Rational design and semisynthesis of betulinic acid analogues as potent topoisomerase inhibitors

Larvicidal Activity against Spodoptera frugiperda of some Constituents from two Diospyros Species. In silico Pesticide-likeness Properties, Acetylcholinesterase Activity and Molecular Docking

This report informs for the first time the chemical constituents of Diospyros xolocotzii and Diospyros digyna, the pesticidal and the acetylcholinesterase (AChE) inhibition potential of some compounds calculated by in silico approaches, the larvicidal activity against Spodoptera frugiperda of available compounds, the AChE inhibition of selected compounds, and the results of the molecular docking of the most active ones with this receptor. From the aerial parts of D. xolocotzii were isolated pentacyclic triterpenes (1-4, 6, 10, 11-13), phytosterols (15-17), and isodiospyrin (18), whereas the analysis of aerial parts of D. digyna conducted to the isolation of pentacyclic triterpenes (4, 5, 7-9, 11-14), (4S)-shinanolone (19), and scopoletin (20). For comparison purposes, origanal (21) was chemically prepared from 11. The in silico analysis showed that the tested compounds have pesticide potential. The larvicidal activities of 11>13>12 indicated that the increase of the oxidation degree at C-28 increases their bioactivity. Compounds 11 and 21 presented the higher inhibition in the acetylcholinesterase assay, and the higher binding energies, and for the interactionswith AChE by molecular docking. Both Diospyros species are sources of triterpenes with pesticidal potential and the molecular changes in lupane triterpenes correlate with the observed bioactivity and molecular docking.

Betulinic acid in the treatment of breast cancer: Application and mechanism progress

Betulinic acid (BA) is a pentacyclic triterpene compound, which can be obtained by separation, chemical synthesis and biotransformation. BA has excellent biological activities, especially its role in the treatment of breast cancer deserves attention. Its mechanisms mainly include inducing mitochondrial oxidative stress, regulating specific protein (Sp) transcription factors, inhibiting breast cancer metastasis, inhibiting glucose metabolism and NF-κB pathway. In addition, BA can also increase the sensitivity of breast cancer cells to other chemotherapy drugs such as paclitaxel and reduce its toxic side effects. This article reviews the application and possible mechanism of BA in the treatment of breast cancer.

Isolation and identification of novel selective antitumor constituents, sidrin and sidroside, from Zizyphus spina-christi

Background

The leaves of Zizyphus spina-christi (L.) Willd contain several compounds exhibiting different pharmacologic activities. However, studies on the cytotoxic activity of these compounds are limited.

Objectives

We aimed to investigate and isolate cytotoxic compounds with selective antitumor effects from the leaves of Z. spina-christi using bioassay-guided fractionation of methanol extract.

Methods

Powdered, dried leaves were subjected to methanol extraction and fractionated using n-hexane, chloroform, ethyl acetate, and n-butanol. Fractions with positive cytotoxicity against HeLa and THP-1 cell lines were further fractionated and eluted using various concentrations of organic solvents. Active compounds were isolated using different chromatographic methods and their chemical structures were determined using extensive spectroscopic methods, such as 1D NMR (¹H NMR, ¹³C NMR, and DEPT), 2D NMR (COSY, HMBC, and HMQC), HRFAB-MS, and IR. Furthermore, the cytotoxic effects of the isolated compounds were evaluated against 62 tumor cell lines (including HeLa and THP-1) in addition to normal bone marrow cells.

