Novel pentacyclic triterpenes exhibiting strong neuroprotective activity in SH-SY5Y cells in salsolinol- and glutamate-induced neurodegeneration models

Novel triterpenoid pyrones, phthalimides and phthalates are selectively cytotoxic in CCRF-CEM cancer cells - Synthesis, potency, and mitochondrial mechanism of action

A series of triterpenoid pyrones was synthesized and subsequently modified to introduce phthalimide or phthalate moieties into the triterpenoid skeleton. These compounds underwent in vitro cytotoxicity screening, revealing that a subset of six compounds exhibited potent activity, with IC50 values in the low micromolar range. Further biological evaluations, including Annexin V and propidium iodide staining experiment revealed, that all compounds induce selective apoptosis in cancer cells. Measurements of mitochondrial potential, cell cycle analysis, and the expression of pro- and anti-apoptotic proteins confirmed, that apoptosis was mediated via the mitochondrial pathway. These findings were further supported by cell cycle modulation and DNA/RNA synthesis studies, which indicated a significant increase in cell accumulation in the G0/G1 phase and a marked reduction in S-phase cells, alongside a substantial inhibition of DNA synthesis. The activation of caspase-3 and the cleavage of PARP, coupled with a decrease in the expression of Bcl-2 and Bcl-XL proteins, underscored the induction of apoptosis through the mitochondrial pathway. Given their high activity and pronounced effect on mitochondria function, trifluoromethyl pyrones 1f and 2f, and dihydrophthalimide 2h have been selected for further development.

Synthesis of N-glycosyl amides: conformational analysis and evaluation as inhibitors of β-galactosidase from E. coli

The synthesis of N-glycosyl amides typically involves the use of glycosyl amines as direct precursors, resulting in low yields due to hydrolysis and the loss of stereocontrol through anomerization processes. In this study, a sequential synthesis of N-glycosyl amides is proposed, employing glycosyl amines as intermediates obtained from glycosyl azides. Derivatives with gluco, galacto, or xylo configurations were synthesized. Hexose derivatives were obtained under stereocontrol to give only the β anomer, while the xylo derivatives provided a mixture of α and β anomers. Conformational analysis revealed that all β anomers adopted the 4C1 conformation, while α anomers were found in the 1C4 chair as the major conformer. After de-O-acetylation, the derivatives containing a galactose unit were evaluated as inhibitors of β-galactosidase from E. coli and were found to be moderate inhibitors.

Synthesis, Cellular Uptake, and Photodynamic Activity of Oligogalactosyl Zinc(II) Phthalocyanines

A series of di-α-substituted zinc(II) phthalocyanines with different number of galactose moieties, ranging from 1 to 8, namely Pc-gal_n (n=1, 2, 4, and 8) were designed and synthesized. The synthesis involved the copper-catalyzed azide-alkyne cycloaddition reaction of a mono- or dialkynyl zinc(II) phthalocyanine with an acetyl-protected galactosyl azide or its dendritic derivative with four acetyl-protected galactosyl groups, followed by removal of the acetyl protecting groups via alkaline hydrolysis. In N,N-dimethylformamide, these oligogalactosyl phthalocyanines were non-aggregated as shown by the strong Q-band absorption and fluorescence emission. Owing to the di-α-substitution, they also behaved as efficient singlet oxygen generators upon light irradiation with a singlet oxygen quantum yield of 0.84. The spectroscopic and photophysical properties were not affected by the number of galactosyl units. In contrast, the compounds became significantly aggregated and quenched in phosphate-buffered saline. Their cellular uptake was then studied using a range of cell lines, which generally followed the order Pc-gal₁ >Pc-gal₂ ≈Pc-gal₄ >Pc-gal₈ . Interestingly, the di-galactosyl analogue exhibited selective uptake against HeLa human cervical carcinoma cells through an energy-dependent pathway instead of the expected asialoglycoprotein receptor. Upon light irradiation, it could effectively kill the cells with a half-maximal inhibitory concentration of 0.58 μM.

Ring-fused 3β-acetoxyandrost-5-enes as novel neuroprotective agents with cholinesterase inhibitory properties

Alzheimer´s disease (AD) is an intellectual disorder caused by organic brain damage and cerebral atrophy, characterized by the loss of memory, judgment, and abstract thinking followed by declining cognitive functions, language, and the ability to perform daily living activities. Many efforts have been made to decrease the effects of the disease but also to block the neurodegenerative process. Cholinesterase inhibitors (ChEIs) are a group of medicines that act at the neurotransmission of acetylcholine, preventing its excessive breakdown and helping to improve cognitive functions in patients with AD. In this work, 16 chiral steroids, namely ring-fused 3β-acetoxyandrost-5-ene derivatives, their precursor and two 16-dehydroprogesterone-derived dioximes, were assessed as cholinesterase inhibitors and neuroprotective agents. The results demonstrated that some of the tested steroids are cholinesterase inhibitors and the majority selective for acetylcholinesterase inhibition. Albeit, one ring-fused 3β-acetoxyandrost-5-ene containing N-methylpiperidine ring (compound 2g) demonstrated to be a selective and potent inhibitor of the butyrylcholinesterase enzyme. (S)- 4,4a,5,6,7,8-(hexahydronaphthalen-2-one)-fused 3β-acetoxyandrost-5-ene (compound 6) showed high neuroprotective effect, high ability to restore the mitochondrial membrane potential from glutamate intoxication, and dramatic improvement in cell morphology. The described results provided relevant structure-activity relationship data.

