New betulinic acid derivatives induce potent and selective antiproliferative activity through cell cycle arrest at the S phase and caspase dependent apoptosis in human cancer cells

Exploring the Phytochemical Profile and Biological Activities of Clerodendrum infortunatum

Clerodendrum infortunatum (C. infortunatum), the hill glory bower, is reputed as the prodigious treasure for Indian folk medicine. The study has focused on exploring the phytochemistry and antitumor potential of the C. infortunatum root extract in vitro and in vivo. The ethyl acetate root extract has demonstrated the highest cytotoxicity in a series of nine human tumor cell lines. Further fractionation of the same has yielded seven compounds. The structures of these compounds were confirmed with spectroscopic techniques. Considering the toxicity observed with the crude extract, cytotoxicity of these compounds was further assessed in two breast carcinoma cell lines (MCF-7[ER/PR-positive HER2-negative] and MDA-MB-231 [ER/PR/HER2-negative]) and in two cervical cancer [human papilloma virus (HPV)-negative C33A and HPV-positive SiHa] cell lines. Betulinic acid (BA) was found as the active principle contributing the cytotoxic activity, and cervical cancer cell lines documented the minimum IC₅₀ value in 24 h. In order to validate the in vitro experimental data, we have established a xenograft model of HPV-positive cervical cancer in female NOD/SCID mice treated with BA using doxorubicin as the positive control. BA treatment gradually reduced the tumor size, maintaining healthy hematological and biochemical parameters, and improved the survival rate of tumor-bearing mice considerably. Thus, our findings suggest that the C. infortunatum root extract has a promising anticancer property against HPV-positive cervical cancer and supports its usage by traditional healers for treating cervical cancer.

Amino acid sequence identification of goji berry cyclic peptides and anticervical carcinoma activity detection

The goji berry is widely used as tonics; however, the antihuman cervical carcinoma effect and underlying mechanism of goji berry peptide remain to be elucidated. The cyclic peptides are appealing targets in antitumor agent development, and in current study, three novel goji berry cyclic peptides (GCPs) were isolated and amino acid sequence identified. Among them, GCP-1 (Cycle-(Trp-Glu-His-Thr)) inhibited proliferation and induced human cervical cancer (HeLa) cells apoptosis and blocked the HeLa cells in G0/G1 phase significantly. Furthermore, the GCP-1 also inhibited the cervical carcinoma growth in vivo. Moreover, GCP-1 suppressed the cyclin expression and activated the caspase cascade and poly(ADP-ribose) polymerase. Of note, GCP-1 may be a promising novel inhibitor of human cervical cancer.

Pentacyclic Triterpenoids with Nitrogen-Containing Heterocyclic Moiety, Privileged Hybrids in Anticancer Drug Discovery

Pentacyclic triterpenoids are well-known phytochemicals with various biological activities commonly found in plants as secondary metabolites. The wide range of biological activities exhibited by triterpenoids has made them the most valuable sources of pharmacological agents. A number of novel triterpenoid derivatives with many skeletal modifications have been developed. The most important modifications are the formation of analogues or derivatives with nitrogen-containing heterocyclic scaffolds. The derivatives with nitrogen-containing heterocyclic compounds are among the most promising candidate for the development of novel therapeutic drugs. About 75% of FDA-approved drugs are nitrogen-containing heterocyclic moieties. The unique properties of heterocyclic compounds have encouraged many researchers to develop new triterpenoid analogous with pharmacological activities. In this review, we discuss recent advances of nitrogen-containing heterocyclic triterpenoids as potential therapeutic agents. This comprehensive review will assist medicinal chemists to understand new strategies that can result in the development of compounds with potential therapeutic efficacy.

