Synthesis and potential anti-inflammatory response of indole and amide derivatives of ursolic acid in LPS-induced RAW 264.7 cells and systemic inflammation mice model: Insights into iNOS, COX2 and NF-κB

Ursolic acid (3-hydroxy-urs-12-ene-28-oic acid, UA) is a pentacyclic triterpene present in numerous plants, fruits and herbs and exhibits various pharmacological effects. However, UA has limited clinical applicability since it is classified as BCS class IV molecule, characterized by low solubility, low oral bioavailability and low permeability. In the present study, UA was isolated from the biomass marc of Lavandula angustifolia and was structurally modified by an induction of indole ring at the C-3 position and amide group at the C-17 position with the aim to enhance its pharmacological potential. This modification resulted in the synthesis of a series of compounds which were investigated for their anti-inflammatory potential both in-vitro and in animal models in comparison to UA. In RAW 264.7 cells, UA and its derivatives were non-cytotoxic up to 10 µM. The derivative UA-1 exhibited a significantly lower IC50 (2.2 ± 0.4 µM) for NO inhibition compared to UA (17.5 ± 2.0 µM). Molecular docking showed strong interactions of UA-1 with TNF-α and NF-κB. UA-1 significantly reduced LPS-induced pro-inflammatory cytokines (TNF-α, IL-6, IL-1β) in RAW 264.7 macrophages with the inhibition levels of 74.2 ± 2.1 % for TNF-α, 55.9 ± 3.7 % for IL-6 and 59.7 ± 4.2 % for IL-1β at 5.0 µM, respectively and reactive oxygen species while upregulating anti-inflammatory cytokine, IL-10. It also downregulated iNOS, COX-2, p-NF-κB p65, and p-IκBα at both mRNA and protein levels. In LPS-induced systemic inflammation mice model, UA-1 significantly lowered NO, TNF-α, IL-6, IL-1β and serum biochemical parameters, reduced tissue damage, and exhibited improved aqueous solubility and moderate lipophilicity. Overall, UA-1 demonstrated superior anti-inflammatory potential, improved solubility, and better therapeutic potential compared to UA.

Sustainable methods for the carboxymethylation and methylation of ursolic acid with dimethyl carbonate under mild and acidic conditions

Ursolic acid is a triterpene plant extract that exhibits significant potential as an anti-cancer, anti-tumour, and anti-inflammatory agent. Its direct use in the pharmaceutical industry is hampered by poor uptake of ursolic acid in the human body coupled with rapid metabolism causing a decrease in bioactivity. Modification of ursolic acid can overcome such issues, however, use of toxic reagents, unsustainable synthetic routes and poor reaction metrics have limited its potential. Herein, we demonstrate the first reported carboxymethylation and/or methylation of ursolic acid with dimethyl carbonate (DMC) as a green solvent and sustainable reagent under acidic conditions. The reaction of DMC with ursolic acid, in the presence of PTSA, ZnCl2, or H2SO4-SiO2 yielded the carboxymethylation product 3β-[[methoxy]carbonyl]oxyurs-12-en-28-oic acid, the methylation product 3β-methoxyurs-12-en-28-oic acid and the dehydration product urs-2,12-dien-28-oic acid. PTSA demonstrated high conversion and selectivity towards the previously unreported carboxymethylation of ursolic acid, while the application of formic acid in the system led to formylation of ursolic acid (3β-formylurs-12-en-28-oic acid) in quantitative yields via esterification, with DMC acting solely as a solvent. Meanwhile, the methylation product of ursolic acid, 3β-methoxyurs-12-en-28-oic acid, was successfully synthesised with FeCl3, demonstrating exceptional conversion and selectivity, >99% and 99%, respectively. Confirmed with the use of qualitative and quantitative green metrics, this result represents a significant improvement in conversion, selectivity, safety, and sustainability over previously reported methods of ursolic acid modification. It was demonstrated that these methods could be applied to other triterpenoids, including corosolic acid. The study also explored the potential pharmaceutical applications of ursolic acid, corosolic acid, and their derivatives, particularly in anti-inflammatory, anti-cancer, and anti-tumour treatments, using molecular ADMET and docking methods. The methods developed in this work have led to the synthesis of novel molecules, thus creating opportunities for the future investigation of biological activity and the modification of a wide range of triterpenoids applying acidic DMC systems to deliver novel active pharmaceutical intermediates.

