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

Structural modification strategies of triazoles in anticancer drug development

The triazole functional group plays a pivotal role in the composition of biomolecules with potent anticancer activities, including numerous clinically approved drugs. The strategic utilization of the triazole fragment in the rational modification of lead compounds has demonstrated its ability to improve anticancer activities, enhance selectivity, optimize pharmacokinetic properties, and overcome resistance. There has been significant interest in triazole-containing hybrids in recent years due to their remarkable anticancer potential. However, previous reviews on triazoles in cancer treatment have failed to provide tailored design strategies specific to these compounds. Herein, we present an overview of design strategies encompassing a structure-modification approach for incorporating triazoles into hybrid molecules. This review offers valuable references and briefly introduces the synthesis of triazole derivatives, thereby paving the way for further research and advancements in the field of effective and targeted anticancer therapies.

Semisynthetic Derivatives of Pentacyclic Triterpenes Bearing Heterocyclic Moieties with Therapeutic Potential

Medicinal plants have been used by humans since ancient times for the treatment of various diseases and currently represent the main source of a variety of phytocompounds, such as triterpenes. Pentacyclic triterpenes have been subjected to numerous studies that have revealed various biological activities, such as anticancer, antidiabetic, anti-inflammatory, antimicrobial, and hepatoprotective effects, which can be employed in therapy. However, due to their high lipophilicity, which is considered to exert a significant influence on their bioavailability, their current use is limited. A frequent approach employed to overcome this obstacle is the chemical derivatization of the core structure with different types of moieties including heterocycles, which are considered key elements in medicinal chemistry. The present review aims to summarize the literature published in the last 10 years regarding the derivatives of pentacyclic triterpenes bearing heterocyclic moieties and focuses on the biologically active derivatives as well as their structure-activity relationships. Predominantly, the targeted positions for the derivatization of the triterpene skeleton are C-3 (hydroxyl/oxo group), C-28 (hydroxyl/carboxyl group), and C-30 (allylic group) or the extension of the main scaffold by fusing various heterocycles with the A-ring of the phytocompound. In addition, numerous derivatives also contain linker moieties that connect the triterpenic scaffold with heterocycles; one such linker, the triazole moiety, stands out as a key pharmacophore for its biological effect. All these studies support the hypothesis that triterpenoid conjugates with heterocyclic moieties may represent promising candidates for future clinical trials.

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

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

Synthesis and Structural Characterization of a New 1,2,3-Triazole Derivative of Pentacyclic Triterpene

The new 30-substituted triazole derivative of 3,28-O,O′-diacetylbetulin was obtained in the copper(I) catalyzed azide-alkyne cycloaddition (CuAAC). The title compound was characterized by NMR, IR, HR-MS, and X-ray diffraction techniques. The X-ray diffraction study showed that the 1,2,3-triazole derivative crystallizes in the orthorhombic space group P212121, Z = 4, and unit cell parameters are as follows a = 9.4860(10) Å, b = 13.9440(2) Å, and c = 30.2347(4) Å. The molecular packing is stabilized by intermolecular hydrogen interactions C-H…O. The Hirshfeld surface analysis showed the presence of the O…H interactions with a percentage of the 16.5% in the total Hirshfeld area. The MEP analysis showed that the nucleophilic regions are located near the oxygen atoms of the acyl and carbonyl groups of betulin moiety and the sulfur atom in the triazole linker. The HOMO and LUMO orbitals are located near the triazole moiety. The obtained results indicated that this new betulin derivative is more reactive with electrophilic than nucleophilic molecules.

Synthesis and biological evaluation of heterocyclic ring-fused dammarane-type ginsenoside derivatives as potential anti-tumor agents

Twenty-one AD-1 derivatives were designed and synthesized by introducing various nitrogen-containing heterocycles into C-2 and C-3 positions. Their anti-proliferative activities were evaluated on two human cancer cell lines (HCT-116 and RM-1 cells) and one normal human gastric mucosal epithelial cell GES-1. Most of derivatives exhibited increased inhibitory potency, compared with lead compound AD-1. The most potent compound 6d had an IC50 value of 6.03 μM against HCT-116 cells, while it did not exhibit obvious cytotoxicity on GES-1 cells. The primary mechanistic study indicated that 6d induced G2/M-phase arrest by regulating the expression levels of p53, p21, Cyclin B1 and CDK1. Furthermore, 6d also induced apoptosis in HCT-116 cells. Moreover, western blot analysis indicated that 6d blocked the activation of MEK/ERK signaling pathway by inhibiting the phosphorylation of MEK and ERK, and remarkably up-regulated the expression of Cyt-c and Cl-caspase-3/9/PARP. The results suggested that 6d caused apoptosis through regulating MEK/ERK signaling pathway and mitochondrial pathway.

