Novel triazoles of 3-acetylbetulin and betulone as anticancer agents

DNA binding studies of antifungal drug posaconazole using spectroscopic and molecular docking methods

The binding studies of DNA with small molecules have been an emerging field of research all the time since DNA as the genetic material is a major biological target for various drugs. Interpretation of small molecule-DNA binding helps in understanding their interactions with designing new drugs of greater medicinal activity. Posaconazole is an antifungal drug in the class of triazoles which are known to possess numerous pharmacological properties. In this work, the nature of the binding of posaconazole with calf-thymus DNA has been studied using spectroscopic techniques and molecular docking studies. A binding constant of the order of 10³ M^-1 was observed from UV-visible and fluorescence studies for the interaction between posaconazole and calf-thymus DNA. The fluorescence property of posaconazole was found to be quenched by calf-thymus DNA with a quenching constant of the order of 10³ M^-1. Competitive displacement of ethidium bromide and Hoechst 33258 by posaconazole using fluorescence technique suggested minor groove binding of posaconazole in calf-thymus DNA. Confirmation of the binding mode was further complemented by the viscosity measurement and DNA melting studies followed by KI quenching experiments. The studies on the effect of ionic strength on the binding suggested a possible role of electrostatic force in the interaction. Molecular docking studies reflected a crescent shape of the posaconazole within the minor groove of calf-thymus DNA validating the experimental findings showing the residues involved in the interaction.

Microbial transformation of betulonic acid by Circinella muscae CGMCC 3.2695 and anti-neuroinflammatory activity of the products

Microbial transformation of betulonic acid with Circinella muscae CGMCC 3.2695 yielded nine undescribed metabolites and eight known compounds. The structures of the metabolites were established based on extensive NMR and HR-ESI-MS data analyses. It is shown that C. muscae could catalyze the regioselective hydroxylation at C-2, C-7, C-15, C-16, C-21, and C-30 along with carbonylation at C-2 and C-21. Furthermore, potential anti-neuroinflammatory activities of the obtained compounds in NO production were tested in lipopolysaccharides-induced BV-2 cells. Some of the metabolites exhibited pronounced inhibitory activities with IC50 values of 4.27-16.68 μM.

28-[1-(3-(Propionyloxy)propyl)-1H-1,2,3-triazol-4-yl]carbonylbetulin

Betulin has a broad spectrum of biological and pharmacological properties, such as anticancer, antibacterial, antifungal, and antiviral. Unfortunately, the low bioavailability makes it difficult to use in medicine. The introduction of a triazole ring to the betulin structure leads to the obtainment of new compounds with higher activity and better bioavailability. The title compound was obtained from the triazole derivative of betulin by conversion of the hydroxyl group to an ester moiety in the Steglich reaction. The chemical structure of the hybrid was characterized by nuclear magnetic resonance (1H NMR, 13C NMR, HSQC, HMBC) and HRMS spectroscopy.

Synthesis and Anticancer Activity of Indole-Functionalized Derivatives of Betulin

Pentacyclic triterpenes, including betulin, are widespread natural products with various pharmacological effects. These compounds are the starting material for the synthesis of substances with promising anticancer activity. The chemical modification of the betulin scaffold that was carried out as part of the research consisted of introducing the indole moiety at the C-28 position. The synthesized new 28-indole-betulin derivatives were evaluated for anticancer activity against seven human cancer lines (A549, MDA-MB-231, MCF-7, DLD-1, HT-29, A375, and C32). It was observed that MCF-7 breast cancer cells were most sensitive to the action of the 28-indole-betulin derivatives. The study shows that the lup-20(29)-ene-3-ol-28-yl 2-(1H-indol-3-yl)acetate caused the MCF-7 cells to arrest in the G1 phase, preventing the cells from entering the S phase. The performed cytometric analysis of DNA fragmentation indicates that the mechanism of EB355A action on the MCF-7 cell line is related to the induction of apoptosis. An in silico ADMET profile analysis of EB355A and EB365 showed that both compounds are bioactive molecules characterized by good intestinal absorption. In addition, the in silico studies indicate that the 28-indole-betulin derivatives are substances of relatively low toxicity.