Results

The chloroform and aqueous methanol fractions of the leaves showed cytotoxic activity. Two compounds were successfully isolated and named "sidrin" (13-β-hydroxy-lup-20(30)-ene-2,3-β-epoxy-28-carboxylate) and "sidroside" (3-O-β-D-glucopyranosyl-(1-3)-α-L-arabinopyranosyl-jujubogenin-20-O-α-L-rhamnopyranoside). Sidrin exhibited cytotoxic activity against the human leukemia (Hl-60, RPMI-8226), lung cancer (A549, EKVX), breast cancer (BT-549, MDA-MB-231/ATCC), colon cancer (KM12), melanoma (M14, SK-MEL-5), and central nervous system (CNS) cancer (SF-295) cell lines, and selectivity was observed against the Hl-60, EKVX, BT-549, KM12, and SF-295 cell lines. In addition, sidrin was more active than sidroside and doxorubicin against the Hl-60 and EKVX cell lines. In contrast, sidrin had a similar effect to doxorubicin against the BT-549 and renal cancer (UO-31) cell lines. Sidroside was more selective against the leukemia (CCRF-CEM, MOLT-4), lung cancer (HOP-92, NCI-H322M), breast cancer (MDA-MB-468), melanoma (LOX IMVI), CNS cancer (SNB-19), ovarian cancer (OVCAR-8), renal cancer (UO-31, RXF 393), and prostate cancer (PC-3) cell lines. Both compounds exhibited similar activity against the breast cancer (MDA-MB-231, T-47D), colon cancer (HCC-2998, HCT-116), ovarian cancer (OVCAR-3), renal cancer (UO-31, 786-0, and SN 12C) cell lines. Normal bone marrow cells were unaffected at the same concentrations of sidrin and sidroside applied to tumor cells.

Conclusions

These results suggest tumor-selective cytotoxicity of sidrin and sidroside.

Betulinic acid: A natural promising anticancer drug, current situation, and future perspectives

Natural products serve as the single most productive source for the discovery of drugs and pharmaceutical leads. Among the various chemicals derived from microbes, plants, and animals, phytochemicals have emerged as potential candidates for the development of anticancer drugs due to their structural diversities, complexities, and pleiotropic effects. Herein, we discuss betulinic acid (BA), a ubiquitously distributed lupane structured pentacyclic triterpenoid, scrutinized as a promising natural agent for the prevention, suppression, and management of various human malignancies. Ease of availability, common occurrences, cell-specific cytotoxicity, and astonishing selectivity are the important factors that contribute to the development of BA as an anticancer agent. The current review delineates the mechanistic framework of BA-mediated cancer suppression through the modulation of multiple signaling pathways and also summarizes the key outcomes of BA in preclinical investigations.

Platanic Acid-Aryl Enones as Potential Anticancer Compounds: Synthesis and Biological Profiling against Breast, Prostate and Lung Cancer Cell Lines

A series of rationally designed platanic acid-based compounds derived from naturally occurring betulinic acid were synthesized through a sequence of Lemieux-Johnson oxidation and Aldol condensation reaction. All the compounds were screened for cytotoxicity against a panel of human cancer and normal cell lines using MTT assay. From the biological data, it was observed that some of these semi-synthetic congeners exhibited potent biological profiles compared to platanic acid. One of the compounds with the p-tolyl substitution was found to be most active in this study, and its cytotoxicity against two of the cell lines, MDA-MB 231 and A-549 were in tune with the standard compound, 5-fluorouracil.

Ursolic and betulinic semisynthetic derivatives show activity against CQ-resistant Plasmodium falciparum isolated from Amazonia

ACT's low levels of Plasmodium parasitemia clearance are worrisome since it is the last treatment option against P. falciparum. This scenario has led to investigations of compounds with different mechanisms of action for malaria treatment. Natural compounds like ursolic acid (UA) and betulinic acid (BA), distinguished by their activity against numerous microorganisms, including P. falciparum, have become relevant. This study evaluated the antiplasmodial activity of imidazole derivatives of UA and BA against P. falciparum in vitro. Eight molecules were obtained by semisynthesis and tested against P. falciparum strains (NF54 and CQ-resistant 106/cand isolated in Porto Velho, Brazil); 2a and 2b showed activity against NF54 and 106/cand strains with IC50  < 10 µM. They presented high selectivity indexes (SI > 25) and showed synergism when combined with artemisinin. 2b inhibited the parasite's ring and schizont forms regardless of when the treatment began. In silico analysis presented a tight bind of 2b in the topoisomerase II-DNA complex. This study demonstrates the importance of natural derivate compounds as new candidates for malarial treatment with new mechanisms of action. Semisynthesis led to new triterpenes that are active against P. falciparum and may represent new alternatives for malaria drug development.

