Identification and occurrence of beta-carboline alkaloids in raisins and inhibition of monoamine oxidase (MAO)

Evaluation of therapeutic role of harmaline: in vitro cytotoxicity targeting nucleic acids

Use of small molecules as valuable drugs against diseases is still an indefinable purpose due to the lack of in-detail knowledge regarding proper bio-target identification, specificity aspects, mode-mechanism of binding and proper in vitro study. Harmaline, an important beta-carboline alkaloid, shows effective anti-proliferative action against different types of human cancers and is also found to be a nucleic acid targeting natural molecule. This review sought to address the different signal pathways of apoptosis by harmaline in different cancer cell lines and simultaneously to characterize the structure activity aspects of the alkaloid with different motifs of nucleic acid to show its preference, biological efficacy and genotoxicity. The results open up new insights for the design and development of small molecule-based nucleic acid therapeutic agents.

The β-Carboline Harmine Has a Protective Immunomodulatory Role in Nonhealing Cutaneous Leishmaniasis

Cutaneous leishmaniasis affects 1 million people worldwide annually. Although conventional treatments primarily target the parasite, there is growing interest in host immune modulation. In this study, we investigated the impact of synthetic β-carboline harmine (ACB1801), previously shown to be immunoregulatory in cancer, on the pathology caused by a drug-resistant Leishmania major strain causing persistent cutaneous lesions. Exposure to ACB1801 in vitro had a modest impact on parasite burden within host macrophages. Moreover, it significantly increased major histocompatibility complex II and costimulatory molecule expression on infected dendritic cells, suggesting an enhanced immune response. In vivo, ACB1801 monotherapy led to a substantial reduction in lesion development and parasite burden in infected C57BL/6 mice, comparable with efficacy of amphotericin B. Transcriptomics analysis further supported ACB1801 immunomodulatory effects, revealing an enrichment of TNF-α, IFN-γ, and major histocompatibility complex II antigen presentation signatures in the draining lymph nodes of treated mice. Flow cytometry analysis confirmed an increased frequency (1.5×) of protective CD4+IFN-γ+TNF-α+ T cells and a decreased frequency (2×) in suppressive IL-10+FoxP3- T cells at the site of infection and in draining lymph nodes. In addition, ACB1801 downregulated the aryl hydrocarbon receptor signaling, known to enhance immunosuppressive cytokines. Thus, these results suggest a potential use for ACB1801 alone or in combination therapy for cutaneous leishmaniasis.

Formation, Identification, and Occurrence of the Furan-Containing β-Carboline Flazin Derived from l-Tryptophan and Carbohydrates

β-Carbolines (βCs) are bioactive indole alkaloids found in foods and in vivo. This work describes the identification, formation, and occurrence in foods of the βC with a furan moiety flazin (1-[5-(hydroxymethyl)furan-2-yl]-9H-pyrido[3,4-b]indole-3-carboxylic acid). Flazin was formed by the reaction of l-tryptophan with 3-deoxyglucosone but not with 5-hydroxymethylfurfural. Its formation was favored in acidic conditions and heating (70-110 °C). The proposed mechanism of formation occurs through the formation of intermediates 3,4-dihydro-β-carboline-3-carboxylic acid (imines), followed by the oxidation to C═O in the carbohydrate chain and aromatization to βC ring with subsequent dehydration steps and cyclization to afford the furan moiety. Flazin is generated in the reactions of tryptophan with carbohydrates. Its formation from fructose was higher than from glucose, whereas sucrose gave flazin under acidic conditions and heating owing to hydrolysis. Flazin was identified in foods by HPLC-MS, and its content was determined by HPLC-fluorescence. It occurred in numerous processed foods, such as tomato products, including crushed tomato puree, fried tomato, ketchup, tomato juices, and jams, but also in soy sauce, beer, balsamic vinegar, fruit juices, dried fruits, fried onions, and honey. Their concentrations ranged from not detected to 22.3 μg/mL, with the highest mean levels found in tomato concentrate (13.9 μg/g) and soy sauce (9.4 μg/mL). Flazin was formed during the heating process, as shown in fresh tomato juice and crushed tomatoes. These results indicate that flazin is widely present in foods and is daily uptaken in the diet.

Heterocyclic aromatic amines in meat: Formation mechanisms, toxicological implications, occurrence, risk evaluation, and analytical methods

Heterocyclic aromatic amines (HAAs) are detrimental substances can develop during the high-temperature cooking of protein-rich foods, such as meat. They are potent mutagens and carcinogens linked to an increased risk of various cancers. HAAs have complex structures with nitrogen-containing aromatic rings and are formed through chemical reactions between amino acids, creatin(in)e, and sugars during cooking. The formation of HAAs is influenced by various factors, such as food type, cooking temperature, time, cooking method, and technique. HAAs exert their toxicity through mechanisms like DNA adduct formation, oxidative stress, and inflammation. The research on HAAs is important for public health and food safety, leading to risk assessment and management strategies. It has also led to innovative approaches for reducing HAAs formation during cooking and minimizing related health risks. Understanding HAAs' chemistry and formation is crucial for developing effective ways to prevent their occurrence and protect human health. The current review presents an overview about HAAs, their formation pathways, and the factors influencing their formation. Additionally, it reviews their adverse health effects, occurrence, and the analytical methods used for measuring them.