Semisynthetic Derivatives of Pentacyclic Triterpenes Bearing Heterocyclic Moieties with Therapeutic Potential

Medicinal plants have been used by humans since ancient times for the treatment of various diseases and currently represent the main source of a variety of phytocompounds, such as triterpenes. Pentacyclic triterpenes have been subjected to numerous studies that have revealed various biological activities, such as anticancer, antidiabetic, anti-inflammatory, antimicrobial, and hepatoprotective effects, which can be employed in therapy. However, due to their high lipophilicity, which is considered to exert a significant influence on their bioavailability, their current use is limited. A frequent approach employed to overcome this obstacle is the chemical derivatization of the core structure with different types of moieties including heterocycles, which are considered key elements in medicinal chemistry. The present review aims to summarize the literature published in the last 10 years regarding the derivatives of pentacyclic triterpenes bearing heterocyclic moieties and focuses on the biologically active derivatives as well as their structure-activity relationships. Predominantly, the targeted positions for the derivatization of the triterpene skeleton are C-3 (hydroxyl/oxo group), C-28 (hydroxyl/carboxyl group), and C-30 (allylic group) or the extension of the main scaffold by fusing various heterocycles with the A-ring of the phytocompound. In addition, numerous derivatives also contain linker moieties that connect the triterpenic scaffold with heterocycles; one such linker, the triazole moiety, stands out as a key pharmacophore for its biological effect. All these studies support the hypothesis that triterpenoid conjugates with heterocyclic moieties may represent promising candidates for future clinical trials.

Rhodococcus strains as a good biotool for neutralizing pharmaceutical pollutants and obtaining therapeutically valuable products: Through the past into the future

Active pharmaceutical ingredients present a substantial risk when they reach the environment and drinking water sources. As a new type of dangerous pollutants with high chemical resistance and pronounced biological effects, they accumulate everywhere, often in significant concentrations (μg/L) in ecological environments, food chains, organs of farm animals and humans, and cause an intense response from the aquatic and soil microbiota. Rhodococcus spp. (Actinomycetia class), which occupy a dominant position in polluted ecosystems, stand out among other microorganisms with the greatest variety of degradable pollutants and participate in natural attenuation, are considered as active agents with high transforming and degrading impacts on pharmaceutical compounds. Many representatives of rhodococci are promising as unique sources of specific transforming enzymes, quorum quenching tools, natural products and novel antimicrobials, biosurfactants and nanostructures. The review presents the latest knowledge and current trends regarding the use of Rhodococcus spp. in the processes of pharmaceutical pollutants’ biodegradation, as well as in the fields of biocatalysis and biotechnology for the production of targeted pharmaceutical products. The current literature sources presented in the review can be helpful in future research programs aimed at promoting Rhodococcus spp. as potential biodegraders and biotransformers to control pharmaceutical pollution in the environment.

Recent Advances in the Discovery and Development of Anti-HIV Natural Products

Acquired immunodeficiency syndrome (AIDS) caused by human immunodeficiency virus (HIV) infection is a serious public problem threatening global health. At present, although "cocktail therapy" has achieved significant clinical effects, HIV still cannot be completely eradicated. Furthermore, long-term antiviral treatment has caused problems such as toxic side effects, the emergence of drug-resistant viruses, and poor patient compliance. Therefore, it is highly necessary to continue to search for high-efficient, low-toxic anti-HIV drugs with new mechanisms. Natural products have the merits of diverse scaffolds, biological activities, and low toxicity that are deemed the important sources of drug discovery. Thus, finding lead compounds from natural products followed by structure optimization has become one of the important ways of modern drug discovery. Nowadays, many natural products have been found, such as berberine, gnidimacrin, betulone, and kuwanon-L, which exert effective anti-HIV activity through immune regulation, inhibition of related functional enzymes in HIV replication, and anti-oxidation. This paper reviewed these natural products, their related chemical structure optimization, and their anti-HIV mechanisms.

