Antioxidant and pro-oxidant properties of boldine on hippocampal slices exposed to oxygen–glucose deprivation in vitro

An Overview of Chemistry, Kinetics, Toxicity and Therapeutic Potential of Boldine in Neurological Disorders

Boldine is an alkaloid obtained from the medicinal herb Peumus boldus (Mol.) (Chilean boldo tree; boldo) and belongs to the family Monimiaceae. It exhibits a wide range of pharmacological effects such as antioxidant, anticancer, hepatoprotective, neuroprotective, and anti-diabetic properties. There is a dearth of information regarding its pharmacokinetics and toxicity in addition to its potential pharmacological activity. Boldine belongs to the aporphine alkaloid class and possesses lipophilic properties which enable its efficient absorption and distribution throughout the body, including the central nervous system. It exhibits potent free radical scavenging activity, thereby reducing oxidative stress and preventing neuronal damage. Through a variety of neuroprotective mechanisms, including suppression of AChE and BuChE activity, blocking of connexin-43 hemichannels, pannexin 1 channel, reduction of NF-κβ mediated interleukin release, and glutamate excitotoxicity which successfully reduces neuronal damage. These results point to its probable application in reducing neuroinflammation and oxidative stress in epilepsy, Alzheimer's disease (AD), and Parkinson's disease (PD). Moreover, its effects on serotonergic, dopaminergic, opioid, and cholinergic receptors were further investigated in order to determine its applicability for neurobehavioral dysfunctions. The article investigates the pharmacokinetics of boldine and reveals that it has a low oral bioavailability and a short half-life, requiring regular dosage to maintain therapeutic levels. The review studies boldine's potential therapeutic uses and mode of action while summarizing its neuroprotective benefits.  Given the favorable results for boldine as a potential neurotherapeutic drug in laboratory animals, more research is required. However, in order to optimise its therapeutic potential, it must be more bioavailable with fewer detrimental side effects.

Topical Delivery of Diacetyl Boldine in a Microemulsion Formulation for Chemoprotection against Melanoma

This study aimed to develop a microemulsion formulation for topical delivery of Diacetyl Boldine (DAB) and to evaluate its cytotoxicity against melanoma cell line (B16BL6) in vitro. Using a pseudo-ternary phase diagram, the optimal microemulsion formulation region was identified, and its particle size, viscosity, pH, and in vitro release characteristics were determined. Permeation studies were performed on excised human skin using Franz diffusion cell assembly. The cytotoxicity of the formulations on B16BL6 melanoma cell lines was evaluated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) assay. Two formulation compositions were selected based on the higher microemulsion area of the pseudo-ternary phase diagrams. The formulations showed a mean globule size of around 50 nm and a polydispersity index of <0.2. The ex vivo skin permeation study demonstrated that the microemulsion formulation exhibited significantly higher skin retention levels than the DAB solution in MCT oil (Control, DAB-MCT). Furthermore, the formulations showed substantially higher cytotoxicity toward B16BL6 cell lines than the control formulation (p < 0.001). The half-maximal inhibitory concentrations (IC50) of F1, F2, and DAB-MCT formulations against B16BL6 cells were calculated to be 1 µg/mL, 10 µg/mL, and 50 µg/mL, respectively. By comparison, the IC50 of F1 was 50-fold lower than that of the DAB-MCT formulation. The results of the present study suggest that microemulsion could be a promising formulation for the topical administration of DAB.

Lipid peroxidation reduction and hippocampal and cortical neurons protection against ischemic damage in animal model using Stellaria media

