Betulin Derivatives Research Articles

Synthesis of Betulonic and Betulinic Acids Derivatives with Sulfonamide Fragment Linked to the Triterpene Core by Amidoalkane Spaser

A series of potentially biologically active sulfonamides of betulonic and betulinic acids with a sulfonamide fragment containing residues of dibutylamine or N-heterocycles, which is linked to a triterpene core by an amidoethane or amidopropane spacer, was synthesized. Betulonic acid sulfonamides were obtained by chlorohydride conjugation of acid with 2-aminoethane and 3-aminopropanesulfonamides and used as precursor compounds for the transition to similar betulinic acid derivatives by selective reduction of the 3-keto group with the action of NaBH4 in EtOH. The structure of all synthesized triterpene sulfonamides was confirmed by 1D and 2D NMR spectroscopy and mass spectrometry.

Synthesis, Structure, and In Vitro Biological Evaluation of Semi-Synthetic Derivatives of Betulin

Betulin and α-lipoic acid are naturally occurring substances with different biological properties. Combining two phytochemical units into a conjugate is a frequently used method to obtain new compounds with better pharmacokinetic parameters. This research concerned the preparation of lipoate derivatives of betulin using the Steglich method. Experimental lipophilicity values were determined for target compounds 6–10 by reversed-phase thin-layer chromatography. In silico methods were used to calculate the physicochemical parameters and lipophilicity of new derivatives and to determine the probable directions of biological activity. α-Lipoic acid, betulin, and lipoate derivatives 6–10 were tested for antiproliferative activity against MV4-11, A549, MCF-7, PC-3, HCT116, MiaPaca-2, and Hs294T cancer cells. 3-(5-(1,2-Dithiolan-3-yl)pentanoyl))betulin 10 showed moderate anticancer activity against MV4-11, PC-3, and HCT116, with IC50 values in the range of 39.8–76.7 µM. The introduction of a dithiolate substituent at the C3 position in 28-acetylbetulin gave compound 9 the highest activity (IC50 = 37.9 µM), in the ratio of biphenotypic B myelomonocytic leukemia cells (MV4-11). All lipoate derivatives were inactive towards normal cells.

In Vitro Hemocompatibility of Arabinogalactan, Betulin, and Betulin Derivatives.

The hemocompatibility of arabinogalactan, betulin and its derivatives was evaluated in vitro and samples suitable for creation of nanostructures or materials in contact with blood were selected. The prospects of arabinogalactan as a component of the construct (nanostructure) for drug delivery are due to the fact that it did not affect blood/plasma coagulation (at concentrations of 0.0033-3.333 mg/ml and 0.00465-4.65 mg/ml, respectively), platelet aggregation (0.00182-0.182 mg/ml), and demonstrated the degree of erythrocyte hemolysis less than 3%. Sodium salt of betulin monosulfate, diarginine salt of betulin disulfate (up to 0.465 mg/ml), and especially betulin and allobetulin formate with procoagulant properties (degree of hemolysis less than 2%) can be used to create a material, for example, sponge, gel, active against blood coagulation.

Assessment of the Lipophilicity of Indole Derivatives of Betulin and Their Toxicity in a Zebrafish Model.

There are scientific studies indicating that the attachment of an indole moiety to the triterpene scaffold can lead to increased anticancer potential. Lipophilicity is one of the factors that may influence biological properties and is therefore an important parameter to determine for newly obtained compounds as drug candidates. In the present study, previously synthesized 3 and/or 28-indole-betulin derivatives were evaluated for lipophilicity by reversed-phase thin-layer chromatography. The experimental values of lipophilicity (logPTLC) were then subjected to correlation analysis with theoretical values of logP, as well as for selected physicochemical and pharmacokinetic parameters and anticancer activity. A toxicity test using zebrafish embryos and larvae was also conducted. High correlation was observed between the experimental and theoretical values of lipophilicity. We presented correlation equations and statistical parameters describing the relationships between logPTLC and several physicochemical and ADME parameters. We also revealed the lack of correlation between the experimental values of lipophilicity and anticancer activity. Moreover, experiments on zebrafish have confirmed no toxicity of the tested compounds, which was consistent with the results of the in silico toxicity analysis. The results demonstrated, using the example of indole derivatives of betulin, the utility of lipophilicity values in the context of predicting the biological activity of new compounds.