Oleanane-Type Triterpene Conjugates with 1H-1,2,3-Triazole Possessing of Fungicidal Activity

The triazole pesticide is an organic nitrogen-containing heterocyclic compound with a 1,2,3-Triazole ring. In order to develop a potential glucosamine-6-phosphate synthase (GlmS) inhibitor bactericide, 18 triazole-derivative compounds were synthesized efficiently. In addition, these compounds have not been reported in the literature. The structure was confirmed by high-resolution mass spectrometry (HRMS), 1H NMR and 13C NMR. The potential use of the most promising derivatives has been investigated by testing their antifungal activity and enzyme inhibitory activity, revealing inhibitory activities in the low micromolar range. Among them, the antifungal effects of compounds 1e, 1f, 1g, 2e, 2f, and 2g on Sclerotinia sclerotiorum were particularly significant, all of which were above 83%. These compounds will be further investigated as potential antifungal lead compounds. Their structure–activity relationships are discussed based on the effects of substituted phenyl groups on compounds.

Design, Synthesis, Molecular Modelling, and Biological Evaluation of Oleanolic Acid-Arylidene Derivatives as Potential Anti-Inflammatory Agents

INTRODUCTION

Oleanolic acid, a pentacyclic triterpenic acid, is widely distributed in medicinal plants and is the most commonly studied triterpene for various biological activities, including anti-allergic, anti-cancer, and anti-inflammatory.

METHODS

The present study was carried out to synthesize arylidene derivatives of oleanolic acid at the C-2 position by Claisen Schmidt condensation to develop more effective anti-inflammatory agents. The derivatives were screened for anti-inflammatory activity by scrutinizing NO production inhibition in RAW 264.7 cells induced by LPS and their cytotoxicity. The potential candidates were further screened for inhibition of LPS-induced interleukin (IL-6) and tumour necrosis factor-alpha (TNF-α) production in RAW 264.7 cells.

RESULTS

The results of in vitro studies revealed that derivatives 3d, 3e, 3L, and 3o are comparable to that of the oleanolic acid on the inhibition of TNF-α and IL-6 release. However, derivative 3L was identified as the most potent inhibitor of IL-6 (77.2%) and TNF-α (75.4%) when compared to parent compound, and compounds 3a (77.18%), 3d (71.5%), and 3e (68.8%) showed potent inhibition of NO than oleanolic acid (65.22%) at 10µM. Besides, from docking score and Cyscore analysis analogs (3e, 3L, 3n) showed greater affinity towards TNF-α and IL-1β than dexamethasone.

CONCLUSION

Herein, we report a series of 15 new arylidene derivatives of oleanolic acid by Claisen Schmidt condensation reaction. All the compounds synthesized were screened for their anti-inflammatory activity against NO, TNF-α and IL-6. From the data, it was evident that most of the compounds exhibited better anti-inflammatory activity.

Preventive effect of ursolic acid derivative on particulate matter 2.5-induced chronic obstructive pulmonary disease involves suppression of lung inflammation

Respiratory diseases like chronic obstructive pulmonary disease (COPD) are associated with the presence of particulate matter 2.5 (PM2.5) in the air. In the present study, the effect of synthesized ursolic acid derivatives on mice model of PM2.5-induced COPD was investigated in vivo. The mice model of COPD was established by the administration of 25 μL of PM2.5 suspension through intranasal route daily for 1 week. The levels of oxidative stress markers and inflammatory cytokines like tumor necrosis factors-α and interleukin-6 in the mice bronchoalveolar fluids increased markedly on administration with PM2.5. However, treatment with ursolic acid derivative caused a significant suppression in PM2.5-induced increase in oxidative stress markers and inflammatory cytokines in dose-dependent manner. Hematoxylin and eosin staining showed excessive inflammatory cell infiltration in pulmonary tissues in mice with COPD. The inflammatory cell infiltration was inhibited on treatment of the mice with ursolic acid derivative. The ursolic acid derivative treatment increased level of superoxide dismutase in mice with COPD. The lung injury induced by PM2.5 in mice was also prevented on treatment with ursolic acid derivative. Thus, ursolic acid derivative inhibits pulmonary tissues damage in mice through suppression of inflammatory cytokine and oxidative enzymes. Therefore, ursolic acid derivative can be of therapeutic importance for treatment of PM2.5-induced COPD.