Discovery of indole analogues from Periplaneta americana extract and their activities on cell proliferation and recovery of ulcerative colitis in mice

Background: As an important medicinal insect, Periplaneta americana (PA) has been applied for the treatment of wounds, burns, and ulcers with fewer side effects and a reduced recurrence rate, which provides great potential for developing new drugs based on its active constituents. Materials and methods: The main chromatographic peaks determined by high performance liquid chromatography (HPLC) in the PA concentrated ethanol-extract liquid (PACEL) were separated, purified, and identified by semi-preparative LC, mass spectrum, and 1H NMR spectroscopic analysis. The biological activities of the identified compounds were investigated by methylthiazolyldiphenyl-tetrazolium bromide (MTT) method based on in vitro human skin fibroblasts (HSF) and in vivo experiments based on dextran sulfate sodium (DSS)-induced ulcerative colitis (UC) mouse model. Furthermore, RT-qPCR of six genes related to inflammation or intestinal epithelial cell proliferation was employed to investigate the molecular mechanism of the indole analogues recovering UC in mice. Results: Five indole analogues were purified and identified from PACEL, including tryptophan (Trp), tryptamine (pa01), 1,2,3,4-tetrahydrogen-β-carboline-3-carboxylic acid (pa02), (1S, 3S)-1-methyl-1,2,3,4-tetrahydrogen-β-carboline-3-carboxylic acid (pa03), and (1R, 3S)-1-methyl-1,2,3,4-tetrahydrogen-β-carboline-3-carboxylic acid (pa04), among which the pa02 and pa04 were reported in PA for the first time. In vitro and in vivo experiments showed that PACEL, Trp, and pa02 had promoting HSF proliferation activity and intragastric administration of them could alleviate symptoms of weight loss and colon length shortening in the UC mice. Although recovery activity of the compound pa01 on the colon length was not as obvious as other compounds, it showed anti-inflammatory activity in histological analysis. In addition, The RT-qPCR results indicated that the three indole analogues could alleviate DSS-induced intestinal inflammation in mice by inhibiting pro-inflammatory cytokines (MMP7, IL1α) and down-regulating BMP8B expression. Conclusion: This study reported the isolation, purification, structure identification, and biological activity of the active indole analogues in PACEL. It was found for the first time that the PA extract contained many indole analogues and Trp, which exhibited good proliferation activity on HSF fibroblasts as well as anti-UC activity in mice. These indole analogues probably are important components related to the pharmacological activity in PA.

Identification, Formation, and Occurrence of Perlolyrine: A β-Carboline Alkaloid with a Furan Moiety in Foods

β-Carbolines are naturally occurring bioactive alkaloids found in foods and in vivo. This research reports the identification, characterization, mechanism of formation, and occurrence of perlolyrine (1-(5-(hydroxymethyl)furan-2-yl)-9H-pyrido[3,4-b]indole), a β-carboline with a furan moiety. Perlolyrine did not arise from l-tryptophan and hydroxymethylfurfural but from the reaction of l-tryptophan with 3-deoxyglucosone, an intermediate of carbohydrate degradation. The mechanism of formation occurs through 3,4-dihydro-β-carboline-3-carboxylic acid intermediates (imines), followed by the oxidation of C1'-OH to ketoimine and oxidative decarboxylation at C-3, along with dehydration and cyclization to afford the β-carboline with a furan moiety. The formation of perlolyrine was favored in acidic conditions and temperatures in the range of 70-110 °C. Perlolyrine occurred in the reactions of tryptophan with carbohydrates. The formation rate from fructose was much higher than from glucose. Sucrose also gave perlolyrine under acidic conditions and heating. Perlolyrine was identified in many foods by HPLC-MS and analyzed by HPLC-fluorescence. It occurred in many processed foods such as tomato products including tomato puree, fried tomato, ketchups, tomato juices, and jams but also in soy sauce, beer, balsamic vinegar, fruit juices, dried fruits, fried onion, and honey. The concentrations ranged from an undetected amount to 3.5 μg/g with the highest average levels found in tomato concentrate (1.9 μg/g) and soy sauce (1.5 μg/mL). The results show that perlolyrine formed during the heating process of foods. It is concluded that perlolyrine is widely present in foods and it is daily ingested in the diet.

β-Carboline Alkaloids in Soy Sauce and Inhibition of Monoamine Oxidase (MAO)

Monoamine oxidase (MAO) oxidizes neurotransmitters and xenobiotic amines, including vasopressor and neurotoxic amines such as the MPTP neurotoxin. Its inhibitors are useful as antidepressants and neuroprotectants. This work shows that diluted soy sauce (1/3) and soy sauce extracts inhibited human MAO-A and -B isozymes in vitro, which were measured with a chromatographic assay to avoid interferences, and it suggests the presence of MAO inhibitors. Chromatographic and spectrometric studies showed the occurrence of the β-carboline alkaloids harman and norharman in soy sauce extracts inhibiting MAO-A. Harman was isolated from soy sauce, and it was a potent and competitive inhibitor of MAO-A (0.4 µM, 44 % inhibition). The concentrations of harman and norharman were determined in commercial soy sauces, reaching 243 and 52 μg/L, respectively. Subsequently, the alkaloids 1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (THCA) and 1-methyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (MTCA) were identified and analyzed in soy sauces reaching concentrations of 69 and 448 mg/L, respectively. The results show that MTCA was a precursor of harman under oxidative and heating conditions, and soy sauces increased the amount of harman under those conditions. This work shows that soy sauce contains bioactive β-carbolines and constitutes a dietary source of MAO-A and -B inhibitors.

Screening of Monoamine Oxidase B Inhibitors from Fragaria nubicola by Ligand Fishing and Their Neuroprotective Effects

Fragaria nubicola, known as Tibetan strawberry, is an edible plant possessing various health-promoting effects. However, its functional compositions were rarely studied. In this work, monoamine oxidase B (MAO-B) inhibitors in this plant were rapidly screened using the enzyme-functionalized magnetic nanoparticles coupled with UPLC-QTOF-MS. Two inhibitors, quercetin-3-O-β-d-glucuronide-6″-methyl ester (1) and kaempferol-3-O-β-d-glucuronide-6″-methyl ester (2), were identified from this plant with the IC₅₀ values of 19.44 ± 1.17 and 22.63 ± 1.78 μM, respectively. Enzyme kinetic analysis and molecular docking were carried out to investigate the mechanism of inhibition. Contents of both compounds as well as those of total phenolics and flavonoids were quantified to be 24.76 ± 1.26, 35.59 ± 1.17, 837.67 ± 10.62, and 593.46 ± 10.37 μg/g, respectively. In addition, both compounds exhibited significant neuroprotective effects on 6-hydroxydopamine-induced PC12 cells. This is the first report on the neuroprotective components of F. nubicola, suggesting its potential for developing neuroprotective functional food.

