Synthesis of β-boswellic acid derivatives as cytotoxic and apoptotic agents

Application of Chalcone in the Structural Modification of Natural Products: An Overview

Natural products frequently display a range of biological activities, yet many exhibit only moderate efficacy during initial evaluations. Often, these natural substances necessitate structural alterations to yield promising lead compounds. Chalcones, characterized by their β-unsaturated carbonyl aromatic ketone structure, are prevalent in plant life and serve as fundamental scaffolds for the biosynthetic precursors of flavonoids and isoflavones. Due to their straightforward synthesis and extensive spectrum of biological effects, chalcones have found extensive application in medicinal chemistry. Chalcone analogs have demonstrated significant potential for drug discovery and development, as structural modifications can both amplify pharmacological efficacy and effectively mitigate toxic side effects. This paper endeavors to delve into the applications of chalcones in the structural modification of natural products, providing a theoretical foundation for future endeavors in derivatization and drug development. The full paper is organized into categories based on the biological activities of the derivatives, including anti-dyslipidemic, antibacterial, antimalarial, anti-inflammatory, anticancer, anti-Alzheimer, and α-glucosidase inhibitory activities.

Nanosponge-Encapsulated Polyoxometalates: Unveiling the Multi-Faceted Potential Against Cancers and Metastases Through Comprehensive Preparation, Characterization, and Computational Exploration

Background/Objectives: This study examined the fabrication and characterization of nanosponges (NS) laden with polyoxometalates (TiW11Co) with the intention of targeting malignancy. Methods: By employing the emulsion solvent diffusion technique, TiW11Co-NS were generated by combining polyvinyl alcohol (PVA) and ethyl cellulose (EC) in different concentrations. Results: A significant numerical results encompassed a hydrodynamic particle diameter of 109.5 nm, loading efficiencies reaching 85.9%, and zeta potentials varying from -24.91 to -27.08 (mV). Scanning and transmission electron microscopy were employed to validate the TiW11Co-NS porous structure and surface morphology. The results of the stability investigation indicated that TiW11Co-NS exhibited prolonged sturdiness. Investigation examining the inhibition of enzymes revealed that TiW11Co-NS exhibited enhanced effectiveness against TNAP. Pharmacological evaluations of TiW11Co-NS demonstrated improved cytotoxicity and apoptotic effects in comparison to pure TiW11Co, thereby indicating their potential utility in targeted cancer therapy. In vivo investigations involving mice revealed that TiW11Co-NS caused a more substantial reduction in tumor weight and increased survival rates in comparison to pure TiW11Co. The resemblance of TiW11Co for crucial proteins associated with cancer proliferation was featured through molecular docking, thereby supporting its therapeutic potential. Conclusions: The TiW11Co-laden nanosponges demonstrated superior stability, enzyme inhibition, cytotoxicity, and in vivo anticancer efficacy, underscoring their potential for targeted cancer therapy.

Biodiversity and Bioactive Potential of Actinomycetes from Unexplored High Altitude Regions of Kargil, India

The effectiveness of currently available antimicrobials and anticancer medications is steadily declining due to the emergence of drug resistance. Since actinobacteria are important producers of bioactive substances, we have isolated them from the soil samples of exotic North-Western Himalayan terrains. Out of 128 isolates, 39 strains were prioritized based on their bioactive potential. The diversity analysis revealed higher abundance distribution of actinomycetes in the soil of an open field (68.7%), followed by the mountainside (34.9%), from which most of the bioactive strains were obtained. The extract of the strain S26-11 was found to be highly active against Gram-positive Staphylococcus aureus and Bacillus subtilis with a MIC of 0.5 μg/mL and 1 μg/mL respectively. A cytotoxicity assay (sulforhodamine B) was performed on a series of cancer cell lines (PC-3, MCF-7, A-549, and HCT-116). The extract of the strain S26-11 showed cytotoxic activity against all cancer cell lines with an IC50 of 2 µg/mL against PC-3, 1.9 µg/mL against MCF-7, 0.52 µg/mL against A-549, and 0.83 µg/mL against HCT-116. Moreover, the antioxidant activity was assessed using a DPPH-based assay and the results revealed that the S17-8 isolate showed the highest antioxidant activity with IC50 of 114.136 μg/mL. The Response Surface Methodology (RSM) had helped to optimize the physical parameters for scaling up of the bioactive strain S26-11. The unexplored soil niches of Kargil (UT, Ladakh), India, is rich in actinomycetes which are having potential bioactivities, would be worth to explore for the discovery of bioactive compounds.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-023-01133-1.