Ursolic acid derivative induces apoptosis in glioma cells through down-regulation of cAMP

The present study was designed to synthesize and evaluate ursolic acid hybrid compounds against glioma cells. Initial screening revealed that most of the synthesized compounds displayed better inhibitory effect on glioma cell proliferation compared to parent ursolic acid. The mechanism of inhibitory effect of the most potent compound 6d on glioma cells was investigated in detail. Treatment with compound 6d significantly (p < 0.001) reduced U251 and C6 cell proliferation at 48 h. The growth of U251 and C6 glioma cells was reduced to minimum level (17 and 21%) on treatment with 10 μM concentration of compound 6d. Treatment of the U251 cells with 10 μM concentration of compound 6d caused a significant (p < 0.05) inhibition of cAMP level. In U251 cell cultures treatment with compound 6d at 10 μM concentration enhanced proportion of apoptotic cells to 69.32% compared to 2.34% in the control cultures. The compound 6d treatment of U251 cells for 48 h caused arrest of cell cycle in the G0/G1 phase with consequent decrease of cell population in G2/M and S phases. The results from TEM showed that compound 6d treatment of U251 cells for 48 h caused blebbing of the cell membranes, chromatin condensation, appearance of foamy cytoplasmic material and autophagic vacuoles. The results from SEM revealed that compound 6d treatment of U251 cells caused a marked inhibition of microvilli and extensions on the cell surfaces. Thus present study demonstrates that compound 6d inhibits glioma cell growth, induces apoptosis and arrest cell cycle through metabolic pathway down-regulation. Therefore, compound 6d can be evaluated further for the treatment of glioma.

Ursolic Acid Isolated from the Leaves of Loquat ( Eriobotrya japonica) Inhibited Osteoclast Differentiation through Targeting Exportin 5

One of the conventional strategies for treating osteoporosis is to eliminate the multinucleated osteoclasts that are responsible for bone resorption. Our previous study revealed that ursolic acid, isolated from leaves of loquat that is used as tasty tea in Japan, suppressed osteoclastogenesis. We confirmed that ursolic acid exhibited osteoclast differentiation inhibitory activity with an 50% inhibitory concentration (IC50) value of 5.4 ± 0.96 μM. To disclose its mechanism of action, this study first uses polymer-coated magnetic nanobeads to identify potential target proteins. As a result, we identified a nuclear exporter protein named exportin 5 (XPO5). Further studies demonstrated that knockdown of XPO5 significantly blocks osteoclast differentiation ( P < 0.01). Expression profiling of mature microRNAs in the cells revealed that downregulation of XPO5 by small interfering RNA or by ursolic acid could downregulate the expression of mature microRNA let-7g-5p during osteoclast differentiation ( P < 0.01). Collectively, our findings suggest that ursolic acid inhibits osteoclast differentiation through targeting XPO5, which provides further evidence for the healthy function of the tea. This study also provides new insights into the role of XPO5 and its mediated microRNAs in treatment for bone resorption diseases.

Anti-inflammatory and antioxidative effects of six pentacyclic triterpenes isolated from the Mexican copal resin of Bursera copallifera

BACKGROUND

Bursera copallifera (Burseraceae) releases a resin known as "copal ancho" which has been used, since pre-Colombian times, as ceremonially burned incense and to treat tooth ache, tumors, arthritis, cold, cough, and various inflammatory conditions; however, its anti-inflammatory potential is poorly studied. The aim of the present study was to isolate, quantify, and to investigate the anti-inflammatory activity of triterpene compounds isolated from the copal resin of B. copallifera.

