Skimmianine and related furoquinolines function as antagonists of 5-hydroxytryptamine receptors in animals

Skimmianine attenuates liver ischemia/reperfusion injury by regulating PI3K-AKT signaling pathway-mediated inflammation, apoptosis and oxidative stress

Liver ischemia/reperfusion (I/R) injury is a common injury after liver transplantation and hepatectomy. Skimmianine (Ski) has antibacterial, antiviral pharmacological effects. However, it is not clear whether Ski has a protective effect against liver I/R injury. In the present study, we established a mouse liver I/R model and an AML12 cell hypoxia-reoxygenation (H/R) model, both pretreated with different concentrations of Ski. Serum transaminase levels, necrotic liver area, cell viability, inflammatory factors, oxidative stress and apoptosis-related levels were measured to assess the protective effect of Ski against liver I/R injury. Western blotting was used to detect apoptosis-related proteins and PI3K-AKT pathway-related proteins. Mice and cells were also treated with PI3K inhibitor LY294002 to assess changes in indicators of liver injury. The results showed that Ski significantly reduced transaminase levels, liver necrosis area, oxidative stress, and apoptosis levels in mice with I/R. Ski also inhibited cell injury and apoptosis after H/R. Moreover, Ski activated phosphorylation of PI3K-AKT pathway-related proteins after liver I/R and cell H/R. Importantly, the PI3K inhibitor LY294002 effectively reversed the alleviation of I/R injury caused by Ski. These results confirm that Ski exerts a protective effect against liver I/R injury through activation of the PI3K-AKT pathway.

Furoquinoline and bisindole alkaloids from the roots of Teclea nobilis and their in-silico molecular docking analysis

Teclea nobilis is a medicinal plant widely used to treat oral pathogens, gonorrhea, fever, analgesics, asthma, joint pains, pneumonia, and intestinal worms in Ethiopia. Anticipated by these claims, column chromatographic separation of the roots extract of T. nobilis led to the isolation of eight alkaloids (1–8). The structures of the isolated compounds were identified based on their NMR (1D and 2D) spectral data analysis and comparison with reported literature data. In-silico molecular docking analysis of the isolated compounds were performed against Staphylococcus aureus DNA Gyrase (PDB ID: 2XCT) and human topoisomerase IIβ DNA (PDB ID: 3QX3) by using AutoDock Vina. ADMET analysis were performed by SwissADME, PreADMET, and OSIRIS Property predictions. The study revealed that the isolated compounds exhibited promising binding affinity to DNA gyrase, especially with compound 5 forms a stable drug-protein complex. Whereas the ADME and drug-likeness analysis revealed that compound 5 is less absorbed from the gastrointestinal tract, crossblood brain barrier and a P-glycoprotein substrate. This indicated that compound 5 could be a good candidate as anticancer agent provided that in vivo analysis done for more confirmation.

Ethyl 2-anilino-4-oxo-4,5-dihydrofuran-3-carboxylate exhibits anti-proliferative activity and induces apoptosis in promyelocytic leukemia HL-60 cells

Furoquinolone and its derivatives exhibit antimicrobial, anti-allergic, anti-inflammatory and anticancer properties. The present study investigated the anti-tumor activity of synthesized intermediates of furoquinolone in human promyelocytic leukemia HL-60 cells. The biological effects of the active compound ethyl 2-anilino-4-oxo-4,5-dihydrofuran-3-carboxylate (compound 131) were examined in HL-60 cells. The following properties were analyzed: Cell survival, cell cycle profile, caspase-3 activity, Bax and Bcl-2 expression, the amount of intracellular Ca²⁺, the number of reactive oxygen species (ROS) and the mitochondrial membrane potential. Compound 131 (50% cytotoxic concentration_, 23.5 µM) significantly reduced the proliferation of HL-60 cells and was revealed to induce apoptosis in HL-60 cells in a concentration-dependent manner. Moreover, this was associated with the activation of caspase-3, upregulation of Bax, an increase in intracellular Ca²⁺ and ROS production, and a decrease in mitochondrial membrane potential and Bcl-2 expression levels. Compound 131, a novel 4,5-dihydrofuran-3-carboxylate, induced apoptosis in HL-60 cells via the increase of intracellular Ca²⁺ and ROS to alter the mitochondrial membrane potential and the protein level of Bax and Bcl-2, as well as activating caspase-3. The results of the current study indicate that compound 131 may represent a promising compound for the development of anti-leukemia therapeutics.

Biologically active quinoline and quinazoline alkaloids part I

Quinoline and quinazoline alkaloids, two important classes of N-based heterocyclic compounds, have attracted tremendous attention from researchers worldwide since the 19th century. Over the past 200 years, many compounds from these two classes were isolated from natural sources, and most of them and their modified analogs possess significant bioactivities. Quinine and camptothecin are two of the most famous and important quinoline alkaloids, and their discoveries opened new areas in antimalarial and anticancer drug development, respectively. In this review, we survey the literature on bioactive alkaloids from these two classes and highlight research achievements prior to the year 2008 (Part I). Over 200 molecules with a broad range of bioactivities, including antitumor, antimalarial, antibacterial and antifungal, antiparasitic and insecticidal, antiviral, antiplatelet, anti-inflammatory, herbicidal, antioxidant and other activities, were reviewed. This survey should provide new clues or possibilities for the discovery of new and better drugs from the original naturally occurring quinoline and quinazoline alkaloids.

