Metal-assisted preparation of the alkenyl ketone and carbonyl complexes from 1-alkyne and H2O: C–C triple bond cleavage of terminal alkyne

Reactions of Cp*RhCl₂(PPh₃) (1) with 1-alkyne and H₂O in the presence of KPF₆ generated alkenyl ketone complexes [Cp*Rh(CRCHCOCH₂R)(PPh₃)](PF₆) (2) (R = Ph (a), C₆H₄−p-Me (b), C₆H₄-p-COOMe (c), C₆H₄-p-NO₂ (d)). A similar complex [Cp*Rh(CPhCHCOCH₂Ph)(PMePh₂)](PF₆) (2e) was obtained by use of Cp*RhCl₂(PMePh₂). It was revealed by X-ray analyses of 2b, 2c and 2e that the complexes 2 consist of the five-membered ring structures bound by the carbon and oxygen atoms of the alkenyl ketone group. Similar reactions of Cp*IrCl₂(PPh₃) (6) or (C₆Me₆)RuCl₂(PPh₃) (7) proceeded with a cleavage of C–C triple bond of 1-alkyne without formation of an alkenyl ketone complex, affording the corresponding carbonyl complexes, [Cp*IrCl(PPh₃)(CO)](PF₆) (8) or [(C₆Me₆)RuCl(PPh₃)(CO)](PF₆) (9). The diphosphine complexes [(Cp*MCl₂)₂{μ-diphos}] (4: M = Rh, diphos = dppm,; 12a: M = Ir, diphos = dppm; 12b: M = Ir, diphos = dppb) gave a Cl-bridged rhodium complex [{Cp*Rh(μ-Cl)}₂{μ-dppm}](PF₆)₂ (5), mono-carbonyl or dicarbonyl iridium complexes,[(Cp*IrCl₂){μ-dppm}{Cp*IrCl(CO)}](PF₆)(13a) or [{Cp*IrCl(CO)}₂{μ-dppb}](PF₆)₂ (14b), respectively.     

Amphipathic short helix-stabilized peptides with cell-membrane penetrating ability

We synthesized four types of arginine-based amphipathic nonapeptides, including two homochiral peptides, R-(l-Arg-l-Arg-Aib)₃-NH₂ (R = 6-FAM-β-Ala: FAM-1; R = Ac: Ac-1) and R-(d-Arg-d-Arg-Aib)₃-NH₂ (R = 6-FAM-β-Ala: ent-FAM-1; R = Ac: ent-Ac-1); a heterochiral peptide, R-(l-Arg-d-Arg-Aib)₃-NH₂ (R = 6-FAM-β-Ala: FAM-2; R = Ac: Ac-2); and a racemic mixture of diastereomeric peptides, R-(rac-Arg-rac-Arg-Aib)₃-NH₂ (R = 6-FAM-β-Ala: FAM-3; R = Ac: Ac-3), and then investigated the relationship between their secondary structures and their ability to pass through cell membranes. Peptides 1 and ent-1 formed stable one-handed α-helical structures and were more effective at penetrating HeLa cells than the non-helical peptides 2 and 3.     

Structure-based virtual screening of Src kinase inhibitors

Src is an important target in multiple processes associated with tumor growth and development, including proliferation, neovascularization, and metastasis. In this study, hit identification was performed by virtual screening of commercial and in-house compound libraries. Docking studies for the hits were performed, and scoring functions were used to evaluate the docking results and to rank ligand-binding affinities. Subsequently, hit optimization for potent and selective candidate Src inhibitors was performed through focused library design and docking analyses. Consequently, we report that a novel compound ‘43’ with an IC₅₀ value of 89 nM, representing (S)-N-(4-(5-chlorobenzo[d][1,3]dioxol-4-ylamino)-7-(2-methoxyethoxy)quinazolin-6-yl)pyrrolidine-2-carboxamide, is highly selective for Src in comparison to EGFR (IC₅₀ ratio > 80-fold) and VEGFR-2 (IC₅₀ ratio > 110-fold). Compound 43 exerted anti-proliferative effects on Src-expressing PC3 human prostate cancer and A431 human epidermoid carcinoma cells, with calculated IC₅₀ values of 1.52 and 0.78 μM, respectively. Moreover, compound 43 (0.1 μM) suppressed the phosphorylation of extracellular signal-regulated kinases and p90 ribosomal S6 kinase, downstream molecules of Src, in a time-dependent manner, in both PC3 and A431 cell lines. The docking structure of compound 43 with Src disclosed that the chlorobenzodioxole moiety and pyrrolidine ring of C-6 quinazoline appeared to fit tightly into the hydrophobic pocket of Src. Additionally, the pyrrolidine NH forms a hydrogen bond with the carboxyl group of Asp348. These results confirm the successful application of virtual screening studies in the lead discovery process, and suggest that our novel compound 43 can be an effective Src inhibitor candidate for further lead optimization.     