This study was aimed to determine the neuroprotective influence of Stellaria media in terms of restoring normal state of the rat’s hippocampus and cortex after oxidative insult caused by in vitro ischemia and reperfusion. Cell viability and membrane integrity were assessed using MTT and lactate dehydrogenase (LDH) assay, respectively. Ischemic insult was introduced in the rat brain’s hippocampal and cortical slivers by exposing oxygen and glucose deficiency (OGD) for 2 h, followed by 1 h of re-perfusion. Cellular oxidative stress levels were quantified by incorporating 2ʹ,7ʹ-dichlorofluorescein diacetate fluorescent probes. Additionally, the lipid peroxidation was assessed using TBARS assay. Findings revealed significant neuroprotection against OGD-induced mitochondrial impairment at 40 µg/mL of S. media in rat’s hippocampal and cortical slices. The LDH levels were decreased significantly (P < 0.001) during pre-incubation and reoxygenation periods using varied concentrations of S. media extract. Cellular oxidative stress levels results showed significant (P < 0.001) reduction in dichlorofluorescein fluorescence in slices homogenate of hippocampus and cortex using S. media extract. The lipid peroxidation assay results showed decreased (P < 0.01) levels of malondialdehyde in liver tissues of treated rats treated (200 mg/kg body weight) when compared to the ischemic animal. In summary, findings clearly indicated the neuroprotective effects of extract against in vitro ischemia in brain hippocampal and cortex slivers. S. media could undoubtedly be utilized as a healing agent in preventing neuronal cells’ loss during is chemic-reperfusion process.

Boldine Attenuates Synaptic Failure and Mitochondrial Deregulation in Cellular Models of Alzheimer's Disease

Alzheimer’s disease (AD) is the most common cause of senile dementia worldwide, characterized by both cognitive and behavioral deficits. Amyloid beta peptide (Aβ) oligomers (AβO) have been found to be responsible for several pathological mechanisms during the development of AD, including altered cellular homeostasis and synaptic function, inevitably leading to cell death. Such AβO deleterious effects provide a way for identifying new molecules with potential anti-AD properties. Available treatments minimally improve AD symptoms and do not extensively target intracellular pathways affected by AβO. Naturally-derived compounds have been proposed as potential modifiers of Aβ-induced neurodysfunction and cytotoxicity based on their availability and chemical diversity. Thus, the aim of this study was to evaluate boldine, an alkaloid derived from the bark and leaves of the Chilean tree Peumus boldus, and its capacity to block some dysfunctional processes caused by AβO. We examined the protective effect of boldine (1–10 μM) in primary hippocampal neurons and HT22 hippocampal-derived cell line treated with AβO (24–48 h). We found that boldine interacts with Aβ in silico affecting its aggregation and protecting hippocampal neurons from synaptic failure induced by AβO. Boldine also normalized changes in intracellular Ca²⁺ levels associated to mitochondria or endoplasmic reticulum in HT22 cells treated with AβO. In addition, boldine completely rescued the decrease in mitochondrial membrane potential (ΔΨm) and the increase in mitochondrial reactive oxygen species, and attenuated AβO-induced decrease in mitochondrial respiration in HT22 hippocampal cells. We conclude that boldine provides neuroprotection in AD models by both direct interactions with Aβ and by preventing oxidative stress and mitochondrial dysfunction. Additional studies are required to evaluate the effect of boldine on cognitive and behavioral deficits induced by Aβ in vivo.

Green Extraction of Alkaloids and Polyphenols from Peumus boldus Leaves with Natural Deep Eutectic Solvents and Profiling by HPLC-PDA-IT-MS/MS and HPLC-QTOF-MS/MS

Peumus boldus Mol., is a Chilean medicinal tree used for gastrointestinal and liver diseases. Such medicinal properties are associated with the presence of bioactive flavonoids and aporphine alkaloids. In this study, a new green and efficient extraction method used seven natural deep eutectic solvents (NADES) as extraction media. The extraction efficiency of these NADES was assessed, determining the contents of boldine and total phenolic compounds (TPC). Chemical profiling of P. boldus was done by high-performance liquid chromatography coupled to photo diode array detector and electrospray ion-trap mass spectrometry (HPLC-PDA-ESI-IT/MS) and electrospray ionization quadrupole time-of-flight high-resolution mass spectrometry (HPLC-ESI-QTOF-MS). Among the NADES tested, NADES4 (choline chloride-lactic acid) and NADES6 (proline-oxalic acid) enable better extraction of boldine with 0.427 ± 0.018 and 2.362 ± 0.055 mg of boldine g^-1 of plant, respectively. Extraction of boldine with NADES4 and NADES6 was more efficient than extractions performed with methanol and water. On the other hand, the highest TPC were obtained using NADES6, 179.442 ± 3.79 mg of gallic acid equivalents (GAE g^-1). Moreover, TPC in extracts obtained with methanol does not show significant differences with NADES6. The HPLC-PAD-MS/MS analysis enable the tentative identification of 9 alkaloids and 22 phenolic compounds. The results of this study demonstrate that NADES are a promising green extraction media to extract P. boldus bioactive compounds and could be a valuable alternative to classic organic solvents.