Discovery of Bivalent GalNAc-Conjugated Betulin as a Potent ASGPR-Directed Agent against Hepatocellular Carcinoma

Herein, we describe the design, synthesis, and biological evaluation of novel betulin and N-acetyl-d-galactosamine (GalNAc) glycoconjugates and suggest them as targeted agents against hepatocellular carcinoma. We prepared six conjugates derived via the C-3 and C-28 positions of betulin with one or two saccharide ligands. These molecules demonstrate high affinity to the asialoglycoprotein receptor (ASGPR) of hepatocytes assessed by in silico modeling and surface plasmon resonance tests. Cytotoxicity studies in vitro revealed a bivalent conjugate with moderate activity, selectivity of action, and cytostatic properties against hepatocellular carcinoma cells HepG2. An additional investigation confirmed the specific engagement with HepG2 cells by the enhanced generation of reactive oxygen species. Stability tests demonstrated its lability to acidic media and to intracellular enzymes. Therefore, the selected bivalent conjugate represents a new potential agent targeted against hepatocellular carcinoma. Further extensive studies of the cellular uptake in vitro and the real-time microdistribution in the murine liver in vivo for fluorescent dye-labeled analogue showed its selective internalization into hepatocytes due to the presence of GalNAc ligand in comparison with reference compounds. The betulin and GalNAc glycoconjugates can therefore be considered as a new strategy for developing therapeutic agents based on natural triterpenoids.

In vitro anti-pancreatic cancer activity of HPLC-derived fractions from Helicteres hirsuta Lour. stem

Pancreatic cancer (PC) is one of the leading causes of cancer death in Western societies. The absence of specific symptoms, late diagnosis and the resistance towards chemotherapy result in significant treatment difficulties. As such, it is important to find more effective therapeutic agents for the treatment of PC. Helicteres hirsuta Lour. (H. hirsuta) has been traditionally used in many countries for the treatment of various ailments, indicating that it contains potential therapeutic agents. This study aimed to derive different fractions from the saponin-enriched extract of H. hirsuta stem using RP-HPLC and examine the in vitro anti-pancreatic cancer activity of the derived fractions (F0-F5). With the exception of F0, the five fractions (F1-F5) possessed strong inhibitory activity against PC cells at IC₅₀ values of 3.11-17.12 μg/mL. The flow cytometry assays revealed the active fractions caused cell cycle arrest at S phase and promoted apoptosis in MIAPaCa-2 PC cells. The LC/MS analysis revealed that the isolated fractions contained bioactive compounds, such as caffeic acid, rosmarinic acid, sagerinic acid, usnic acid, cucurbitacins and absinthin. It can be concluded that the fractions isolated from H. hirsuta stem exhibit potent in vitro anti-pancreatic cancer activity and thus warrant further in vivo studies to assess their activity against PC followed by isolation of individual bioactive compounds and the evaluation of their anti-pancreatic cancer activity.

Betulin and its derivatives as novel compounds with different pharmacological effects

Betulin (B) and Betulinic acid (BA) are natural pentacyclic lupane-structure triterpenoids which possess a wide range of pharmacological activities. Recent evidence indicates that B and BA have several properties useful for the treatment of metabolic disorders, infectious diseases, cardiovascular disorders, and neurological disorders. In the current review, we discuss B and BA structures and derivatives and then comprehensively explain their pharmacological effects in relation to various diseases. We also explain antiviral, antibacterial and anti-cancer effects of B and BA. Finally, we discuss the delivery methods, in which these compounds most effectively target different systems.

Betulinic Acid Induces ROS-Dependent Apoptosis and S-Phase Arrest by Inhibiting the NF-κB Pathway in Human Multiple Myeloma

