Simultaneous determination of tetrahydro-β-carbolines and β-carbolines

Bioactive β-Carbolines in Food: A Review

Harman and norharman, two neuroactive β-carbolines, are present in several plants and in thermally processed foods. They exhibited a wide spectrum of biological and pharmacological effects, including antioxidant, neuroprotective, and anti-inflammatory effects. In this article, we review the progress of recent research on the presence of these compounds in food, as well as their various biological and neuroactive properties. Our findings strongly suggest that some foods, especially coffee, can act as a rich source of β-carbolines, which may possibly be associated with a reduced risk for serious neurodegenerative diseases, such as Parkinson's and Alzheimer's.

Neurogenic Potential Assessment and Pharmacological Characterization of 6-Methoxy-1,2,3,4-tetrahydro-β-carboline (Pinoline) and Melatonin-Pinoline Hybrids

6-Methoxy-1,2,3,4-tetrahydro-β-carboline (pinoline) and N-acetyl-5-methoxytryptamine (melatonin) are both structurally related to 5-hydroxytryptamine (serotonin). Here we describe the design, synthesis, and characterization of a series of melatonin rigid analogues resulting from the hybridization of both pinoline and melatonin structures. The pharmacological evaluation of melatonin-pinoline hybrids comprises serotonergic and melatonergic receptors, metabolic enzymes (monoamine oxidases), antioxidant potential, the in vitro blood-brain barrier permeability, and neurogenic studies. Pinoline at trace concentrations and 2-acetyl-6-methoxy-1,2,3,4-tetrahydro-β-carboline (2) were able to stimulate early neurogenesis and neuronal maturation in an in vitro model of neural stem cells isolated from the adult rat subventricular zone. Such effects are presumably mediated via serotonergic and melatonergic stimulation, respectively.

Second derivative synchronous fluorimetric method for simultaneous determination of harman and norharman in coffee samples

The simultaneous determination of harman and norharman using second derivative synchronous fluorescence method has been developed based on their natural fluorescence. Due to their similar molecular structures, it is difficult to determine them simultaneously in the mixture using conventional fluorimetry. Overlapping of fluorescence spectra was resolved by using a constant second derivative synchronous fluorimetry. The derivative synchronous spectrum, maintaining a constant difference of Δλ=150 nm between emission and excitation for both the compounds, has been selected for the analysis. The range of application is between 0.182 and 18.2 μg/mL (correlation coefficient, R=0.9982) for harman and between 0.504 and 16.8 μg/mL (correlation coefficient, R=0.9962) for norharman. The recovery ranges of 98.5-101.1% for harman and 97.5-99.1% for norharman from their synthetic mixture was reported. The detection limits are 0.016 μg/mL and 0.038 μg/mL for harman and norharman, respectively. Similarly, the quantitation limit of the two compounds was found to be 0.049 and 0.109 μg/mL, respectively. The method was applied to the simultaneous determination of both compounds in coffee samples with satisfactory results.

Screening of non-polar heterocyclic amines in urine by microextraction in packed sorbent-fluorimetric detection and confirmation by capillary liquid chromatography

A rapid and simple procedure for the direct screening of urine samples is described. The method involves microextraction in a packed sorbent (MEPS) that is on-line coupled to a capillary liquid chromatograph with fluorimetric detection. The overall arrangement works as a screening/confirmatory system for monitoring non-polar heterocyclic aromatic amines (HAAs) in urine samples. This configuration allows the selective retention of HAAs from urine on a C(18) MEPS cartridge integrated in the needle of a micro-well plate autosampler. Retained HAAs were eluted with methanol/water (90:10, v/v) and directly injected into the fluorimetric detector. This screening method provides a yes/no binary response that may require confirmation. The samples for which the concentration of HAAs was close to or above the established threshold limit (30 ng mL(-1)) were subjected to capillary liquid chromatography (CLC) for confirmation purposes. A mobile phase of acetonitrile and triethylamine (25 mM) at pH 2.5, through a gradient of composition at a flow rate of 20 μL min(-1), resulted in good separations between the analytes in less than 11 min. This confirmation method allowed the determination of the analytes in the 10-100 ng mL(-1) range for harmane and norharmane and from 20 to 200 ng mL(-1) for 3-amino-1,4-dimethyl-5H-pyrido-[4,3-b] indole (Trp-P-1), 3-amino-1-methyl-5H-pyrido-[4,3-b] indole (Trp-P-2), 2-amino-9H-pyrido-[2,3-b] indole (AαC) and 2-amino-3-methyl-9H-pyrido-[2,3-b] indole (MeAαC), with relative standard deviation (RSD) values between 2.12% and 3.73%, and limits of detection between 1.6 and 5.6 ng mL(-1) for all the HAAs.