An Approach to Treatment of Liver Cancer by Novel Glycyrrhizin Derivative

BACKGROUND

Liver cancer is a life threating disease as it is the fifth most common cancer and the third most common cause of death worldwide with no safe, efficient, and economic drug available for treatment.

METHODS

This study intended to investigate glycyrrhizin and its derivatives for possible use as a cytotoxic agent and as a drug for liver cancer treatment. Thus, after treatment of liver cancer cell line HepG-2 with 50 μM of each compound, cell viability was determined.

RESULTS

The cytotoxicity assay showed glycyrrhizin derivatives ME-GA (18β-Glycyrrhetinic-30-methyl ester) and AKBA (3-acetyl-11- keto-β-Boswellic acid) to be the most potent drug against liver cancer cell line HepG-2 with IC50 values 25.50 ± 1.06 and 19.73 ± 0.89 μM, respectively. Both the compounds showed higher selectivity towards hepatocellular carcinoma rather than the normal lung fibroblast cell line WI-38. The presence of methyl ester at C-30 greatly increased the cytotoxicity of ME-GA which might be attributed to its higher activity and selectivity. Both ME-GA and AKBA contributed to inhibit cancer cell migration in the wound healing assay and impeded colony formation. The use of flow cytometry to carry out cell cycle analysis and the determination of possible mechanisms of action for apoptosis revealed that ME-GA arrested the cell cycle at G2/M that led to the inhibition of hepatocellular carcinoma and induced apoptosis via the extrinsic pathway and its ability to increase p53 transactivation.

CONCLUSION

This work highlights the cytotoxicity of glycyrrhizin and its derivatives for possible use as a chemotherapeutic agent against hepatocellular carcinoma cells HepG-2. The most cytotoxic compound was ME-GA (18β-Glycyrrhetinic-30-methyl ester) with no cytotoxic effect on the normal cell line. In summary, this new derivative may be used as an alternative or complementary medicine for liver cancer.

Effect of phenolic compounds from the leaves of Psidium guajava on the activity of three metabolism-related enzymes

Enzyme activity modulation by synthetic compounds provide strategies combining the inhibitory and therapeutic mode of action of the confirmed inhibitors. However, natural modulators could offer a valuable alternative for synthetic ones for the treatment of different chronic diseases (diabetes, hypertension, cancer); due to the numerous side effects of the latter. In vitro screening assays were conducted for Psidium guajava leaf methanolic extract against three metabolism-related enzymes; α-amylase, tyrosinase, and hyaluronidase. The obtained results showed that the examined extract retained weak and moderate multitarget inhibition against α-amylase, tyrosinase, and hyaluronidase, respectively; however, the leaf fractions exhibited stronger inhibitions for the three investigated enzymes. Fractionation of P. guajava leaf extract revealed that anthraquinones and ellagic acid are of the major active compounds with inhibitory activities for α-amylase, tyrosinase, and hyaluronidase. Kinetic studies showed that quinalizarin inhibition is competitive for both α-amylase and hyaluronidase, and ellagic acid inhibition for tyrosinase and hyaluronidase is competitive and un-competitive, respectively. The molecular docking studies of quinalizarin and ellagic acid with α-amylase, tyrosinase, and hyaluronidase showed high binding energies with different bonds stabilizing the ligand-protein complex. Compiling all obtained results led to conclude that both P. guajava leaf fractions, quinalizarin and ellagic acid, have multitarget activities with potential therapeutic applications in many metabolic disorders.