New Type of Ferrocene‐Betulonic Acid Hybrids. Bioactivity, Synthesis, Structure, IR and CD versus DFT Calculations

AbstractFerrocene‐modified natural compounds are of interest for the development of new pharmaceuticals due to improved bioavailability, increased bioactivity, and also as redox markers or vectors. Betulin is a natural plant‐derived product with a wide range of pharmacological properties. However, it is limited in its bioavailability and efficacy. In order to enhance its pharmacological profile, the ferrocene modification of betulin was used in this study. A hybrid of the betulin core (up to 30 % betulin in birch bark) with a ferrocene moiety combined through a piperazine linker (compound 12) was prepared in good yield from readily available ferrocene carboxylic acid and betulonic acid, a natural betulin derivative, via coupling reactions. Spectroscopic techniques, including 1H and 13C NMR, IR and UV‐vis spectroscopy, as well as circular dichroism (CD), were applied to characterize the physicochemical and chiroptical properties. The cytotoxicity of the synthesized hybrid 12 and its ferrocene precursor 13 on MCF‐7 human cancer cell lines were in vitro evaluated by the MTT assay. The IC50 cytotoxicity index of 12 was found to be 26 μM. The theoretically calculated energies of the HOMO‐LUMO orbitals and electronic characteristics of betulin 10, betulonic acid 11, hybrid 12 and ferrocenyl piperazine 13 were determined by the DFT method with hybrid functionals ωB97XD, LC‐ωPBE and B3LYP‐D3 and pure M06 L functionals, with a 6‐311+G(d), 6‐31G(d) or TZV basis set.

Synthesis and anticancer evaluation of new lupane triterpenoid derivatives containing various substituent at the 2 or 3 position

Betulonic acid benzyl ester 1 has been subjected to a series of structural modifications for the purpose of new triterpenoid synthesis and evaluating for anticancer activity. The one-pot two step synthesis of 2α-(aminomethyl)betulinic acid benzyl ester derivatives 3a–f (yield 46–69 %) was achieved by the Mannich reaction of compound 1 with methyleneiminium salts, generated in situ from N,N-disubstituted bis(amino)methanes 2a–f by the action of acetyl chloride in dichloromethane, and subsequent reduction of aminomethylation products with sodium borohydride. Minor 2β-(aminomethyl) triterpenoids 4c,d,f were also isolated (yield 6–15 %). We found, that the stereoselective reaction of triterpenoid 1 with acetylides, generated at –78 °C from alkynes in the presence of n-BuLi, has been useful and noteworthy as the key step in providing of new alkyne substituted triterpenoids – benzyl 3-alkynyl-3-deoxy-2(3),20(29)-lupadiene-28-oates or 3-deoxy-2(3)-dehydro-28-oxoallobetulin derivative. The new compounds were examined for anticancer activity against the human cell lines (MTT assay). All tested derivatives were non-toxic on human fibroblasts. The 3‐(phenylethynyl)lupa-2(3),20(29)-diene 9 showed selective cytotoxicity on cervical cancer cell lines. Tumor cells death trigged by the most active compound 4f resulted from apoptotic processes. These data make the series of synthesized 2 or 3 substituted lupane derivatives as promising compounds with anticancer potential.