An evaluation of the rat intestinal monoamine biogeography days following exposure to acute stress

Stress-induced abnormalities in gut monoamine levels (e.g., serotonin, dopamine, norepinephrine) have been linked to gastrointestinal (GI) dysfunction, as well as the worsening of symptoms in GI disorders. However, the influence of stress on changes across the entire intestinal monoamine biogeography has not been well-characterized, especially in the days following stress exposure. Therefore, the aim of this study was to comprehensively assess changes to monoamine neurochemical signatures across the entire rat intestinal tract days after exposure to an acute stressor. To the end, adult male F344 rats were subjected to an episode of unpredictable tail shocks (acute stress) or left undisturbed. Forty-eight hours later rats were euthanized either following a 12 h period of fasting or 30 min of food access to evaluate neurochemical profiles during the peri- and early postprandial periods. Monoamine-related neurochemicals were measured via UHPLC in regions of the small intestine (duodenum, jejunum, ileum), large intestine (cecum, proximal colon, distal colon), cecal contents, fecal contents, and liver. The results suggest a relatively wide-spread increase in measures of serotonin activity across intestinal regions can be observed 48 h after exposure to acute stress, however some evidence was found supporting localized differences in serotonin metabolization. Moreover, acute stress exposure reduced catecholamine-related neurochemical concentrations most notably in the ileum, and to a lesser extent in the cecal contents. Next, stress-related fecal serotonin concentrations were consistent with intestinal profiles. However, fecal dopamine was elevated in association with stress, which did not parallel findings in any other intestinal area. Finally, stress exposure and the food access period together only had minor effects on intestinal monoamine profiles. Taken together, these data suggest nuanced differences in monoaminergic profiles exist across intestinal regions the days following exposure to an acute stressor, highlighting the importance of assessments that consider the entire intestinal tract biogeography when investigating stress-related biological outcomes that may be relevant to GI pathophysiology.

Salsolinol Induces Parkinson's Disease Through Activating NLRP3-Dependent Pyroptosis and the Neuroprotective Effect of Acteoside

Endogenous neurotoxin 1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroiso-quinoline (Salsolinol, SAL) is a dopamine metabolite that is toxic to dopaminergic neurons in vitro and in vivo, and is involved in the pathogenesis of Parkinson's disease (PD). However, the molecular mechanism by which SAL induces neurotoxicity in PD remains challenging for future investigations. This study found that SAL induced neurotoxicity in SH-SY5Y cells and mice. RNA sequencing (RNAseq) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were used to detect differentially expressed genes in SAL-treated SH-SY5Y cells. We found that NLR family pyrin domain-containing 3 (NLRP3)-dependent pyroptosis was enriched by SAL, which was validated by in vitro and in vivo SAL models. Further, NLRP3 inflammasome-related genes (ASC, NLRP3, active caspase 1, IL-1β, and IL-18) were increased at the mRNA and protein level. Acteoside mitigates SAL-induced neurotoxicity by inhibiting NLRP3 inflammasome-related pyroptosis in in vitro and in vivo PD models. In summary, the present study suggests for the first time that NLRP3-dependent pyroptosis plays a role in the pathogenesis of SAL-induced PD, and acteoside mitigates SAL-induced pyroptosis-dependent neurotoxicity in in vitro and in vivo PD models. The present results demonstrated a new mechanism whereby SAL mediates neurotoxicity by activating NLRP3-dependent pyroptosis, further highlighting SAL-induced pyroptosis-dependent neurotoxicity as a potential therapeutic target in PD.

28-[1-(3-(Propionyloxy)propyl)-1H-1,2,3-triazol-4-yl]carbonylbetulin

Betulin has a broad spectrum of biological and pharmacological properties, such as anticancer, antibacterial, antifungal, and antiviral. Unfortunately, the low bioavailability makes it difficult to use in medicine. The introduction of a triazole ring to the betulin structure leads to the obtainment of new compounds with higher activity and better bioavailability. The title compound was obtained from the triazole derivative of betulin by conversion of the hydroxyl group to an ester moiety in the Steglich reaction. The chemical structure of the hybrid was characterized by nuclear magnetic resonance (1H NMR, 13C NMR, HSQC, HMBC) and HRMS spectroscopy.

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.

