′,5′-trimethoxychalcone (22) showed moderate growth inhibition in Colon 205 cells, while has no such effect on NO production and Hep G2 cells proliferation. These results provide insight into the correlation between some structural properties of 3′,4′,5′-trimethoxychalcones and their in vitro anti-inflammatory and anti-cancer differentiation activity.     

Anti-inflammatory components of Euphorbia humifusa Willd.

Two new compounds, euphorbinoside (1) and dehydropicrorhiza acid methyl diester (2), along with 24 known compounds (3–26) were isolated from Euphorbia humifusa Willd. The effects of these compounds on soluble epoxide hydrolase (sEH) inhibitory activity were evaluated. Flavonoid compounds (10–21) exhibited high sEH inhibitory activity. Among them, compounds 12, 13, and 19 greatly inhibited sEH enzymatic activity, with IC₅₀ values as low as 18.05 ± 1.17, 18.64 ± 1.83, and 17.23 ± 0.84 μM, respectively. In addition, the effects of these compounds on lipopolysaccharide (LPS)-induced nitric oxide (NO) and tumor necrosis factor alpha (TNF-α) production by RAW 264.7 cells were investigated. Compounds 3–6, 8, 18, 20–23, and 25–26 inhibited the production of both NO and TNF-α, with IC₅₀ values ranging from 11.1 ± 0.9 to 45.3 ± 1.6 μM and 14.4 ± 0.5 to 44.5 ± 1.2 μM, respectively.     

Potential anti-inflammatory phenolic glycosides from the medicinal plant Moringa oleifera fruits

Bioassay-guided isolation and purification of the ethyl acetate extract of Moringa oleifera fruits yielded three new phenolic glycosides; 4-[(2′-O-acetyl-α-l-rhamnosyloxy) benzyl]isothiocyanate (1), 4-[(3′-O-acetyl-α-l-rhamnosyloxy)benzyl]isothiocyanate (2), and S-methyl-N-{4-[(α-l-rhamnosyloxy)benzyl]}thiocarbamate (3), together with five known phenolic glycosides (4–8). The structures of the new metabolites were determined on the basis of spectroscopic analyses including 1D- and 2D-NMR and mass spectrometry. The anti-inflammatory activity of isolated compounds was investigated with the lipopolysaccharide (LPS)-induced murine macrophage RAW 264.7 cell line. It was found that 4-[(2′-O-acetyl-α-l-rhamnosyloxy)benzyl]isothiocyanate (1) possessed potent NO–inhibitory activity with an IC₅₀ value of 1.67 μM, followed by 2 (IC₅₀ = 2.66 μM), 4 (IC₅₀ = 2.71 μM), and 5 (IC₅₀ = 14.4 μM), respectively. Western blots demonstrated these compounds reduced LPS-mediated iNOS expression. In the concentration range of the IC₅₀ values, no significant cytotoxicity was noted. Structure–activity relationships following NO-release indicated: (1) the isothiocyanate group was essential for activity, (2) acetylation of the isothiocyanate derivatives at C-2′ or at C-3′ of rhamnose led to higher activity, (3) un-acetylated isothiocyanate derivatives displayed eight times less activity than the acetylated derivatives, and (4) acetylation of the thiocarbamate derivatives enhanced activity. These data indicate compounds 1, 2, 4 and 5 are responsible for the reported NO-inhibitory effect of Moringa oleifera fruits, and further studies are warranted.     

Synthesis of novel 3,5-diaryl pyrazole derivatives using combinatorial chemistry as inhibitors of tyrosinase as well as potent anticancer,anti-inflammatory agents

