Enhanced effect of the hallucinogen DOI in L-DOPA receptor Gpr143-deficient mice.

In this study, an integrated hurdle modelling workflow combining ATR-FTIR and machine learning was developed for the simultaneous quantification of levodopa (LD), carbidopa (CD), and benserazide (BZ) in anti-Parkinson's medication. A calibration set of 103 synthetic pellets was prepared with wide concentration ranges for the three active pharmaceutical ingredients (APIs), 0–80% w/w for LD, 0–40% w/w for BZ; and 0–8% w/w for CD, and analysed by ATR-FTIR and HPLC-DAD reference method. Nine pellets prepared from three commercial medications were used for external evaluation and calibration transfer. A two-stage hurdle model was employed for each analyte, including a classifier for presence/absence and a regressor fitted only on positive samples to predict concentration. The modelling workflow comprised four modules, in which the Savitzky–Golay first derivative, combined with the standard normal variate (SNV) on mean spectra, was the most suitable preprocessing method. Logistic regression for LD and BZ, and supported vector classification (SVC) for CD were selected as optimal classifiers, while random forest (RF) regression in the half spectral region (675–1800 cm−1) was the best overall regressor for all APIs. When applied to commercial samples, the model classifiers correctly identified the presence/absence of all APIs, and calibration transfer using only six additional commercial pellets significantly reduced bias for all three APIs and achieved a high AGREE green score (0.75) at the same time. These results show that ATR-FTIR, combined with a carefully designed hurdle model workflow, can provide a rapid and green screening tool for multi-API in anti-Parkinson's medications.

Pyrroloquinoline quinone (PQQ) is a water-soluble quinone derived from bacteria, known for its antioxidant properties and ability to enhance mitochondrial function. These characteristics make PQQ a promising bioactive molecule for anti-aging applications in dermatology. This study aimed to improve PQQ production by developing a UV-induced mutant strain and optimizing the culture medium, and to evaluate the potential of the produced PQQ as a cosmetic ingredient. The mutant strain, NPP-230, was compared with the wild-type strain, Hyphomicrobium denitrificans ATCC51888, for growth and PQQ production after 96 h of cultivation. The effect of optimized medium on both strains was also assessed. The PQQ obtained from the cultures was evaluated for skin-related biological activities, including collagen synthesis, melanin inhibition, tyrosinase inhibition, and L-3,4-dihydroxyphenylalanine (L-DOPA) oxidation inhibition. The mutant strain cultured in optimized medium showed higher biomass and PQQ production than the wild type. Furthermore, PQQ promoted collagen synthesis and inhibited melanin production and tyrosinase activity in a concentration-dependent manner. These findings indicate that PQQ production in H. denitrificans can be enhanced under optimized conditions, and that the produced PQQ exhibits anti-aging and skin-whitening properties.

Parkinson’s disease (PD) is characterized by the progressive depletion of dopamine (DA), a key neurotransmitter involved in the regulation of voluntary movement. Levodopa (L-DA), the gold-standard treatment for PD, effectively restores DA levels; however, its clinical efficacy is limited by a short half-life and a narrow therapeutic window, often resulting in motor and non-motor fluctuations. Therefore, accurate monitoring of L-DA levels in patients with PD is essential to optimize therapeutic outcomes. Herein, a fully integrated microfluidic platform for the detection of L-DA in sweat based on a plasma-activated carbon sensor is reported. The core of this technology is a single-step oxygen plasma treatment deliberately designed to serve a dual purpose: enabling robust sealing of the PDMS microfluidic layers while simultaneously activating the carbon electrode surface. This strategy yields a substantial enhancement in electrocatalytic performance without the need for complex nanomaterials or biorecognition elements, thereby simplifying fabrication and improving scalability. The resulting plasma-activated sensor exhibits a 22-fold signal amplification compared to untreated electrodes and achieves a limit of detection (LoD) of 4 μM in synthetic human sweat, underscoring its potential for wearable and point-of-care applications.