Antiproliferative and cell cycle arrest potentials of 3-O-acetyl-11-keto-β-boswellic acid against MCF-7 cells in vitro

INTRODUCTION

Cancer is a major issue in medical science with increasing death cases every year worldwide. Therefore, searching for alternatives and nonorthodox methods of treatments with high efficiency, selectivity and less toxicity is the main goal in fighting cancer. Acetyl-11-keto-β-boswellic acid (AKBA), is a derivative pentacyclic triterpenoid that exhibited various biological activities with potential anti-tumoral agents. In this research, AKBA was utilized to examine the potential cytotoxic activity against MCF-7 cells in vitro and monitor the cellular and morphological changes with a prospective impact on apoptosis induction.

METHODS

The cytotoxic activity of AKBA was measured by 3(4,5dimethylthiazole- 2-yl)-2,5 diphyneltetrazolium bromide (MTT) assay. A dose-dependent inhibition in MCF-7 cell viability was detected. The clonogenicity of MCF-7 cells was significantly suppressed by AKBA increment in comparison with untreated cells.

RESULT

Morphologically, exposure of MCF-7 cells to high AKBA concentrations caused changes in cell nuclear morphology which was indicated by increasing in nuclear size and cell permeability intensity. The mitochondrial membrane potential (ΔΨm) was reduced by increasing AKBA concentration with a significant release of cytochrome c. Acridine orange/ethidium bromide dual staining experiment confirmed that MCF-7 cells treated with AKBA (IC50 concentration) displayed a late stage of apoptosis indicated by intense and bright reddish colour.

CONCLUSION

A significant increase in reactive oxygen species formation was observed. Caspase 8 and caspase 9 activities were estimated and AKBA activated the production of caspase 8 and caspase 9 in a dose-dependent pattern. Finally, the cell phase distribution analysis was conducted, and flow cytometric analysis showed that AKBA at 200 μg mL-1 significantly arrest MCF-7 cells at the G1 phase and triggered apoptosis.

Phytochemical and In Vitro Cytotoxic Screening of Chloroform Extract of Ehretia microphylla Lamk

Ehretia microphylla of the Boraginaceae family has been extensively used as a folklore remedy for the treatment of a wide range of ailments such as cough, cancer, allergies, and gastrointestinal and venereal disorders. Extensive literature review reports have revealed these findings due to the presence of numerous phytomolecules. To validate traditional claims for cytotoxic activity of E. microphylla, the present study was undertaken. Dried leaves of the plant were powdered and defatted with petroleum ether followed by hot continuous extraction with chloroform. The chloroform extract was subjected to in vitro cytotoxic screening against a panel of human cancer cell lines such as HCT-116 (colon), MCF-7 (breast), PC-3 (prostate), A-549 (lung), HL-60 (leukemia) and MiaPaCa-2 (pancreatic) at 50 µM using SRB assay. The extract exhibited noteworthy cytotoxicity activity against breast and lung cancer. It exhibited 85.55% and 77.93% inhibition against MCF-7 and A-549 cancer cell lines, respectively. The mechanism behind cell death was determined using the DAPI staining method, which induces alteration in nuclear morphology in MCF-7 cell lines evidenced through DAPI staining. Phytochemical screening of E. microphylla extract showed the presence of saponins, steroids, lipids, tannins and triterpenoids. The chemoprofile of the chloroform extract of E. microphylla leaves was established using an n-hexane:ethyl acetate solvent system in a ratio of 6:4. The developed chromatogram showed five spots both in visible and UV light at 254 nm. The information provided in the present study will enable further studies on the isolation and characterization of bioactive compounds/fractions by following bioactivity-guided fractionation, and thus, the plant has the potential to reduce proliferation and may induce cell death via apoptosis in breast cancer cells.

