Synthesis and biological evaluation of betulonic acid derivatives as antitumor agents

Betulonic acid: A review on its sources, biological activities, and molecular mechanisms

Pentacyclic triterpenoids represent a significant class of phytochemicals, categorized into oleanane, ursane, friedelane, and lupane. Among these, betulonic acid stands out as a lupane-type pentacyclic triterpenoid found in numerous plants. Its diverse biological properties, including anti-tumor, anti-viral, anti-inflammatory, anti-bacterial, and hepato-protective effects, have been extensively documented. To further explore the therapeutic potential of betulonic acid and its derivatives, we provide a comprehensive review of their sources, biological activities, and molecular mechanisms. We aim for this synthesis of data to stimulate fresh perspectives on betulonic acid and its potential in drug discovery.

Emodin derivatives as promising multi-aspect intervention agents for amyloid aggregation: molecular docking/dynamics simulation, bioactivities evaluation, and cytoprotection

Alzheimer's disease (AD) is a progressive neurodegenerative disease with complex pathogenesis. Despite the pathogenesis is unknown, the misfolding and accumulation of β-amyloid (Aβ) peptide play the important role in the occurrence and development of AD. Hence, multi-aspect intervention of the misfolded Aβ peptides aggregation is a promising therapy for AD. In previous work, we obtained the emodin derivatives (a-d) with multifunctional anti-AD activities, including metal ions chelation, cholinesterase inhibition, and hydroxyl/superoxide anion radical elimination. In this work, we predicted the interaction of emodin derivatives (a-d) with Aβ by combining molecular docking simulation and molecular dynamics simulation, and evaluated the ability to intervene with the self-, Cu2+- and AChE-induced Aβ aggregation via in vitro methods. The results indicated that a-d could act as the potent multi-aspect intervention agents for Aβ aggregation. In addition, a-d could effectively eliminate peroxyl radical, had virtually no neurotoxicity, and protect cells from oxidative and Aβ-induced damage. The prediction results of ADMET properties showed that a-d had suitable pharmacokinetic characteristics. It suggested that a-d could act as the promising multi-targeted directed ligands (MTDLs) for AD. These results may provide meaningful information for the development of the potential MTDLs for AD which are modified from natural-origin scaffolds.

Liquidambaric acid inhibits the proliferation of hepatocellular carcinoma cells by targeting PPARα-RXRα to down-regulate fatty acid metabolism

Hepatocellular carcinoma (HCC) is a primary malignant tumor of the liver. As the global obesity rate rises, non-alcoholic fatty liver disease (NAFLD) has emerged as the most rapidly increasing cause of HCC. Consequently, the regulation of lipid metabolism has become a crucial target for the prevention and treatment of HCC. Liquidambaric acid (LDA), a pentacyclic triterpenoid compound derived from various plants, exhibits diverse biological activities. We found that LDA could inhibit HCC cell proliferation by arresting cell cycle and prompting apoptosis. Additionally, LDA can augment the therapeutic efficacy of Regorafenib in HCC in vitro and vivo. Our study utilized transcriptome analysis, luciferase reporter assays, and co-immunocoprecipitation experiments to elucidate the anti-HCC mechanism of LDA. We discovered that LDA disrupts the formation of the PPARα-RXRα heterodimer, leading to the down-regulation of the ACSL4 gene and subsequently impacting the fatty acid metabolism of HCC cells, ultimately inhibiting HCC proliferation. Our research contributes to the identification of novel therapeutic agents and targets for the treatment of HCC.

Synthesis and Investigation of Biological Activity of New Betulonic Acid Derivatives Containing 1,2,3-Triazole Fragments

The results of this study showed that the compounds synthesized by the authors have significant potential due to their antibacterial and cytotoxic properties. The apparent antibacterial activity demonstrated by the compounds suggests that they are active antimicrobial agents against common microbial pathogens that cause various socially significant infectious diseases. Compound 6 showed pronounced antimicrobial activity against the Gram-positive test strain Staphylococcus aureus ATCC 6538, and compound 7 demonstrated pronounced antimicrobial activity against the Gram-negative test strain Escherichia coli ATCC 25922 (MIC = 6.3 µg/mL). This allowed us to consider these compounds to have great potential.