Assay of MAO Inhibition by Chromatographic Techniques (HPLC/HPLC-MS)

Monoamine oxidase (MAO) enzymes (MAO A and B) catalyze the oxidative deamination of biogenic amines, neurotransmitters, and xenobiotic amines and contribute to the regulation of the content of these active substances in mammalian organisms. The oxidation of biogenic amines by MAO produces hydrogen peroxide (H₂O₂) and aldehydes that represent risk factors for oxidative injury. The inhibitors of MAO are useful as antidepressants and neuroprotective agents. Usually, the assays of MAO determine amine deamination products or measure the H₂O₂ released by using direct spectrophotometric or fluorimetric methods. Direct methods are more prone to interferences and can afford inaccurate results. Those limitations can be avoided by using chromatographic techniques. This work describes a chromatographic method to assay MAO A and MAO B activity by using kynuramine as a nonselective substrate and the subsequent analysis of 4-hydroxyquinoline by RP-HPLC-DAD-fluorescence and mass spectrometry (MS). Alternatively, the assay uses the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxin as a substrate of MAO that is oxidized (bioactivated) to neurotoxic pyridinium cations which are analyzed by HPLC. These methods are applied to assess the inhibition of MAO by bioactive β-carboline alkaloids occurring in foods, plants, and biological systems.

Application of High-Performance Liquid Chromatography with Fluorescence Detection for Non-Polar Heterocyclic Aromatic Amines and Acridine Derivatives Determination in Pork Loin Roasted in a Roasting Bag

Heat treatment of meat can lead to the formation of carcinogenic organic compounds. The influence of dried fruits on the formation of non-polar heterocyclic aromatic amines (carbolines) and nitrogen derivatives of polycyclic aromatic hydrocarbons (azaarenes) in roasted pork loin was elucidated. Two hundred grams of fruit per 1 kg of meat were used as stuffing. Carbolines, derivatives of pyridoimidazole and pyridoindole, and azaarenes (benzoacridines and dibenzoacridines) were determined by means of high-performance liquid chromatography with fluorescence detection. The total concentration of six δ-, γ- and α-carbolines in roasted pork loin was 1.3 ng/g. This content decreased by 64%, 58%, and 54% in pork loin stuffed with prunes, apricots, and cranberries, respectively. Concentrations of β-carbolines (harmane and norharmane) increased under the influence of added fruits. The norharmane content increased the most, from 2.2 ng/g in the control sample to 12.3 ng/g in meat prepared with cranberries. The harmane content increased from 1.0 ng/g to 3.6 ng/g in meat with prunes. The total concentration of azaarenes (two benzoacridines and dibenzo[a,c]acridine), which was close to 0.1 ng/g, decreased in dishes with prunes and apricots by 54% and 12%, respectively. Azaarenes were not found in samples of meat stuffed with cranberries.

Formation, Characterization, and Occurrence of β-Carboline Alkaloids Derived from α-Dicarbonyl Compounds and l-Tryptophan

β-Carbolines (βCs) are naturally occurring bioactive alkaloids, whereas α-dicarbonyl compounds are reactive substances generated in foods and in vivo. In this work, l-tryptophan reacted with α-dicarbonyl compounds affording new β-carbolines. Glyoxal afforded 1-hydroxymethyl-β-carboline (HME-βC) and its 3-carboxylic acid, and methylglyoxal afforded 1-(1-hydroxyethyl)-β-carboline (HET-βC) and its 3-carboxylic acid. 3-Deoxyglucosone afforded 1-(1,3,4,5-tetrahydroxypent-1-yl)-β-carboline isomers (1a/b), 1-(1,4,5-trihydroxypent-1-yl)-β-carboline (2), and 1-(1,5-dihydroxypent-3-en-1-yl)-β-carboline (3). The formation of these βCs increased under acidic conditions and with increasing temperature. A mechanism is proposed explaining the conversion of a carbonyl into a hydroxy group based on tautomerism and cyclization to the dihydro-βC-3-COOH intermediates, which were isolated and gave the βCs. These α-dicarbonyl-derived βCs occurred in model reactions of l-tryptophan with fructose or glucose incubated under heating and can be considered as advanced glycation end products (AGEs). They were also present in foods and formed during heating processes. HET-βC appeared in processed foods, reaching up to 309 ng/g, with the highest amount found in dried tomato, fried onion, toasted bread, and Manuka honey. HME-βC was only detected in some foods with lower amounts than HET-βC. HET-βC appeared in foods as a racemic mixture of enantiomers suggesting the same mechanism of formation as the synthetized product. α-Dicarbonyl-derived βCs (HET-βC, HME-βC, and 1a/b-3) occur in foods and food processing and, therefore, they are ingested during diet.

Bioactive β-Carbolines Harman and Norharman in Sesame Seed Oils in China

The β-carbolines in our diet, mainly including harman and norharman, are a group of biologically active, naturally occurring plant-derived alkaloids. Fragrant sesame seed oil is one of the most popular flavor edible oils in China. Considering that sesame seeds are roasted at 200–240 °C during the processing of flavor sesame seed oils, it is meaningful to investigate the levels of β-carboline compounds in various sesame seed oils. In this work, the levels of β-carbolines (harman and norharman) in different types of sesame seed oils in China (e.g., pressed fragrant sesame oil, ground fragrant sesame oil) have been determined systematically. The results showed that the levels of total β-carbolines in pressed fragrant sesame oils (700.5~2423.2 μg/kg) were higher than that in ground fragrant sesame oils (660.4~1171.7 μg/kg). Roasting sesame seeds at high temperatures (200–240 °C) led to higher levels of β-carbolines (660~2400 μg/kg) in fragrant sesame seed oils. In addition, the loss of tryptophan might be attributed to the formation of β-carbolines in sesame seeds during the roasting process. In general, fragrant sesame seed oils (pressed fragrant sesame oils, ground fragrant sesame oils) contain higher levels of β-carbolines due to the formation of harman and norharman during the roasting sesame seed process.