Triterpenoids with modified A-ring as modulators of P-gp-dependent drug-resistance in cancer cells

Semi-synthetic A-cycle modified triterpenic derivatives with A-cycle condensed with a heterocyclic fragment (compound 1) and fragmented A-ring (compound 2) were tested for cytotoxicity against several tumor cell cultures and doxorubicin (Dox)-resistant cell lines. The equal cytotoxicity of the tested compounds to the parental tumor cell lines (HBL-100, K562) and their resistant subclones (HBL-100/Dox, K562/i-S9) was revealed. The overexpression of ABCB1 (MDR1) gene and P-glycoprotein (P-gp) was confirmed for both resistant subclones of tumor cells. Compounds 1 and 2 were shown to inhibit the ABC-transporter gene expression (MDR1, MRP, MVP, and BCRP) and the transport of well-known P-gp substrate Rhodamine 123 from resistant cells. The docking of triterpenoids 1 and 2 into the drug binding site of P-gp revealed a similarity between the conformation of the tested triterpenoids and that of classical inhibitor verapamil, thus assuming these compounds to be more likely the inhibitors than the substrates of P-gp. Any tested triterpenic derivatives, when combined at non-toxic concentrations with doxorubicin, improved cytotoxic effect of the therapeutic drug against resistant subclones of tumor cells.

1,2,3-Triazole-Containing Compounds as Anti-Lung Cancer Agents: Current Developments, Mechanisms of Action, and Structure-Activity Relationship

Lung cancer is the most common malignancy and leads to around one-quarter of all cancer deaths. Great advances have been achieved in the treatment of lung cancer with novel anticancer agents and improved technology. However, morbidity and mortality rates remain extremely high, calling for an urgent need to develop novel anti-lung cancer agents. 1,2,3-Triazole could be readily interact with diverse enzymes and receptors in organisms through weak interaction. 1,2,3-Triazole can not only be acted as a linker to tether different pharmacophores but also serve as a pharmacophore. This review aims to summarize the recent advances in 1,2,3-triazole-containing compounds with anti-lung cancer potential, and their structure-activity relationship (SAR) together with mechanisms of action is also discussed to pave the way for the further rational development of novel anti-lung cancer candidates.

2-Pyrazine-PPD, a novel dammarane derivative, showed anticancer activity by reactive oxygen species-mediate apoptosis and endoplasmic reticulum stress in gastric cancer cells

20 (R)-Dammarane-3β, 12β, 20, 25-tetrol (25-OH-PPD), a ginsenoside, was derived from Panax ginseng (C. A. Meyer) and inhibited growth of several cancer cell lines. To improve the anti-cancer activity, we introduced the pyrazine ring to 25-OH-PPD and obtained the compound 20(R)-[2,3-β]-Pyrazine-dammarane-12β,20,25-triol (2-Pyrazine-PPD). we evaluated the anti-cancer activity of 2-Pyrazine-PPD and investigated the main anti-cancer mechanisms of 2-Pyrazine-PPD in gastric cancer cells. We found that 2-Pyrazine-PPD remarkably suppressed the proliferation of gastric cancer cells in a concentration-dependent, and showed little toxicity to the normal cell (human gastric epithelial cell line-GES-1). Further study indicated that 2-Pyrazine-PPD induced apoptosis by mitochondria pathway in BGC-803 cancer cells, and activated unfolded protein response and the protein kinase RNA-activated (PKR)-like ER kinase (PERK)/Eukaryotic translation initiation factor-2α (eIF-2α)/Activating transcription factor 4 (ATF4) axis, the expression level of the protein C/EBP homologous protein (CHOP), the marker of endoplasmic reticulum stress, and the apoptosis inducing by 2-Pyrazine-PPD can partly be inhibited by siRNA-mediated knockdown of CHOP. Moreover, the production of reactive oxygen species was remarkably up-regulated in BGC-803 cancer cells treated with 2-Pyrazine-PPD. N-acetylcysteine (NAC, a reactive oxygen species scavenger) can attenuate 2-Pyrazine-PPD-induced apoptosis and endoplasmic reticulum stress. Taken together, we suggested that 2-Pyrazine-PPD exhibited remarkable anti-cancer activity by reactive oxygen species-mediate cell apoptosis and endoplasmic reticulum stress in gastric cancer cells. Our results uncovered the mechanism of 2-Pyrazine-PPD as a promising anti-tumor candidate for gastric cancer therapy.

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.