Synthesis and Biological Evaluation of Novel Allobetulon/Allobetulin-Nucleoside Conjugates as AntitumorAgents

Allobetulin is structurally similar tobetulinic acid, inducing the apoptosis of cancer cells with low toxicity. However, both of them exhibited weak antiproliferation against several tumor cell lines. Therefore, the new series of allobetulon/allobetulin–nucleoside conjugates 9a–10i were designed and synthesized for potency improvement. Compounds 9b, 9e, 10a, and 10d showed promising antiproliferative activity toward six tested cell lines, compared to zidovudine, cisplatin, and oxaliplatin based on their antitumor activity results. Among them, compound 10d exhibited much more potent antiproliferative activity against SMMC-7721, HepG2, MNK-45, SW620, and A549 human cancer cell lines than cisplatin and oxaliplatin. In the preliminary study for the mechanism of action, compound 10d induced cell apoptosis and autophagy in SMMC cells, resulting in antiproliferation and G0/G1 cell cycle arrest by regulating protein expression levels of Bax, Bcl-2, and LC3. Consequently, the nucleoside-conjugated allobetulin (10d) evidenced that nucleoside substitution was a viable strategy to improve allobetulin/allobetulon’s antitumor activity based on our present study.

Study of the potential neuroprotective effect of Dunaliella salina extract in SH-SY5Y cell model

Alzheimer’s disease (AD) is the most common form of dementia caused by a progressive loss of neurons from different regions of the brain. This multifactorial pathophysiology has been widely characterized by neuroinflammation, extensive oxidative damage, synaptic loss, and neuronal cell death. In this sense, the design of multi-target strategies to prevent or delay its progression is a challenging goal. In the present work, different in vitro assays including antioxidant, anti-inflammatory, and anti-cholinergic activities of a carotenoid-enriched extract from Dunaliella salina microalgae obtained by supercritical fluid extraction are studied. Moreover, its potential neuroprotective effect in the human neuron-like SH-SY5Y cell model against remarkable hallmarks of AD was also evaluated. In parallel, a comprehensive metabolomics study based on the use of charged-surface hybrid chromatography (CSH) and hydrophilic interaction liquid chromatography (HILIC) coupled to high-resolution tandem mass spectrometry (Q-TOF MS/MS) was applied to evaluate the effects of the extract on the metabolism of the treated cells. The use of advanced bioinformatics and statistical tools allowed the identification of more than 314 metabolites in SH-SY5Y cells, of which a great number of phosphatidylcholines, triacylglycerols, and fatty acids were significantly increased, while several phosphatidylglycerols were decreased, compared to controls. These lipidomic changes in cells along with the possible role exerted by carotenoids and other minor compounds on the cell membrane might explain the observed neuroprotective effect of the D. salina extract. However, future experiments using in vivo models to corroborate this hypothesis must be carried out.

Pentacyclic triterpene carboxylic acids derivatives integrated piperazine-amino acid complexes for α-glucosidase inhibition in vitro

Eighteen derivatives of pentacyclic triterpene carboxylic acids (Maslinic acid, Corosolic acid and Asiatic acid) have been prepared by coupling the piperazine complex of l-amino acids at the C-28 site of the parent compounds. The α-glucosidase inhibitory activities of the pristine derivatives were evaluated in vitro. The results indicated that the inhibitory activity of some compounds (15e IC₅₀ = 591 μM, 16e IC₅₀ = 423 μM) was closed to that of the reference acarbose (IC₅₀ = 347 μM) in ethanol-water system. In addition, compound 16e (IC₅₀ = 380 μM) showed superior inhibitory activity than acarbose (IC₅₀ = 493 μM) in the measurement system with DMSO as solvent. The comparison of two different solvent systems showed that the derivatives had better α-glucosidase inhibitory activity in the DMSO system than that of in ethanol-water system. Regrettably, all of the as-synthesized derivatives exhibited inferior α-glucosidase inhibitory activities than those of the parent compounds in both test solvent systems. Furthermore, the result of enzyme kinetics demonstrated that the inhibition mechanism of compound 16e was noncompetitive inhibition with the inhibition constant K_i = 552 μM.

Substituted dienes prepared from betulinic acid - Synthesis, cytotoxicity, mechanism of action, and pharmacological parameters

A set of new substituted dienes were synthesized from betulinic acid by its oxidation to 30-oxobetulinic acid followed by the Wittig reaction. Cytotoxicity of all compounds was tested in vitro in eight cancer cell lines and two noncancer fibroblasts. Almost all dienes were more cytotoxic than betulinic acid. Compounds 4.22, 4.30, 4.33, 4.39 had IC₅₀ below 5 μmol/L; 4.22 and 4.39 were selected for studies of the mechanism of action. Cell cycle analysis revealed an increase in the number of apoptotic cells at 5 × IC₅₀ concentration, where activation of irreversible changes leading to cell death can be expected. Both 4.22 and 4.39 led to the accumulation of cells in the G0/G1 phase with partial inhibition of DNA/RNA synthesis at 1 × IC₅₀ and almost complete inhibition at 5 × IC₅₀. Interestingly, compound 4.39 at 5 × IC₅₀ caused the accumulation of cells in the S phase. Higher concentrations of tested drugs probably inhibit more off-targets than lower concentrations. Mechanisms disrupting cellular metabolism can induce the accumulation of cells in the S phase. Both compounds 4.22 and 4.39 trigger selective apoptosis in cancer cells via intrinsic pathway, which we have demonstrated by changes in the expression of the crucial apoptosis-related protein. Pharmacological parameters of derivative 4.22 were superior to 4.39, therefore 4.22 was the finally selected candidate for the development of anticancer drug.