Antiretroviral (HIV-1) activity of azulene derivatives

Integrated computational and experimental approach for novel anti-leishmanial molecules by targeting Dephospho-coenzyme A kinase

Coenzyme A acts as a necessary cofactor for many enzymes and is a part of many biochemical processes. One of the critical enzymes involved in Coenzyme A synthesis is Dephospho-coenzyme A-kinase (DPCK). In this study, we have used integrated computational and experimental approaches for promising inhibitors of DPCK using the natural products available in the ZINC database for anti-leishmanial drug development. The top hit compounds chosen after molecular docking were Veratramine, Azulene, Hupehenine, and Hederagenin. The free binding energy of Veratramine, Azulene, Hupehenine, and Hederagenin was estimated. Besides the favourable binding point, the ligands also showed good hydrogen bonding and other interactions with key residues of the enzyme's active site. The natural compounds were also experimentally investigated for their effect on the L. donovani promastigotes and murine macrophage (J774A.1). A good antileishmanial activity by the compounds on the promastigotes was observed as estimated by the MTT assay. The in-vitro experiments revealed that Hupehenine (IC₅₀ = 7.34 ± 0.37 μM) and Veratramine (IC₅₀ = 12.46 ± 2.28 μM) exhibited better inhibition than Hederagenin (IC₅₀ = 23.36 ± 0.54 μM) and Azulene (IC₅₀ = 24.42 ± 3.28 μM). This work has identified novel anti-leishmanial molecules possibly acting through the inhibition of DPCK.

Design, Synthesis, and Biological Activity of Guaiazulene Derivatives

Guaiazulene and related derivatives were famous for diverse biological activities. In an effort to discover new highly efficient candidate drugs derived from guaiazulene, four series of guaiazulene derivatives were designed, synthesized, and evaluated for antiproliferation, antiviral, anti-inflammatory and peroxisome proliferators-activated receptor γ (PPARγ) signalling pathway agonist activities. Among them, two guaiazulene condensation derivatives showed selective cytotoxic activities towards K562 cell with IC₅₀ values 5.21 μM and 5.14 μM, respectively, accompanied by slight effects on normal cell viability. For the first time, one guaiazulene derivative from series I exhibited potent antiviral activity towards influenza A virus with IC₅₀ of 17.5 μM. A guaiazulene-based chalcone showed higher anti-inflammatory activity than positive drug indomethacin with an inhibitory rate of 34.29 % in zebrafish model in vivo. One guaiazulene-based flavonoid could strongly agitate PPARγ pathway at 20 μM, indicating the potential of guaiazulene derivatives to reduce obesity development and ameliorate hepatic steatosis. Preliminary in silico ADME studies predicted the excellent drug-likeness properties of bioactive guaiazulene derivatives.

Olive Oil Produced from Olives Stored under CO2 Atmosphere: Volatile and Physicochemical Characterization

In this study, an alternative debittering technique for olives, invented and patented by Prof. Vassilis Dourtoglou, was employed. Olive fruits (Olea europaea cv. Megaritiki) were stored under CO₂ atmosphere immediately after harvest for a period of 15 days. After the treatment, a sensory evaluation between the olives stored under CO₂ and those stored under regular atmospheric conditions (control) was performed. Additionally, the CO₂-treated olives were used for the cold press of olive oil production. The volatile profile of the olive oil produced was analyzed using headspace solid-phase microextraction (HS-SPME) and gas chromatography coupled to mass spectrometry (GC-MS). A total of thirty different volatile compounds were detected. The volatile characteristics of olive oil are attributed, among others, to aldehydes, alcohols, esters, hydrocarbons, alkanes, and terpenes. The volatile compounds' analysis showed many differences between the two treatments. In order to compare the volatile profile, commercial olive oil was also used (produced from olives from the same olive grove with a conventional process in an industrial olive mill). The antioxidant activity, the content of bioactive compounds (polyphenols, α-tocopherol, carotenoids, and chlorophylls), and the fatty acids' profile were also determined. The results showed that the oil produced from CO₂-treated olives contains different volatile components, which bestow a unique flavor and aroma to the oil. Moreover, this oil was found comparable to extra virgin olive oil, according to its physicochemical characteristics. Finally, the enhanced content in antioxidant compounds (i.e., polyphenols) not only rendered the oil more stable against oxidation but also better for human health. The overall quality of the olive oil was enhanced and, as such, this procedure holds great promise for future developments.