Effect of phenolic compounds from the rind of Punica granatum on the activity of three metabolism-related enzymes

Enzyme activity modulation by synthetic compounds provide strategies combining the inhibitory and therapeutic mode of action of the confirmed inhibitors. However, natural modulators could offer a valuable alternative for synthetic ones for the treatment of different chronic diseases (diabetes, hypertension, cancer) due to the numerous side effects of the latter. In vitro screening assays were conducted for Punica granatum rind methanolic extract against three metabolism-related enzymes: α-amylase, tyrosinase, and hyaluronidase. The obtained results showed that the examined extract retained high multitarget inhibition with inhibition percentages 31.5 ± 1.3%, 75.9 ± 4.7%, and 68.5 ± 5.3% against α-amylase, tyrosinase, and hyaluronidase, respectively. Bioguided fractionation of P. granatum rind extract revealed that quercetin is the major active compound with inhibitory activities: 54.3 ± 2.7%, 94.2 ± 3.5%, and 90.9 ± 2.7% against α-amylase, tyrosinase, and hyaluronidase, respectively. Kinetic studies of enzymes showed that quercetin inhibition was noncompetitive, uncompetitive, and competitive for α-amylase, tyrosinase, and hyaluronidase, respectively. The molecular docking of quercetin with α-amylase and hyaluronidase showed high binding energy with different bonds stabilizing the ligand-protein complex. Compiling all obtained results led to conclude that both P. granatum rind extract and quercetin have multitarget activities with potential therapeutic applications in many metabolic disorders.

Evaluation of the Betulinic Acid-Cisplatin conjugate APC and its precursor DE9B for the treatment of human malignant glioma

Despite the existence of multimodal therapy concepts, glioblastoma remains a tumor type with one of the worst prognoses. In particular, the poor prognosis is due to the lack of therapeutic efficacy of chemical agents and irradiation in hypoxic tumor areas. New therapeutic strategies could improve the treatment of glioblastoma. In this study, we investigated the therapeutic efficacy of a conjugate of cisplatin (DDP), a widely used chemotherapeutic agent, and betulinic acid (BA), a natural product from plane tree bark, in glioblastoma cells under different oxygen conditions. We investigated the effects of the BA-DDP conjugate κN',N''-{3-acetyloxy-BA-28-[2-(2-aminoethyl)aminoethyl]amide} dichlorido platinum(II) (APC) and its precursor 3-acetyloxy-BA-28-[2-(2-aminoethyl)aminoethyl]amide (DE9B) on cytotoxicity, cell growth, apoptosis, migration and radiosensitivity compared to BA or DDP alone under different oxygen conditions. Based on the EC₅₀ values, the precursor DE9B exhibited the strongest cytotoxic effects of the analyzed chemotherapeutic agents. The BA-DDP conjugate APC achieved a moderate cytotoxic effect in glioma cells. Both of the newly developed agents induced cell growth delay, apoptosis and inhibition of migration. Furthermore, additive effects could be achieved in combination with irradiation. In contrast to those of BA and DDP, the cell biological effects of APC and DE9B were not influenced by the oxygen concentration. In this study, the linking of BA and DDP did not produce a compound with additive therapeutic effects on glioblastoma cell lines in vitro. Nevertheless, the results of this study suggest that the precursor DE9B is an effective BA derivative for the treatment of glioblastoma in vitro.

Nanoencapsulated betulinic acid analogue distinctively improves colorectal carcinoma in vitro and in vivo

Betulinic acid, a plant secondary metabolite, has gained significant attention due to its antiproliferative activity over a range of cancer cells. A promising betulinic acid analogue (2c) with better therapeutic efficacy than parent molecule to colon carcinoma cells has been reported. Despite impressive biological applications, low aqueous solubility and bioavailability create difficulties for its therapeutic applications. To overcome these lacunae and make it as a promising drug candidate we have encapsulated the lead betulinic acid derivative (2c) in a polymeric nanocarrier system (2c-NP) and evaluated its in vitro and in vivo therapeutic efficacy. Apoptosis that induces in vitro antiproliferative activity was significantly increased by 2c-NP compared to free-drug (2c), as assured by MTT assay, Annexin V positivity, JC1 analysis and cell cycle study. The therapeutic potential measured in vitro and in vivo reflects ability of 2c-NP as an effective therapeutic agent for treatment of colon carcinoma and future translation to clinical trials.