Synthesis, Pharmacokinetic Profile, Anticancer Activity and Toxicity of the New Amides of Betulonic Acid-In Silico and In Vitro Study

Betulonic acid (B(O)A) is a pentacyclic lupane-type triterpenoid that widely exists in plants. There are scientific reports indicating anticancer activity of B(O)A, as well as the amides and esters of this triterpenoid. In the first step of the study, the synthesis of novel amide derivatives of B(O)A containing an acetylenic moiety was developed. Subsequently, the medium-soluble compounds (EB171 and EB173) and the parent compound, i.e., B(O)A, were investigated for potential cytotoxic activity against breast cancer (MCF-7 and MDA-MB-231) and melanoma (C32, COLO 829 and A375) cell lines, as well as normal human fibroblasts. Screening analysis using the WST-1 test was applied. Moreover, the lipophilicity and ADME parameters of the obtained derivatives were determined using experimental and in silico methods. The toxicity assay using zebrafish embryos and larvae was also performed. The study showed that the compound EB171 exhibited a significant cytotoxic effect on cancer cell lines: MCF-7, A-375 and COLO 829, while it did not affect the survival of normal cells. Moreover, studies on embryos and larvae showed no toxicity of EB171 in an animal model. Compared to EB171, the compound EB173 had a weaker effect on all tested cancer cell lines and produced less desirable effects against normal cells. The results of the WST-1 assay obtained for B(O)A revealed its strong cytotoxic activity on the examined cancer cell lines, but also on normal cells. In conclusion, this article describes new derivatives of betulonic acid-from synthesis to biological properties. The results allowed to indicate a promising direction for the functionalization of B(O)A to obtain derivatives with selective anticancer activity and low toxicity.

In silico evaluation of some commercially available terpenoids as spike glycoprotein of SARS-CoV-2 - inhibitors using molecular dynamic approach

Coronavirus, an extremely contagious infections disease had a harmful effect on the world's population. It is a family of enveloped, single-stranded, positive-strand RNA viruses of Nidovirales order belongs to coroviridae family. At present, worldwide several lakhs of deaths and several billions of infections have been reported. Hence, the focus of the present study was to assess the SARS-CoV-2 enzyme inhibitory potential of certain commercially available terpenoids using Lamarckian genetic algorithm as a working principle and molecular dynamic studies was also performed. AutoDock 4.2 software was used to perform the computational docking calculations of terpenoids against SARS-CoV-2 enzyme. The terpenoids such as, Andrographolide, Betulonic acid, Erythrodiol, Friedelin, Mimuscopic acid, Moronic acid, and Retinol were selected based on the drug likeness properties. Remdesivir a well-known anti-viral drug was selected as the standard drug. Molecular dynamic simulation studies were carried using Desmond module of Schrodinger Suite. In the current study we observed that, Friedelin was exhibited excellent SARS-CoV-2 enzyme inhibitory potential than the standard drug and other selected terpenoids. Friedelin and the standard Remdesivir was undergone the molecular dynamic studies and Friedelin showed a good number of hydrogen bonds over the simulation time of 100 ns. Based on the in silico computational evaluation, it can be concluded that Friedelin could be worthwhile terpenoid against SARS-CoV-2 spike protein. A further study on Friedelin is required to develop a potential chemical entity against the management of COVID disease.Communicated by Ramaswamy H. Sarma.

Synthesis of methotrexate-betulonic acid hybrids and evaluation of their effect on artificial and Caco-2 cell membranes

An efficient protocol for the synthesis of novel methotrexate-betulonic acid hybrids with a (tert-butoxycarbonylamino)-3,6-dioxa-8-octanamine (Boc-DOOA) linkage has been developed. Reaction of N-(2-(2-(2-aminoethoxy)ethoxy)ethyl)-betulonamide with methotrexate resulted in a mixture of isomeric conjugates which were separated by column chromatography. Their structures and composition have been fully established by 1H NMR, 13C spectra, FAB mass spectrometry and elemental analysis. The identity of conjugates was confirmed by LC-MS data. Membranotropic properties of the new hybrids were assessed on the basis of their interactions with artificial lipid membranes by differential scanning calorimetry (DSC) method. The ability of the conjugates to penetrate Caco-2 cells is inferior to methotrexate. Probably, this is due to the increasing lipophilicity, the affinity of these hybrid molecules for the lipid bilayer increases, which is confirmed by experiments with artificial membranes.