Design, synthesis and biological evaluation of novel betulinic acid derivatives containing 1,2,4-triazole-derived schiff bases as α-glucosidase inhibitors

A series of novel betulinic acid (BA) derivatives containing 1,2,4-triazole- derived schiff base have been designed and synthesized as α-glucosidase inhibitors. All the title compounds showed higher α-glucosidase inhibitory activity than acarbose and BA, with compound f32 showing the highest α-glucosidase inhibitory activity (IC50 = 1.52±0.16 μM). Lineweaver-Burk plot analysis suggested that compound f32 was a non-competitive inhibitor for α-glucosidase. 3D fluorescence and circular dichroism spectroscopy disclosed the interaction of compound f32 with α-glucosidase by changing the secondary structure of α-glucosidase. Molecular docking showed that compound f32 could bind to the active site of α-glucosidase through hydrogen bonding and hydrophobic interaction. More importantly, compound f32 could not only reduce the level of fasting blood glucose and postprandial blood glucose in mice, but also ameliorate dyslipidemia. The current findings suggest that compound f32 may serve as a leading compound for the discovery of α-glucosidase inhibitors in the treatment of type 2 diabetes.

1,2,3-Triazole-based betulinic acid derivatives as α-glucosidase inhibitors: Synthesis and in vitro and in vivo biological evaluation

A series of 1, 2, 3-triazole-based betulinic acid derivatives d1–d31 were synthesized as α-glucosidase inhibitors with hypoglycemic activity. All the derivatives exhibited excellent inhibition against α-glucosidase, and compound d23 was the most active (IC50 = 2.83 ± 0.19 μM). Inhibition kinetics showed that compound d23 was a mixed-type inhibitor for α-glucosidase. Spectroscopic studies based on 3D fluorescence and circular dichroism spectra suggested that compound d23 exerted its inhibitory activity by changing the conformation of α-glucosidase. Molecular docking revealed that compound d23 was well nested into the active pocket of α-glucosidase through hydrogen-bonding and hydrophobic interactions. In vivo experiments showed that compound d23 could not only reduce the level of fasting blood glucose, but also improve glucose tolerance and dyslipidemia. The present findings strongly suggest that compound d23 is exploitable as a leading compound for the development of α-glucosidase inhibitors in the treatment of type 2 diabetes.

New Biodegradable Copolymers Based on Betulin and Hydroxycarboxylic Acid Derivatives.

In this study, we propose an approach to the synthesis of new biodegradable polymer materials based on renewable raw feedstock (betulin) and derivatives of hydroxycarboxylic acids using a catalyst/catalytic system (γ-Al2O3, γ-Al2O3/TBHP) that is safe for health and the environment. The resulting polymers are linear thermoplastic polymers that undergo collapse upon melting in the presence of atmospheric oxygen. Moreover, these polymers demonstrate non-toxicity towards a range of Gram-positive and Gram-negative bacteria. The polycondensation of betulin with butyl lactate is particularly noteworthy.

Assessment of Bioavailability Parameters of Mono- and Bistriazole Derivatives of Propynoylbetulin

Bioavailability describes the properties that determine the passage of a compound through biological barriers. In many cases, bioavailability depends on the lipophilicity of the compound. In this study, the lipophilicity as well as other bioavailability properties of the mono- and bistriazole derivatives of betulin are presented. The lipophilicity was determined using RP-TLC and theoretical methods. The experimental lipophilicity of mono- and bistriazole derivatives is in the range from 4.39 to 7.85 and from 3.75 to 8.83, respectively. The lipophilicity of mono- and bistriazoles is similar, and the logPTLC depends on the type of substituent at the triazole ring. The introduction of a substituent with oxygen and nitrogen atoms decreases lipophilicity. Comparing the experimental and theoretical lipophilicity shows that the milogP and XLOGP3 programs best reproduce the experimental values. The in silico-determined pharmacokinetic parameters show that monotriazole derivatives could be used as oral drugs while bistriazoles show low availability after oral administration. Triazoles could be used as transdermal drugs. The analysis of in silico bioavailability parameters shows that the type of substituent at the triazole ring influences the pharmacokinetic properties, while the number of triazole rings slightly affects the bioavailability properties of the compound.