A selective and eco-friendly spectrophotometric approach was developed for the quantitative determination of entacapone (ENT) in the presence of its co-formulated drugs carbidopa (CAR) and levodopa (LEV) which exhibit severe spectral overlap. Three simple spectrophotometric methods; direct zero-order, factorized dual wavelength, and ratio subtraction coupled with constant multiplication techniques were optimized to enable effective resolution of the ENT spectrum without the need for prior separation or complex mathematical treatment. The proposed approaches demonstrated high selectivity toward ENT in laboratory-prepared mixtures and pharmaceutical dosage forms confirming the successful minimization of interference from CAR and LEV. The proposed methods showed excellent linearity over the concentration range of 1.5-14.0µg/mL with a correlation coefficient (r) of 0.9998. The limit of detection (LOD) and limit of quantification (LOQ) were 0.226µg/mL and 0.685µg/mL, respectively confirming high sensitivity. The methods were validated according to international guidelines and proved suitable for routine quality control analysis. In addition, the environmental impact of the developed methods was comprehensively evaluated using multiple greenness assessment tools such as Analytical Eco-Scale, NEMI, GAPI, and AGREE tools confirming their excellent sustainability profile. In conclusion, the developed spectrophotometric methods provide a simple, accurate, precise, and green alternative for determining entacapone in the presence of spectral similar compounds without the need for separation or sophisticated instrumentation.

Dopamine agonist withdrawal syndrome (DAWS) comprises a wide range of neuropsychiatric and autonomic symptoms that occur in temporal relation with the reduction or withdrawal of dopamine agonists (DAs) in a dose-dependent manner. This syndrome was described as an important complication in Parkinson's disease (PD) and restless legs syndrome (RLS) treatment. Dopamine agonist withdrawal syndrome affects even up to 24% of PD patients treated with DAs in whom the medication was tapered. Predominant symptoms include the following: anxiety, depression, irritability, panic attacks, sleep disorders, and suicidal thoughts along with autonomic problems such as fatigue, orthostatic hypotension, nausea, and vomiting. Dopamine agonist withdrawal syndrome remains a therapeutic challenge as it is refractory to levodopa (LD), other PD therapies, anti-depressants, and anti-psychotics. The therapy-resistant syndrome may be a pitfall for patients trapped between intolerable side effects of DAs (impulse control disorder [ICD]) and withdrawal symptoms. Recognition of DAWS as a threatening condition is important for choosing the best treatment option for the patient. Due to the increasingly widespread use and efficacy of advanced therapies such as deep brain stimulation, enteral and subcutaneous LD, as well as apomorphine infusions, the risk of DAWS development should be considered. Dose reduction or discontinuation of DAs should be carefully planned and managed individually (personalized, based on main symptoms). Further research should focus on the natural evolution, risk factors, and duration of DAWS. Development of new generation DAs, such as tavapadon, which may reduce the side effects of dopaminergic therapy, may set new standards for treatment. Guidelines on the taper velocity of DAs, risk factors, and management therapies are to be established to improve detection and treatment of DAWS.

Mucuna pruriens (L.) DC. (Fabaceae), commonly known as velvet bean, is an annual tropical legume widely distributed in India, Africa, and the Americas. It has a long history of use in traditional medicine for managing various health conditions. It is renowned for its anti-inflammatory, antimicrobial, aphrodisiac, and anti-Parkinson effects. The entire plant is considered health-promoting, particularly the seeds. They have been used for their neuroprotective, fertility-enhancing, and antioxidant effects. This review aims to compile all available information regarding the chemical composition of all parts of this medicinal plant. For this purpose, the complete databases of Google Scholar, Scopus, PubMed, and Web of Science available to date were utilized. All studies reported the presence of a diverse range of secondary metabolites, including phenolic compounds, such as phenolic acids, flavonoids, and tannins, as well as saponins and alkaloids. Most studies concentrated on the chemical characterization of the seeds, whereas the leaves, roots, and pods have received comparatively limited scientific attention. The seeds of M. pruriens are renowned for their high concentration of L-3,4-dihydroxyphenylalanine (L-DOPA), a metabolic precursor of dopamine. A large proportion of these studies originated from countries where M. pruriens naturally occurs. Few studies have been conducted on the chemical composition of velvet bean outside these regions. Despite the existing information on the chemical composition of M. pruriens. (seeds, leaves, and roots), further research beyond its natural habitat is required to gain a broader understanding of its chemical profile and pharmacological effects.