The effect of onion and garlic on non-polar heterocyclic aromatic amines (α-, β-, γ- and δ-carbolines) formation in pan-fried meat and gravy

Thermal treatment of protein-rich food can lead to the formation of biologically active heterocyclic aromatic amines (HAAs). One of the methods to learn how to reduce the content as well as the influence of these compounds on heath is the study of factors inhibiting their synthesis. In the current investigation, the effect of onion and garlic on the formation of six possibly carcinogenic non-polar HAAs (α-, γ- and δ-carbolines) and two co-mutagenic β-carbolines (harmane and norharmane) was evaluated by comparing their contents in meat and gravy samples obtained from pan-fried pork dishes prepared in the presence and absence of these vegetables. Carbolines were isolated from food samples by solid phase extraction. The quantitative analysis was performed by high-performance liquid chromatography with fluorescence detection. The concentrations of individual compounds in dishes prepared without added vegetables ranged from 0.02 ng g^-1 (3-amino-1,4-dimethyl-5 H-pyrido(4,3-b)indole; Trp-P-1) to 10.1 ng g^-1 of meat (2-amino-9 H-pyrido[2,3-b]indole; AαC). Onion (30 g/100 g of meat) and garlic (15 g/100 g of meat) lowered the total content (in meat and gravy) of the α-, δ- and γ-carbolines in the range from 52% to 87%. In contrast, onion caused an increase in the norharmane concentration both in meat and gravy. The percentage of carbolines in the gravies (assuming that their total content in meat and gravy is 100%) was higher in dishes prepared with onion and garlic than in dishes without these seasonings.

Xenobiotic transport and metabolism in the human brain

Organisms have metabolic pathways responsible for eliminating endogenous and exogenous toxicants. Generally, we associate the liver par excellence as the organ in charge of detoxifying the body; however, this process occurs in all tissues, including the brain. Due to the presence of the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB), the Central Nervous System (CNS) is considered a partially isolated organ, but similar to other organs, the CNS possess xenobiotic transporters and metabolic pathways associated with the elimination of xenobiotic agents. In this review, we describe the different systems related to the detoxification of xenobiotics in the CNS, providing examples in which their association with neurodegenerative processes is suspected. The CNS detoxifying systems include carrier-mediated, active efflux and receptor-mediated transport, and detoxifying systems that include phase I and phase II enzymes, as well as those enzymes in charge of neutralizing compounds such as electrophilic agents, reactive oxygen species (ROS), and free radicals, which are products of the bioactivation of xenobiotics. Moreover, we discuss the differential expression of these systems in different regions of the CNS, showing the different detoxifying needs and the composition of each region in terms of the cell type, neurotransmitter content, and the accumulation of xenobiotics and/or reactive compounds.

Recent Update on the Anti-infective Potential of β-carboline Analogs

β-Carboline, a naturally occurring indole alkaloid, holds a momentous spot in the field of medicinal chemistry due to its myriad of pharmacological actions like anticancer, antiviral, antibacterial, antifungal, antileishmanial, antimalarial, neuropharmacological, anti-inflammatory and antithrombotic among others. β-Carbolines exhibit their pharmacological activity via diverse mechanisms. This review provides a recent update (2015-2020) on the anti-infective potential of natural and synthetic β-carboline analogs focusing on its antibacterial, antifungal, antiviral, antimalarial, antileishmanial and antitrypanosomal properties. In cases where enough details are available, a note on its mechanism of action is also added.

On-line screening of indoleamine 2,3-dioxygenase 1 inhibitors by partial filling capillary electrophoresis combined with rapid polarity switching

Indoleamine 2,3-dioxygenase 1 (IDO1) has been shown to play an important role in the immune escape process of tumors, and therefore is considered as a promising target for tumor immunotherapy. In this study, off-line and on-line capillary electrophoresis methods were developed for IDO1 inhibitors screening from natural product extracts. The optimized separation conditions of CE were achieved with 32 mM sodium tetraborate (pH 9.22) as background electrolyte, using a separation voltage of 21 kV. The off-line CE method was verified by the determination of enzymatic kinetic parameters and inhibitory mechanisms of two known inhibitors. A partial filling on-line CE method combined with rapid polarity switching was used for rapid screening of IDO1 inhibitors. The whole reaction and separation process was completed within 5 min. The on-line CE screening results showed that six of 18 natural products had inhibitory effect on IDO1, namely Carthamus tinctorius, Schisandra chinensis, Raisin, Coffee, Hawthorn and Radix angelicae sinensis. The results of on-line CE experiments were consistent with the off-line results, which proved the practicability and effectiveness of the method for inhibitors screening.

Occurrence, Formation from d-Fructose and 3-Deoxyglucosone, and Activity of the Carbohydrate-Derived β-Carbolines in Foods

β-Carbolines are naturally occurring bioactive alkaloids. In this work, carbohydrate-derived β-carbolines (βCs), 1-(1,3,4,5-tetrahydroxypent-1-yl)-β-carboline isomers (1a/b), 1-(1,4,5-trihydroxypent-1-yl)-β-carboline (2), 1-(1,5-dihydroxypent-3-en-1-yl)-β-carboline (3), and 1-(1,2,3,4,5-pentahydroxypent-1-yl)-β-carboline (4) were identified and analyzed in commercial foods. The concentrations of βCs 1-4 in foods ranged from undetectable to 11.4 μg/g levels, suggesting their intake in the diet. Processed foods contained higher amounts than fresh or unprocessed foods, and the highest content was found in processed tomato and fruit products, sauces, and baked foods. βCs 1-3 were formed in foods during heating, and 1a/b were the main compounds. The formation of carbohydrate-derived βCs was studied in model reactions of tryptophan and carbohydrates. They formed in reactions of tryptophan with glucose under acidic conditions at temperatures higher than 80 °C. The formation of 1a/b was favored, but 2-3 increased at high temperatures. Noticeably, the βCs 1-3 formed in the reactions of tryptophan with fructose or sucrose, and the formation from fructose was much higher than from glucose. Thus, fructose was the main carbohydrate involved in the formation of 1-3, whereas sucrose gave these βCs after acid hydrolysis. It is shown for the first time that the mechanism of formation of βCs 1-3 occurs from the sugar intermediate 3-deoxyglucosone that reacts with tryptophan affording these carbohydrate-derived βCs. A mechanism of reaction to give βCs 1-3 is proposed that relies on the tautomerism (keto-enediol or enamine-imine) of intermediates involved in the reaction. Carbohydrate βCs 1-4 were assessed as inhibitors of monoamine oxidase (MAO), as antioxidants, and for their interaction with DNA. They were not good inhibitors of MAO-A or -B, were poor antioxidants, and did not appreciably interact with DNA.