Derivatives of Betulin and Betulinic Acid Containing a Phosphonate Group—In Silico Studies and Preliminary In Vitro Assessment of Antiviral Activity

Viral diseases affecting both humans and animals are a serious public problem. Chemical modifications of the structure of compounds of natural origin, e.g., betulin, seem to be a promising model in the search for new antiviral agents. The subject of our work was to conduct preliminary tests on the antiviral activity of phosphonic derivatives of betulin and betulinic acid and to assess the pharmacokinetic profile of target compounds. Human (HHV-1, HAdV-5) and animal viruses (BEV, VSV) were used in the in vitro tests. Additionally, this paper presents the results of research using in silico methods (ADMET and molecular docking). Two compounds (betulin 29-phosphonate 3 and 3-(3′,3′-dimethylsuccinyl)betulin acid 29-phosphonate 8a) showed antiviral activity against BEV, and compound 3 was also active against HAdV-5. For compound 3, which showed advantageous pharmacokinetic parameters, molecular docking was performed to determine possible interactions with the cellular target HAdV-5 endopeptidase, which plays an important role in various functions of the virus. Selecting the most active derivatives makes it possible to plan tests on an animal model.

One-pot Synthesis of Some New Betulinic Acid Derivatives with Cytotoxicity Against Human Pancreatic Cancer Cells

Background: One-pot synthesis of new and biologically important betulinic acid derivatives has been designed and efficiently achieved in this work. Methods: The utilization of the carboxylic and hydroxyl moieties of betulinic acid has resulted in the development of a one-pot strategy towards the synthesis of some target compounds. Results: One-pot synthesis of new betulinic acid derivatives 3-9 has been achieved in moderate to high yields by way of esterification of the carboxylic functionality with a variety of alkylating agents. These were fully characterized by spectroscopic techniques. Conclusion: The synthesized new derivatives of betulinic acid were screened for their cytotoxic effect against human pancreatic cancer cells.

Discovery of betulinic acid derivatives as gut-restricted TGR5 agonists: Balancing the potency and physicochemical properties

The pleiotropic effects of TGR5 make it an appealing target for intervention of metabolic and inflammatory disorders, but systemic activation of TGR5 faces challenges of on-target side effects, especially gallbladder filling. Gut-restricted agonists were proved to be sufficient to circumvent these side effects, but extremely low systemic exposure may not be effective in activating TGR5 since it is located on the basolateral membrane. Herein, to balance potency and physicochemical properties, a series of gut-restricted TGR5 agonists with diversified kinetophores had been designed and synthesized. Compound 22-Na exhibited significant antidiabetic effect, and showed favorable gallbladder safety after 7 days of oral administration in humanized TGR5H88Y mice, confirming that gut-restricted agonism of TGR5 is a viable strategy to alleviate systemic target-related effects.

Novel betulin derivatives as multidrug reversal agents targeting P-glycoprotein

Chemotherapy is a powerful means of cancer treatment but its efficacy is compromised by the emergence of multidrug resistance (MDR), mainly linked to the efflux transporter ABCB1/P-glycoprotein (P-gp). Based on the chemical structure of betulin, identified in our previous work as an effective modulator of the P-gp function, a series of analogs were designed, synthesized and evaluated as a source of novel inhibitors. Compounds 6g and 6i inhibited rhodamine 123 efflux in the P-gp overexpressed leukemia cells, K562/Dox, at concentrations of 0.19 µM and 0.39 µM, respectively, and increased the intracellular accumulation of doxorubicin at the submicromolar concentration of 0.098 µM. Compounds 6g and 6i were able to restore the sensitivity of K562/Dox to Dox at 0.024 µM and 0.19 µM, respectively. Structure–activity relationship analysis and molecular modeling revealed important information about the structural features conferring activity. All the active compounds fitted in a specific region involving mainly transmembrane helices (TMH) 4–6 from one homologous half and TMH 7 and 12 from the other, also showing close contacts with TMH 6 and 12. Compounds that bound preferentially to another region were inactive, regardless of their free energy of binding. It should be noted that compounds 6g and 6i were devoid of toxic effects against peripheral blood mononuclear normal cells and erythrocytes. The data obtained indicates that both compounds might be proposed as scaffolds for obtaining promising P-gp inhibitors for overcoming MDR.