Synthesis,characterization, structure and luminescence studies of dinuclear gold(I) alkynyls of bis(diphenylphosphino)alkyl- and aryl-amines

A series of alkynylgold(I) bis(diphenylphosphino)alkyl- and aryl-amine complexes, [{Ph₂PN(R)PPh₂}Au₂(CCR′)₂] [R = ⁿPr, R′ = Ph (1), C₆H₄OMe-p (2), C₆H₄Me-p (3), C₆H₄Cl-p (4); R = C₆H₄OMe-p, R′ = Ph (5)], has been synthesized. The X-ray crystal structures of 1 and 2 revealed the presence of short intramolecular Au⋯Au contacts with the distances of 2.8404(8) and 3.0708(7) Å. The luminescence behavior of the complexes were studied.     

Prenylated C6–C3 compounds from the roots of Illicium henryi

Eleven prenylated C₆–C₃ compounds, illihenryifunones A, B (1, 2), illihenryifunol A (3), illihenryipyranol A (4), illihenryiones A−G (5–11), and three known prenylated C₆–C₃ compounds (12–14), were isolated from the roots of Illicium henryi. Structures of 1–11 were elucidated by spectroscopic methods including NMR, HRESIMS, and CD. The absolute configuration of the 11,12-diol moiety in 5 was determined by observing its induced circular dichroism after addition of Mo₂(OAc)₄ in DMSO. The absolute configuration of C-11 in 4 was determined as S based on the Rh₂(OCOCF₃)₄-induced CD data; the absolute configuration of 3 was determined as R by comparison of its experimental and calculated electronic circular dichroism (ECD). The antioxidant activities of compounds 1–14 were also evaluated. Compound 4 exhibited strong antioxidant activity with an IC₅₀ value of 2.97 ± 1.30 μM, whereas compounds 3 and 8 showed antioxidant activities with IC₅₀ values of 44.36 ± 0.30 and 48.00 ± 2.01 μM, respectively.     

Aspernolides F and G,new butyrolactones from the endophytic fungus Aspergillus terreus

Two new butyrolactones: aspernolides F (6) and G (7), together with three stigmasterol derivatives: (22E,24R)-stigmasta-5,7,22-trien-3-β-ol (1), stigmast-4-ene-3-one (2), and stigmasta-4,6,8(14), 22-tetraen-3-one (3), two meroterpenoids: terretonin A (4) and terretonin (5), and a butyrolactone derivative: butyrolactone VI (8) have been isolated from the endophytic fungus Aspergillus terreus isolated from the roots of Carthamus lanatus (Asteraceae). Their structures were determined by spectroscopic means (1D, 2D NMR, and HRESIMS), as well as optical rotation measurement and comparison with literature data. The isolated compounds were evaluated for their anti-microbial, anti-malarial, anti-leishmanial, and cytotoxic activities. Compound 1 displayed a potent activity against MRSA and C. neoformans with IC₅₀ values of 0.96 μg/mL and 4.38 μg/mL, respectively compared to ciprofloxacin (IC₅₀ 0.07 μg/mL) and amphotericin B (IC₅₀ 0.34 μg/mL), respectively. While, 6 showed good activity against C. neoformans (IC₅₀ 5.19 μg/mL) and mild activity against MRSA (IC₅₀ 6.39 μg/mL). Moreover, 1 and 2 exhibited very good anti-leishmanial activity towards L. donovani with IC₅₀ values of 4.61 and 6.31 μg/mL, respectively and IC₉₀ values of 6.02 and 16.71 μg/mL, respectively.     