Boldine Supplementation Regulates Mitochondrial Function and Oxidative Stress in a Rat Model of Hepatotoxicity

Background: The xenobiotics-induced liver injury is a clinical complication. Hence, finding new hepatoprotective strategies has clinical value. Oxidative stress and its subsequent complications are major mechanisms involved in xenobiotics-induced hepatotoxicity. Boldine is one of the most potent antioxidant molecules widely investigated for its protective properties in different experimental models. In the current study, the hepatoprotective properties of boldine and its potential mechanisms of hepatoprotection have been investigated. Methods: Rats received thioacetamide (TAA; 200 mg/kg, i.p) as a model of acute liver injury. Boldine (5, 10, 1nd 20 mg/kg; 24 hours intervals; oral) was administered as the hepatoprotective agent. Results: Liver injury was evident in TAA-treated animals (48 hours after TAA exposure) as a severe increase in serum level of liver injury biomarkers and histopathological alterations. Moreover, markers of oxidative stress were increased in liver tissue of TAA-treated rats. Assessment of mitochondrial indices of functionality revealed a significant decrease in mitochondrial dehydrogenases activity, the collapse of mitochondrial membrane potential, mitochondrial swelling and depletion of ATP content. It was found that boldine supplementation mitigated liver tissue markers of oxidative stress and improved mitochondrial indices of functionality in TAA-treated animals. Conclusion: The hepatoprotective properties of boldine might primarily rely on antioxidant and mitochondria protecting effects of this alkaloid.

Neuroinflammatory response to experimental stroke is inhibited by boldine

Inflammation plays a pivotal role in the development of ischemic brain damage. Astrocyte activation promotes the production of several proinflammatory mediators, such as TNF-α and iNOS. Eventually, neuronal death occurs, leading to the development of motor and memory deficits in patients. Boldine is the main alkaloid in the leaves and bark of the Peumus boldus Molina, and has anti-inflammatory and antioxidant properties. The aim of this work was to investigate the neuroprotective effect of boldine on neuroinflammation and memory deficits induced by permanent middle cerebral artery occlusion (pMCAO) in mice. Thirty minutes before pMCAO and during the next 5 days, animals received vehicle (0.025 µmol/l HCl) or boldine (8, 16 and 25 mg/kg, intraperitoneally). The extension of the infarct area, neurological scores, and myeloperoxidase activity were evaluated 24 h after pMCAO. Locomotor activity, working, and aversive memory were evaluated 72 h after pMCAO, object recognition memory was tested 96 h after pMCAO, and spatial memory was tested 120 h after pMCAO. Cresyl violet, Fluoro-Jade C staining, and immunohistochemical for GFAP, TNF-α, and iNOS were also carried out. The treatment with boldine significantly decreased the infarct area, improved the neurological scores, and increased cell viability. The vertical exploratory activity and aversive, spatial, object recognition, and working memory deficits induced by pMCAO were prevented by boldine. Moreover, myeloperoxidase activity and GFAP, TNF-α, and iNOS immunoreactivity were decreased significantly by boldine. Although various mechanisms such as its antioxidant activity should be considered, these results suggest that the neuroprotective effect of boldine might be related in part to its anti-inflammatory properties.