Betulinic acid (BA), as a prospective natural compound, shows outstanding antitumor bioactivities against many solid malignancies. However, its mechanism against multiple myeloma (MM) remains elusive. Herein, for the first time, we studied the antitumor activity of BA against MM both in vivo and in vitro. We showed that BA mediated cytotoxicity in MM cells through apoptosis, S-phase arrest, mitochondrial membrane potential (MMP) collapse, and overwhelming reactive oxygen species (ROS) accumulation. Moreover, when the ROS scavenger N-acetyl cysteine (NAC) effectively abated elevated ROS, the BA-induced apoptosis was partially reversed. Our results revealed that BA-mediated ROS overproduction played a pivotal role in anticancer activity. Molecularly, we found that BA resulted in marked inhibition of the aberrantly activated NF-κB pathway in MM. As demonstrated by using the NF-κB pathway-specific activator TNF-α and the inhibitor BAY 11-7082, BA-mediated inhibition of the NF-κB pathway directly promoted the overproduction of ROS and, ultimately, cell death. Furthermore, BA also exerted enormous tumor-inhibitory effects via repressing proliferation and inhibiting the NF-κB pathway in our xenograft model. Overall, by blocking the NF-κB pathway that breaks redox homeostasis, BA, as a potent NF-κB inhibitor, is a promising therapeutic alternative for MM.

Transcriptome sequencing combined with bioinformatics predicts potential genes and pathways associated with bupivacaine-induced apoptosis

This study aimed to explore the potential genes and pathways associated with bupivacaine-induced apoptosis. Human neuroblastoma cell line SH-SY5Y was used in this study. The effect of bupivacaine on cell viability of SH-SY5Y was detected by Cell Counting Kit-8. Transcriptome sequencing was performed for SH-SY5Y cells that were treated and untreated with bupivacaine based on the HiSeq 4000 sequencing platform. The sequencing results were analyzed using bioinformatics methods, including differentially expressed genes (DEGs) identification, functional enrichment analysis, protein-protein interaction (PPI) network analysis and module analysis. The cell viability of SH-SY5Y cells decreased significantly after bupivacaine treatment (p < .01). Based on the HiSeq 4000 sequencing platform, we obtained a global overview of the transcriptome of SH-SY5Y treated with/without bupivacaine. Bioinformatics analysis identified 335 up-regulated and 294 down-regulated DEGs in bupivacaine group. They were significantly enriched in cell cycle-associated functions and pathways and cAMP signaling pathway. In the PPI network, proliferating cell nuclear antigen (PCNA), v-Akt murine thymoma viral oncogene homolog 3 (AKT3), cyclin-dependent kinase inhibitor 1A (CDKN1A) and cell division cycle 6 (CDC6) had high topology scores. Module analysis obtained two sub-network modules (cluster 1 and cluster 2). PCNA, CDC6, CDKN1A and AKT3 may play important roles in bupivacaine-induced apoptosis. Additionally, bupivacaine may also induce apoptosis via pathways of cell cycle and cAMP signaling pathway.

Synthesis, Characterization and Anti-Cancer Activity of Hydrazide Derivatives Incorporating a Quinoline Moiety

Identification of the novel (E)-N′-((2-chloro-7-methoxyquinolin-3-yl)methylene)-3-(phenylthio)propanehydrazide scaffold 18 has led to the development of a new series of biologically active hydrazide compounds. The parent compound 18 and new quinoline derivatives 19–26 were prepared from the corresponding quinoline hydrazones and substituted carboxylic acids using EDC-mediated peptide coupling reactions. Further modification of the parent compound 18 was achieved by replacement of the quinoline moiety with other aromatic systems. All the newly synthesized compounds were evaluated for their anti-cancer activity against the SH-SY5Y and Kelly neuroblastoma cell lines, as well as the MDA-MB-231 and MCF-7 breast adenocarcinoma cell lines. Analogues 19 and 22 significantly reduced the cell viability of neuroblastoma cancer cells with micromolar potency and significant selectivity over normal cells. The quinoline hydrazide 22 also induced G₁ cell cycle arrest, as well as upregulation of the p27^kip1 cell cycle regulating protein.