Design, synthesis and evaluation of antiproliferative activity of fluorinated betulinic acid

Betulinic acid (BA), a pentacyclic triterpenoid, exhibits broad spectrum antiproliferative activity, but generally with only modest potency. To improve BA's pharmacological properties, fluorine was introduced as a single atom at C-2, creating two diastereomers, or in a trifluoromethyl group at C-3. We evaluated the impact of these groups on antiproliferative activity against five human tumor cell lines. A racemic 2-F-BA (compound 6) showed significantly improved antiproliferative activity, while each diastereomer exhibited similar effects. We also demonstrated that 2-F-BA is a topoisomerase (Topo) I and IIα dual inhibitor in cell-based and cell-free assays. A hypothetical mode of binding to the Topo I-DNA suggested a difference between the hydrogen bonding of BA and 2-F-BA to DNA, which may account for the difference in bioactivity against Topo I.

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.

Synthesis, cytotoxic evaluation, and molecular docking studies of the semi-synthetic "triterpenoid-steroid" hybrids

Synthetic transformations of steroids for drug discovery and improvement of drug effectiveness have been an important part of modern medicinal chemistry and pharmaceutical sciences. Pentacyclic triterpenoids, being represented in the nature by various structures and biogenetically related to steroids, can largely expand the spectrum of biologically active steroidal agents via synthesis of the so-called "triterpenoid-steroid" hybrids. In the presented work, the nitrile anion cyclizations of 3,4-secolupane and 3,4-seco-oleanane nitriles and follow-up synthetic transformations of the cyclized products with formation of the gemm-dimethyl-free A ring "triterpenoid-steroid" hybrids were studied. Furthermore, the resulting cyclic compounds were modified at C3, C4, and/or C5 positions of ring A, as well as at C20, C28, and C30 positions of the isopropylidene moiety in the case of lupane triterpenoids. The cytotoxic effect of the synthesized compounds against seven cancer cell lines HEp-2, HCT 116, MS, RD TE32, A549, MCF7, and PC3 was evaluated. The in silico identification of potential anticancer protein targets with regard to the compounds, which were active at micromolar concentrations against tested cell lines, was carried out. The molecular docking studies showed that compound 19, which demonstrated most pronounced cytotoxicity (IC₅₀ 0.64-3.17 μM) against all tested cell lines, fits well the active sites of CDK6 and HER2/neu.

Betulinic acid impairs metastasis and reduces immunosuppressive cells in breast cancer models

Breast cancer is the most common female cancer with considerable metastatic potential, explaining the need for new candidates that inhibit tumor metastasis. In our study, betulinic acid (BA), a kind of pentacyclic triterpenoid compound derived from birch trees, was evaluated for its anti-metastasis activity in vitro and in vivo. BA decreased the viability of three breast cancer cell lines and markedly impaired cell migration and invasion. In addition, BA could inhibit the activation of stat3 and FAK which resulted in a reduction of matrix metalloproteinases (MMPs), and increase of the MMPs inhibitor (TIMP-2) expression. Moreover, in our animal experiment, intraperitoneal administration of 10 mg/kg/day BA suppressed 4T1 tumor growth and blocked formation of pulmonary metastases without obvious side effects. Furthermore, histological and immunohistochemical analyses showed a decrease in MMP-9 positive cells, MMP-2 positive cells and Ki-67 positive cells and an increase in cleaved caspase-3 positive cells upon BA administration. Notably, BA reduced the number of myeloid-derived suppressor cells (MDSCs) in the lungs and tumors. Interestingly, in our caudal vein model, BA also obviously suppressed 4T1 tumor pulmonary metastases. These findings suggested that BA might be a potential agent for inhibiting the growth and metastasis of breast cancer.