Determination of beta-carboline alkaloids in foods and beverages by high-performance liquid chromatography with electrochemical detection at a glassy carbon electrode modified with carbon nanotubes

Simple and sensitive methods for the separation and quantification of beta-carboline alkaloids in foods and beverages by HPLC with electrochemical detection at carbon nanotubes-modified glassy carbon electrodes (CNTs-GCE) are reported. Electrode modification with multi-wall CNTs produced an improved amperometric response to beta-carbolines, in spite of the working medium consisting of methanol:acetonitrile: 0.05 mol L(-1) Na(2)HPO(4) solution of pH 9.0 (20:20:60). On the contrary to that observed at a bare GCE, a good repeatability of the amperometric measurements carried out at +900 mV versus Ag/AgCl (R.S.D. of 3.2% for i(p), n=20) was achieved at the CNTs-GCE. Using an Ultrabase C(18) column and isocratic elution with the above mentioned mobile phase, a complete resolution of the chromatographic peaks for harmalol, harmaline, norharmane, harmane and harmine, was achieved. Calibration graphs over the 0.25-100 microM range with detection limits ranging between 4 and 19 ng mL(-1), were obtained. The HPLC-ED at CNTs-GCE method was applied to the analysis of beer, coffee and cheese samples, spiked with beta-carbolines at concentration levels corresponding to those may be found in the respective samples. The steps involved in sample treatment, such as extraction and clean-up, were optimized for each type of sample. Recoveries ranging between 92 and 102% for beer, 92 and 101% for coffee, and 88 and 100% for cheese, at sub-microg mL(-1) or g(-1) analytes concentration levels were achieved.

High-performance liquid chromatographic analysis of beta-carbolines in human scalp hair

A chromatographic method was studied for the quantitation of beta-carbolines in hair as potent biomarkers. Under optimal conditions, human scalp hair was enzymatically digested to release analytes effectively. The hair digests were treated with fluorescamine before serial extractions to inhibit the artifactual production of beta-carbolines during analysis and purify them selectively, followed by reversed-phase high-performance liquid chromatography with fluorometric detection. Hair samples were found to contain beta-carboline and 1-methyl-beta-carboline, which were identified by tandem mass spectrometry, but not their reduced form 1,2,3,4-tetrahydro-beta-carboline and 1-methyl-1,2,3,4-tetrahydro-beta-carboline. Both beta-carboline and 1-methyl-beta-carboline were quantified in the concentration range of 0.1-10.0 ng/ml. Their mean recoveries from hair digests were 70-72%, and the intra- and inter-assay RSD ranged between 6.0 and 10.3% in spiking experiments with standards (1.0 ng/ml). When quantitatively analyzing scalp hair collected from alcoholics, smokers, non-smokers and autistics, beta-carboline and 1-methyl-beta-carboline showed the concentrations of ng/mg levels or less which characterized different hair samples. The proposed method will be useful for detecting the in vivo concentration changes of beta-carbolines associated with alcohol abuse, smoking behavior and neuropsychiatric disorder.