Dose-dependent cytotoxic effects of boldine in HepG-2 cells-telomerase inhibition and apoptosis induction

Plant metabolites are valuable sources of novel therapeutic compounds. In an anti-telomerase screening study of plant secondary metabolites, the aporphine alkaloid boldine (1,10-dimethoxy-2,9-dihydroxyaporphine) exhibited a dose and time dependent cytotoxicity against hepatocarcinoma HepG-2 cells. Here we focus on the modes and mechanisms of the growth-limiting effects of this compound. Telomerase activity and expression level of some related genes were estimated by real-time PCR. Modes of cell death also were examined by microscopic inspection, staining methods and by evaluating the expression level of some critically relevant genes. The growth inhibition was correlated with down-regulation of the catalytic subunit of telomerase (hTERT) gene (p < 0.01) and the corresponding reduction of telomerase activity in sub-cytotoxic concentrations of boldine (p < 0.002). However, various modes of cell death were stimulated, depending on the concentration of boldine. Very low concentrations of boldine over a few passages resulted in an accumulation of senescent cells so that HepG-2 cells lost their immortality. Moreover, boldine induced apoptosis concomitantly with increasing the expression of bax/bcl2 (p < 0.02) and p21 (p < 0.01) genes. Boldine might thus be an interesting candidate as a potential natural compound that suppresses telomerase activity in non-toxic concentrations.

Boldine and Related Aporphines: From Antioxidant to Antiproliferative Properties

Plant and folk medicine represent nowadays a source of either new therapeutic substances or substrates for drug synthesis. One such promising group for possible further exploitation is the family of aporphine alkaloids containing boldine and related compounds. In this mini-review we focus on boldine and its newly described effects, which predominantly arise from its antioxidant properties. Moreover, we try to compare its antiproliferative properties with other better known members of the aporphine group.

Modeling natural anti-inflammatory compounds by molecular topology

One of the main pharmacological problems today in the treatment of chronic inflammation diseases consists of the fact that anti-inflammatory drugs usually exhibit side effects. The natural products offer a great hope in the identification of bioactive lead compounds and their development into drugs for treating inflammatory diseases. Computer-aided drug design has proved to be a very useful tool for discovering new drugs and, specifically, Molecular Topology has become a good technique for such a goal. A topological-mathematical model, obtained by linear discriminant analysis, has been developed for the search of new anti-inflammatory natural compounds. An external validation obtained with the remaining compounds (those not used in building up the model), has been carried out. Finally, a virtual screening on natural products was performed and 74 compounds showed actual anti-inflammatory activity. From them, 54 had been previously described as anti-inflammatory in the literature. This can be seen as a plus in the model validation and as a reinforcement of the role of Molecular Topology as an efficient tool for the discovery of new anti-inflammatory natural compounds.

The aporphine alkaloid boldine induces adiponectin expression and regulation in 3T3-L1 cells

Adiponectin is an adipokine secreted by differentiated adipocytes. Clinical studies suggest a negative correlation between oxidative stress and adiponectin levels in patients with metabolic syndrome or cardiovascular disease. Natural compounds that can prevent oxidative stress mediated inhibition of adiponectin may be potentially therapeutic. Boldine, an aporphine alkaloid abundant in the medicinal plant Peumus boldus, is a powerful antioxidant. The current study demonstrates the effects of boldine on the expression of adiponectin and its regulators, CCAAT/enhancer binding protein-alpha (C/EBPalpha) and peroxisome proliferator-activated receptor (PPAR)-gamma, in 3T3-L1 cells. Differentiated 3T3-L1 adipocytes were exposed to either hydrogen peroxide (H(2)O(2)) (100 microM) or tumor necrosis factor-alpha (TNFalpha) (1 ng/mL) for 24 hours in the presence or absence of increasing concentrations of boldine (5-100 microM). Quantitative polymerase chain reaction showed that both the oxidants decreased the mRNA levels of adiponectin, PPARgamma, and C/EBPalpha to half of the control levels. Boldine, at all concentrations, counteracted the inhibitory effect of H(2)O(2) or TNFalpha and increased the expression of adiponectin and its regulators. The effect of boldine on adiponectin expression was biphasic, with the lower concentrations (5-25 microM) having a larger inductive effect compared to higher concentrations (50-100 microM). Boldine treatment alone in the absence of H(2)O(2) or TNFalpha was also able to induce adiponectin at the inductive phase of adipogenesis. Peroxisome proliferator response element-luciferase promoter transactivity analysis showed that boldine interacts with the PPAR response element and could potentially modulate PPAR responsive genes. Our results indicate that boldine is able to modulate the expression of adiponectin and its regulators in 3T3-L1 cells and has the potential to be beneficial in obesity-related cardiovascular disease.