Synthesis and biological evaluation of triterpenoid thiazoles derived from betulonic acid, dihydrobetulonic acid, and ursonic acid

In this work, 35 new derivatives of betulonic, dihydrobetulonic and ursonic acid were prepared including 30 aminothiazoles and all of them were tested for their in vitro cytotoxic activity in eight cancer cell lines and two non-cancer fibroblasts. Compounds with the IC₅₀ below 5 μM in CCRF-CEM cells and low toxicity in non-cancer fibroblasts (4m, 5c, 5m, 6c, 6m, 7b, and 7c) were further subjected to tests of pharmacological parameters yielding the final set for advanced biological evaluation (4m, 5m, 6m, and 7b). It was proved by several methods, that all of them trigger apoptosis via the intrinsic pathway and derivatives 5m and 7b are the most effective (IC₅₀ 2.4 μM and 3.6 μM). They are the best candidates to become potentially new anticancer drugs and will be subjected to in vivo tests in mice. In addition, compounds 6b and 6c deserve more attention because their activity is not limited only to chemosensitive CCRF-CEM cell line. Specifically, compound 6b is highly active against K562 leukemic cell line (0.7 μM) and its IC₅₀ activity in colon cancer HCT116 cell line is 1.0 μM. Compound 6c is active in both normal K562 and resistant K562-TAX cell lines (IC₅₀ 3.4 μM and 5.4 μM) and both colon cancer cell lines (HCT116 and HCT116p53^-/-, IC₅₀ 3.5 μM and 3.4 μM).

Recent Achievements in Medicinal and Supramolecular Chemistry of Betulinic Acid and Its Derivatives ‡

The subject of this review article refers to the recent achievements in the investigation of pharmacological activity and supramolecular characteristics of betulinic acid and its diverse derivatives, with special focus on their cytotoxic effect, antitumor activity, and antiviral effect, and mostly covers a period 2015–2018. Literature sources published earlier are referred to in required coherences or from historical points of view. Relationships between pharmacological activity and supramolecular characteristics are included if such investigation has been done in the original literature sources. A wide practical applicability of betulinic acid and its derivatives demonstrated in the literature sources is also included in this review article. Several literature sources also focused on in silico calculation of physicochemical and ADME parameters of the developed compounds, and on a comparison between the experimental and calculated data.

1,2,3-Triazole-containing hybrids as potential anticancer agents: Current developments, action mechanisms and structure-activity relationships

Anticancer agents are critical for the cancer treatment, but side effects and the drug resistance associated with the currently used anticancer agents create an urgent need to explore novel drugs with low side effects and high efficacy. 1,2,3-Triazole is privileged building block in the discovery of new anticancer agents, and some of its derivatives have already been applied in clinics or under clinical trials for fighting against cancers. Hybrid molecules occupy an important position in cancer control, and hybridization of 1,2,3-triazole framework with other anticancer pharmacophores may provide valuable therapeutic intervention for the treatment of cancer, especially drug-resistant cancer. This review emphasizes the recent advances in 1,2,3-triazole-containing hybrids with anticancer potential, covering articles published between 2015 and 2019, and the structure-activity relationships, together with mechanisms of action are also discussed.

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, characterization and cytotoxic activity evaluation of ginsengdiol oxidation and nitrogen hybrid derivatives

Panaxadiol (PD), a diol-type ginseng saponin, with a dammarane skeleton plays a potential role in the apoptosis of tumor cells. In this study, 28 oxidation and nitrogen hybrid derivatives of PD were synthesized, of which 20 were novel compounds. All the obtained compounds were screened for their cytotoxic activity in six cell lines. As compared with the positive control, some compounds showed better anti-proliferative activities while having much weaker effect on the growth of normal cells. Among them, ring-A fused pyrazoline of PD (1j) displayed impressive cytotoxic activity with IC₅₀ 9.62 ± 1.34, 11.65 ± 1.71, and 13.45 ± 1.60 μM against A549, HeLa and 8901 cell lines, respectively. Additionally, compound 2f exhibited the most potent activity with an IC₅₀ value of 8.93 ± 1.11 μM against cell line A549. Therefore, our results indicated that 1j and 2f can be promising lead candidates for further studies.

Synthesis of cytotoxically active derivatives based on alkylated 2,3-seco-triterpenoids

Extremely low content of biologically active triterpenoids with the fragmented or contracted ring A extractable from plants is the main disadvantage of their use in drug discovery and practical pharmacology. Development of new methods for synthesis of these compounds and their structural analogs from bioavailable triterpene precursors gives an opportunity to obtain promising agents for pharmacology with excellent yields. A new approach to synthesis of alkylated A-seco-triterpenoids, including the Beckmann fragmentation of 3-methyl-substituted allobetulin or betulinic acid methyl ester with 2-hydroxyimino group in the ring A was proposed. These compounds were used to prepare a series of 2,3-seco- and five-membered ring A lupane and oleanane derivatives, cytotoxicity of which was screened in vitro against the cancer (HEp-2, HCT 116, A549, RD TE32, MS) and non-cancerous (HEK 293) cell lines. Methyl 3-bromomethyl-1-cyano-3-oxo-2,3-seco-2-norlup-20(29)-en-30-al-28-oate was selected as the most active compound (IC₅₀ 3.4-10.4 μM for HEp-2, HCT 116, RD TE32, MS cells) capable of triggering caspase-8-mediated apoptosis in HCT 116 cells accompanied by typical apoptotic chromatin condensation, without any loss of mitochondrial membrane permeability.