Synthesis and anticancer activity of novel fluorinated asiatic acid derivatives

A series of novel fluorinated Asiatic Acid (AA) derivatives were successfully synthesized, tested for their antiproliferative activity against HeLa and HT-29 cell lines, and their structure activity relationships were evaluated. The great majority of fluorinated derivatives showed stronger antiproliferative activity than AA in a concentration dependent manner. The most active compounds have a pentameric A-ring containing an α,β-unsaturated carbonyl group. The compounds with better cytotoxic activity were then evaluated against MCF-7, Jurkat, PC-3, A375, MIA PaCa-2 and BJ cell lines. Derivative 14 proved to be the most active compound among all tested derivatives and its mechanism of action was further investigated in HeLa cell line. The results showed that compound 14 induced cell cycle arrest in G0/G1 stage as a consequence of up-regulation of p21(cip1/waf1) and p27(kip1) and down-regulation of cyclin D3 and Cyclin E. Furthermore, compound 14 was found to induce caspase driven-apoptosis with activation of caspases-8 and caspase-3 and the cleavage of PARP. The cleavage of Bid into t-Bid, the up-regulation of Bax and the down-regulation of Bcl-2 were also observed after treatment of HeLa cells with compound 14. Taken together, these mechanistic studies revealed the involvement of extrinsic and intrinsic pathways in the apoptotic process induced by compound 14. Importantly, the antiproliferative activity of this compound on the non-tumor BJ human fibroblast cell line is weaker than in the tested cancer cell lines. The enhanced potency (between 45 and 90-fold more active than AA in a panel of cancer cell lines) and selectivity of this new AA derivative warrant further preclinical evaluation.

In vitro anticancer activity of Betulinic acid and derivatives thereof on equine melanoma cell lines from grey horses and in vivo safety assessment of the compound NVX-207 in two horses

Betulinic acid, a pentacyclic triterpene, and its derivatives are promising compounds for cancer treatment in humans. Melanoma is not only a problem for humans but also for grey horses as they have a high potential of developing melanoma lesions coupled to the mutation causing their phenotype. Current chemotherapeutic treatment carries the risk of adverse health effects for the horse owner or the treating veterinarian by exposure to antineoplastic compounds. Most treatments have low prospects for systemic tumor regression. Thus, a new therapy is needed. In this in vitro study, Betulinic acid and its two derivatives B10 and NVX-207, both with an improved water solubility compared to Betulinic acid, were tested on two equine melanoma cell lines (MelDuWi and MellJess/HoMelZh) and human melanoma (A375) cell line. We could demonstrate that all three compounds especially NVX-207 show high cytotoxicity on both equine melanoma cell lines. The treatment with these compounds lead to externalization of phosphatidylserines on the cell membrane (AnnexinV-staining), DNA-fragmentation (cell cycle analysis) and activation of initiator and effector caspases (Caspase assays). Our results indicate that the apoptosis is induced in the equine melanoma cells by all three compounds. Furthermore, we succeed in encapsulating the most active compound NVX-207 in 2-Hydroxyprolyl-β-cyclodextrine without a loss of its activity. This formulation can be used as a promising antitumor agent for treating grey horse melanoma. In a first tolerability evaluation in vivo the formulation was administered every one week for 19 consecutive weeks and well tolerated in two adult melanoma affected horses.

Betulinic Acid: Recent Advances in Chemical Modifications, Effective Delivery, and Molecular Mechanisms of a Promising Anticancer Therapy

An important method of drug discovery is examination of diverse life forms, including medicinal plants and natural products or bioactive compounds isolated from these sources. In cancer research, lead structures of compounds from natural sources can be used to design novel chemotherapies with enhanced biological properties. Betulinic acid (3β-hydroxy-lup-20(29)-en-28-oic acid or BetA) is a naturally occurring pentacyclic triterpene with a wide variety of biological activities, including potent antitumor properties. Non-malignant cells and normal tissues are not affected by BetA. Because BetA exerts its effects directly on the mitochondrion and triggers death of cancerous cells, it is an important alternative when certain chemotherapy drugs fail. Mitochondrion-targeted agents such as BetA hold great promise to circumvent drug resistance in human cancers. BetA is being developed by a large network of clinical trial groups with the support of the U.S. National Cancer Institute. This article discusses recent advances in research into anticancer activity of BetA, relevant modes of delivery, and the agent's therapeutic efficacy, mechanism of action, and future perspective as a pipeline anticancer drug. BetA is a potentially important agent in cancer therapeutics.