Comparison of In Vitro Antimelanoma and Antimicrobial Activity of 2,3-Indolo-betulinic Acid and Its Glycine Conjugates

Malignant melanoma is one of the most pressing problems in the developing world. New therapeutic agents that might be effective in treating malignancies that have developed resistance to conventional medications are urgently required. Semisynthesis is an essential method for improving the biological activity and the therapeutic efficacy of natural product precursors. Semisynthetic derivatives of natural compounds are valuable sources of new drug candidates with a variety of pharmacological actions, including anticancer ones. Two novel semisynthetic derivatives of betulinic acid-N-(2,3-indolo-betulinoyl)diglycylglycine (BA1) and N-(2,3-indolo-betulinoyl)glycylglycine (BA2)-were designed and their antiproliferative, cytotoxic, and anti-migratory activity against A375 human melanoma cells was determined in comparison with known N-(2,3-indolo-betulinoyl)glycine (BA3), 2,3-indolo-betulinic acid (BA4) and naturally occurring betulinic acid (BI). A dose-dependent antiproliferative effect with IC₅₀ values that ranged from 5.7 to 19.6 µM was observed in the series of all five compounds including betulinic acid. The novel compounds BA1 (IC₅₀ = 5.7 µM) and BA2 (IC₅₀ = 10.0 µM) were three times and two times more active than the parent cyclic structure B4 and natural BI. Additionally, compounds BA2, BA3, and BA4 possess antibacterial activity against Streptococcus pyogenes ATCC 19615 and Staphylococcus aureus ATCC 25923 with MIC values in the range of 13-16 µg/mL and 26-32 µg/mL, respectively. On the other hand, antifungal activity toward Candida albicans ATCC 10231 and Candida parapsilosis ATCC 22019 was found for compound BA3 with MIC 29 µg/mL. This is the first report of antibacterial and antifungal activity of 2,3-indolo-betulinic acid derivatives and also the first extended report on their anti-melanoma activity, which among others includes data on anti-migratory activity and shows the significance of amino acid side chain on the observed activity. The obtained data justify further research on the anti-melanoma and antimicrobial activity of 2,3-indolo-betulinic acid derivatives.

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.

Design, synthesis and cytotoxic evaluation of novel betulonic acid-diazine derivatives as potential antitumor agents

With the purpose to improve antiproliferative activity, 26 new betulonic acid-diazine derivatives were designed and synthesized from betulinic acid. The anticancer activity of these semi-synthetic compounds was evaluated by MTT assay in both tumor cell lines and normal cell line. The results indicated that majority of new compounds exhibited improved antitumor activity compared with the parent compound betulonic acid. Compound BoA2C, in particular, had the most significant action with IC50 value of 3.39 μM against MCF-7 cells, while it showed lower cytotoxicity on MDCK cell line than cisplatin. Furthermore, we discovered that BoA2C strongly increased MCF-7 cell damage mostly by influencing arginine and fatty acid metabolism. In addition, the structure-activity relationships were briefly discussed. The results of this study suggested that the introduction of different diazines at C-28 could selectively inhibit different kinds of cancer cells and might be an effective way to synthesize potent anticancer lead compound from betulonic acid.

Anticancer Potential of Betulonic Acid Derivatives

Clinical trials have evidenced that several natural compounds, belonging to the phytochemical classes of alkaloids, terpenes, phenols and flavonoids, are effective for the management of various types of cancer. Latest research has proven that natural products and their semisynthetic variants may serve as a starting point for new drug candidates with a diversity of biological and pharmacological activities, designed to improve bioavailability, overcome cellular resistance, and enhance therapeutic efficacy. This review was designed to bring an update regarding the anticancer potential of betulonic acid and its semisynthetic derivatives. Chemical derivative structures of betulonic acid including amide, thiol, and piperidine groups, exert an amplification of the in vitro anticancer potential of betulonic acid. With the need for more mechanistic and in vivo data, some derivatives of betulonic acids may represent promising anticancer agents.