Effects of Natural Monoamine Oxidase Inhibitors on Anxiety-Like Behavior in Zebrafish

Monoamine oxidases (MAO) are a valuable class of mitochondrial enzymes with a critical role in neuromodulation. In this study, we investigated the effect of natural MAO inhibitors on novel environment-induced anxiety by using the zebrafish novel tank test (NTT). Because zebrafish spend more time at the bottom of the tank when they are anxious, anxiolytic compounds increase the time zebrafish spend at the top of the tank and vice versa. Using this paradigm, we found that harmane, norharmane, and 1,2,3,4-tetrahydroisoquinoline (TIQ) induce anxiolytic-like effects in zebrafish, causing them to spend more time at the top of the test tank and less time at the bottom. 2,3,6-trimethyl-1,4-naphtoquinone (TMN) induced an interesting mix of both anxiolytic- and anxiogenic-like effects during the first and second halves of the test, respectively. TIQ was unique in having no observable effect on general movement. Similarly, a reference MAO inhibitor clorgyline—but not pargyline—increased the time spent at the top in a concentration-dependent manner. We also demonstrated that the brain bioavailability of these compounds are high based on the ex vivo bioavailability assay and in silico prediction models, which support the notion that the observed effects on anxiety-like behavior in zebrafish were most likely due to the direct effect of these compounds in the brain. This study is the first investigation to demonstrate the anxiolytic-like effects of MAO inhibitors on novel environment-induced anxiety in zebrafish.

Recent Advances in the Synthesis of β-Carboline Alkaloids

β-Carboline alkaloids are a remarkable family of natural and synthetic indole-containing heterocyclic compounds and they are widely distributed in nature. Recently, these alkaloids have been in the focus of interest, thanks to their diverse biological activities. Their pharmacological activity makes them desirable as sedative, anxiolytic, hypnotic, anticonvulsant, antitumor, antiviral, antiparasitic or antimicrobial drug candidates. The growing potential inherent in them encourages many researchers to address the challenges of the synthesis of natural products containing complex β-carboline frameworks. In this review, we describe the recent developments in the synthesis of β-carboline alkaloids and closely related derivatives through selected examples from the last 5 years. The focus is on the key steps with improved procedures and synthetic approaches. Furthermore the pharmacological potential of the alkaloids is also highlighted.

Structure-activity insights of harmine targeting DNA, ROS inducing cytotoxicity with PARP mediated apoptosis against cervical cancer, anti-biofilm formation and in vivo therapeutic study

Harmine exhibits pH dependent structural equilibrium and possesses numerous biological and pharmacological activities. Mode and mechanism of DNA binding and its cytotoxicity were studied by multiple spectroscopic, calorimetric, molecular docking and in vitro apoptotic as well as in vivo biochemical and histological studies. It exists as cationic (structure I) and decationic form (structure II) in the pH range 3.0-7.8 and 8.5-12.4, respectively, with a pK_a of 8.0. Structure I at pH 6.8 binds strongly to DNA with a cooperative mode of binding of K_iω 1.03 × 10⁶ M^-1and stoichiometry of 5.0 nucleotide phosphates. Structure I stabilized DNA by 10 °C, showed85%quenching of fluorescence intensity, perturbation in circular dichroism, partial intercalation and enthalpy driven exothermic binding. While, structure II at pH 8.5 has very weak interaction with CT DNA. Cytotoxic potencies of structure I was tested on four different cancer cell lines along with normal embryonic cell. It showed maximum cytotoxicity with GI₅₀of 20 µM, against HeLa causing several apoptotic induction abilities. Harmine exhibited G2M arrest with ROS induced effective role in PARP mediated apoptosis as well as anti-inflammatory action on HeLa cells. Harmine further presented MIC and antibiofilm activity against Staphylococcus aureus in presence of <160 and 30 µg/ml, respectively. Mice with post harmine treatment (30 mg/kg b.w., I.P.) showed maximum recovery from damaged to near normal architecture of cervical epithelial cells. This study may be of prospective use in a framework to design novel beta carboline compounds for improved therapeutic applications in future against cervical cancer. HighlightsHarmine exists in structure I and structure II forms in the pH 6.8 and 8.5with a pK_a of 8.0.Structure I at pH 6.8 binds strongly to DNA compared to structure II.Structure I showed maximum cytotoxicity with GI₅₀ of 20 µM against HeLa.ROS mediated cytotoxicitywithG2M arrest with PARP mediated apoptosis was studied.Harmine (30µg/ml) exhibited antibiofilm activity against Staphylococcus aureus.Post harmine dose (30 mg/kg b.w., I.P.) in mice showed recovery of cervical epithelial cells.Communicated by Ramaswamy H. Sarma.

A review on β-carboline alkaloids and their distribution in foodstuffs: A class of potential functional components or not?

Pharmacologically active β-carboline alkaloids (βCs) such as harman, norharman and some others are naturally present in plants and occur in many foodstuffs. They have a lot of pharmacological properties, including antitumor, antioxidant, anti-inflammatory and antimicrobial effects, and possess the potential for treating Alzheimer's disease, Parkinson's disease, depression and other central nervous system diseases. Dietary intake is proven to be an important source of βCs. Therefore, it is important to know the amounts of βCs that can be gotten from daily diets. This review summarizes the pharmacological activities, toxicology and formation of βCs, and gives collective information on contents of βCs in different foodstuffs.

Recent evolution on synthesis strategies and anti-leishmanial activity of β-carboline derivatives - An update

Leishmaniasis is the most widespread pathogenic disease in several countries. Currently, no effective vaccines are available, and the control of Leishmaniasis primarily relies on decade-old chemotherapy. The treatment for the Leishmaniasis is not up to the mark. Current therapy for Leishmaniasis is ancient and requires hospitalization for the administration. These medications are also highly toxic and resistant. β-carboline, a natural indole containing alkaloid, holds a vital position in the field of medicinal chemistry with a diversified pharmacological action. The current review focuses mainly on the anti-leishmanial effects of β-carboline analogs and their synthetic strategies, structural activity relationship studies (SAR). The past ten years alterations unveiled by β-carboline analogs present in phytoconstituents and various derivatives of synthesized analogs with the mechanism of action were briefly shortlisted and illustrated.