New 30-norlupane derivatives through chemical-microbial semi-synthesis of betulinic acid and their neuroprotective effect

In this study, seven 30-norlupane derivatives (2–8) was obtained from the chemical oxidation of betulinic acid followed by biotransformation via Bacillus megaterium CGMCC 1.1741. And metabolites 2–4 and 6–8 were newly identified products. In the first step, betulinic acid was chemically oxidized to platanic acid (1). Following the chemical oxidation, B. megaterium catalyzed the hydroxylation at C-7, C-11, C-15 and C-23 of platanic acid (1) as well as the oxidation of C-3 hydroxyl group. Compared to the labor-intensive isolation from natural plants, this chemical-microbial semi-synthesis is more capable to provide increased structural diversity of oxygenated 30-norlupane. Finally, the potential neuroprotective effect of the derivatives was assessed on neuron-like PC12 cells induced by cobalt chloride (CoCl₂). Metabolite 6 showed a potent neuroprotective activity.     

Expanding the 4,4′-bipyridine ligand: Structural variation in {M(pytpy)2}2+ complexes (pytpy = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine,M = Fe,Ni, Ru) and assembly of the hydrogen-bonded,one-dimensional polymer {[Ru(pytpy)(Hpytpy)]}n3n+

The solid state structures of [Ni(1)₂][NO₃]₂ · 2MeOH · 2H₂O, [Fe(1)₂][ClO₄]₂ · 2MeOH · 0.5H₂O, [Ru(1)₂][PF₆]₂ and [Ru(1)₂][PF₆][NO₃] (1 = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine) are presented and the structural variation observed for the {M(1)₂}²⁺ unit is discussed. Protonation of the pendant pyridine group in [Ru(1)₂]²⁺ leads to the formation of a hydrogen-bonded, one-dimensional polymer [{Ru(1)(H1)}_n]³ⁿ⁺ exemplifed by the solid-state structure of [{Ru(1)(H1)}{Fe(NCS)₆} · 1.25H₂O]_n.     

3-Anhydro-6-hydroxy-ophiobolin A,a new sesterterpene inhibiting the growth of methicillin-resistant Staphylococcus aureus and inducing the cell death by apoptosis on K562, from the phytopathogenic fungus Bipolaris oryzae

A new ophiobolin derivative, 3-anhydro-6-hydroxy-ophiobolin A (1), as well as two known ophiobolin derivatives 3-anhydro-ophiobolin A (2) and 3-anhydro-6-epi-ophiobolin A (3) were isolated from the PDB culture of a phytopathogenic fungus Bipolaris oryzae. The structure of 1 was elucidated through 2D NMR and other spectroscopic techniques. Compound 1 exhibited strong antimicrobial activity against Bacille Calmette–Guerin, Bacillus subtilis, Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus with MIC value of 12.5 μg/mL, and potent antiproliferative activity against cell lines HepG2 and K562 with IC₅₀ of 6.49 μM and 4.06 μM, respectively. Further studies on the cytotoxicity of compound 1 against K562 cells demonstrated that it induced apoptosis, observed by flow cytometric method. Preliminary structure–activity relationships of these ophiobolins and the mechanism of apoptosis induced by 1 were analyzed.     

Design and synthesis of 1-(benzothiazol-5-yl)-1H-1,2,4-triazol-5-ones as protoporphyrinogen oxidase inhibitors

Protoporphyrinogen oxidase (PPO, E.C. 1.3.3.4) is the action target for several structurally diverse herbicides. A series of novel 4-(difluoromethyl)-1-(6-halo-2-substituted-benzothiazol-5-yl)-3-methyl-1H-1,2,4-triazol-5(4H)-ones 2a–z were designed and synthesized via the ring-closure of two ortho-substituents. The in vitro bioassay results indicated that the 26 newly synthesized compounds exhibited good PPO inhibition effects with K_i values ranging from 0.06 to 17.79 μM. Compound 2e, ethyl 2-{[5-(4-(difluoromethyl)-3-methyl-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl)-6-fluorobenzo-thiazol-2-yl]thio}acetate, was the most potent inhibitor with K_i value of 0.06 μM against mtPPO, comparable to (K_i = 0.03 μM) sulfentrazone. Further green house assays showed that compound 2f (K_i = 0.24 μM, mtPPO), ethyl 2-{[5-(4-(difluoromethyl)-3-methyl-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl)-6-fluorobenzothiazol-2-yl]thio}propanoate, showed the most promising post-emergence herbicidal activity with broad spectrum even at concentrations as low as 37.5 g ai/ha. Soybean exhibited tolerance to compound 2f at the dosages of 150 g ai/ha, whereas they are susceptible to sulfentrazone even at 75 g ai/ha. Thus, compound 2f might be a potential candidate as a new herbicide for soybean fields.     