Synthesis of C3-functionalized indole derivatives via Brønsted acid-catalyzed regioselective arylation of 2-indolylmethanols with guaiazulene

The first Brønsted acid catalyzed method for the construction of guaiazulenyl C3-functionalized indole derivatives was established. The reactions proceeded smoothly at ambient temperature by used (±)-10-camphorsulfonic acid (CSA) as catalyst,...

Essential oils from Melia azedarach L. (Meliaceae) leaves: chemical variability upon environmental factors

The chemical composition of the essential oils extracted from the leaves of Melia azedarach L. collected monthly from July 2019 to June 2020 was examined via gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) techniques. Analysis of the essential oils identified about 17 compounds representing more than 85% of the oil. Oil yields were higher in the months of June and August, and the primary compounds identified were β-caryophyllene (3.50-63.41%), benzaldehyde (3.50-55.98%), and azulene (1.27-19.05%). A correlation analysis was performed to determine the relationship between yields and climatic conditions, and between constituent concentration and temperature and precipitation values during the study period. As per our findings, although not significant, a positive correlation was determined between yield and climatic parameters. However, the oil components were categorized into four groups based on their correlation with temperature and precipitation indices. Among the major components of the essential oils, only azulene and β-caryophyllene exhibited a negative correlation with both precipitation and temperature. The results show substantial differences in the chemical composition of M. azedarach essential oils and provide further insight into the phytochemical constituents that are sensitive to climate fluctuations. Furthermore, it provides an indication of the optimal time that the plant produces the important mono- and sesquiterpene components and the biological significance of their regulation.

C4-aldehyde of guaiazulene: synthesis and derivatisation

Guaiazulene is an alkyl-substituted azulene available from natural sources and is a much lower cost starting material for the synthesis of azulene derivatives than azulene itself. Here we report an approach for the selective functionalisation of guaiazulene which takes advantage of the acidity of the protons on the guaiazulene C4 methyl group. The aldehyde produced by this approach constitutes a building block for the construction of azulenes substituted on the seven-membered ring. Derivatives of this aldehyde synthesised by alkenylation, reduction and condensation are reported, and the halochromic properties of a subset of these derivatives have been studied.

Quantum-Chemical Search for Keto Tautomers of Azulenols in Vacuo and Aqueous Solution

Keto-enol prototropic conversions for carbonyl compounds and phenols have been extensively studied, and many interesting review articles and even books appeared in the last 50 years. Quite a different situation takes place for derivatives of biologically active azulene, for which only scanty information on this phenomenon can be found in the literature. In this work, quantum-chemical studies have been undertaken for symmetrically and unsymmetrically substituted azulenols (constitutional isomers of naphthols). Stabilities of two enol (OH) rotamers and all possible keto (CH) tautomers have been analyzed in the gas phase {DFT(B3LYP)/6-311+G(d,p)} and also in aqueous solution {PCM(water)//DFT(B3LYP)/6-311+G(d,p)}. Contrary to naphthols, for which the keto forms can be neglected, at least one keto isomer (C1H, C2H, and/or C3H) contributes significantly to the tautomeric mixture of each azulenol to a higher degree in vacuo (non-polar environment) than in water (polar amphoteric solvent). The highest amounts of the CH forms have been found for 2- and 5-hydroxyazulenes, and the smallest ones for 1- and 6-hydroxy derivatives. The keto tautomer(s), together with the enol rotamers, can also participate in deprotonation reaction leading to a common anion and influence its acid-base properties. The strongest acidity in vacuo exhibits 6-hydroxyazulene, and the weakest one displays 1-hydroxyazulene, but all azulenols are stronger acids than phenol and naphthols. Bond length alternation in all DFT-optimized structures has been measured using the harmonic oscillator model of electron delocalization (HOMED) index. Generally, the HOMED values decrease for the keto tautomers, particularly for the ring containing the labile proton. Even for the keto tautomers possessing energetic parameters close to those of the enol isomers, the HOMED indices are low. However, some kind of parallelism exists for the keto forms between their relative energies and HOMEDs estimated for the entire molecules.