2-Pyridin-4-yl-methylene-beta-boswellic Acid-A Potential Candidate for Targeting O6-Methylguanine-DNA Methyltransferase Epi-transcriptional Reprogramming in KRAS G13D-Microsatellite Stable, G12V-Microsatellite Instable Mutant Colon Cancer

PMBA (2-Pyridin-4-yl-methylene-beta-boswellic acid), screened from among the 21 novel series of semisynthetic analogues of β-boswellic acid, is being presented as a lead compound for integrative management of KRAS mutant colorectal cancer (CRC), upon testing and analysis for its anticancerous activity on a panel of NCI-60 cancer cell lines and in vivo models of the disease. PMBA (1.7-29 μM) exhibited potent proliferation inhibition on the cell lines and showed sensitivity in microsatellite instability and microsatellite stable (GSE39582 and GSE92921) subsets of KRAS gene (Kirsten rat sarcoma viral oncogene homolog)-mutated colon cell lines, as revealed via flow cytometry analysis. A considerable decrease in mitogen-activated protein kinase pathway downstream effectors was observed in the treated cell lines via the western blot and STRING (Search tool for the retrieval of interacting genes/proteins) analysis. PMBA was further found to target KRAS at its guanosine diphosphate site. Treatment of the cell lines with PMBA showed significant reduction in MGMT promoter methylation but restored MGMT (O⁶-methylguanine-DNA methyltransferase) messenger ribonucleic acid expression via significant demethylation of the hypermethylated CpG (Cytosine phosphate guanine) sites in the MGMT promoter. A significant decrease in dimethylated H3K9 (Dimethylation of lysine 9 on histone 3) levels in the MGMT promoter in DNA hypo- and hypermethylated HCT-116^G13D and SW-620^G12V cells was observed after treatment. In the MNU (N-methyl-N-nitrosourea)-induced CRC in vivo model, PMBA instillation restricted and repressed polyp formation, suppressed tumor proliferation marker Ki67 (Marker of proliferation), ablated KRAS-associated cytokine signaling, and decreased mortality. Clinical trial data for the parent molecule revealed its effectiveness against the disease, oral bioavailability, and system tolerance. Comprehensively, PMBA represents a new class of KRAS inhibitors having a therapeutic window in the scope of a drug candidate. The findings suggest that the PMBA analogue could inhibit the growth of human CRC in vivo through downregulation of cancer-associated biomarkers as well as reactivate expression of the MGMT gene associated with increased H3K9 acetylation and H3K4 methylation with facilitated transcriptional activation, which might be important in silencing of genes associated with upregulation in the activity of KRAS.

Hollongdione arylidene derivatives induce antiproliferative activity against melanoma and breast cancer through pro-apoptotic and antiangiogenic mechanisms

The use of natural compounds as starting point for semisynthetic derivatives has already been proven as a valuable source of active anticancer agents. Hollongdione (4,4,8,14-tetramethyl-18-norpregnan-3,20-dion), obtained by few steps from dammarane type triterpenoid dipterocarpol, was chemically modified at C2 and C21 carbon atoms by the Claisen-Schmidt aldol condensation to give a series of arylidene derivatives. The anticancer activity of the obtained compounds was assessed on NCI-60 cancer cell panel, revealing strong antiproliferative effects against a large variety of cancer cells. 2,21-Bis-[3-pyridinyl]-methylidenohollongdione 9 emerged as the most active derivative as indicated by its GI₅₀ values in the micromolar range which, combined with its high selectivity index values, indicated its suitability for deeper biological investigation. The mechanisms involved in compound 9 antiproliferative activity, were investigated through in vitro (DAPI staining) and ex vivo (CAM assay) tests, which exhibited its apoptotic and antiangiogenic activities. In addition, compound 9 showed an overall inhibition of mitochondrial respiration. rtPCR analysis identified the more intimate activity at pro-survival/pro-apoptotic gene level. Collectively, the hollongdione derivative stand as a promising therapeutic option against melanoma and breast cancer provided that future in vivo analysis will certify its clinical efficacy.

Mechanistic investigation of synergistic interaction of tocopherol succinate with a quinoline-based inhibitor of mammalian target of rapamycin

OBJECTIVES

Cancer monotherapy is associated with various limitations; therefore, combination chemotherapy is widely explored for optimum drug efficacy. In this study, 4-(N-Phenyl-N'-substituted benzenesulfonyl)-6-(4-hydroxyphenyl) quinoline-based mammalian target of rapamycin (mTOR) inhibitor (IIIM-4Q) was investigated in combination with tocopherol succinate (TOS), and the mechanism of cytotoxicity was elucidated.