Identification and characterization of a type III polyketide synthase involved in quinolone alkaloid biosynthesis from Aegle marmelos Correa

Quinolone alkaloids, found abundantly in the roots of bael (Aegle marmelos), possess various biological activities and have recently gained attention as potential lead molecules for novel drug designing. Here, we report the characterization of a novel Type III polyketide synthase, quinolone synthase (QNS), from A. marmelos that is involved in the biosynthesis of quinolone alkaloid. Using homology-based structural modeling, we identify two crucial amino acid residues (Ser-132 and Ala-133) at the putative QNS active site. Substitution of Ser-132 to Thr and Ala-133 to Ser apparently constricted the active site cavity resulting in production of naringenin chalcone from p-coumaroyl-CoA. Measurement of steady-state kinetic parameters demonstrates that the catalytic efficiency of QNS was severalfold higher for larger acyl-coenzymeA substrates as compared with smaller precursors. Our mutagenic studies suggest that this protein might have evolved from an evolutionarily related member of chalcone synthase superfamily by mere substitution of two active site residues. The identification and characterization of QNS offers a promising target for gene manipulation studies toward the production of novel alkaloid scaffolds.

Evidence for the complementary and synergistic effects of the three-alkaloid combination regimen containing berberine, hypaconitine and skimmianine on the ulcerative colitis rats induced by trinitrobenzene-sulfonic acid

Ulcerative colitis involves complicated etiology and presents diverse symptoms including intestine inflammation, bowel pain and diarrhea. Anti-inflammatory drugs are the mainstay in patient care, accompanied with antidiarrhea and analgesic agents used as symptomatic treatment. A classic traditional Chinese medicine formula, Fructus Mume pill (FMP), showed remarkable therapeutic efficacy in treating ulcerative colitis. However, since it contains many herbs and countless chemicals, the underlying mechanism is not clear. In this study, we selected three alkaloids from FMP, namely, berberine, hypaconitine and skimmianine to study the individual drug effect and compare these results with the BHS combination on: 1) The recovery of ulcerative colitis rats induced by trinitrobenzene-sulfonic acid. 2) Mice with xylene-induced acute exudative edema and acetic acid-induced writhing. 3) Gastrointestinal transit inhibition, and 4) the response of HT29 cells after treatment with lipopolysaccharide. We found that the compound hypaconitine showed a potent analgesic effect, while skimmianine acted as an antidiarrhea agent and the component berberine was the key agent exerting anti-inflammatory effect. However, since berberine killed the commensal bacteria and induced lipopolysaccharide release, it could at the same time aggravate colon inflammation. The three-alkaloid combination BHS produced complementary and synergistic effects in colon inflammation recovery, relieving acetic acid-induced bowel pain and xylene-induced acute exudative edema. BHS also decreased lipopolysaccharide production and enhanced the therapeutic efficacy. It is hoped that this study will lay the foundation to further dissect and understand the FMP formula to improve the treatment with simplified and well defined drug combinations for this dreadful disease.

Electrophysiological basis for the antiarrhythmic action and positive inotropy of HA-7, a furoquinoline alkaloid derivative, in rat heart

1. HA-7, a new synthetic derivative of furoquinoline alkaloid, increased the contractile force of right ventricular strips and effectively suppressed the ischaemia-reperfusion induced polymorphic ventricular tachyrhythmias in adult rat heart (EC50 = 2.8 microM). 2. In rat ventricular myocytes, HA-7 concentration-dependently prolonged the action potential duration (APD) and decreased the maximal rate of rise of the action potential upstroke (Vmax). The action potential amplitude and resting membrane potential were also reduced, but to a smaller extent. The prolongation of APD by HA-7 was prevented by pretreating the cells with 1 mM 4-AP. 3. Voltage clamp experiments revealed that HA-7 decreased the maximal current amplitude of I(Na) (IC50 = 4.1 microM) and caused a negative shift of its steady-state inactivation curve and slowed its rate of recovery from inactivation. The use-dependent inhibition of I(Na) by HA-7 was enhanced at a higher stimulation rate. The L-type Ca2+ current (I(Ca)) was also reduced, but to a lesser degree (IC50 = 5.3 microM, maximal inhibition = 31.8%). 4. This agent also influenced the time- and voltage-dependent K currents. The prolongation of APD was associated with an inhibition of a 4-AP sensitive transient outward K current (I(to)) (IC50 = 2.9 microM) and a slowly inactivating, steady-state outward current (I(SS)) (IC50 = 2.5 microM). The inhibition of I(to) by HA-7 was associated with an acceleration of its time constant of inactivation. HA-7 suppressed I(to) in a time-dependent manner and caused a significant negative shift of the voltage-dependent steady-state inactivation curve but did not affect its rate of recovery from inactivation. 5. At higher concentrations, the inward rectifier K+ current (I(KI)) was also inhibited but to a less extent. Its slope conductance after 3, 10 and 30 microM HA-7 was decreased by 24+/-4%, 41+/-5% and 54+/-8%. respectively. 6. We conclude that HA-7 predominantly blocks I(to) and Na+ channels and that it also weakly blocks Ca2+ and I(KI) channels. These changes alter the electrophysiological properties of the heart and terminate the ischaemia reperfusion induced ventricular arrhythmia. The significant I(to) inhibition and minimal I(Ca) suppression may afford an opportunity to develop an effective antiarrhythmic agent linked with positive inotropy.