3′-[4-({[3β,28-Bis(acetyloxy)lup-20(29)-en-30-yl]oxy}carbonyl)-1H-1,2,3-triazol-1-yl]-3′-deoxythymidine

The reaction of the azidothymidine (AZT) with the 30-propynoylated derivative of 3,28-O,O′-diacetylbetulin gave a 1,4-disubstituted 1,2,3-triazole. The chemical structure of new derivative was characterized by 1H NMR, 13C NMR and HR-MS. The triterpene-AZT conjugate was tested against a human cancer cell lines such as glioblastoma (SNB-19), amelanotic melanoma (C-32), ovarian adenocarcinoma (SKOV-3) and breast cancer (T47D, and MCF-7). 3′-[4-({[3β,28-Bis(acetyloxy)lup-20(29)-en-30-yl]oxy}carbonyl)-1H-1,2,3-triazol-1-yl]-3′-deoxythymidine shown significant activity against MCF-7 cells, with an IC50 value of 4.37 µM.

Synthesis and Structural Characterization of a New 1,2,3-Triazole Derivative of Pentacyclic Triterpene

The new 30-substituted triazole derivative of 3,28-O,O′-diacetylbetulin was obtained in the copper(I) catalyzed azide-alkyne cycloaddition (CuAAC). The title compound was characterized by NMR, IR, HR-MS, and X-ray diffraction techniques. The X-ray diffraction study showed that the 1,2,3-triazole derivative crystallizes in the orthorhombic space group P212121, Z = 4, and unit cell parameters are as follows a = 9.4860(10) Å, b = 13.9440(2) Å, and c = 30.2347(4) Å. The molecular packing is stabilized by intermolecular hydrogen interactions C-H…O. The Hirshfeld surface analysis showed the presence of the O…H interactions with a percentage of the 16.5% in the total Hirshfeld area. The MEP analysis showed that the nucleophilic regions are located near the oxygen atoms of the acyl and carbonyl groups of betulin moiety and the sulfur atom in the triazole linker. The HOMO and LUMO orbitals are located near the triazole moiety. The obtained results indicated that this new betulin derivative is more reactive with electrophilic than nucleophilic molecules.

Biotransformation of Betulonic Acid by the Fungus Rhizopus arrhizus CGMCC 3.868 and Antineuroinflammatory Activity of the Biotransformation Products

Biotransformation of betulonic acid (1) by Rhizopus arrhizus CGMCC 3.868 resulted in the production of 16 new (3, 5, 6, and 9-21) and five known compounds. Structures of the new compounds were established by analysis of spectroscopic data. Hydroxylation, acetylation, oxygenation, glycosylation, and addition reactions involved the C-20-C-29 double bond. Antineuroinflammatory activities of the obtained compounds in NO production were tested in lipopolysaccharides-induced BV-2 cells. Compared with the substrate betulonic acid, biotransformation products 3, 8, 9, 14, and 21 exhibited an improved inhibitory effect, with IC₅₀ values of 10.26, 11.09, 5.38, 1.55, and 4.69 μM, lower than that of the positive control, N^G-monomethyl-l-arginine.

Bile-Acid-Appended Triazolyl Aryl Ketones: Design, Synthesis, In Vitro Anticancer Activity and Pharmacokinetics in Rats

A library of bile-acid-appended triazolyl aryl ketones was synthesized and characterized by detailed spectroscopic techniques such as ¹H and ¹³C NMR, HRMS and HPLC. All the synthesized conjugates were evaluated for their cytotoxicity at 10 µM against MCF-7 (human breast adenocarcinoma) and 4T1 (mouse mammary carcinoma) cells. In vitro cytotoxicity studies on the synthesized conjugates against MCF-7 and 4T1 cells indicated one of the conjugate 6cf to be most active against both cancer cell lines, with IC₅₀ values of 5.71 µM and 8.71 µM, respectively, as compared to the reference drug docetaxel, possessing IC₅₀ values of 9.46 µM and 13.85 µM, respectively. Interestingly, another compound 6af (IC₅₀ = 2.61 µM) was found to possess pronounced anticancer activity as compared to the reference drug docetaxel (IC₅₀ = 9.46 µM) against MCF-7. In addition, the potent compounds (6cf and 6af) were found to be non-toxic to normal human embryonic kidney cell line (HEK 293), as evident from their cell viability of greater than 86%. Compound 6cf induces higher apoptosis in comparison to 6af (46.09% vs. 33.89%) in MCF-7 cells, while similar apoptotic potential was observed for 6cf and 6af in 4T1 cells. The pharmacokinetics of 6cf in Wistar rats showed an MRT of 8.47 h with a half-life of 5.63 h. Clearly, these results suggest 6cf to be a potential candidate for the development of anticancer agents.