[Synthesis and Anticancer Activity of Betulonic Acid Imidazolides]

Synthesis of lupane C28-imidazolides, contained 3-oxo-, 3-oximino- and 2-cyano-2,3-seco-4(23)-en-frag ments in cycle A was carried out. The most antitumor activity at. in vitro testing showed 3-oximino-lup- 20(29)-en-28-yl-1H-imidazole-1-carboxylate; which inhibited the growth or induced apoptosis of non-small lung cancer, colon cancer, breast cancer, CNS cancer, ovarian cancer, prostate cancer, leucosis, melanoma cells. In experiments in mice its moderate antitumor activity against grafted breast adenocarcinoma Ca 755 and adenocarcinima of colon was observed.

Betulinic Acid and its Derivatives as Potential Antitumor Agents

Betulinic acid (BA) is a lupane-type pentacyclic triterpene, distributed ubiquitously throughout the plant kingdom. BA and its derivatives demonstrate multiple bioactivities, particularly an antitumor effect. This review critically describes the recent research on isolation, synthesis, and derivatization of BA and its natural analogs betulin and 23-hydroxybetulinic acid. The subsequent part of the review focuses on the current knowledge of antitumor properties, combination treatments, and pharmacological mechanisms of these compounds. A 3D-QSAR analysis of 62 BA derivatives against human ovarian cancer A2780 is also included to provide information concerning the structure-cytotoxicity relationships of these compounds.

Glycolytic switch in response to betulinic acid in non-cancer cells

The naturally occurring triterpenoid betulinic acid (BA) shows pronounced polypharmacology ranging from anti-inflammatory to anti-lipogenic activities. Recent evidence suggests that rather diverse cellular signaling events may be attributed to the same common upstream switch in cellular metabolism. In this study we therefore examined the metabolic changes induced by BA (10 µM) administration, with focus on cellular glucose metabolism. We demonstrate that BA elevates the rates of cellular glucose uptake and aerobic glycolysis in mouse embryonic fibroblasts with concomitant reduction of glucose oxidation. Without eliciting signs of obvious cell death BA leads to compromised mitochondrial function, increased expression of mitochondrial uncoupling proteins (UCP) 1 and 2, and liver kinase B1 (LKB1)-dependent activation AMP-activated protein kinase. AMPK activation accounts for the increased glucose uptake and glycolysis which in turn are indispensable for cell viability upon BA treatment. Overall, we show for the first time a significant impact of BA on cellular bioenergetics which may be a central mediator of the pleiotropic actions of BA.

Proteomic investigation into betulinic acid-induced apoptosis of human cervical cancer HeLa cells

Betulinic acid is a pentacyclic triterpenoid that exhibits anticancer functions in human cancer cells. This study provides evidence that betulinic acid is highly effective against the human cervical cancer cell line HeLa by inducing dose- and time-dependent apoptosis. The apoptotic process was further investigated using a proteomics approach to reveal protein expression changes in HeLa cells following betulinic acid treatment. Proteomic analysis revealed that there were six up- and thirty down-regulated proteins in betulinic acid-induced HeLa cells, and these proteins were then subjected to functional pathway analysis using multiple analysis software. UDP-glucose 6-dehydrogenase, 6-phosphogluconate dehydrogenase decarboxylating, chain A Horf6-a novel human peroxidase enzyme that involved in redox process, was found to be down-regulated during the apoptosis process of the oxidative stress response pathway. Consistent with our results at the protein level, an increase in intracellular reactive oxygen species was observed in betulinic acid-treated cells. The proteins glucose-regulated protein and cargo-selection protein TIP47, which are involved in the endoplasmic reticulum pathway, were up-regulated by betulinic acid treatment. Meanwhile, 14-3-3 family proteins, including 14-3-3β and 14-3-3ε, were down-regulated in response to betulinic acid treatment, which is consistent with the decrease in expression of the target genes 14-3-3β and 14-3-3ε. Furthermore, it was found that the antiapoptotic bcl-2 gene was down-regulated while the proapoptotic bax gene was up-regulated after betulinic acid treatment in HeLa cells. These results suggest that betulinic acid induces apoptosis of HeLa cells by triggering both the endoplasmic reticulum pathway and the ROS-mediated mitochondrial pathway.