Comparative neurochemical and neuroprotective effects of lauric acid, ribose-cysteine, and levodopa in an α-synuclein Drosophila model of Parkinson's disease.

Voltammetric analysis of entacapone, levodopa, and carbidopa in tablets: A chemometric approach.

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra, a region within the ventral midbrain known to accumulate iron. While L-3,4-dihydroxyphenylalanine (L-DOPA) remains the gold standard treatment for PD, its impact on brain iron homeostasis, particularly under varying systemic iron conditions, remains poorly understood. In this study, we investigate how dietary iron status and anti-PD treatments influence brain iron accumulation and regulation in the ventral midbrain, with a focus on sex-specific differences. Male and female Long-Evans rats were placed on iron-adequate (IA), iron-deficient (ID), or iron-repletion (IR) diets from postnatal day (PND) 21 for eight weeks. In the final three weeks, animals received daily subcutaneous injections of L-DOPA, selegiline, or vehicle. Our findings revealed that L-DOPA treatment in IR males significantly increased brain iron levels in the ventral midbrain, whereas females showed no such effect. This sex-specific accumulation was accompanied by the upregulation of iron uptake protein transferrin receptor 1 (TfR1), increased ferroportin (FPN1), and reduced expression of the iron storage protein ferritin heavy chain (FTH1), indicating disrupted iron homeostasis. Furthermore, L-DOPA-treated males on the IR diet exhibited elevated glial fibrillary acidic protein (GFAP) and lipocalin-2 (LCN2), suggesting enhanced oxidative stress and astrocyte activation. Consistent with this, antioxidant enzymes catalase (CAT) and superoxide dismutase 2 (SOD2) were significantly decreased in L-DOPA-treated males on the IR diet, highlighting increased vulnerability to oxidative damage. In contrast, selegiline did not significantly alter brain iron levels or iron-regulatory protein expression, regardless of diet or sex. These findings demonstrate that systemic iron repletion after deficiency sensitizes the male brain to L-DOPA-induced iron accumulation, potentially increasing susceptibility to neurodegeneration. This study highlights the importance of considering that both dietary iron status and biological sex may impact PD treatment strategies.

Parkinson's disease (PD) imposes a heavy burden on the aging population. Current oral levodopa (LD) treatment faces dual challenges: poor brain bioavailability due to systemic barriers and motor complications from fluctuating drug levels. While intranasal delivery offers direct brain access, bypassing the blood-brain barrier, existing formulations still struggle to maintain stable drug concentrations needed to prevent motor fluctuations. Moreover, focusing solely on dopamine supplements overlooks the underlying oxidative stress that drives disease progression. Herein, we report an intranasal conformal patch composed of silk fibroin nanofibers that achieves stable drug delivery through moisture-responsive adhesion, sustained release, and enhanced LD stability. The patch further incorporates a dual-drug strategy combining LD supplementation with reactive oxygen species scavenging to delay neurodegeneration. In vivo results demonstrate that this daily patch effectively delivers nanomedicines to the brain, reverses pathological status, and restores normal behavioral patterns in PD models. This wearable drug reservoir enables sustained therapeutic effects while addressing oxidative damage, representing a significant advancement in PD treatment.

Levodopa-induced dyskinesia (LID) is a side effect of Parkinson's disease (PD) treated with L-3,4-dihydroxyphenylalanine (L-DOPA). Nardosinone is the major active component of the dried root and rhizome of Nardostachys jatamansi DC, which is effective for treating PD. The purpose of this study was to explore the effects of nardosinone on LID and the underlying mechanism involving the microbiota-gut-brain axis. A PD rat model was established with rotenone. Behavioral and immunohistochemical staining experiments were used to investigate the synergistic effect of nardosinone on L-DOPA in PD rats. Then, the LID model was established by using high-dose L-DOPA and benserazide, and the effect of nardosinone on LID was evaluated by abnormal involuntary movement scale (AIMS) and western blotting (WB). Hematoxylin‒eosin staining (on intestinal tissues), 16S rRNA (on gut microbiota), and ELISA (on serum and brain tissues) were used to investigate the mechanism of action of nardosinone in the treatment of LID. Behavioral tests revealed that nardosinone increased the ability of L-DOPA to treat forelimb dysfunction and autonomic activity disorders in PD, and immunohistochemical staining experiments revealed that nardosinone exerted a protective effect on dopaminergic neurons as PD-induced neuronal damage was reversed, which complements the therapeutic effect of L-DOPA. AIMS and WB analyses indicated that high-dose L-DOPA induced LID, but nardosinone exerted an effect in reducing LID by not only improving rats' abnormal involuntary movements but also downregulating ∆FosB expression. Analysis of 16S rRNA revealed that nardosinone can regulate the intestinal flora in rats with LID. In addition, nardosinone can protect the colonic structure and reduce intestinal permeability. Moreover, nardosinone can reduce the expression of inflammatory factors in the colon and striatum of rats with LID and improve intestinal inflammation and neuroinflammation. Nardosinone can improve the effect of L-DOPA on ameliorating motor function in PD rats while alleviating LID, and its mechanism for improving LID may be related to regulating intestinal flora balance, repairing intestinal barrier integrity, and inhibiting inflammatory responses via the microbiota-gut-brain axis.