[1,2,4]triazines – as potential drugs in cancer chemotherapy

Cancers are a high risk for humanity. In 2018, approximately 18 million new cancer cases were diagnosed in the world. The choice of treatment depends on the type of cancer and its stage at diagnosis. The treatment of cancer consists mainly of surgical methods, radiotherapy, immunotherapy, hormone therapy and chemotherapy. Cytotoxic drugs can be used both in monotherapy and combination therapy. In 2009-2018, the US. Food and Drug Administration (FDA) approved about 356 new drugs for cancer therapy. However, it should be noted that despite the increasing availability of modern drugs, this disease is the second leading cause of death in the world. Research on the development of a cytotoxic drug is aimed at designing a compound structure, whose action is directed at cancer cells while not affecting normal cells. Triazine derivatives might be the chemical structure with potential anticancer activity. This scaffold has been used in oncological therapy since 1965. Depending on the location of the nitrogen atoms in the ring, three isomers can be distinguished: [1,2,3]triazines, [1,2,4]triazines, [1,3,5]triazines. Modification of the structure of the [1,2,4]triazine derivatives should provide stronger cytotoxic properties and reduce the side effects of the novel drug. Designing new preparations also aims to improve the patient’s quality of life. This review will briefly present how the modification of the chemical structure of [1,2,4]triazine derivatives increases their cytotoxic activity against cancer and why these compounds may be better tolerated than current therapy.

Ultrastructure of the Liver in Response to Cyclophosphamide and Triterpenoids

Ultrastructural reorganization of liver cells after isolated injections of cyclophosphamide, betulonic acid or its β-alanylamide, and combined treatment with the cytostatic and each of the triterpenoids is studied. Cyclophosphamide causes significant ultrastructural changes in all intracellular compartments of hepatocytes. Both triterpenoids cause moderate cytotoxic and stimulatory effects on the liver cell populations (hepatocytes, sinusoidal endotheliocytes, and Kupffer cells), when used alone. The cytotoxic effect of betulonic acid manifests in modification of the fine structure of hepatocyte mitochondria, sequestration of glycogen, intensification of autophagic processes, emergence of necrobiotic changes in hepatocytes and endotheliocytes; betulonic acid amide actively modifies the mitochondrial fine structure (hypertrophic organelles, matrix rarefaction, uneven dilatation of cristae). The effects of combinations of cyclophosphamide with betulonic acid or its amide on liver are polytarget: the cytotoxic activity of the cytostatic is potentiated towards some cells, while in other cells the regeneratory reactions are stimulated. The common cytological cytoprotective effects of betulonic acid and its amide used alone and in combination with cytostatics include stimulation of the endocytotic (pinocytotic) activities of the cells and stimulation of intracellular regeneration processes in them.

Lupane-type conjugates with aminoacids, 1,3,4- oxadiazole and 1,2,5-oxadiazole-2-oxide derivatives: Synthesis, anti-inflammatory activity and in silico evaluation of target affinity

With the purpose to improve anti-inflammatory activity, the impact of introduction of 1,2,5- and 1,3,4-oxadiazole fragments to betulonic acid core as well as hybrids tethered with short ω-amino acids has been studied. The anti-inflammatory activity of synthesized compounds was tested in vivo using models of inflammation induced by concanavalin A and histamine. The majority of new compounds demonstrated higher anti-inflammatory activity compared with starting betulonic acid. To confirm the molecular targets of new derivatives in NRf2 and NFκB pathways the docking at Kelch and BTB active sites of Keap1 as well as IKK was done. The novelty of the present work is the development of new class of low toxic anti-inflammatory substances consisting of amino acid-linked betulonic acid - oxadiazole conjugates. These compounds can be considered as prospective chemopreventive agents.