Supported Silver Nanoparticles as Catalysts for Liquid-Phase Betulin Oxidation

Herein, it has been shown that betulin can be transformed into its biologically active oxo-derivatives (betulone, betulinic and betulonic aldehydes) by liquid-phase oxidation over supported silver catalysts under mild conditions. In order to identify the main factors determining the catalytic behavior of nanosilver catalysts in betulin oxidation, silver was deposited on various alumina supports (γ-alumina and boehmite) using deposition–precipitation with NaOH and incipient wetness impregnation methods, followed by treatment in H₂ or O₂. Silver catalysts and the corresponding supports were characterized by X-ray diffraction, nitrogen physisorption, inductively coupled plasma optical emission spectroscopy, photoelectron spectroscopy and transmission electron microscopy. It was found that the support nature, preparation and treatment methods predetermine not only the average Ag nanoparticles size and their distribution, but also the selectivity of betulin oxidation, and thereby, the catalytic behavior of Ag catalysts. In fact, the support nature had the most considerable effect. Betulin conversion, depending on the support, increased in the following order: Ag/boehmite < Ag/boehmite (calcined) < Ag/γ-alumina. However, in the same order, the share of side reactions catalyzed by strong Lewis acid centers of the support also increased. Poisoning of the latter by NaOH during catalysts preparation can reduce side reactions. Additionally, it was revealed that the betulin oxidation catalyzed by nanosilver catalysts is a structure-sensitive reaction.

Dataset on in-silico investigation on triazole derivatives via molecular modelling approach: A potential glioblastoma inhibitors

In this work, ten molecular compounds were optimised using density functional theory (DFT) method via Spartan 14. The obtained descriptors were used to develop quantitative structural activities relationship (QSAR) model using Gretl and Matlab software and the similarity between predicted IC₅₀ and observed IC₅₀ was investigated. Also, docking study revealed the non-bonding interactions between the studied compounds and the receptor. The molecular interactions between the observed ligands and brain cancer protein (PDB ID: 1q7f) were investigated. Adsorption, distribution, metabolism, excretion and toxicity (ADMET) properties were also investigated.

In Vitro Calli Production Resulted in Different Profiles of Plant-Derived Medicinal Compounds in Phyllanthus amarus

The efficient production of plant-derived medicinal compounds (PDMCs) from in vitro plants requires improvements in knowledge about control of plant or organ development and factors affecting the biosynthesis pathway of specific PDMCs under in vitro conditions, leading to a realistic large-scale tool for in vitro secondary metabolite production. Thus, this study aimed to develop an in vitro technique, through the induction and proliferation of calli, for production of plant fresh weight, and to compare the PDMC profile obtained from the plants versus in vitro calli of Phyllanthus amarus. It was successfully possible to obtain and proliferate two types of calli, one with a beige color and a friable appearance, obtained in the dark using Murashige and Skoog (MS) medium plus 2,4-dichlorophenoxyacetic acid (2,4-D), and a second type with a green color, rigid consistency, and nonfriable appearance obtained under light conditions and MS medium plus 6-benzyladenine (6-BA). In vitro micropropagated plants that gave rise to calli were also acclimatized in a greenhouse and cultivated until obtaining the mass for PDMC analysis and used as a control. While the micropropagated-derived plants concentrated the lignans niranthin, nirtetralin, and phyllanthin, the Phyllanthus amarus calli proliferated in vitro concentrated a completely different biochemical profile and synthesis of compounds, such as betulone, squalene, stigmasterol, and β-sitosterol, in addition to others not identified by GC-MS database. These results demonstrate the possibility of applying the calli in vitro from Phyllanthus amarus for production of important PDMCs unlike those obtained in cultures of differentiated tissues from field plants.