The locus coeruleus is the primary site of norepinephrine (NE) synthesis in the brain. Its dysfunction has been implicated in the pathogenesis of Alzheimer's disease. Vascular risk factors, thyroid dysfunction, and vitamin deficiencies have also been associated with an increased risk of dementia. This study aimed to evaluate the relationship between the catecholaminergic system-by measuring cerebrospinal fluid (CSF) levels of L-3,4-dihydroxyphenylalanine (L-DOPA), dopamine (DA), and NE-and vascular risk factors, thyroid dysfunction, and vitamin deficiencies. We conducted a cross-sectional observational study in which CSF levels of L-DOPA, DA and NE were measured in 117 participants. Data on Blood Pressure (BP), heart rate, glycaemic and lipid profiles, smoking history, thyroid function and vitamin B12 and folic acid levels were collected for each participant. We found significant correlations between NE and CSF glucose levels (r = 0.308, p = 0.003) in participants without diabetes mellitus, between L-DOPA and orthostatic variation of diastolic BP (r = -0.288, p = 0.014) and high-density lipoprotein (r = 0.404, p = 0.001) and between NE and triglycerides (r = 0.271, p = 0.030) and folic acid (r = 0.298, p = 0.009). This is the first study to demonstrate correlations between CSF NE levels and CSF glucose, probably due to the effect of NE on astrocytes, and between CSF NE levels and folic acid, possibly related to its role in catecholamine synthesis. CSF L-DOPA levels were correlated with cardiovascular risk factors such as the orthostatic regulation of diastolic BP. These findings may contribute to a better understanding of the pathophysiology of neurodegenerative diseases.

Mucuna pruriens (MP), or velvet bean, has been used as an alternative medicine in India for over 4500 years, predominantly due to the natural abundance of the non-protein amino acid L-3,4-dihydroxyphenylalanine (L-DOPA). L-DOPA (levodopa) is used to treat Parkinson's disease (PD), a condition in which the progressive loss of dopaminergic neurons causes dopamine deficiency and impaired motor function. Although L-DOPA increases dopamine synthesis in the remaining dopaminergic neurones in the PD brain, the rate of disease progression appears to remain unchanged. Some studies have demonstrated improved outcomes in patients taking MP preparations compared to those undergoing traditional L-DOPA therapy. There is evidence that the canonical amino acids and L-DOPA precursors L-phenylalanine (L-Phe) and L-tyrosine (L-Tyr) can increase dopamine synthesis and also protect against the mistaken incorporation of L-DOPA into proteins during protein synthesis. The current study developed and validated a sensitive HILIC-TQMS method for the quantification of L-DOPA and related amino acids in MP preparations. Analysis revealed that L-DOPA levels were 66.2% to 82.7% of the values reported by manufacturers. Tyr and Phe were present in both free and protein bound forms in all 5 preparations analysed, potentially offering protection against the mistaken incorporation of L-DOPA into proteins and promoting increased dopamine synthesis. These findings suggest that the additional reported benefits of MP supplements for PD treatment might, in part, be attributable to the presence of these amino acids, further supporting the need to investigate the administration of L-DOPA and its cognate amino acid in symptomatic treatment of PD.