Two New Cyclobutane Dimers from Diospyros macrocarpa

A biochemical and phytochemical study of Diospyros macrocarpa Hiern, an endemic plant of New Caledonia, was realized. Indeed, bark and leaf extracts were tested for their cytotoxic and antibiotic activities as well as for their radical scavenging properties. Methanol extracts showed promising radical scavenging activity with an IC50 value of 5.6 ± 0.9 μg/mL for the leaves and 8.1 ± 1.4 μg/mL for the barks. The ethyl acetate extract from the barks showed strong and selective activity against NCI-H727 cancer cell line with an IC50 value of 9.5 ± 0.6 μg/mL.. Two new cyclobutane dimers: macrocarpasin A (1) and B (2) (figure 1) together with six known compounds: yangonin (3), betulinic acid (4), α-amyrin (5), β–amyrin (6), loliolide (7) and oleanderolide (8) were isolated from leaf extracts. Their structures were established by 1D and 2D NMR along with HRMS analyses. Cytotoxic activities of isolated compounds were also evaluated. None of them showed interesting cytotoxicity against the seven tested cancer cell lines.

Bioactive Pentacyclic Triterpene Ester Derivatives from Alnus viridis ssp. viridis Bark

Seven derivatives of pentacyclic triterpene acids (1-7) were isolated from the bark of Alnus viridis ssp. viridis using a combination of column chromatography and semipreparative HPLC. Compounds 1-3, 6, and 7 were determined to be new after spectroscopic data interpretation and were assigned as 27-hydroxyalphitolic acid derivatives (1-3), a 27-hydroxybetulinic acid derivative (6), and a 3-epi-maslinic acid derivative (7), respectively. Pentacyclic triterpenoids with a C-27 hydroxymethyl group have been found in species of the genus Alnus for the first time. These compounds were subjected to cytotoxicity testing against a number of cancer cell lines. Also, selected pentacyclic triterpenoids were selected as potential inhibitors of topoisomerases I and IIα for an in silico investigation.

Synthesis of 11C-labeled Sulfonyl Carbamates through a Multicomponent Reaction Employing Sulfonyl Azides, Alcohols, and [11C]CO

We describe the development of a new methodology focusing on 11C-labeling of sulfonyl carbamates in a multicomponent reaction comprised of a sulfonyl azide, an alkyl alcohol, and [11C]CO. A number of 11C-labeled sulfonyl carbamates were synthesized and isolated, and the developed methodology was then applied in the preparation of a biologically active molecule. The target compound was obtained in 24±10 % isolated radiochemical yield and was evaluated for binding properties in a tumor cell assay; in vivo biodistribution and imaging studies were also performed. This represents the first successful radiolabeling of a non-peptide angiotensin II receptor subtype 2 agonist, C21, currently in clinical trials for the treatment of idiopathic pulmonary fibrosis.

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.

Protective effect and mechanism of action of lupane triterpenes from Cornus walteri in cisplatin-induced nephrotoxicity

The present study reports a renoprotective effect and the mechanism of action of lupane triterpenes isolated from Cornus walteri in cisplatin-induced renal toxicity. A phytochemical investigation of the MeOH extract of the stems and stem bark of C. walteri resulted in the isolation and identification of twelve lupane triterpenes. Among these, betulinic acid, 29-oxobetulinic acid, betulin 3-acetate, and lupeol ameliorated cisplatin-induced nephrotoxicity to 80% of the control value at 125 μM. Upregulated phosphorylation of JNK, ERK, and p38 following cisplatin treatment were markedly decreased after co-treatment with betulinic acid, 29-oxobetulinic acid, betulin 3-acetate, and lupeol. In addition, the protein expression level of cleaved caspase-3 and the percentage of apoptotic cells were also significantly reduced after co-treatment with betulinic acid, 29-oxobetulinic acid, betulin 3-acetate, and lupeol. These results show that blocking the MAPK signaling cascade plays a critical role in mediating the renoprotective effect of betulinic acid, 29-oxobetulinic acid, betulin 3-acetate, and lupeol isolated from C. walteri extract.

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.