Design, synthesis and biological activity of 1,4-quinone moiety attached to betulin derivatives as potent DT-diaphorase substrate

In this research, betulin derivatives were bonded to the 1,4-quinone fragment by triazole linker. Furthermore, the enzymatic assay used has shown that these compounds are a good DT-diaphorase (NQO1) substrates as evidenced by increasing enzymatic conversion rates relative to that of streptonigrin. The anticancer activities of the hybrids were tested against a panel of human cell lines, like: melanoma, ovarian, breast, colon, and lung cancers. The structure-activity relationship showed that the activity depends on the type of 1,4-quinone moiety and the tumor cell lines used. It was also found that the anticancer effects were increasing against the cell line with higher NQO1 protein level, like: breast (T47D, MCF-7), colon (Caco-2), and lung (A549) cancers. The transcriptional activity of the gene encoding a proliferation marker (H3 histone), cell cycle regulators (p53 and p21) and apoptosis pathway (BCL-2 and BAX) for selected compounds were determined. The molecular docking study was carried out to examine the interaction between the hybrids and NQO1 enzyme. The computational simulation showed that the type of the 1,4-quinone moiety influences location of the compound in the active site of the enzyme. It is worth noting that the study of new hybrids of betulin as substrate for NQO1 protein may lead to new medical therapeutic applications in the future.

Effect of betulin and betulonic acid on isolated rat liver mitochondria and liposomes

The paper considers the effects of plant triterpenoid betulin and its derivative betulonic acid on rat liver mitochondria and liposomes. It was found that betulonic acid and, to a lesser extent, betulin, activate mitochondrial respiration in states 2 and 4 and inhibit ADP- and DNP-stimulated (uncoupled) respiration. The effect of betulonic acid resulted in a significant decrease of the respiratory control and ADP/O ratios and decrease in Δψ. The effects of both compounds were most pronounced in the case of succinate-fueled mitochondrial respiration. This may include both the possible protonophore effect of betulonic acid and the inhibition of respiratory chain complexes by both compounds. Both agents enhanced H₂O₂ production in succinate-fueled mitochondria, while betulonic acid exerted an antioxidant effect with NAD-dependent substrates. Betulin was found to induce mitochondrial aggregation, but had no effect on membrane permeability. A similar pattern was found on liposomes. As revealed by the laurdan generalized polarization (GP) technique, betulin increased laurdan GP in lecithin liposomes, indicating a decrease in membrane fluidity. Measurements of GP as a function of fluorescence excitation wavelength gave an ascending line for high concentrations of betulin, which can be interpreted as phase heterogeneity of the lipid/betulin system. High concentrations of betulin (> 60 mol%) was also demonstrated to cause permeabilization of lecithin liposomes. Betulonic acid was much less effective in inducing the aggregation of mitochondria and liposomes and had no effect on membrane permeability. The possible mechanisms of betulin and betulonic acid effect on rat liver mitochondria and liposomes are discussed.

1,2,3-Triazole-containing hybrids as leads in medicinal chemistry: A recent overview

The 1,2,3-triazole ring is a major pharmacophore system among nitrogen-containing heterocycles. These five-membered heterocyclic motifs with three nitrogen heteroatoms can be prepared easily using 'click' chemistry with copper- or ruthenium-catalysed azide-alkyne cycloaddition reactions. Recently, the 'linker' property of 1,2,3-triazoles was demonstrated, and a novel class of 1,2,3-triazole-containing hybrids and conjugates was synthesised and evaluated as lead compounds for diverse biological targets. These lead compounds have been demonstrated as anticancer, antimicrobial, anti-tubercular, antiviral, antidiabetic, antimalarial, anti-leishmanial, and neuroprotective agents. The present review summarises advances in lead compounds of 1,2,3-triazole-containing hybrids, conjugates, and their related heterocycles in medicinal chemistry published in 2018. This review will be useful to scientists in research fields of organic synthesis, medicinal chemistry, phytochemistry, and pharmacology.

Biological Activity and In Silico Study of 3-Modified Derivatives of Betulin and Betulinic Aldehyde

A series of 3-substituted derivatives of betulin and betulinic aldehyde were synthesized as promising anticancer agents. The newly triterpenes were tested against five human cancer cell lines like biphenotypic B myelomonocytic leukaemia (MV-4-11), adenocarcinoma (A549), prostate (Du-145), melanoma (Hs294T), breast adenocarcinoma (MCF-7) and normal human mammary gland (MCF-10A). The compound 9 showed towards Du-145, MCF-7 and Hs294T cells significant antiproliferative activity with IC₅₀ ranging from 7.3 to 10.6 μM. The evaluation of ADME properties of all compounds also includes their pharmacokinetic profile. The calculated TPSA values for synthetized derivatives are in the range between 43.38 Ų and 55.77 Ų suggesting high oral bioavailability. The molecular docking calculations showed that triterpene 9 fits the active site of the serine/threonine protein kinase Akt.