Synthetic carboline compounds targeting protein: biophysical and biological perspective

Pictet-Spengler cyclization method has been adopted for the synthesis of three carboline derived compounds: two compounds with tetrahydro gama- and beta-having CF₃ group and amino alkyl chain at delta and alpha position, respectively, and another with guanidine alkyl chain at alpha-position. Structure-activity relationship of the analogues with human serum albumin was studied by fluorescence and Fourier-transform infrared spectroscopy  followed by molecular docking. The data showed maximum affinity of human serum albumin with comp7 (S0-820) followed by comp3 (S0-1040) and least with comp1 (S0-728). The compounds were tested for cytotoxic potencies. Comp3, showed maximum cytotoxicity with GI₅₀ 6.2 µM, against HCT-116, followed by comp7, and poor cytotoxicity with comp1. Comp3 and 7 induced oxidative stress mediated autophagy led programmed cell death in HCT-116. Furthermore, the compounds effectively inhibit DNA topoisomerase I activity and showed anti-inflammatory actions. In vivo studies regarding therapeutic protective action of Comp3, as a representative carboline analogue, against colon toxicant, 1,2-dimethylhydrazine dihydrochloride (DMH), showed the efficacy of the compound against organ toxicity. The existing studies on biological evaluation showed that these synthetic compounds may have a major role as anticancer agents having myriad of proven therapeutic applications. Communicated by Ramaswamy H. Sarma.

Validation of analytical methods for heterocyclic amines in seven food matrices using high-performance liquid chromatography-tandem mass spectrometry

Heterocyclic amines (HCAs) are potent mutagens generated by the high temperatures of the cooking process. The purpose of this study was to develop and validate analytical methods for HCAs determination using high-performance liquid chromatography-tandem mass spectrometry in seven food matrices: corn oil, milk, 20% ethanol, pork, flat fish, sea mustard (Undaria pinnatifida), and radish. Six isotopically labelled internal standards were used for quantitation, and Chem Elut and Oasis hydrphilic-liphophilic balance cartridges were applied for sample preparation to remove interferences. Calibration curves showed good linearity (R² > 0.99) in all matrices. The ranges of the method detection limit and method quantitation limit were 0.009-2.35 ng g^-1 and 0.025-7.13 ng g^-1, respectively. The recoveries ranged from 67.5% to 119.6%. The coefficients of variation ranged from 0.3% to 15.1% for intra-day and ranged from 0.8% to 19.1% for inter-day. The methods were applied to 24 total diet study samples for HCAs quantitation. These results indicate that the established methods are reliable for determining HCAs in various foods.

Discovery and Validation of Banana Intake Biomarkers Using Untargeted Metabolomics in Human Intervention and Cross-sectional Studies

BACKGROUND

Banana is one of the most widely consumed fruits in the world. However, information regarding its health effects is scarce. Biomarkers of banana intake would allow a more accurate assessment of its consumption in nutrition studies.

OBJECTIVES

Using an untargeted metabolomics approach, we aimed to identify the banana-derived metabolites present in urine after consumption, including new candidate biomarkers of banana intake.

METHODS

A randomized controlled study with a crossover design was performed on 12 healthy subjects (6 men, 6 women, mean ± SD age: 30.0 ± 4.9 y; mean ± SD BMI: 22.5 ± 2.3 kg/m2). Subjects underwent 2 dietary interventions: 1) 250 mL control drink (Fresubin 2 kcal fiber, neutral flavor; Fresenius Kabi), and 2) 240 g banana + 150 mL control drink. Twenty-four-hour urine samples were collected and analyzed with ultra-performance liquid chromatography coupled to a quadrupole time-of-flight MS and 2-dimensional GC-MS. The discovered biomarkers were confirmed in a cross-sectional study [KarMeN (Karlsruhe Metabolomics and Nutrition study)] in which 78 subjects (mean BMI: 22.8; mean age: 47 y) were selected reflecting high intake (126-378 g/d), low intake (47.3-94.5 g/d), and nonconsumption of banana. The confirmed biomarkers were examined singly or in combinations, for established criteria of validation for biomarkers of food intake.

RESULTS

We identified 33 potentially bioactive banana metabolites, of which 5 metabolites, methoxyeugenol glucuronide (MEUG-GLUC), dopamine sulfate (DOP-S), salsolinol sulfate, xanthurenic acid, and 6-hydroxy-1-methyl-1,2,3,4-tetrahydro-β-carboline sulfate, were confirmed as candidate intake biomarkers. We demonstrated that the combination of MEUG-GLUC and DOP-S performed best in predicting banana intake in high (AUCtest = 0.92) and low (AUCtest = 0.87) consumers. The new biomarkers met key criteria establishing their current applicability in nutrition and health research for assessing the occurrence of banana intake.

CONCLUSIONS

Our metabolomics study in healthy men and women revealed new putative bioactive metabolites of banana and a combined biomarker of intake. These findings will help to better decipher the health effects of banana in future focused studies. This study was registered at clinicaltrials.gov as NCT03581955 and with the Ethical Committee for the Protection of Human Subjects Sud-Est 6 as CPP AU 1251, IDRCB 2016-A0013-48; the KarMeN study was registered with the German Clinical Trials Register (DRKS00004890). Details about the study can be obtained from https://www.drks.de.

Pre-clinical investigations of β-carboline alkaloids as antidepressant agents: A systematic review

Depressive disorders remain a current public health problem whose prevalence has increased in the past decades. In the constant search for new therapeutic alternatives, β-carboline alkaloids have been identified as good candidates for new antidepressant drugs. In this systematic review, we summarized all pre-clinical investigations involving the use of natural or semisynthetic β-carboline in depression models. A literature search was conducted in August 2018, using PubMed, Scopus and Science Direct databases. All reports were carefully analyzed, and data extraction was conducted through standardized forms. Methodological quality assessment of in vivo studies was also performed. The entire systematic review was performed according to PRISMA statement. From a total of 373 articles, 26 met all inclusion criteria. In vitro and in vivo studies have evaluated a wide variety of β-carbolines through enzymatic and binding assays, and acute or chronic animal models. Most of the in vivo and in vitro studies is concentrated on two molecules: harman and harmine. They have been investigated in several animal models and some mechanisms of action have been proposed for their antidepressant activity. In general, β-carbolines modulate 5-HT and GABA systems, promote neurogenesis, induce neuroendocrine response and restore astrocytic function, being effective when administrated acutely or chronically in different animal models, including chronic mild stress protocols. In short, β-carbolines are multi-target antidepressant compounds and may be useful in the treatment of depressive disorders.