In the present article, we have synthesized a combinatorial library of 3,5-diaryl pyrazole derivatives using 8-(2-(hydroxymethyl)-1-methylpyrrolidin-3-yl)-5,7-dimethoxy-2-phenyl-4H-chromen-4-one (1) and hydrazine hydrate in absolute ethyl alcohol under the refluxed conditions. The structures of the compounds were established by IR, ¹H NMR and mass spectral analysis. All the synthesized compounds were evaluated for their anticancer activity against five cell lines (breast cancer cell line, prostate cancer cell line, promyelocytic leukemia cell line, lung cancer cell line, colon cancer cell line) and anti-inflammatory activity against TNF-α and IL-6. Out of 15 compounds screened, 2a and 2d exhibited promising anticancer activity (61–73% at 10 μM concentration) against all selected cell lines and IL-6 inhibition (47% and 42% at 10 μM concentration) as in comparison to standard flavopiridol (72–87% inhibition at 0.5 μM) and dexamethasone (85% inhibition at 1 μM concentration), respectively. Cytotoxicity of the compounds checked using CCK-8 cell lines and found to be nontoxic to slightly toxic. Out of 15, four 3,5-diaryl pyrazole derivatives exhibiting potent inhibitory activities against both the monophenolase and diphenolase actions of tyrosinase. The IC₅₀ values of compounds (2a, 2d, 2h and 2l) for monophenolase inhibition were determined to range between 1.5 and 30 μM. Compounds 2a, 2d, 2h and 2l also inhibited diphenolase significantly with IC₅₀ values of 29.4, 21.5, 2.84 and 19.6 μM, respectively. All four 3,5-diaryl pyrazole derivatives were active as tyrosinase inhibitors (2a, 2d, 2h and 2l), and belonging to competitive inhibitors. Interestingly, they all manifested simple reversible slow-binding inhibition against diphenolase.     

Antitumor agents 273. Design and synthesis of N-alkyl-thiocolchicinoids as potential antitumor agents

As a part of our continuing study of colchicinoids as therapeutically useful antitumor drugs, thiocolchicine derivatives, including their phosphate and other water soluble salts, were synthesized and evaluated for inhibition of tubulin polymerization and for in vitro cytotoxicity. Three compounds, 7, 10, and 11, showed potent inhibition of tubulin assembly (IC₅₀ = 0.88–1.1 μM). In addition, compound 7, a water soluble succinic acid salt of N-deacetylthiocolchicine (4), showed potent cytotoxicity against a panel of tumor cell lines, suggesting it might be a potential lead to be developed as a therapeutic antitumor agent. Compound 8, a water soluble succinic acid salt of N,N-dimethyl-N-deacetylthiocolchicine (5), showed selective activities against HCT-8 and SK-BR-3 cells. N,N-Diethyl-N-deacetylthiocolchicine (6) seemed not to be a substrate for the P-gp efflux pump, based on the similar ED₅₀ values obtained against P-gp over-expressing KBvin (0.0146 μg/mL) cells and the parent KB (0.0200 μg/mL) cell line.     

Tanzawaic acid derivatives from a marine isolate of Penicillium sp. (SF-6013) with anti-inflammatory and PTP1B inhibitory activities

Chemical investigation of a marine-derived fungus Penicillium sp. SF-6013 resulted in the discovery of a new tanzawaic acid derivative, 2E,4Z-tanzawaic acid D (1), together with four known analogues, tanzawaic acids A (2) and D (3), a salt form of tanzawaic acid E (4), and tanzawaic acid B (5). Their structures were mainly determined by analysis of NMR and MS data, along with chemical methods. Preliminary screening for anti-inflammatory effects in lipopolysaccharide (LPS)-activated microglial BV-2 cells showed that compounds 1, 2, and 5 inhibited the production of nitric oxide (NO) with IC₅₀ values of 37.8, 7.1, and 42.5 μM, respectively. Compound 2 also inhibited NO production in LPS-stimulated RAW264.7 murine macrophages with an IC₅₀ value of 27.0 μM. Moreover, these inhibitory effects correlated with the suppressive effect of compound 2 on inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression in LPS-stimulated RAW264.7 and BV2 cells. In addition, compounds 2 and 5 significantly inhibited the activity of protein tyrosine phosphatase 1B (PTP1B) with the same IC₅₀ value (8.2 μM).     

Oleanolic acid analogs as NO,TNF-α and IL-1β inhibitors: Synthesis,biological evaluation and docking studies

A series of oleanolic acid analogs, characterized by structural modifications at position C-3 and C-28 of oleanane skeleton were synthesized and assessed for antiinflammatory potential towards lipopolysaccharide (LPS) induced nitric oxide (NO) production in macrophages. Results revealed that all the synthesized analogs of oleanolic acid inhibit NO production with an IC₅₀ of 2.66–41.7 μM as compared to the specific nitric oxide synthase (NOS) inhibitor, L-NAME (IC₅₀ = 69.21 and 73.18 μM on RAW 264.7 and J774A.1 cells, respectively) without affecting the cell viability when tested at their half maximal concentration. The most potent NO inhibitors (2, 8, 9 and 10) at a concentration of 20 μg/mL also demonstrated mild inhibition (27.9–51.9%) of LPS-induced tumor necrosis factor alpha (TNF-α) and weak inhibition (11.1–37.5%) towards interleukin 1-beta (IL-1β) production in both the cells. The present study paves a direction that analogs of oleanolic acid can be employed as a lead in the development of potent NO inhibitors. Molecular docking studies also showed that 10 (with top Goldscore docking pose 19.05) showed similar interaction as that of co-crystallized inhibitor and, thereby, helps to design the potent inhibitors of TNF-α.     