In vitro and in vivo biological activities of azulene derivatives with potential applications in medicine

Azulene is an aromatic hydrocarbon that possesses a unique chemical structure and interesting biological properties. Azulene derivatives, including guaiazulene or chamazulene, occur in nature as components of many plants and mushrooms, such as Matricaria chamomilla, Artemisia absinthium, Achillea millefolium, and Lactarius indigo. Due to physicochemical properties, azulene and its derivatives have found many potential applications in technology, especially in optoelectronic devices. In medicine, the ingredients of these plants have been widely used for hundreds of years in antiallergic, antibacterial, and anti-inflammatory therapies. Herein, the applications of azulene, its derivatives and their conjugates with biologically active compounds are presented. The potential use of these compounds concerns various areas of medicine, including anti-inflammatory with peptic ulcers, antineoplastic with leukemia, antidiabetes, antiretroviral with HIV-1, antimicrobial, including antimicrobial photodynamic therapy, and antifungal.

Quorum sensing modulatory and biofilm inhibitory activity of Plectranthus barbatus essential oil: a novel intervention strategy

The essential oil (EO) from the roots of Plectranthus barbatus Andr. (Syn. Coleus forskohlii Briq.) was evaluated for quorum sensing (QS) inhibitory activity. P. barbatus EO was screened for inhibition of QS regulated violacein production in Chromobacterium violaceum (ATCC 12472) wild-type strain. At inhibitory (6.25% v/v) and sub-inhibitory concentrations (3.125% v/v) of the EO, dose-dependent response in the inhibition of violacein production was observed in C. violaceum. Similarly, sub-MIC (6.25% v/v) of P. barbatus EO disrupted QS regulated biofilm formation by 27.87% and inhibited swarming and twitching motility in Pseudomonas aeruginosa PA01 implying its anti-infective and QS modulatory activity. Fluorescence microscopy studies confirmed the disruption of biofilm formation by EO in P. aeruginosa PAO1. Promising antibacterial activity was recorded at concentrations as low as 3.12% v/v for Listeria monocytogenes (ATCC 13932) and at 6.25% v/v for both Salmonella enterica subsp. enterica serovar Typhimurium (ATCC 25241) and Escherichia coli (ATCC 11775). Furthermore, significant dose-dependent inhibition was observed for biofilm formation and motility in all the tested pathogens in different treated concentrations. GC-MS analysis revealed α-pinene, endo-borneol, bornyl acetate, 1-Hexyl-2-Nitrocyclohexane as the major phytoconstituents. P. barbatus EO or its constituent compounds with QS modulatory, antimicrobial and biofilm inhibitory property could be potential new-age dietary source based intervention and preservation technologies.

Azulene-A Bright Core for Sensing and Imaging

Azulene is a hydrocarbon isomer of naphthalene known for its unusual colour and fluorescence properties. Through the harnessing of these properties, the literature has been enriched with a series of chemical sensors and dosimeters with distinct colorimetric and fluorescence responses. This review focuses specifically on the latter of these phenomena. The review is subdivided into two sections. Section one discusses turn-on fluorescent sensors employing azulene, for which the literature is dominated by examples of the unusual phenomenon of azulene protonation-dependent fluorescence. Section two focuses on fluorescent azulenes that have been used in the context of biological sensing and imaging. To aid the reader, the azulene skeleton is highlighted in blue in each compound.

Direct synthesis of 2-arylazulenes by [8+2] cycloaddition of 2H-cyclohepta[b]furan-2-ones with silyl enol ethers

We developed a procedure for the direct synthesis of 2-arylazulenes, which were obtained in moderate to excellent yields, by [8+2] cycloaddition of 2H-cyclohepta[b]furan-2-ones with aryl-substituted silyl enol ethers. The structures of some 2-arylazulenes were clarified by single-crystal X-ray analysis. The 2-phenylazulene derivatives obtained by this study showed noticeable fluorescence in acidic media.

Brønsted-acid-catalyzed one-pot tandem annulation/[5 + 2]-cycloaddition of o-propargyl alcohol benzaldehydes with alkynes: regioselective and stereoselective synthesis of dibenzo[a,f]azulen-12-ones

The one-pot synthesis of dibenzo[a,f]azulen-12-ones has been established starting from o-propargyl alcohol benzaldehydes and alkynes.

Azulenes with aryl substituents bearing pentafluorosulfanyl groups: synthesis, spectroscopic and halochromic properties

Azulenes with SF₅-containing substituents gave significantly different spectroscopic responses to protonation depending on the regioisomer in question.

Synthesis of azulene-substituted benzofurans and isocoumarins via intramolecular cyclization of 1-ethynylazulenes, and their structural and optical properties

The preparation of azulene-substituted benzofurans and isocoumarins was established by two types of intramolecular cyclization reaction of 1-ethynylazulenes.