Dillenia species: A review of the traditional uses, active constituents and pharmacological properties from pre-clinical studies

CONTEXT

Dillenia (Dilleniaceae) is a genus of about 100 species of flowering plants in tropical and subtropical trees of Southern Asia, Australasia, and the Indian Ocean Islands. Until now, only eight Dillenia species have been reported to be used traditionally in different countries for various medical purposes. Out of eight species, D. pentagyna (Roxb), D. indica (Linn.) and D. suffruticosa (Griffith Ex. Hook. F. & Thomsom Martelli) have been reported to be used to treat cancerous growth.

OBJECTIVE

The present review explored and provided information on the therapeutic potential of Dillenia species.

METHODS

Comprehensive and relevant literature on the therapeutic potential of Dillenia species was gathered through electronic databases including Google Scholar, Scopus, PubMed, and books, without limiting the dates of publication.

RESULTS AND CONCLUSION

The review demonstrated that only a few Dillenia species have been proven scientifically for their therapeutic potential in pre-clinical studies, including D. pentagyna, D. indica, D. papuana (Martelli), D. meliosmifolia (Hook. F. Ex. Thomsom) and D. suffruticosa (Griffith Ex Hook. F. & Thomson). A few species of Dillenia have undergone isolation and characterization of compounds with lupeol and betulinic acids having tremendous pharmacological potential. Dillenia species warrant further studies on their therapeutic potential, which may eventually lead to the development of new drug candidates for treatment of various diseases.

Betulinic acid in complex with a gamma-cyclodextrin derivative decreases proliferation and in vivo tumor development of non-metastatic and metastatic B164A5 cells

Betulinic acid, a very promising anti-melanoma agent, has very low water solubility that causes low bioavailability. To overcome this inconvenience, a highly water-soluble cyclodextrin was used (octakis-[6-deoxy-6-(2-sulfanyl ethanesulfonic acid)]-γ-cyclodextrin). The complex was physico-chemically analyzed using differential scanning calorimetry (DSC), X-ray and scanning electron microscopy (SEM) methods and then in vitro tested for its antiproliferative activity by the MTT assay and by cell cycle analysis. Finally, the complex was tested in vivo using an animal model of murine melanoma developed in C57BL/6J mice, where it caused a reduction in tumor volume and weight. The study revealed the beneficial influence of betulinic acid inclusion into the cyclodextrin in terms of antiproliferative activity and in vivo tumor development.

Antileishmanial activity of semisynthetic lupane triterpenoids betulin and betulinic acid derivatives: synergistic effects with miltefosine

Leishmaniasis is a neglected tropical disease (NTDs), endemic in 88 countries, affecting more than 12 million people. The treatment consists in pentavalent antimony compounds, amphotericin B, pentamidine and miltefosine, among others. However, these current drugs are limited due to their toxicity, development of biological resistance, length of treatment and high cost. Thus, it is important to continue the search for new effective and less toxic treatments.