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.

A convergent synthesis of novel alkyne-azide cycloaddition congeners of betulinic acid as potent cytotoxic agent

In an endeavour to develop potent anti-tumor agents from betulinic acid (BA), a series of C-28 derived 1,2,3-triazolyl derivatives were designed and synthesized by employing Cu(I) catalyzed Huisgen 1,3-dipolar cycloaddition reaction. All the derivatives were evaluated for cytotoxic activity by MTT assay against five different human cancer cell lines: lung (A549), colon (HCT116), prostate (PC3), pancreatic (MIA PaCa-2) and breast (T47D). The data revealed that compounds 11c, 11d, 11g, 11h and 13a possess most promising cytotoxic potential. The compound 11h was one of the most active compounds, with IC₅₀ values in the range of 4-6µM against all the five cancer cell lines. The results of this study suggested that derivatives with free -OH (11c, 11d and 11g) and free -COOH (11h and 13a) substitutions in the triazole moiety introduced at the C-28 position significantly improved the anti-tumor activity and may be the favourable position to synthesize potent anticancer leads from BA. Introduction of a non polar alkyl groups at C-28 position (10, 12 and 14) resulted in the significant loss of the activity. Further, DAPI staining, ROS generation and wound healing experiments revealed that compound 11h induces apoptosis in HCT-116 cells.

Synthesis of novel lupane triterpenoid-indazolone hybrids with oxime ester linkage

An efficient protocol for the synthesis of novel lupane triterpenoid-indazolone hybrids with oxime ester linkage has been developed from naturally accessible precursor betulin. For the first time a series of betulonic acid-indazolone hybrids have been synthesized via an acylation of corresponding 6,7-dihydro-1H-indazol-4(5H)-one oximes with betulonic acid chloride. Diastereoselective reduction of the obtained betulonic acid conjugates with NaBH₄ resulted in a formation of betulinic acid-indazolone hybrids in excellent yields. The configuration of the key compounds has been fully established by X-ray and 2D NMR analysis.

Preparation of novel ring-A fused azole derivatives of betulin and evaluation of their cytotoxicity

An efficient scheme to synthesize novel ring-A fused heterocyclic derivatives of betulin was developed. The starting reaction of this synthesis was one-pot selective bacterial oxidation of betulin to betulone used as the key compound to synthesize the substituted azoles such as C(2)-C(3)-fused 1,2,3-triazoles, oxazoles and 1,2,4-triazine, as well as C(1)-C(2)-fused isoxazoles. The semi-synthetic compounds were screened for their cytotoxic activity against human cancer cell lines A549, HCT 116, HEp-2, MS and RD TE32 with use of the photometric MTT assays. Among the tested compounds, N-acetyltriazole of betulin (10) displayed impressive cytotoxic activity with IC₅₀ 2.3-7.5 μM against HCT 116, HEp-2, MS and RD TE32 cell lines as well as 3-methyl-4-oxido-1,2,4-triazine-derivative of betulonic acid (12) that was active against HCT 116 and HEp-2 cell lines with IC₅₀ 1.4 and 1.5 μM, respectively. Comparative experiments showed triazole (10) to have a lower cytotoxicity to normal epithelial cells, in comparison with compound (12). In accord with the in vivo acute toxicity test, the LD₅₀ of triazole (10) exceeded 600 mg/kg. The ability of the most potent active triazole (10) to trigger apoptotic cell death was explored in the Annexin V-FITC test and by analyzing of caspase activity and morphological alterations in mitochondria and nuclei of HCT 116 cells.

Solid-State Characterization and Biological Activity of Betulonic Acid Derivatives

Betulonic acid belongs to the pentacyclic triterpenic derivative class and can be obtained through the selective oxidation of betulin. In this study we set obtaining several functionalized derivatives of this compound by its condensation with several amino compounds such as aminoguanidine, hydroxylamine, n-butylamine and thiosemicarbazide as our goal. The functionalization of the parent compound led to several molecules with antiproliferative potential, the most promising being 3-2-carbamothioylhydrazonolup-20(29)-en-28-oic acid.