Are glutathionylated aldehyde reductases the missing piece of the "catecholaldehyde hypothesis" in Parkinson's disease? A medical hypothesis concerning the detoxification of 4-hydroxynonenal (HNE) and 3,4-dihydroxyphenylacetaldehyde (DOPAL).

L-DOPA (LD) is the gold-standard treatment of motor symptoms in Parkinson’s disease (PD), conventionally used to prove the predictive value of PD animal models. This study aimed to investigate the predictive validity of an adaptation of the conventional reserpine model of PD: the repeated low-dose reserpine administration in rodents, which promotes progressive motor impairment in catalepsy, vacuous chewing behavior tests, and neurochemical deficits. Specifically, we investigated the effects of acute and chronic treatment with LD on motor alterations induced in mice by this modified protocol. Swiss mice were treated with 20 reserpine injections (0.1 mg/kg, s.c., every other day). Acute LD (25, 50, 100, and 200 mg/kg) administration was performed at the end of reserpine protocol to assess immediate motor recovery. Additionally, concomitant chronic LD (50 and 100 mg/kg) treatment was conducted to investigate potential attenuation of motor impairment and dopamine depletion quantified by HPLC. Repeated reserpine protocol induced motor deficits in catalepsy and vacuous chewing evaluations and striatal dopamine depletion. Acute LD administration significantly improved catalepsy in higher doses, while chronic LD treatment attenuated motor impairments and reduced dopamine depletion in the striatum. These findings support the predictive validity of the reserpine rodent model for studying parkinsonism. Together with the ability to promote chronic and progressive parkinsonian alterations, the reversion of these deficits by LD reinforces the potential of the repeated low-dose reserpine protocol for studies of potential therapies and the pathophysiology underlying neurodegenerative processes in PD.

IntroductionAlthough numerous neurons expressing tyrosine hydroxylase (TH), the first enzyme of catecholamine synthesis, were discovered in the supraoptic nucleus (SON) of hypothalamus in animals almost forty years ago, mainly under osmotic stress, the functional significance of TH there remains unclear. Therefore, the aim of this study was to test our hypothesis that TH in these neurons has enzymatic activity capable of converting L-tyrosine to L-3,4-dihydroxyphenylalanine (L-DOPA).MethodsIn this study, 8–10 week old male C57BL/6 mice (n = 77), intact (n = 20), and intraperitoneally injected with 0.9% NaCl (n = 29) or 8.5% NaCl (n = 28) were used. To assess gene expression and synthesis of TH, as well as the hypothetical synthesis of L-DOPA in neurons of the SON, the following methods were used: immunohistochemistry for vasopressin (VP), laser microdissection of individual VP-immunopositive neurons, polymerase chain reaction (PCR), Western blotting, and high-performance liquid chromatography with electrochemical detection of dopamine and L-DOPA.ResultsThe genes for TH, a key-protein required for L-DOPA synthesis in dopaminergic neurons, is expressed in neurons of the SON in both intact, control and salt-loaded mice. However, some data suggest that TH in neurons of the SON does not have enzymatic activity. Indeed, in intact mice and in mice with varying degrees of osmotic stress: (i) the SON did not show expression of the gene encoding guanosine triphosphate cyclohydrolase 1, the first enzyme in synthesis of tetrahydrobiopterin, a cofactor responsible for regulating the enzymatic activity of TH, and (ii) the amount of L-DOPA remained at the same very low level, regardless of the TH content in SON neurons. We suggest that TH in neurons of the SON does not have enzymatic activity, since, as we have shown, the TH molecule in the SON, unlike TH in dopaminergic neurons of the substantia nigra, could possibly not have an N-terminus motif responsible for regulation of its enzymatic activity.ConclusionDespite the expression of the TH gene in neurons of the SON, the protein it encodes does not have enzymatic activity, most probably due to the absence of the N-terminus, characteristic of TH in dopaminergic neurons.