Betulinic acid derivatives NVX-207 and B10 for treatment of glioblastoma--an in vitro study of cytotoxicity and radiosensitization

Betulinic acid (BA), a pentacyclic triterpene, represents a new therapeutic substance that has potential benefits for treating glioblastoma. Recently, new strategies for producing BA derivatives with improved properties have evolved. However, few studies have examined the combination of BA or BA derivatives using radiotherapy. The effects of two BA derivatives, NVX-207 and B10, on cellular and radiobiological behavior were analyzed using glioblastoma cell lines (U251MG, U343MG and LN229). Based on IC50 values under normoxic conditions, we detected a 1.3-2.9-fold higher cytotoxicity of the BA derivatives B10 and NVX-207, respectively, compared to BA. Incubation using both BA derivatives led to decreased cell migration, cleavage of PARP and decreased protein expression levels of Survivin. Weak radiation sensitivity enhancement was observed in U251MG cells after treatment with both BA derivatives. The enhancement factors at an irradiation dose of 6 Gy after treatment with 5 µM NVX-207 and 5 µM B10 were 1.32 (p=0.029) and 1.55 (p=0.002), respectively. In contrast to BA, neither NVX-207 nor B10 had additional effects under hypoxic conditions. Our results suggest that the BA derivatives NVX-207 and B10 improve the effects of radiotherapy on human malignant glioma cells, particularly under normoxic conditions.

Optimization, pharmacophore modeling and 3D-QSAR studies of sipholanes as breast cancer migration and proliferation inhibitors

Sipholenol A, a triterpene isolated from the Red Sea sponge Callyspongia siphonella, was previously shown to reverse multidrug resistance in P-glycoprotein-overexpressing cancer cells. Moreover, sipholanes showed promising in vitro inhibitory effects against the invasion and migration of the metastatic human breast cancer cell line MDA-MB-231. The breast tumor kinase (Brk), a mediator of cancer cell phenotypes important for proliferation, survival, and migration, was proposed as a potential target. This study reports additional semisynthetic optimization of sipholenol A esters to improve the breast cancer antimigratory and antiproliferative activities as well as Brk phosphorylation inhibition. Fifteen new sipholenol A analogs (25-39) were semisynthesized. Sipholenol A 4β-4',5'-dichlorobenzoate ester (29) was the most potent, with an IC50 value of 1.3 μM in the migration assay. The level of Brk phosphorylation inhibition of 29 was assessed using the Z'-LYTE™ kinase assay and Western blot analysis. Active analogs showed no toxicity on the non-tumorigenic epithelial breast cell line MCF10A at doses equal to their IC50 values or higher in migration and proliferation assays, suggesting their selectivity towards malignant cells. Pharmacophore modeling and 3D-QSAR studies were conducted to identify important pharmacophoric features and correlate 3D-chemical structure with activity. These studies provided the evidence for future design of novel antimigratory compounds based on a simplified sipholane structure possessing rings A and B (perhydrobenzoxepine) connected to substituted aromatic esters, with the elimination of rings C and D ([5,3,0]bicyclodecane system). This will enable the future synthesis of the new active entities feasibly and cost-effectively. These results demonstrate the potential of marine natural products for the discovery of novel scaffolds for the control and management of metastatic breast cancer.

Indole diterpene alkaloids as novel inhibitors of the Wnt/β-catenin pathway in breast cancer cells

Penitrems are indole diterpene alkaloids best known for their BK channel inhibition and tremorgenic effects in mammals. In a previous study, penitrems A-F (1-5), their biosynthetic precursors, paspaline (6) and emindole SB (7), and two brominated penitrem analogs 8 and 9 demonstrated promising in vitro antiproliferative, antimigratory, and anti-invasive effects in the MTT (MCF-7 and MDA-MB-231), wound-healing, and Cultrex BME cell invasion (MDA-MB-231) assays, respectively. The study herein reports the novel ability of penitrem A to suppress total β-catenin levels in MDA-MB-231 mammary cancer cells. Nine new penitrem analogs (10-18) were semisynthetically prepared, in an attempt to identify pharmacophores correlated with BK channel inhibition and tremorgenicity of penitrems and decrease their toxicity. The degree of BK channel inhibition was assessed using the nematode Caenorhabditis elegans, and in vivo tremorgenic EC₅₀ was calculated using CD-1 male mice following an Up-and-Down Procedure (UDP). Although new analogs were generally less active than parent compound 1, some showed no BK channel inhibition or tremorgenicity and retained the ability of penitrem A (1) to suppress total β-catenin levels in MDA-MB-231 cells. Paspaline (6) and emindole SB (7), both lacking BK channel inhibition and tremorgenicity, represent the simplest indole diterpene skeleton that retains the antiproliferative, antimigratory and total β-catenin suppressing effects shown by the more complex penitrem A (1).