In vitro relationship between serum protein binding to beta-carboline alkaloids: a comparative cytotoxic, spectroscopic and calorimetric assays

The work highlighted interaction of harmalol, harmaline and harmine with human serum albumin by biophysical and biochemical assays. Presence of serum protein in the media negatively affects the cytotoxicity of the alkaloids. MTT assay indicates concentration-dependent growth inhibitory effect of the alkaloids on A375, MDA-MB-231, HeLa, A549, ACHN and HepG₂ cell, having maximum cytotoxicity with GI₅₀ value of 6.5 μM on ACHN by harmine in 1% of fetal bovine serum. Detail cytotoxic studies on ACHN cell by harmine, the most cytotoxic among the three, reveal nucleosomal fragmentation, formation of comet tail, generation of reactive oxygen species, decreased mitochondrial membrane potential, up regulation of p53, caspase 3 and significant increase in G₂/M population that made the cancer cells prone to apoptosis. Furthermore, the findings unequivocally pointed out that harmine binds strongly to the protein with a binding constant of 5.53 × 10⁴ M^-1 followed by harmaline and least with harmalol. Thermodynamic results revealed enthalpy dominated, entropy favored, 1:1 binding. Molecular docking and circular dichroism suggested changed conformation of protein by partial unfolding on complexation. Further supported by infrared analysis where protein secondary structure was altered with a major decrease of α-helix from 53.68% (free protein) to 8-11% and change in β-sheet from 25.31% (free protein) to 1-6% upon binding, inducing partial protein destabilization. Site markers demonstrated site I (subdomain IIA) binding of the alkaloids to the protein. The results serve as data for the future development of serum protein-based targeted drugs. AbbreviationsCD: circular dichroism; FBS: fetal bovine serumFRETForster resonance energy transferFTIRFourier transform infraredHSAhuman serum albumin; ROS: reactive oxygen speciesCommunicated by Ramaswamy H. Sarma.

Direct Biomimetic Synthesis of β-Carboline Alkaloids from Two Amino Acids

The increasing importance of enzyme mimics in organic synthesis inspired us to design a novel biomimetic synthesis of β-carboline alkaloids directly from tryptophan and a second amino acid. This novel one-pot protocol utilizes abundant and readily available starting materials and thus presents a green and user-friendly alternative to conventional methods that rely on stepwise synthesis. Driven by molecular iodine and TFA, decarboxylation, deamination, Pictet-Spengler reaction, and oxidation reactions proceeded sequentially, transforming biomass amino acids into value-added alkaloid motifs.

Monoamine Oxidase-A Inhibition and Associated Antioxidant Activity in Plant Extracts with Potential Antidepressant Actions

Monoamine oxidase (MAO) catalyzes the oxidative deamination of amines and neurotransmitters and is involved in mood disorders, depression, oxidative stress, and adverse pharmacological reactions. This work studies the inhibition of human MAO-A by Hypericum perforatum, Peganum harmala, and Lepidium meyenii, which are reported to improve and affect mood and mental conditions. Subsequently, the antioxidant activity associated with the inhibition of MAO is determined in plant extracts for the first time. H. perforatum inhibited human MAO-A, and extracts from flowers gave the highest inhibition (IC₅₀ of 63.6 μg/mL). Plant extracts were analyzed by HPLC-DAD-MS and contained pseudohypericin, hypericin, hyperforin, adhyperforin, hyperfirin, and flavonoids. Hyperforin did not inhibit human MAO-A and hypericin was a poor inhibitor of this isoenzyme. Quercetin and flavonoids significantly contributed to MAO-A inhibition. P. harmala seed extracts highly inhibited MAO-A (IC₅₀ of 49.9 μg/L), being a thousand times more potent than H. perforatum extracts owing to its content of β-carboline alkaloids (harmaline and harmine). L. meyenii root (maca) extracts did not inhibit MAO-A. These plants may exert protective actions related to antioxidant effects. Results in this work show that P. harmala and H. perforatum extracts exhibit antioxidant activity associated with the inhibition of MAO (i.e., lower production of H₂O₂).

Privileged scaffolds as MAO inhibitors: Retrospect and prospects

This review aims to be a comprehensive, authoritative, critical, and readable review of general interest to the medicinal chemistry community because it focuses on the pharmacological, chemical, structural and computational aspects of diverse chemical categories as monoamine oxidase inhibitors (MAOIs). Monoamine oxidases (MAOs), namely MAO-A and MAO-B represent an enormously valuable class of neuronal enzymes embodying neurobiological origin and functions, serving as potential therapeutic target in neuronal pharmacotherapy, and hence we have coined the term "Neurozymes" which is being introduced for the first time ever. Nowadays, therapeutic attention on MAOIs engrosses two imperative categories; MAO-A inhibitors, in certain mental disorders such as depression and anxiety, and MAO-B inhibitors, in neurodegenerative disorders like Alzheimer's disease (AD) and Parkinson's disease (PD). The use of MAOIs declined due to some potential side effects, food and drug interactions, and introduction of other classes of drugs. However, curiosity in MAOIs is reviving and the recent developments of new generation of highly selective and reversible MAOIs, have renewed the therapeutic prospective of these compounds. The initial section of the review emphasizes on the detailed classification, structural and binding characteristics, therapeutic potential, current status and future challenges of the privileged pharmacophores. However, the chemical prospective of privileged scaffolds such as; aliphatic and aromatic amines, amides, hydrazines, azoles, diazoles, tetrazoles, indoles, azines, diazines, xanthenes, tricyclics, benzopyrones, and more interestingly natural products, along with their conclusive SARs have been discussed in the later segment of review. The last segment of the article encompasses some patents granted in the field of MAOIs, in a simplistic way.