METHODS

The cytotoxic potential of IIIM-4Q and TOS was evaluated in five cell lines. Further, to understand the mechanism of cytotoxicity of IIIM-4Q, TOS and their combination, various studies including morphological analysis using scanning electron microscopy and 6-diamidino-2-phenylindole (DAPI) staining, estimation of reactive oxygen species (ROS) level, measurement of mitochondrial membrane potential (MMP), in-vitro cell migration assay, Western blotting and staining with acridine orange (AO) for autophagy detection were performed.

KEY FINDINGS

Investigated combination was synergistic in nature and exhibited greater oxidative stress and mitochondrial dysfunction in pancreatic cancer cells. The migration potential of MIA PaCa-2 cells was significantly mitigated under the influence of this combination, and morphological changes such as chromatin condensation and nuclear blebbing were observed. Also, poly (adenosine diphosphate-ribose) polymerase cleavage and caspase-3 activation were observed in IIIM-4Q and TOS combination-treated cells.

CONCLUSIONS

The investigated combination synergistically inhibited proliferation of MIA PaCa-2 cells through simultaneous induction of autophagy followed by apoptosis, and this combination demonstrated potential for further translational studies.

Synthesis of messagenin and platanic acid chalcone derivatives and their biological potential

The chalcone derivatives of 20-oxo-lupanes have been synthesised and screened for some types of biological activity. Ozonolysis of lupanes afforded 20-oxo-derivatives with the following condensation using different aromatic aldehydes by Claisen‒Schmidt reaction to the target compounds. The E configuration of 19-[3-(pyridin-3-yl)-prop-2-en-1-one]-fragment was established by X-ray analysis. Screening of cytotoxic activity against NCI-60 cancer cell line panel revealed, that messagenin derivative 9 has the highest activity with GI₅₀ value ranged from 0.304 to 0.804 μM. A colorimetric SRB assay revealed for the 2,30-bis-furfurylidene derivative 11 and 30-bromo-20-oxo-29-nor-3,28-diacetoxy-betulin 16 cytotoxic activity against breast carcinoma MCF-7 and ovarian carcinoma A2780 cell lines. Compounds 11 and 13 acted also as inhibitors of the enzyme α-glucosidase (from S. saccharomyces) with IC₅₀ values of 1.76 μM and 3.3 μM thus being 97- and 52-fold more active than standard acarbose. Antiviral potency of compounds 12 and 14 against HCMV, HSV-1 and HPV is also discussed.

Boswellic acids: privileged structures to develop lead compounds for anticancer drug discovery

Introduction: Cancer has been identified to be the second major cause of death internationally as exemplified by ca. 9.6 million deaths in 2018 along with ca. 18 million new patients in 2018 that have been recorded. Natural boswellic acids (BAs) and their source, frankincense, have been reported to possess in vitro and in vivo anticancer effects toward various cancer cells.Areas covered: This comprehensive review focuses on the importance of boswellic acids (BAs) for the establishment of future treatments of cancer. Moreover, potent semisynthetic derivatives of BAs have been described along with their mode of action. In addition, important structural features of the semisynthetic BAs required for cytotoxic effects are also discussed.Expert opinion: Numerous semisynthetic BAs illustrate excellent cytotoxic effects. Of note, compounds bearing cyanoenone moieties in ring A, endoperoxides and hybrids display increased and more potent cytotoxic effects compared with other semisynthetic BAs. Moreover, BAs have the potential to conjugate or couple with other anticancer compounds to synergistically increase their combined anticancer effects. In addition, to get derived BAs to become lead anticancer compounds, future research should focus on the preparation of ring A cyanoenones, endoperoxides, and C-24 amide analogs.

Synthesis and anti-cancer activity studies of dammarane-type triterpenoid derivatives

Two series of novel derivatives of AD-2, an active ginsenoside derived from ginseng were designed and synthesized. Five human cancer cell lines (MGC-803, SGC-7901, A549, MCF-7, PC-3 cells) and one normal ovarian cell IOSE144 were employed to evaluate the anti-proliferative activity. Most of derivatives possessed obvious enhanced activity compared with AD-2. Among them, compound 4c displayed the most excellent activity in all tested cancer cell lines, especially A549 cells with an IC50 value of 1.07 ± 0.05 μM. The underlying mechanism study suggested that 4c induced S-phase arrest and apoptosis in A549 cells. Increasing the level of ROS and inducing collapse of MMP in cells treated with 4c were also proved. Moreover, Western blot analysis showed that the expression level of p53 and p21 were obviously increased. 4c could remarkably up-regulate the expression of cyt c in cytosol, the ratio of Bax to Bcl-2 and activate caspase-3/9/PARP. Besides, the expression level of MDM2 was remarkably decreased. The results indicated that 4c caused apoptosis through the mitochondrial pathway, which ROS generation was probably involved in, and had the potent to serve as anti-proliferative agent.