The anti-Leishmania activity of sixteen semisynthetic lupane triterpenoids derivatives of betulin (BT01 to BT09) and betulinic acid (AB10 to AB16) were evaluated. Drug interactions between the active compounds and one current antileishmanial drug, miltefosine, were assessed using the fixed ratio isobologram method. In addition, effects on the cell cycle, apoptosis/necrosis events, morphology and DNA integrity were studied. The derivatives BT06 (3β-Hydroxy-(20R)-lupan-29-oxo-28-yl-1H-imidazole-1-carboxylate) and AB13 (28-(1H-imidazole-1-yl)-3,28-dioxo-lup-1,20(29)-dien-2-yl-1H-imidazole-1-carboxylate) were found to be the most active, with IC₅₀ values of 50.8 µM and 25.8 µM, respectively. Interactions between these two compounds and miltefosine were classified as synergistic, with the most effective association being between AB13 and miltefosine, where decreases of IC₅₀ values to 6 µM were observed, similar to the miltefosine activity alone. AB13 induced significant morphological changes, while both derivatives produced anti-proliferative activity through cell cycle arrest at the G0/G1 phase. Neither of these derivatives induced significant apoptosis/necrosis, as indicated by phosphatidylserine externalization and DNA fragmentation assays. In addition, neither of the derivatives induced death in macrophage cell lines. Thus, they do not present any potential risk of toxicity for the host cells.

This study has identified the betulin derivative BT06 and the betulinic acid derivative AB13 as promising molecules in the development of new alternative therapies for leishmaniasis, including those involving combined-therapy with miltefosine.

A 3D QSAR study of betulinic acid derivatives as anti-tumor agents using topomer CoMFA: model building studies and experimental verification

Betulinic acid (BA) is a natural product that exerts its cytotoxicity against various malignant carcinomas without side effects by triggering the mitochondrial pathway to apoptosis. Betulin (BE), the 28-hydroxyl analog of BA, is present in large amounts (up to 30% dry weight) in the outer bark of birch trees, and shares the same pentacyclic triterpenoid core as BA, yet exhibits no significant cytotoxicity. Topomer CoMFA studies were performed on 37 BA and BE derivatives and their in vitro anti-cancer activity results (reported as IC₅₀ values) against HT29 human colon cancer cells in the present study. All derivatives share a common pentacyclic triterpenoid core and the molecules were split into three pieces by cutting at the C-3 and C-28 sites with a consideration toward structural diversity. The analysis gave a leave-one-out cross-validation q² value of 0.722 and a non-cross-validation r² value of 0.974, which suggested that the model has good predictive ability (q² > 0.2). The contour maps illustrated that bulky and electron-donating groups would be favorable for activity at the C-28 site, and a moderately bulky and electron-withdrawing group near the C-3 site would improve this activity. BE derivatives were designed and synthesized according to the modeling result, whereby bulky electronegative groups (maleyl, phthalyl, and hexahydrophthalyl groups) were directly introduced at the C-28 position of BE. The in vitro cytotoxicity values of the given analogs against HT29 cells were consistent with the predicted values, proving that the present topomer CoMFA model is successful and that it could potentially guide the synthesis of new betulinic acid derivatives with high anti-cancer activity. The IC₅₀ values of these three new compounds were also assayed in five other tumor cell lines. 28-O-hexahydrophthalyl BE exhibited the greatest anti-cancer activities and its IC₅₀ values were lower than those of BA in all cell lines, excluding DU145 cells.

Antitumour activity on extrinsic apoptotic targets of the triterpenoid maslinic acid in p53-deficient Caco-2 adenocarcinoma cells

We report that a novel triterpenoid, (2a,3b)-2,3-dihydroxyolean-12-en-28-oic acid (maslinic acid), isolated from olive pomace from Olea europaea, triggers primarily the extrinsic and later the intrinsic apoptotic pathways in Caco-2 human colon-cancer cells. Apoptosis induced by maslinic acid was confirmed by FACS analysis using annexine-V FICT staining. This induction of apoptosis was correlated with the early activation of caspase-8 and caspase-3, the activation of caspase-8 was also correlated with higher levels of Bid cleavage and decreased Bcl-2, but with no change in Bax expression. Maslinic acid also induced a sustained activation of c-Jun N-terminal kinase (JNK). Incubation with maslinic acid also resulted in the later activation of caspase-9, which, together with the lack of any Bax activation, suggests that the mitochondrial pathway is not required for apoptosis induced by maslinic acid in this cell line. In this study we found that the mechanism of apoptotic activation in p53-deficient Caco-2 cells differs significantly from that found in HT-29 cells. Natural agents able to activate both the extrinsic and intrinsic apoptotic pathways by avoiding the mitochondrial resistance mechanisms may be useful for treatment against colon cancer regardless of its aetiology.