METHODS

The constituents present in the total resin of B. copallifera were obtained by successive chromatographic procedures, and quantitative analysis was performed by High Performance Liquid Chromatography (HPLC). Anti-inflammatory effects of the isolated triterpenes were investigated to determine their inhibitory effects on phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced edema in mice, viability and nitric oxide (NO) production inhibition on lipopolysaccharide (LPS)-activated RAW 264.7 macrophages, and inhibition of cyclooxygenase (COX)-1, COX-2 and secretory Phospholipase A2 (sPLA2) activities in vitro.

RESULTS

Quantitative phytochemical analysis of the copal resin showed the presence of six pentacyclic triterpenes of which, 3-epilupeol (59.75 % yield) and α-amyrin (21.1 % yield) are the most abundant. Among the isolated triterpenes, 3-epilupeol formiate (Inhibitory Concentration 50 % (IC50) = 0.96 μmol), α.amyrin acetate (IC50 = 1.17 μmol), lupenone (IC50 = 1.05 μmol), and 3-epilupeol (IC50 = 0.83 μmol) showed marked inhibition of the edema induced by TPA in mice. α-amyrin acetate and 3-epilupeol acetate, at 70 μM, also inhibited the activity of COX-2 by 62.85 and 73.28 % respectively, while α-amyrin and 3-epilupeol were the best inhibitors of the production of NO in LPS-activated RAW 264.7 cells with IC50 values of 15.5 and 8.98 μM respectively, and did not affected its viability. All compounds moderately inhibited the activity of PLA2.

CONCLUSIONS

This work supports the folk use of B. copallifera and provides the basis for future investigations about the therapeutic use of this resin in treating inflammation.

Solid inclusion complexes of oleanolic acid with amino-appended β-cyclodextrins (ACDs): Preparation, characterization, water solubility and anticancer activity

Oleanolic acid (OA) is a pentacyclic triterpenoid acid of natural abundance in plants which possesses important biological activities. However, its medicinal applications were severely impeded by the poor water solubility and resultant low bioavailability and potency. In this work, studies on solid inclusion complexes of OA with a series of amino-appended β-cyclodextrins (ACDs) were conducted in order to address this issue. These complexes were prepared by suspension method and were well characterized by NMR, SEM, XRD, TG, DSC and Zeta potential measurement. The 2:1 inclusion mode of ACDs/OA complexes was elucidated by elaborate 2D NMR (ROESY). Besides, water solubility of OA was dramatically promoted by inclusion complexation with ACDs. Moreover, in vitro anticancer activities of OA against human cancer cell lines HepG2, HT29 and HCT116 were significantly enhanced after formation of inclusion complexes, while the apoptotic response results indicated their induction of apoptosis of cancer cells. This could provide a novel approach to development of novel pharmaceutical formulations of OA.

Synthesis and screening of ursolic acid-benzylidine derivatives as potential anti-cancer agents

Ursolic acid present abundantly in plant kingdom is a well-known compound with various promising biological activities including, anti-cancer, anti-inflammatory, hepatoprotective, antiallergic and anti-HIV properties. Herein, a library of ursolic acid-benzylidine derivatives have been designed and synthesized using Claisen Schmidt condensation of ursolic acid with various aromatic aldehydes in an attempt to develop potent antitumor agents. The compounds were evaluated against a panel of four human carcinoma cell lines including, A-549 (lung), MCF-7 (breast), HCT-116 (colon), THP-1 (leukemia) and a normal human epithelial cell line (FR-2). The results from MTT assay revealed that all the compounds displayed high level of antitumor activities compared with the triazole analogs (previously reported) and the parent ursolic acid. However, compound 3b, the most active derivative was subjected to mechanistic studies to understand the underlying mechanism. The results revealed that compound 3b induced apoptosis in HCT-116 cell lines, arrest cell cycle in the G1 phase, caused accumulation of cytochrome c in the cytosol and increased the expression levels of caspase-9 and caspase-3 proteins. Therefore, compound 3b induces apoptosis in HCT-116 cells through mitochondrial pathway.