Rheediinosides A and B,two antiproliferative and antioxidant triterpene saponins from Entada rheedii

Two triterpenoid saponins have been isolated from the seed kernels of Entada rheedii. Their structures have been established using 1D- and 2D-NMR and mass spectrometry as 3-O-β-d-xylopyranosyl-(1 → 3)-O-α-l-arabinopyranosyl-(1 → 6)-2-acetylamino-2-deoxy-β-d-glucopyranosylentagenic acid 28-O-β-apiofuranosyl-(1 → 3)-β-d-xylopyranosyl-(1 → 2)-β-d-glucopyranoside (Rheediinoside A, 1) and 3-O-β-d-glucopyranosyl-(1 → 3)-O-[β-d-xylopyranosyl-(1 → 3)-α-l-arabinopyranosyl-(1 → 6)]-2-acetylamino-2-deoxy-β-d-glucopyranosylentagenic acid 28-O-β-apiofuranosyl-(1 → 3)-β-d-xylopyranosyl-(1 → 2)-β-d-glucopyranoside (Rheediinoside B, 2). Compounds 1 and 2 were tested for their antiproliferative activity against T98G, A431, PC3 and B16-F1 cell lines, and further for their antioxidant properties. Moderate cytotoxic potency and antioxidant properties were found for these compounds whereas Rheediinoside B was in all assays more active than Rheediinoside A.     

Synthesis,structures and reactivity of N-donor-functionalised Cu(I) aryloxides

The preparation and characterisation of the Cu(I) aryloxides [Cu₁₆(3-pyO)₁₆(dppm)₈] (1), [{Cu₂(2-pyO)₂(dppm)}₂] (2) and [{Cu₃(μ₃-6-OQ)₂(dppm)₃}{(6-HOQ)₂(μ-6-OQ)}] (3) (dppm = 1,2-bis-diphenylphosphinomethane, 6-HOQ = 6-hydroxyquinoline, py = pyridine) are described. A first attempt to employ organic anhydrides in insertion reactions with Cu(I) aryloxides was made producing the one-dimensional coordination polymer 1/_∞[Cu₃(3-pyO)(CO₂C₂H₄Boc)(dppm⁻)(dppm)]_∞ (4) (Boc = tert-butoxycarbonyl).     

Coumarin-thiazole and -oxadiazole derivatives: Synthesis,bioactivity and docking studies for aldose/aldehyde reductase inhibitors

In continuation of our previous efforts directed towards the development of potent and selective inhibitors of aldose reductase (ALR2), and to control the diabetes mellitus (DM), a chronic metabolic disease, we synthesized novel coumarin-thiazole 6(a–o) and coumarin-oxadiazole 11(a–h) hybrids and screened for their inhibitory activity against aldose reductase (ALR2), for the selectivity against aldehyde reductase (ALR1). Compounds were also screened against ALR1. Among the newly designed compounds, 6c, 11d, and 11g were selective inhibitors of ALR2. Whereas, (E)-3-(2-(2-(2-bromobenzylidene)hydrazinyl)thiazol-4-yl)-2H-chromen-2-one 6c yielded the lowest IC₅₀ value of 0.16 ± 0.06 μM for ALR2. Moreover, compounds (E)-3-(2-(2-benzylidenehydrazinyl)thiazol-4-yl)-2H-chromen-2-one (6a; IC₅₀ = 2.94 ± 1.23 μM for ARL1 and 0.12 ± 0.05 μM for ARL2) and (E)-3-(2-(2-(1-(4-bromophenyl)ethylidene)hydrazinyl)thiazol-4-yl)-2H-chromen-2-one (6e; IC₅₀ = 1.71 ± 0.01 μM for ARL1 and 0.11 ± 0.001 μM for ARL2) were confirmed as dual inhibitors. Furthermore, compounds 6i, 6k, 6m, and 11b were found to be selective inhibitors for ALR1, among which (E)-3-(2-(2-((2-amino-4-chlorophenyl)(phenyl)methylene)hydrazinyl)thiazol-4-yl)-2H-chromen-2-one (6m) was most potent (IC₅₀ = 0.459 ± 0.001 μM). Docking studies performed using X-ray structures of ALR1 and ALR2 with the given synthesized inhibitors showed that coumarinyl thiazole series lacks the carboxylate function that could interact with the anionic binding site being a common ALR1/ALR2 inhibitors trait. Molecular docking study with dual inhibitor 6e also suggested plausible binding modes for the ALR1 and ALR2 enzymes. Hence, the results of this study revealed that coumarinyl thiazole and oxadiazole derivatives could act as potential ALR1/ALR2 inhibitors.     