The potential of click reactions for the synthesis of bioactive triterpenes

Click reactions between alkynes and azides using the privileged scaffold of triterpenes have been of interest for biological chemistry. Many publications deal with the synthesis of novel bioactive molecules; these conjugates have also been used for bioanalytical and diagnostic purposes. As a result, conjugates of better physicochemical properties were obtained; even compounds of improved solubility in water and physiological fluids were made through the introduction of a triazol residue. "Hybrid-structures", i.e. molecules consisting of two independently bioactive subunits linked by a triazole residue were higher bioactive than their parent compounds but not as active as expected, and with a few exceptions the ultimate breakthrough has not yet been achieved. Only in the synthesis of compounds with anti-leishmanial activity some new and promising lead structures were found. As a consequence, triazole modified triterpenes seem to hold their greatest future prospect rather as diagnostic reagents and molecular probes than as drugs.

Recent Developments in the Functionalization of Betulinic Acid and Its Natural Analogues: A Route to New Bioactive Compounds

Betulinic acid (BA) and its natural analogues betulin (BN), betulonic (BoA), and 23-hydroxybetulinic (HBA) acids are lupane-type pentacyclic triterpenoids. They are present in many plants and display important biological activities. This review focuses on the chemical transformations used to functionalize BA/BN/BoA/HBA in order to obtain new derivatives with improved biological activity, covering the period since 2013 to 2018. It is divided by the main chemical transformations reported in the literature, including amination, esterification, alkylation, sulfonation, copper(I)-catalyzed alkyne-azide cycloaddition, palladium-catalyzed cross-coupling, hydroxylation, and aldol condensation reactions. In addition, the synthesis of heterocycle-fused BA/HBA derivatives and polymer‒BA conjugates are also addressed. The new derivatives are mainly used as antitumor agents, but there are other biological applications such as antimalarial activity, drug delivery, bioimaging, among others.

Application of TLC for Evaluation of the Lipophilicity of Newly Synthetized Esters: Betulin Derivatives

The problem of designing a new drug is nowadays very important for researches representing many branches of science. This work considers the usefulness of the analytical method such as thin-layer chromatography for the lipophilicity of newly synthesized compounds, betulin derivatives, which could be potential drugs with anticancer activity. The two mobile phases were used for the purpose of experimental determination of lipophilicity for mono- and diesters investigated. The first mobile phase consists of acetate and Tris buffer, whilst the second consists of 1,4-dioxane and acetate buffer. The value of the retardation factor was recalculation into the R _M value, and then R _M0 values were obtained by extrapolating acetone or 1,4-dioxane concentration to zero. The chromatographic data of lipophilicity were correlated with theoretically obtained values of ALOGPS, AClogP, miLogP, ALOGP, MLOGP, XLOGP2, and XLOGP3. The particular correlation equations were obtained. The cluster analysis was also used to find similarity between the esters investigated on the basis of the experimental or theoretical value of lipophilicity obtained. The good correlation between experimentally and theoretically calculated lipophilicity gives the possibility of prediction of this value on the basis of the correlation equation. On the basis of similarity analysis was stated strong connections between the structure and the value of lipophilicity, for both experimental and theoretical values.

Synthesis and Structure Elucidation of N′-(4-Methoxybenzylidene)-5-methyl-1-phenyl-1H-1,2,3-triazole-4-carbohydrazide

N′-(4-Methoxybenzylidene)-5-methyl-1-phenyl-1H-1,2,3-triazole-4-carbohydrazide (3) was synthesized in a yield of 88% from an acid-catalyzed reaction of 5-methyl-1-phenyl-1H-1,2,3- triazole-4-carbohydrazide and 4-methoxybenzaldehyde in ethanol under reflux for 2.5 h. The structure of 3 was confirmed by the data obtained from infrared, nuclear magnetic resonance, mass spectroscopy, single crystal X-ray diffraction, and microanalysis.