Design,synthesis and biological evaluation of heterocyclic azoles derivatives containing pyrazine moiety as potential telomerase inhibitors

Three series of novel heterocyclic azoles derivatives containing pyrazine (5a–5k, 8a–8k and 11a–11k) have been designed, synthesized, structurally determined, and their biological activities were evaluated as potential telomerase inhibitors. Among the oxadiazole derivatives, compound 5c showed the most potent biological activity against SW1116 cancer cell line (IC₅₀ = 2.46 μM against SW1116 and IC₅₀ = 3.55 μM for telomerase). Compound 8h performed the best in the thiadiazole derivatives (IC₅₀ = 0.78 μM against HEPG2 and IC₅₀ = 1.24 μM for telomerase), which was comparable to the positive control. While compound 11f showed the most potent biological activity (IC₅₀ = 4.12 μM against SW1116 and IC₅₀ = 15.03 μM for telomerase) among the triazole derivatives. Docking simulation by positioning compounds 5c, 8h and 11f into the telomerase structure active site was performed to explore the possible binding model. The results of apoptosis demonstrated that compound 8h possessed good antitumor activity against HEPG2 cancer cell line. Therefore, compound 8h with potent inhibitory activity in tumor growth inhibition may be a potential antitumor agent against HEPG2 cancer cell. Therefore, the introduction of oxadiazole, thiadiazole and triazole structures reinforced the combination of our compounds and the receptor, resulting in progress of bioactivity.     

Triterpenes from the roots of Lantana montevidensis with antiprotozoal activity

Bioassay guided fractionation of the roots of Lantana montevidensis (Verbenaceae) has resulted in the isolation and identification of three new triterpenoids; 13β-hydroxy-3-oxo-olean-11-en-28-oic acid (1), 12β,13β-dihydroxyolean-3-oxo-28-oic acid (2) and 12β,13β,22β-trihydroxyolean-3-oxo-28-oic acid (3) in addition to nine known compounds: oleanonic acid (4), oleanolic acid (5), 3β,25β-dihydroxy-olean-12-en-28-oic acid (6), lantadene A (7), 19α-hydroxy-3-oxo-olean-12-en-28-oic acid (8) pomolic acid (9), camaric acid (10) together with β-sitosterol (11) and β-sitosterol-3-O-β-d-glucoside (12). The structures of the isolated metabolites were elucidated based on comprehensive 1D and 2D NMR spectroscopic data as well as HR-ESI–MS. The extracts and the isolated metabolites were evaluated for their antiprotozoal and antimicrobial activities. Compound 2 showed antibacterial activity against Staphylococcus aureus and methicillin resistant S. aureus with IC₅₀ values against both organisms of 2.1 μM and compound 10 showed activity against same organisms with IC₅₀ values 8.74 and 8.09 μM, respectively, compared to the positive control ciprofloxacin (IC₅₀ = 0.3 μM against S. aureus and MRSA). Compounds 1, 4, 5, 6, and 10 showed moderate antileishmanial activity with IC₅₀ values ranging between (2.54–14.95 μM) and IC₉₀ values ranging between (11.90–19.47 μM), using pentamidine as a control (IC₅₀ values 2.09 ≥ 16.8 μM) and IC₉₀ values ranging between (4.72 ≥ 16.8 μM). These compounds also showed highly potent antitrypanosomal activity with IC₅₀ values ranging between (0.39–7.12 μM) and IC₉₀ values ranging between (1.91–10.51 μM), which are more efficient than the DFMO, the antitrypanosomal drug employed as positive control (IC₅₀ and IC₉₀values 11.82 and 30.82 μM).     