Chemical modifications by ionic liquid-inspired cations improve the activity and the stability of formate dehydrogenase in [MMIm][Me2PO4]

The formate dehydrogenase (FDH, EC: 1.2. 1.2) from Candida boidinii was found to be inactivated and unstable in the presence of high concentration (>50%) of the water soluble dimethylimidazolium dimethyl phosphate ([MMIm][Me₂PO₄]) ionic liquid. In order to circumvent this problem, the enzyme was chemically modified by cations usually present in ionic liquids: cholinium (1), hydroxyethyl-methylimidazolium (2) and hydroxypropyl-methylimidazolium (3) cations were activated with carbonyldiimidazole before being reacted with the FDH leading to a heterogeneous population of 6–7 biocatalysts. FDH modified by (1) or (3) led to 3–9 modifications while FDH modified by (2) led to 6 proteins presenting 7–12 grafted cations. Specific activity of the modified enzymes was decreased by a 2.5–3-fold factor (0.10–0.15 μmol min⁻¹ mg⁻¹) compared to the non-modified FDH (0.33 μmol min⁻¹ mg⁻¹) when assayed in carbonate buffer (pH 9.7, 25 mM). After modification, the FDH still present 0.06 μmol min⁻¹ mg⁻¹ in 70% [MMIm][Me₂PO₄] (v:v) (30–45% of their activity in aqueous buffer) while the native enzyme is inactive at this ionic liquid concentration, proving the efficiency of this strategy. The half-life of the modified enzyme is also increased by a 5-fold factor after modification by (1) (t_1/2 of 9 days) and by a 3-fold factor after modification by (2) or (3) (t_1/2 of 6 and 5 days respectively) in aqueous solution. When stored in 37.5% [MMIm][Me₂PO₄] (v:v), both modified and unmodified FDH have an increased half-life (t_1/2 of 6–9 days). This grafting strategy is found to be good methods to mimic and study the stabilizing effect of ionic liquids on enzymes.     

Synthesis of novel chromenones linked to 1,2,3-triazole ring system: Investigation of biological activities against Alzheimer’s disease

In this work, novel chromenones linked to 1,2,3-triazole ring system were synthesized and evaluated for their anti-ChE activity. Among them, N-((1-(2-chlorobenzyl)-1H-1,2,3-triazol-5-yl)methyl)-8-methoxy-2-oxo-2H-chromene-3-carboxamide (6m) showed good anti-acetylcholinesterase activity (IC₅₀ = 15.42 μM). Also, compound 6m demonstrated neuroprotective effect against H₂O₂-induced cell death in PC12 neurons, however, it showed no beta-secretase (BACE1) inhibitory activity. Docking and kinetic studies separately confirmed dual binding activity of compound 6m since it targeted both the catalytic active site (CAS) and the peripheral anionic site (PAS) of AChE.     