Cu-catalyzed mild and efficient oxidation of THβCs using air: application in practical total syntheses of perlolyrine and flazin

A mild, efficient and environmentally benign method for synthesis of aromatic β-carbolines via Cu(ii)-catalyzed oxidation of 1,2,3,4-tetrahydro-β-carbolines (THβCs) was developed, in which air (O₂) was used as the clean oxidant. This method has advantages such as environmentally friendliness, mildness, very good tolerance of functional groups, high yielding and easy experiment operation. In addition, this new methodology was successfully applied in the efficient and practical total syntheses of β-carboline alkaloids perlolyrine and flazin.

A mild, efficient and ecofriendly method for synthesis of β-carbolines via Cu-catalyzed aerobic oxidation of 1,2,3,4-tetrahydro-β-carbolines (THβCs) was developed. In addition, this method was successfully applied in the practical total syntheses of perlolyrine and flazin.

Monoamine oxidase inhibitory constituents of propolis: kinetics and mechanism of inhibition of recombinant human MAO-A and MAO-B

Propolis is the resinous material that bees gather from leaf buds, flowers and vegetables. Propolis extracts contain constituents with a broad spectra of pharmacological properties and are important ingredients of popular dietary supplements. Propolis extracts were evaluated in vitro for inhibition of recombinant human monoamine oxidase (MAO)-A and MAO-B. The dichloromethane extract of propolis showed potent inhibition of human MAO-A and MAO-B. Further fractionation identified the most active fractions as rich in flavonoids. Galangin and apigenin were identified as the principal MAO-inhibitory constituents. Inhibition of MAO-A by galangin was about 36 times more selective than MAO-B, while apigenin selectivity for MAO-A vs. MAO-B was about 1.7 fold. Apigenin inhibited MAO-B significantly more potently than galangin. Galangin and apigenin were further evaluated for kinetic characteristics and the mechanism for the enzymes’ inhibition. Binding of galangin and apigenin with MAO-A and -B was not time-dependent and was reversible, as suggested by enzyme-inhibitor binding and dissociation-dialysis assay. The inhibition kinetics studies suggested that galangin and apigenin inhibited MAO-A and -B by a competitive mechanism. Presence of prominent MAO inhibitory constituents in propolis products suggests their potential for eliciting pharmacological effects that might be useful in depression or other neurological disorders. The results may also have important implications in drug-dietary supplement interactions.

Monoamine oxidase inhibition by monoterpene indole alkaloids and fractions obtained from Psychotria suterella and Psychotria laciniata

Alkaloid fractions of Psychotria suterella (SAE) and Psychotria laciniata (LAE) as well as two monoterpene indole alkaloids (MIAs) isolated from these fractions were evaluated against monoamine oxidases (MAO-A and -B) obtained from rat brain mitochondria. SAE and LAE were analysed by HPLC-PDA and UHPLC/HR-TOF-MS leading to the identification of the compounds 1, 2, 3 and 4, whose identity was confirmed by NMR analyses. Furthermore, SAE and LAE were submitted to the enzymatic assays, showing a strong activity against MAO-A, characterized by IC(50) values of 1.37 ± 1.05 and 2.02 ± 1.08 μg/mL, respectively. Both extracts were also able to inhibit MAO-B, but in higher concentrations. In a next step, SAE and LAE were fractionated by RP-MPLC affording three and four major fractions, respectively. The RP-MPLC fractions were subsequently tested against MAO-A and -B. The RP-MPLC fractions SAE-F3 and LAE-F4 displayed a strong inhibition against MAO-A with IC(50) values of 0.57 ± 1.12 and 1.05 ± 1.15 μg/mL, respectively. The MIAs 1 and 2 also inhibited MAO-A (IC(50) of 50.04 ± 1.09 and 132.5 ± 1.33 μg/mL, respectively) and -B (IC(50) of 306.6 ± 1.40 and 162.8 ± 1.26 μg/mL, respectively), but in higher concentrations when compared with the fractions. This is the first work describing the effects of MIAs found in neotropical species of Psychotria on MAO activity. The results suggest that species belonging to this genus could consist of an interesting source in the search for new MAO inhibitors.

Mass spectrometric dereplication of nitrogen-containing constituents of black cohosh (Cimicifuga racemosa L.)

Black cohosh preparations are popular dietary supplements among women seeking alternative treatments for menopausal complaints. For decades, triterpene glycosides and phenolic acids have dominated the phytochemical and biomedical research on this plant. In this study, we provide evidence that black cohosh contains an unexpected and highly diverse group of secondary nitrogenous metabolites previously unknown to exist in this plant. Using a dereplication approach that combines accurate mass measurements, database searches and general knowledge of biosynthetic pathways of natural products, we identified or tentatively identified 73 nitrogen-containing metabolites, many of which are new natural products. The identified compounds belong to several structural groups including alkaloids, amides or esters of hydroxycinnamic acids and betains. Among the alkaloids, several classes such as guanidino alkaloids, isoquinolines and β-carbolines were identified. Fragmentation patterns for major compound classes are discussed, which provides a framework for the discovery of these compounds from other sources. Identification of alkaloids as a well-known group of bioactive natural products represents an important advance in better understanding of the pharmacological profile of black cohosh.

β-carboline derivatives and diphenols from soy sauce are in vitro quinone reductase (QR) inducers

A murine hepatoma (Hepa 1c1c7) cellular bioassay was used to guide the isolation of phase II enzyme inducers from fermented soy sauce, using quinone reductase (QR) as a biomarker. A crude ethyl acetate extract, accounting for 8.7% of nonsalt soluble solids of soy sauce, was found to double relative QR specific activity at 25 μg/mL (concentration required to double was defined as a "CD value"). Further silica gel column fractionation yielded 17 fractions, 16 of which exhibited CD values for QR induction of <100 μg/mL. The four most potent fractions were subfractionated by column and preparative thin layer chromatography, leading to the isolation and identification of two phenolic compounds (catechol and daidzein) and two β-carbolines (flazin and perlolyrin), with respective CD values of 8, 35, 42, and 2 μM. Western blots confirmed that the increases in QR activity corresponded to dose-dependent increases in cellular levels of NAD[P]H:quinone oxidoreductase 1 protein by these four QR inducers. To the authors' knowledge, this is the first report on the ability of β-carboline-derived alkaloids to induce phase II enzymes.