1-(4-Methane(amino)sulfonylphenyl)-3-(4-substituted-phenyl)-5-(4-trifluoromethylphenyl)-1H-2-pyrazolines/pyrazoles as potential anti-inflammatory agents

2-Pyrazolins 14a–l and pyrazoles 15a–l were designed as celecoxib analogs for the evaluation of their in vitro COX-1/COX-2 inhibitory activity and the in vivo anti-inflammatory activity. Compounds 14i, 15a, 15d and 15f were the most COX-2 selective derivatives (S.I. = 5.93, 6.08, 5.03 and 5.27 respectively) while the pyrazoline derivatives 14g and 14i exhibited the highest AI activity (ED₅₀ = 190.5 and 160.1 μmol/kg po, respectively).     

1,4-Dihydropyrazolo[4,3-d]imidazole phenyl derivatives: A novel type II Raf kinase inhibitors

The synthesis of a novel series of 1,4-dihydropyrazolo[4,3-d]imidazole phenyl derivatives 1a–b, 2a–v and their antiproliferative activities against A375P and WM3629 human melanoma cell line were described. Most compounds showed competitive antiproliferative activities to sorafenib, the reference standard. Among them, pyrazoloimidazole phenyl urea compounds 2a, 2d, 2g, 2i, 2t exhibited potent activities on WM3629 cell lines (IC₅₀ = 0.56–0.86 μM). Especially, 2t was found to be a potent and selective C-Raf inhibitor, showing a possibility as melanoma therapeutics.     

Daphnane-type diterpenes with inhibitory activities against human cancer cell lines from Daphne genkwa

Four new daphnane-type diterpenes, genkwadanes A–D (1–4), together with 19 known ones, were isolated from ethanol extract of the flower buds of Daphne genkwa. Their structures were determined on the basis of extensive spectroscopic data. Among them, daphnane-type diterpene with a 1,10-double bond (1) was isolated from this plant for the first time. The cytotoxicity of all compounds 1–23 against the 10 selected human cancer cell lines was assayed. A number of compounds exhibited significant activities against the 10 cancer cell lines (IC₅₀ < 9.56 μM). and most interestingly, all the compounds revealed preferred cytotoxicities on the HT-1080 cell line and displayed much stronger inhibitory activities (IC₅₀ < 29.94 μM) compared with positive control 5-fluorouracil (IC₅₀ = 35.62 μM), particularly, compounds 9–11, 13, 16 and 19 exhibited the strongest cytotoxicity activities against the HT-1080 cell line (IC₅₀ < 0.1 μM).     

Neolignans from Piper kadsura and their anti-neuroinflammatory activity

Bioassay-guided column chromatographic separation of the methanolic extract of dried aerial parts of Piper kadsura (Piperaceae) led to the isolation of a new neolignan, piperkadsin C (1), together with eight known neolignans (2–9). The structures of the isolated compounds were elucidated by combined spectroscopic methods. The anti-neuroinflammatory activities of these compounds were evaluated by assessing nitric oxide (NO) production in LPS-activated BV-2 cells, a microglia cell line. Piperkadsin C (1) and futoquinol (2) potently inhibited NO production with an IC₅₀ value of 14.6 and 16.8 μM in microglia cells, respectively. Compounds 3, 4, 5, 8, and 9 also exhibited moderate inhibition of NO production in BV-2 cells.     

The application of Heck reaction in the synthesis of guaianolide sesquiterpene lactones derivatives selectively inhibiting resistant acute leukemic cells

A series of guaianolide-type sesquiterpene lactones derivatives with arylation of α-methylene-γ-lactone moiety was synthesized using Heck reactions, and was evaluated for their activities against acute myelogenous leukemia (AML) cell line HL-60 and doxorubicin-resistant cell line HL-60/A. Although all compounds were significantly less active against HL-60 than the parent molecules, surprisingly, compounds 3a, 4c–4e, 5e, and 8d exhibited high potency against doxorubicin-resistant cell line HL-60/A (IC₅₀ = 6.2–19 μM), and their activities against HL-60/A were comparable to that of their parent molecules. In view of their novel activities against HL-60/A, compound 5e with inhibitory activity against HL-60/A (IC₅₀ = 6.2 ± 0.5 μM) was selected for study its preliminary mechanism. The result reveals that compound 5e can obviously induce apoptosis.     