In vitro cytotoxic activity of isolated acridones alkaloids from Zanthoxylum leprieurii Guill. et Perr

Chemical investigation of the roots and fruits of Zanthoxylum leprieurii Guill. et Perr. led to the isolation of three new alkaloids including two acridone derivatives, 3-hydroxy-1,4-dimethoxy-10-methyl-9-acridone (2) and 3-hydroxy-1,2-dimethoxy-10-methyl-9-acridone (3) named helebelicine A and B, respectively, and one secobenzo[c]phenantridine, 10-O-demethyl-12-O-methylarnottianamide (10), together with thirteen other compounds. The structures of compounds 2, 3 and 10 as well as those of the known compounds were elucidated by using spectroscopic methods and by comparison with reported data. The brine-shrimp (artemia salina) lethality bioassay of the chloroform extract of the fruits showed modest cytotoxicity with LD₅₀ at 13.1 μg/mL. Isolated compounds 1, 4–6 were found to be moderately active against lung carcinoma cells (A549), colorectal adenocarcinoma cells (DLD-1) and normal cells (WS1) with IC₅₀ values ranging from 27 to 77 μM. In contrast to the positive control etoposide used, the cytotoxicity of the most active compound 4 was found to be selective against cancer cells in comparison to normal cells WS1 with IC₅₀ of 51 ± 8 μM and 4.3 ± 0.4 μM, respectively.     

New pentafluorophenyl complexes with phosphine-amide ligands

A series of nickel(II) and palladium(II) complexes containing one or two pentafluorophenyl ligands and the phosphino-amides o-Ph₂PC₆H₄CONHR [R = ⁱPr (a), Ph (b)] displaying different coordination modes have been synthesised. The chelating ability of these ligands and the influence of both coligands and the metal centre in their potential hemilabile behaviour have been explored. The crystal structure of (b) has been determined and reveals N–H⋯O intermolecular hydrogen bonding. Bis-pentafluorophenyl derivatives [M(C₆F₅)₂(o-Ph₂PC₆H₄CO-NHR)] [M = Ni; R = ⁱPr (1a); R = Ph (1b); M = Pd; R = ⁱPr (2a); R = Ph (2b)] in which (a) and (b) act as rigid P, O-chelating ligands were readily prepared from the labile precursors cis-[M(C₆F₅)₂(PhCN)₂]. X-ray structures of (1a), (1b) and (2a) have been established, allowing an interesting comparative structural discussion. Dinuclear [{Pd(C₆F₅)(tht)(μ-Cl)}₂] reacted with (a) and (b) yielding the monopentafluorophenyl complexes [Pd(C₆F₅)Cl{PPh₂(C₆H₄–CONH–R)}] (R = ⁱPr (3a), Ph (3b)) that showed a P, O-chelating behaviour of the ligands, confirmed by the crystal structure determination of (3a). New cationic palladium(II) complexes in which (a) and (b) behave as P-monodentate ligands have been synthesised by reacting them with [{Pd(C₆F₅)(tht)(μ-Cl)}₂], stoichiometric Ag(O₃SCF₃) and external chelating reagents such as cod [Pd(C₆F₅)(cod){PPh₂(C₆H₄-CONH-R)}](O₃SCF₃)(R = ⁱPr (4a), Ph (4b)) and 2,2′-bipy [Pd(C₆F₅)(bipy){PPh₂(C₆H₄-CONH-R)}](O₃SCF₃) (R = ⁱPr (5a), Ph (5b)). When chloride abstraction in [{Pd(C₆F₅)(tht)(μ-Cl)}₂] is promoted by means of a dithioanionic salt as dimethyl dithiophospate in the presence of (a) or (b), the corresponding neutral complexes [Pd(C₆F₅){S(S)P(OMe)₂}{PPh₂(C₆H₄-CONH-R)}] (R = ⁱPr (6a), Ph (6b)) were obtained.     

Novel oxazolinyl derivatives of pregna-5,17(20)-diene as 17α-hydroxylase/17,20-lyase (CYP17A1) inhibitors