New derivatives of 11-keto-β-boswellic acid (KBA) induce apoptosis in breast and prostate cancers cells

A series of new 11-keto-β-boswellic acid were partially-synthesized by modifying the hydroxyl and carboxylic acid functional groups of ring A. The structures of the new analogs were confirmed by detailed spectral data analysis. Compounds 4, 5 and 9 exhibited potent anti-cancer results against two human tumor cancer cell lines having IC₅₀ value of MCF-7 (breast) and LNCaP (prostate): 123.6, 9.6 and 88.94 μM and 9.6, 44.12 and 12.03 μM, respectively. Additionally, a maximum nuclear fragmentation was observed for 4 (78.44%) in AKBA treated cells after 24 hr followed by 5 and 9 with (74.25 and 66.9% respectively). This study suggests that the presence of hydrazone functionality (4 and 9) has effectively improved the potency of AKBA. Interestingly, compound 5 with a lost carboxylic acid group of ring A showed comparable potent activity. Highly selective AKBA requires further modification to improve its bioavailability and solubility inside the cancer cells.

Synthesis of axially disubstituted silicon phthalocyanines and investigation of photodynamic effects on HCT-116 colorectal cancer cell line

Photodynamic therapy is one of the hot topics in cancer studies. Photosensitizing chemical substrates are stimulated by light having a specific wavelength to cause fatal effect on different kinds of targets. In this study, axially 4-{[(1E)-2-furylmethylene]amino}phenol, 4-{[(1E)-2-thienylmethylene]amino}phenol and 4-{[(1E)-(4-nitro-2-thienyl)methylene]amino}phenol disubstituted silicon phthalocyanines were synthesized as Photosensitizers for photodynamic therapy in cancer treatment. The structural characterizations of these novel compounds were performed by a combination of FT-IR, ¹H-NMR, UV-vis and mass. All these newly prepared compounds did not show aggregation at the concentration range of 2 × 10^-6-12 × 10^-6 M in tetrahydrofurane and also did not show aggregation in different organic solvents at 2 × 10^-6 M concentration. Phthalocyanines synthesized in this study were tested on HCT-116 colorectal cancer cells and stimulated by light has wavelength of 680 nm. The toxic effects on cancer cells which are caused by different concentrations of photosensitizing molecules have been examined and compared with the toxic effects on cancer cells that were kept in the dark. It is confirmed that these molecules caused toxic effects on colorectal cancer cells when they were stimulated by light but there was no toxic effect in the dark.

Pentacyclic Triterpene Bioavailability: An Overview of In Vitro and In Vivo Studies

Pentacyclic triterpenes are naturally found in a great variety of fruits, vegetables and medicinal plants and are therefore part of the human diet. The beneficial health effects of edible and medicinal plants have partly been associated with their triterpene content, but the in vivo efficacy in humans depends on many factors, including absorption and metabolism. This review presents an overview of in vitro and in vivo studies that were carried out to determine the bioavailability of pentacyclic triterpenes and highlights the efforts that have been performed to improve the dissolution properties and absorption of these compounds. As plant matrices play a critical role in triterpene bioaccessibility, this review covers literature data on the bioavailability of pentacyclic triterpenes ingested either from foods and medicinal plants or in their free form.

PLGA nanoparticles augmented the anticancer potential of pentacyclic triterpenediol in vivo in mice

A novel pentacyclic triterpenediol (TPD), an anticancer lead fromBoswellia serrata, was encapsulated into PLGA nanoparticles, leading to enhancement in anticancer potential in EAT bearing mice model.

Analogues of boswellic acids as inhibitors of pro-inflammatory cytokines TNF-α and IL-6

A library of boswellic acid analogues were synthesized and tested for their anti-inflammatory potential on key inflammatory mediators, TNF-α and IL-6. The study led to the identification of lead compounds showing significant inhibition of the cytokines, TNF-α and IL-6 both in vitro and in vivo.