DNA topoisomerases participate in fragility of the oncogene RET

Fragile site breakage was previously shown to result in rearrangement of the RET oncogene, resembling the rearrangements found in thyroid cancer. Common fragile sites are specific regions of the genome with a high susceptibility to DNA breakage under conditions that partially inhibit DNA replication, and often coincide with genes deleted, amplified, or rearranged in cancer. While a substantial amount of work has been performed investigating DNA repair and cell cycle checkpoint proteins vital for maintaining stability at fragile sites, little is known about the initial events leading to DNA breakage at these sites. The purpose of this study was to investigate these initial events through the detection of aphidicolin (APH)-induced DNA breakage within the RET oncogene, in which 144 APH-induced DNA breakpoints were mapped on the nucleotide level in human thyroid cells within intron 11 of RET, the breakpoint cluster region found in patients. These breakpoints were located at or near DNA topoisomerase I and/or II predicted cleavage sites, as well as at DNA secondary structural features recognized and preferentially cleaved by DNA topoisomerases I and II. Co-treatment of thyroid cells with APH and the topoisomerase catalytic inhibitors, betulinic acid and merbarone, significantly decreased APH-induced fragile site breakage within RET intron 11 and within the common fragile site FRA3B. These data demonstrate that DNA topoisomerases I and II are involved in initiating APH-induced common fragile site breakage at RET, and may engage the recognition of DNA secondary structures formed during perturbed DNA replication.

Prevention and Treatment of Colorectal Cancer by Natural Agents From Mother Nature

Colorectal cancer (CRC) is the third most commonly diagnosed cancer in the United States after cancers of the lung and the breast/prostate. While the incidence of CRC in the United States is among the highest in the world (approximately 52/100,000), its incidence in countries in India is among the lowest (approximately 7/100,000), suggesting that lifestyle factors may play a role in development of the disease. Whereas obesity, excessive alcohol consumption, a high-calorie diet, and a lack of physical activity promote this cancer, evidence indicates that foods containing folates, selenium, Vitamin D, dietary fiber, garlic, milk, calcium, spices, vegetables, and fruits are protective against CRC in humans. Numerous agents from "mother nature" (also called "nutraceuticals,") that have potential to both prevent and treat CRC have been identified. The most significant discoveries relate to compounds such as cardamonin, celastrol, curcumin, deguelin, diosgenin, thymoquinone, tocotrienol, ursolic acid, and zerumbone. Unlike pharmaceutical drugs, these agents modulate multiple targets, including transcription factors, growth factors, tumor cell survival factors, inflammatory pathways, and invasion and angiogenesis linked closely to CRC. We describe the potential of these dietary agents to suppress the growth of human CRC cells in culture and to inhibit tumor growth in animal models. We also describe clinical trials in which these agents have been tested for efficacy in humans. Because of their safety and affordability, these nutraceuticals provide a novel opportunity for treatment of CRC, an "old age" disease with an "age old" solution.

Betulinic acid, a natural compound with potent anticancer effects

New therapies using novel mechanisms to induce tumor cell death are needed with plants playing a crucial role as a source for potential anticancer compounds. One highly promising class of natural compounds are the triterpenoids with betulinic acid (BetA) as the most prominent representative. In-vitro studies have identified this agent as potently effective against a wide variety of cancer cells, also those derived from therapy-resistant and refractory tumors, whereas it has been found to be relatively nontoxic for healthy cells. In-vivo preclinically applied BetA showed some remarkable anticancer effects and a complete absence of systemic toxicity in rodents. BetA also cooperated with other therapies to induce tumor cell death and several potent derivatives have been discovered. Its antitumor activity has been related to its direct effects on mitochondria where it induces Bax/Bak-independent cytochrome-c release.