New oxazolinyl derivatives of [17(20)E]-pregna-5,17(20)-diene: 2′-{[(E)-3β-hydroxyandrost-5-en-17-ylidene]methyl}-4′,5′-dihydro-1′,3′-oxazole 1 and 2′-{[(E)-3β-hydroxyandrost-5-en-17-ylidene]methyl}-4′,4′-dimethyl-4′,5′-dihydro-1′,3′-oxazole 2 were evaluated as potential CYP17A1 inhibitors in comparison with 17-(pyridin-3-yl)androsta-5,16-dien-3β-ol 3 (abiraterone). Differential absorption spectra of human recombinant CYP17A1 in the presence of compound 1 (λ_max = 422 nm, λ_min = 386 nm) and compound 2 (λ_max = 416 nm) indicated significant differences in enzyme/inhibitors complexes. CYP17A1 activity was measured using electrochemical methods. Inhibitory activity of compound 1 was comparable with abiraterone 3 (IC₅₀ = 0.9 ± 0.1 μM, and IC₅₀ = 1.3 ± 0.1 μM, for compounds 1 and 3, respectively), while compound 2 was found to be weaker inhibitor (IC₅₀ = 13 ± 1 μM). Docking of aforementioned compounds to CYP17A1 revealed that steroid fragments of compound 1 and abiraterone 3 occupied close positions; oxazoline cycle of compound 1 was coordinated with heme iron similarly to pyridine cycle of abiraterone 3. Configuration of substituents at 17(20) double bond in preferred docked position corresponded to Z-isomers of compounds 1 and 2. Presence of 4′-substituents in oxazoline ring of compound 2 prevents coordination of oxazoline nitrogen with heme iron and worsens its docking score in comparison with compound 1. These data indicate that oxazolinyl derivative of [17(20)E]-pregna-5,17(20)-diene 1 (rather than 4′,4′-dimethyl derivative 2) may be considered as potential CYP17A1 inhibitor and template for development of new compounds affecting growth and proliferation of prostate cancer cells.     

Constituents of Nelumbo nucifera leaves and their antimalarial and antifungal activity

From the leaves of Nelumbo nucifera (an aquatic plant), one new compound, 24(R)-ethylcholest-6-ene-5α-ol-3-O-β-d-glucopyranoside (1), along with 11 known metabolites (2–12), were isolated and identified by spectroscopic methods including 1D- and 2D NMR. Antifungal activity for (R)-roemerine (3) (IC₅₀/MIC = 4.5/10 μg/mL against Candida albicans) and antimalarial activity for (R)-roemerine (3) and N-methylasimilobine (5) (IC₅₀ = 0.2 and 4.8 μg/mL for the D6 clone, respectively, and 0.4 and 4.8 μg/mL for the W2 clone, respectively) was observed. None of the compounds were cytotoxic to Vero cells up to a concentration of 23.8 μg/mL. NMR data for 10-eicosanol (7) and 7,11,15-trimethyl-2-hexadecanone (10) are presented for the first time. An analysis of the structure–activity relationship shows that the substituents in position C-1 and C-2 of aporphine alkaloids are crucial for the antimalarial activity.     

Synthesis and initial in vitro biological evaluation of two new zinc-chelating compounds: Comparison with TPEN and PAC-1

The lipophilic, cell-penetrating zinc chelator N,N,N′,N′,-tetrakis(2-pyridylmethyl) ethylenediamine (TPEN, 1) and the zinc chelating procaspase-activating compound PAC-1 (2) both have been reported to induce apoptosis in various cell types. The relationship between apoptosis-inducing ability and zinc affinity (K_d), have been investigated with two new model compounds, ZnA-DPA (3) and ZnA-Pyr (4), and compared to that of TPEN and PAC-1. The zinc-chelating o-hydroxybenzylidene moiety in PAC-1 was replaced with a 2,2′-dipicoylamine (DPA) unit (ZnA-DPA, 3) and a 4-pyridoxyl unit (ZnA-Pyr, 4), rendering an order of zinc affinity TPEN > ZnA-Pyr > ZnA-DPA > PAC-1. The compounds were incubated with the rat pheochromocytoma cell line PC12 and cell death was measured in combination with ZnSO₄, a caspase-3 inhibitor, or a ROS scavenger. The model compounds ZnA-DPA (3) and ZnA-Pyr (4) induced cell death at higher concentrations as compared to PAC-1 and TPEN, reflecting differences in lipophilicity and thereby cell-penetrating ability. Addition of ZnSO₄ reduced cell death induced by ZnA-Pyr (4) more than for ZnA-DPA (3). The ability to induce cell death could be reversed for all compounds using a caspase-3-inhibitor, and most so for TPEN (1) and ZnA-Pyr (4). Reactive oxygen species (ROS), as monitored using dihydro-rhodamine (DHR), were involved in cell death induced by all compounds. These results indicate that the Zn-chelators ZnA-DPA (3) and ZnA-Pyr (4) exercise their apoptosis-inducing effect by mechanisms similar to TPEN (1) and PAC-1 (2), by chelation of zinc, caspase-3 activation, and ROS production.