Covering: primarily from 2021 to the end of 2025L-Tyrosine (L-Tyr) and its derivatives are high-value aromatic compounds with broad applications in food, pharmaceutical, and chemical industries. The traditional methods for producing these natural products through natural extraction and chemical synthesis are often limited by sustainability, efficiency, and environmental concerns. Advances in synthetic biology have enabled the construction of microbial cell factories for green and scalable production, with Escherichia coli and yeast emerging as the preferred chassis organisms due to their well-characterized genetics and extensive toolkits. This review systematically summarizes the engineering strategies applied for the biosynthesis of L-Tyr and its derivatives in these hosts at the enzymatic, metabolic, and cellular levels. Focusing on tyrosol, p-coumaric acid, and L-3,4-dihydroxyphenylalanine (L-DOPA) as the key nodes, it highlights the cutting-edge advances primarily within the last five years. Finally, the review critically assesses the persistent challenges and future opportunities, offering a strategic roadmap to accelerate the biomanufacturing of L-Tyr-derived natural products.

Neurodegeneration due to exposure to oxidants has severe effects on neuronal loss when exposed for a prolonged period, causing them to loss neurons. The degeneration of neurons in the substantia nigra decreases the production of dopamine in the brain, which can further act as an initiator for the early onset of Parkinson’s disease (PD). Carbidopa-levodopa is the standard drug used in the treatment of PD, but it comes with a drawback of drug side effects in the long run. Marine compounds exhibit potential for drug discovery and are rising to overcome these shortcomings in the existing drugs. We assessed and optimised the half maximum inhibitory concentration (IC50) of stress-induced models for hydrogen peroxide and acrylamide, as well as the standard drug levodopa (LD) and squid ink (SI) extract using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and evaluated their cytotoxic effects. Reactive oxygen species (ROS), cell apoptosis, colony formation, DNA fragmentation, cell migration and gene expression studies were evaluated through 2',7'-dichlorofluorescein diacetate (DCFH-DA), flow cytometry, proliferation assay, 4′,6-diamidino-2-phenylindole (DAPI), scratch test assay and real-time quantitative polymerase chain reaction (RT-qPCR) respectively. The cell viability assay exhibited IC50 values of 77±0.14, 79±0.17 and 82±0.21 μg/ml concentrations for control, hydrogen peroxide and acrylamide groups respectively. The ROS assay showed significant antioxidant activity in the stress-induced groups compared to the LD-treated group. Likewise, DAPI staining showed lesser DNA fragmentation in stress-induced cells in SI-treated groups. Similarly, the flow cytometry exhibited increased cell viability in SI-treated stress-induced cells. The gene expression studies in SI-treated revealed the downregulation of pro-apoptotic genes. SI-extract exhibited potential antioxidant properties. Further, we recommend performing extensive screening of these marine compounds to obtain potential therapeutics to overcome neurodegenerative diseases caused due to oxidative stress.

To explore the inhibitory effects of Nardostachys Jatamansi DC. volatile oil (NJVO) on psychological factors substance P (SP)/cortisol (CORT)-induced hyperpigmentation. The model of psychologically-induced hyperpigmentation of B16F10 cells was created using SP (10 nmol/L) + CORT (10 µmol/L) for 72 h. The levels of melanin content, tyrosinase (TYR) activity using NaOH lysis and L-dihydroxyphenylalanine (L-DOPA) oxidation methods were assessed, respectively. The effect of NJVO on SP/CORT-induced normal human skin tissue pigmentation was detected by Masson staining. Protein expressions of tyrosinase-related protein 1 (TRP-1), tyrosinase-relative protein 2 (DCT), and microphthalmia-associated transcription factor were determined using Western blot. The melanosome number, maturation, and melanosomal structure changes were detected through transmission electron microscopy and immunofluorescence experiments. In vivo, zebrafish pigment content was evaluated in SP/CORT-induced zebrafish hyperpigmentation model. NJVO significantly reduced the melanin content (P<0.01) and inhibited tyrosinase activity (P<0.01), the pigmentation of the normal skin tissue in the NJVO group was significantly lower than that in the SP/CORT group (P<0.05). And NJVO considerably downregulated expressions of melanogenesis-related proteins (TYR, TRP-1, DCT) in cells (P<0.01). In addition, the number of melanosomes was decreased and the dentrites formation of B16F10 cells was inhibited after NJVO treatment (P<0.01). In vivo, NJVO significantly reduced the pigment content in the zebrafish body (P<0.01). NJVO effectively reversed SP/CORT-induced hyperpigmentation by suppressing the activity and expression of TYR and TRPs and inhibiting melanosome maturation in mouse B16F10 melanoma cells.