Investigation of some properties of a composite biomaterial based on betulin treat infected wounds and burns

An urgent problem of modern medicine is the problem of treatment of infected wounds, which is associated with the prevalence of wounds of various etiologies, purulent complications, high mortality, and high material costs of treatment. For the treatment of wounds most often used local effects of drugs, in particular, use a variety of coatings and dressings. Types of these dressings are quite diverse. They can be created on the basis of bioresorbable materials, contain other therapeutic substances such as enzymes, anesthetics, antibiotics in order to have a complex effect on the wound healing process. The choice of optimal local wound coatings or their effective combinations with physiotherapeutic methods of treatment of local superficial and deep wounds and prevention of wound infection remains an unsolved problem. In this regard, the creation of new wound healing preparations and wound coatings based on them seems to be very relevant. At the moment, there are many biologically active substances suitable for the therapy of wounds and burns. These substances can have a variety of origins - both synthetic and natural. Recently, the attention of specialists to drugs of natural origin is constantly growing. Interest in the use of such drugs is justified by their high efficiency, the lack of the need for complex synthesis, a wide range of pharmacological activity, as well as the possibility of using them for a long time without complications and side effects. The specific weight and volume of production of medicines obtained by synthetic transformations of substances extracted from wild and cultivated plants is increasing worldwide. Substances of plant origin are now increasingly being used in medical products for a wide range of purposes. One of such substances are derivatives of natural pentacyclic triterpenoid betulin extracted from birch bark. Betulin and its derivatives have high biological activity. This substance and its derivatives exhibit a complex of biologically active properties such as wound healing, antibacterial, antitumor, hypolipidemic, hepatoprotective, antiviral and others. Betulin, overcoming resistance, induces apoptosis of malignized cells in various human cancers. It should also be noted that sufficient raw material base and biological activity of betulin put it in a number of valuable natural sources for use both in the native state and in the form of various transformation products, which makes it relevant to develop drugs based on it.

Novel Betulin-1,2,4-Triazole Derivatives Promote In Vitro Dose-Dependent Anticancer Cytotoxicity

Betulin is a birch bark-derived lupane-type pentacyclic triterpene with a wide spectrum of biological activities. Given their enhanced antiproliferative potential and enhanced pharmacological profile, betulin derivatives are continuously investigated in scientific studies. The objective of the current study was to in vitro assess the antiproliferative properties of novel synthesized 1,2,4-triazole derivatives of diacetyl betulin. The compounds were investigated using three cancer cell lines: A375 (melanoma), MCF-7 (breast cancer), HT-29 (colorectal cancer), and HaCaT (human keratinocytes). Bet-TZ1 had the lowest recorded IC50 values (ranging from 22.41 to 46.92 μM after 48 h of exposure) than its precursor and other tested compounds in every scenario, with the highest cytotoxicity against the A375 cell line. Bet-TZ3 demonstrated comparable cytotoxicity to the previously mentioned compound, with an IC50 of 34.34 μM against A375. Both compounds caused apoptosis in tested cells, by inducing specific nuclear morphological changes and by increasing the expression of caspase 9, indicating significant cytotoxicity, which was consistent with the literature and viability evaluation. Bet-TZ1 and Bet-TZ3 inhibit cancer cell migration, with the former having a stronger effect than the latter. The HET−CAM test indicated that all compounds have no irritative potential, suggesting that they can be used locally.

Design, synthesis and biological evaluation of betulinic acid derivatives as potential inhibitors of 3CL-protease of SARS-CoV-2

During the coronavirus reproduction process, 3-chymotrypsin-like protease (3CLpro) and papain-like protease (PLpro) are accountable for the fragmentation of two polyprotein precursors (pp1a/pp1ab) into substructural proteins. These two proteins are vital for the replication and transcription of the viral genome. Therefore, 3CLpro is a key protein and target for the design of coronavirus inhibitors. In previous studies, we found that betulinic acid has an inhibitory effect on 3CLpro, with 51.5 % inhibition of 3CLpro at 20 µM. Then, series of betulinic acid derivatives were designed, synthesized, and evaluated for their inhibition activities. The results showed that BA02 and BA05 showed significant inhibitory activity on 3CLpro with inhibitory rates of 78.1 % and 82.5 % at 20 µM, respectively. Further evaluation of these two compounds shows that their IC50 values are 7.22 ± 0.14 μM and 6.40 ± 0.14 μM, respectively.