Triterpenoid saponins from Clematis chinensis and their inhibitory activities on NO production

Four new triterpenoid saponins, clematochinenoside H–K (1–4), and five known structures (5–9), were isolated from the roots and rhizomes of Clematis chinensis. Their structures were elucidated on the basis of spectroscopic evidence and hydrolysis products. All isolates were evaluated for inhibitory effects against nitric oxide (NO) production in LPS-induced RAW 246.7 macrophages. Monodesmosidic saponins (1–3, 5, and 6) with a free carboxylic acid function at C-28 exhibited potent inhibitory activities with IC₅₀ values in the range of 12.9–32.3 μM, where as bisdesmosidic saponin (4, and 7–9) showed modest inhibitory effects with the inhibition ratios (%) from 39.9 to 59.0 at 50 μM. In addition, the hydroxyl group at C-21 showed negative effect on the NO production inhibitory activity.     

Acylated iridoid glycosides and acylated rhamnopyranoses from Gmelina arborea flowers

Nine acylated iridoid glycosides (1–9), five acylated rhamnopyranoses (10–14) and verbascoside (15) were isolated from Gmelina arborea flowers, including 5 new compounds (1, 2, and 10–12). The cytoprotective activity of 11 selected compounds (1–8, 10, 11, and 15) against CCl₄-induced cytotoxicity on liver was determined. Compounds 1, 2, 4, 7, 8 and 15 displayed hepatoprotective activity. 6-O-α-l-(2″, 3″-di-O-trans-p-hydroxycinnamoyl)rhamnopyranosylcatalpol (2) exhibited the most potent cytoprotective effect with an EC₅₀ value of 42.5 μM (SI = 19.3) compared with biphenyldimethylesterate (DDB, EC₅₀ = 277.3 μM, SI = 9.8) and bicylo-ethanol (EC₅₀ = 279.2 μM, SI = 12.2). Among the acylated iridoid glycosides, the compounds (2 and 8) containing phenolic hydroxy groups were more active than were those lacking them.     

Semisynthetic studies identify mitochondria poisons from botanical dietary supplements—Geranyloxycoumarins from Aegle marmelos

Bioassay-guided isolation and subsequent structure elucidation of a Bael tree Aegle marmelos lipid extract yielded two unstable acylated geranyloxycoumarin mixtures (1–2), six geranyloxycoumarins (3–8), (+)-9′-isovaleroxylariciresinol (9), and dehydromarmeline (10). In a T47D cell-based reporter assay, 1 and 2 potently inhibited hypoxia-induced HIF-1 activation (IC₅₀ values 0.18 and 1.10 μg mL^?1, respectively). Insufficient material and chemical instability prevented full delineation of the fatty acyl side chain olefin substitution patterns in 1 and 2. Therefore, five fatty acyl geranyloxycoumarin ester derivatives (11–15) were prepared from marmin (3) and commercial fatty acyl chlorides by semisynthesis. The unsaturated C-6′ linoleic acid ester derivative 14 that was structurally most similar to 1 and 2, inhibited HIF-1 activation with comparable potency (IC₅₀ 0.92 μM). The octanoyl (11) and undecanoyl (12) ester derivatives also suppressed HIF-1 activation (IC₅₀ values 3.1 and 0.87 μM, respectively). Mechanistic studies revealed that these geranyloxycoumarin derivatives disrupt mitochondrial respiration, primarily at complex I. Thus, these compounds may inhibit HIF-1 activation by suppressing mitochondria-mediated hypoxic signaling. One surprising observation was that, while less potent, the purported cancer chemopreventive agent auraptene (8) was found to act as a mitochondrial poison that disrupts HIF-1 signaling in tumors.     

[RuIII(medtra)(H2O)] (medtra = N-methylethylenediaminetriacetate) complex – A highly efficient NO inhibitor with low toxicity

Stopped-flow kinetic measurements were used to compare the reactivities of [Ru(medtra)(H₂O)] (medtra³⁻ = N-methylethylenediaminetriacetate) (1) and [Ru(hedtra)(H₂O)] (2) (hedtra³⁻ = N-hydroxyethylethylenediaminetriacetate) with NO in aqueous solution at 15 °C, pH 7.2 (phosphate buffer). The measured second-order rate constants (3 × 10³ and 6 × 10⁴ M⁻¹ s⁻¹ for 1 and 2, respectively) are three to four order of magnitudes lower than that for the reaction between [Ru^III(edta)(H₂O)]⁻ (3) with NO. However, NO scavenging studies of complexes 1–3, conducted by measuring the difference in nitrite production between treated and untreated murine macrophage cells, revealed that despite being less kinetically reactive toward NO, the [Ru(medtra)(H₂O)] complex exhibited the highest NO scavenging ability and lowest toxicity of compounds 1–3.