Ursane-type pentacyclic triterpenoids as useful platforms to discover anticancer drugs

This review highlights the potential of natural and semisynthetic ursane-type triterpenoids as candidates for the design of multi-target bioactive compounds, with focus on their anticancer effects. A brief illustration of the biosynthesis, sources, and general biological effects of the main classes of naturally occurring pentacyclic triterpenoids (PTs) are provided.

Synthesis of novel ursolic acid heterocyclic derivatives with improved abilities of antiproliferation and induction of p53, p21waf1 and NOXA in pancreatic cancer cells

A series of new heterocyclic derivatives of ursolic acid 1 were synthesized and evaluated for their antiproliferative activity against AsPC-1 pancreatic cancer cells. Compounds 24-32, with an α,β unsaturated ketone in conjugation with an heterocyclic ring in ring A have improved antiproliferative activities. Compound 32 is the most active compound with an IC(50) of 1.9 μM which is sevenfold more active than ursolic acid 1. Compound 32 arrests cell cycle in G1 phase and induces apoptosis in AsPC-1 cells with upregulation of p53, p21(waf1) and NOXA protein levels.

Semisynthetic ursolic acid fluorolactone derivatives inhibit growth with induction of p21(waf1) and induce apoptosis with upregulation of NOXA and downregulation of c-FLIP in cancer cells

A series of ursolic acid ((1S,2R,4aS,6aR,6aS,6bR,8aR,10S,12aR,14bS)-10-hydroxy-1,2,6a,6b,9,9,12a-heptamethyl-2,3,4,5,6,6a,7,8,8a,10,11,12,13,14b-tetradecahydro-1H-picene-4a-carboxylic acid) derivatives with a 12-fluoro-13,28β-lactone moiety were synthesized using the electrophilic fluorination reagent Selectfluor. The antiproliferative effects of these novel compounds were evaluated in AsPC-1 pancreatic cancer cells, and the structure-activity relationships (SARs) were evaluated. Of the compounds synthesized, ursolic acid derivatives carrying a heterocyclic ring, such as imidazole or methylimidazole, and cyanoenones were among the more potent inhibitors of AsPC-1 pancreatic cancer cell growth. 2-Cyano-3-oxo-12α-fluoro-urs-1-en-13,28β-olide, compound 20, was the most effective inhibitor with IC(50) values of 0.7, 0.9 and 1.8 μM in pancreatic cancer cell lines AsPC-1, MIA PaCa-2 and PANC-1, respectively. This compound also exhibited better antiproliferative activities against breast (MCF7), prostate (PC-3), hepatocellular (Hep G2) and lung (A549) cancer cell lines, with IC(50) values lower than 1 μM. The mechanism of action by which these compounds exert their biological effect was evaluated in AsPC-1 cells using the most potent inhibitor synthesized, compound 20. At 1 μM, the cell cycle arrested at the G1 phase with upregulation of p21(waf1). Apoptosis was induced at an inhibitor concentration of 8 μM with upregulation of NOXA and downregulation of c-FLIP. These data indicate that fluorolactone derivatives of ursolic acid have improved antiproliferative activity, acting through arrest of the cell cycle and induction of apoptosis.

Synthesis and biological activity of 23-hydroxybetulinic acid C-28 ester derivatives as antitumor agent candidates

23-Hydroxybetulinic acid (1) served as the precursor for the synthesis of C-28 ester derivatives. The target compounds were evaluated in vitro for their antitumor activities against five cell lines (A549, BEL-7402, SF-763, B16 and HL-60). Among the obtained compounds, 6i had the most potent antitumor activity, with the IC₅₀ values of 8.35 µM in HL-60 cells and showed similar antitumor activity as cyclophosphamide in H22 liver tumor and as 5-fluorouracil in B16 melanoma in vivo.