A Series of New Ligustrazine-Triterpenes Derivatives as Anti-Tumor Agents: Design, Synthesis, and Biological Evaluation

A series of novel ligustrazine-triterpenes derivatives was designed, synthesized and screened for their cytotoxicity against five cancer cell lines (Bel-7402, HepG2, HT-29, Hela, and MCF-7) and Madin-Darby canine kidney (MDCK). Current study suggested that most of the ligustrazine-triterpenes conjunctions showed better cytotoxicity than the starting materials. In particular, compound 4a exhibited better cytotoxic activity (IC₅₀ < 5.23 μM) against Bel-7402, HT-29, MCF-7, Hela, and HepG2 than the standard anticancer drug cisplatin (DDP). The cytotoxicity selectivity detection revealed that 4a exhibited low cytotoxicity (IC₅₀ > 20 μM) towards MDCK cells. A combination of fluorescence staining observation and flow cytometric analysis indicated that 4a could induce HepG2 cell apoptosis. Further studies suggested that 4a-induced apoptosis is mediated through depolarization of the mitochondrial membrane potential and increase of intracellular free Ca²⁺ concentration. In addition, the structure-activity relationships of these derivatives were briefly discussed.

Design and optimization of oleanolic/ursolic acid-loaded nanoplatforms for ocular anti-inflammatory applications

Oleanolic acid (OA) and ursolic acid (UA) are ubiquitous pentacyclic triterpenes compounds in plants with great interest as anti-inflammatory therapeutics. The aim of this study was the design and optimization of polymeric nanoparticles (NPs) loaded with natural and synthetic mixtures (NM, SM) of these drugs for ophthalmic administration. A 2(3) + star central rotatable composite design was employed to perform the experiments. Results showed optimal and stable formulations with suitable physicochemical properties (mean diameter<225 nm), homogeneous distribution (polydispersity index∼0.1), negatively charged surface (∼-27 mV) and high entrapment efficiency (∼77%). Release and corneal permeation studies showed that NM release was faster than SM. Amounts of drug retained in the corneal tissue were also higher for NM. In vitro and in vivo tests showed no signs of irritation or toxicity and successful in vivo anti-inflammatory efficacy for both formulations, being NM-OA/UA NPs the most effective. From the clinical editor: Oleanolic acid (OA) and ursolic acid (UA) are compounds found in plants with anti-inflammatory properties. The authors in this paper designed nanoparticles (NPs) using poly(dl-lactide-coglycolide) acid (PLGA) loaded with these compounds for ophthalmic administration. Both in vitro and in vivo experiments showed no toxicity and significant anti-inflammatory efficacy. This may provide new drugs for ocular anti-inflammatory treatment.

Ursolic acid and its natural derivative corosolic acid suppress the proliferation of APC-mutated colon cancer cells through promotion of β-catenin degradation

Ursolic acid (UA) and corosolic acid (CA), naturally occurring pentacyclic triterpene acids, exhibit antiproliferative activities against various cancer cells, but a clear chemopreventive mechanism of these triterpenoids in colon cancer cells remains to be answered. Here we used a cell-based reporter system for detection of β-catenin response transcription (CRT) to identify UA as an antagonist of the Wnt/β-catenin pathway. UA promoted the degradation of intracellular β-catenin that was accompanied by its N-terminal phosphorylation at Ser33/37/Thr41 residues, marking it for proteasomal degradation. Consistently, UA down-regulated the intracellular β-catenin level in colon cancer cells with inactivating mutations of adenomatous polyposis coli (APC). In addition, UA repressed the expression of β-catenin/T-cell factor (TCF)-dependent genes, thereby inhibiting cell proliferation in colon cancer cells. The functional group analysis revealed that the major structural requirements for UA-mediated β-catenin degradation are a carboxyl group at position 17 and a methyl group at position 19. Notably, CA (2α-hydroxyursolic acid) was also found to decrease the level of intracellular β-catenin and to suppress the growth of APC-mutated colon cancer cells. Our findings suggest that UA and CA exert their anticancer activities against colon cancer cells by promoting the N-terminal phosphorylation and subsequent proteasomal degradation of β-catenin.