The Influence of Betulin Derivatives EB5 and ECH147 on the Expression of Selected TGFβ Superfamily Genes, TGFβ1, GDF15 and BMP2, in Renal Proximal Tubule Epithelial Cells.

Betulin derivatives are proposed to serve as an alternative to the drugs already established in oncologic treatment. Drug-induced nephrotoxicity leading to acute kidney injury frequently accompanies cancer treatment, and thus there is a need to research the effects of betulin derivatives on renal cells. The objective of our study was to assess the influence of the betulin derivatives 28-propynylobetulin (EB5) and 29-diethoxyphosphoryl-28-propynylobetulin (ECH147) on the expression of TGFβ1, BMP2 and GDF15 in renal proximal tubule epithelial cells (RPTECs) cultured in vitro. The changes in mRNA expression and copy numbers were assessed using real-time reverse transcription quantitative polymerase chain reaction (RT-qPCR) and the standard curve method, respectively. An enzyme-linked immunosorbent assay (ELISA) was used to evaluate the effect of the betulin derivatives on the protein concentration in the culture media's supernatant. The assessment of the betulin derivatives' influence on gene expression demonstrated that the mRNA level and protein concentration did not always correlate with each other. Each of the tested compounds affected the mRNA expression. The RT-qPCR analyses showed that EB5 and ECH147 induced effects similar to those of betulin or cisplatin and resulted in a decrease in the mRNA copy number of all the analyzed genes. The ELISA demonstrated that EB5 and ECH147 elevated the protein concentration of TGFβ1 and GDF15, while the level of BMP2 decreased. The concentration of the derivatives used in the treatment was crucial, but the effects did not always exhibit a simple linear dose-dependent relationship. Betulin and its derivatives, EB5 and ECH147, influenced the gene expression of TGFβ1, BMP2 and GDF15 in the renal proximal tubule epithelial cells. The observed effects raise the question of whether treatment with these compounds could promote the development of renal fibrosis.

Antiproliferative and Cytotoxic Properties of Propynoyl Betulin Derivatives against Human Ovarian Cancer Cells: In Vitro Studies.

Due to the incidence of ovarian cancer (OC) and the limitations of available therapeutic strategies, it is necessary to search for novel therapeutic solutions. The aim of this study was to evaluate the cytotoxic effect of betulin 1 and its propynoyl derivatives 2-6 against ovarian cancer cells (SK-OV-3, OVCAR-3) and normal myofibroblasts (18Co). Paclitaxel was used as the reference compound. The propynoyl derivatives 2-6 exhibited stronger antiproliferative and cytotoxic activities compared to betulin 1. In both ovarian cancer cell lines, the most potent compound was 28-propynoylbetulin 2. In the case of compound 2, the calculated IC50 values were 0.2 µM for the SK-OV-3 cells and 0.19 µM for the OVCAR-3 cells. Under the same culture conditions, the calculated IC50 values for compound 6 were 0.26 µM and 0.59 µM, respectively. It was observed that cells treated with compounds 2 and 6 caused a decrease in the potential of the mitochondrial membrane and a significant change in cell morphology. Betulin 1, a diol from the group of pentacyclic triterpenes, has a confirmed wide spectrum of biological effects, including a significant anticancer effect. It is characterized by low bioavailability, which can be improved by introducing changes to its structure. The results showed that chemical modifications of betulin 1 only at position C-28 with the propynoyl group (compound 2) and additionally at position C-3 with the phosphate group (compound 3) or at C-29 with the phosphonate group (compound 6) allowed us to obtain compounds with greater cytotoxic activity than their parent compounds, which could be used to develop novel therapeutic systems effective in the treatment of ovarian cancer.

Performic acid—dichloromethane system as chemoselective reagent in the synthesis of 29-nor-20-O-formyl derivatives of betulin

Performic acid—dichloromethane system as chemoselective reagent in the synthesis of 29-nor-20-O-formyl derivatives of betulin