Exposure to beta-carbolines norharman and harman

The aromatic beta-carbolines norharman and harman have been implicated in a number of human diseases including Parkinson's disease, tremor, addiction and cancer. It has been shown that these compounds are normal body constituents formed endogenously but external sources have been identified. Here, we summarise literature data on levels of norharman and harman in fried meat and fish, meat extracts, alcoholic drinks, and coffee brews. Other sources include edible and medicinal plants but tobacco smoke has been identified as a major source. Exposure levels from these different dietary sources are estimated to a maximum of 4 microg norharman per kg body weight (bw) per day and 1 microg harman per kg bw per day. Exposure via tobacco smoke depends on smoking habits and type of cigarettes but can be estimated to 1.1 microg/kg bw for norharman and 0.6 microg/kg bw for harman per package of cigarettes smoked. Studies on toxicokinetics indicate that inhalative exposure leads to a rapid increase in plasma levels and high bioavailability of norharman and harman. Oral bioavailability is lower but there are indications that sublingual absorption may increase dietary uptake of beta-carbolines. Endogenous formation can be estimated to be 50-100 ng/kg bw per day for norharman and about 20 ng/kg bw per day for harman but these rates may increase with high intake of precursors. Biomarker studies on plasma levels of beta-carbolines reported on elevated levels of norharman, harman or both in diseased patients, alcoholics and following tobacco smoking or consumption of beta-carboline-containing food. Cigarette smoking has been identified as major influence but dietary exposure may contribute to exposure.

Biphasic effects of acetaldehyde-biogenic amine condensation products on membrane fluidity

I have studied the effects of four acetaldehyde-biogenic amine condensation products on membrane fluidity of liposomes, consisting of 1-palmitoyl-2-oleoylphosphatidylcholine and cholesterol, by measuring fluorescence polarization using different probes. The condensation products were 1-methyl-1,2,3,4-tetrahydro-beta-carboline (MTBC), 6-hydroxy-1-methyl-1,2,3,4-tetrahydro-beta-carboline (6-OH-MTBC), 3-carboxy-1-methyl-1,2,3,4-tetrahydro-beta-carboline (3-C-MTBC) and 6,7-dihydroxy-1-methyl-1,2,3,4-tetrahydroisoquinoline (salsolinol). They changed the fluidity of the hydrophobic and hydrophilic regions of liposomal membranes at micromolar levels almost corresponding to their antibacterial and antiplatelet concentrations, but their membrane effects varied by structure, concentration and membrane lipid composition. MTBC and salsolinol showed biphasic effects on the inner layers of membranes to enhance the fluidity at 250-1000 microM and reduce the fluidity at 50-100 microM, whereas both of them fluidized the outer layers of the membranes. 3-C-MTBC concentration-dependently fluidized both layers of membranes. 6-OH-MTBC most weakly enhanced and reduced the fluidity of the outer and inner layers, respectively. The membrane effect of MTBC was the greatest of the four condensation products. MTBC (50-1000 nM) significantly reduced the fluidity by exclusively acting on the membrane core, but was less effective in fluidizing the membrane surface. However, the others were not active at low nanomolar levels. The membrane effects may be partly responsible for the antibacterial and antiplatelet actions of the acetaldehyde-biogenic amine condensation products, although they do not appear to be simple membrane fluidizers.

Tetrahydro-beta-carbolines, potential neuroactive alkaloids, in chocolate and cocoa

Tetrahydro-beta-carbolines (THbetaCs), potential neuroactive alkaloids, were found in chocolate and cocoa. 6-Hydroxy-1-methyl-1,2, 3,4-tetrahydro-beta-carboline (6OHMTHbetaC), 1,2,3, 4-tetrahydro-beta-carboline-3-carboxylic acid (THCA), 1-methyl-1,2,3, 4-tetrahydro-beta-carboline-3-carboxylic acid (MTCA) in both diastereoisomers (1S,3S and 1R,3S), and 1-methyl-1,2,3, 4-tetrahydro-beta-carboline (MTHbetaC), besides serotonin and tryptamine biogenic amines, were identified and quantified in dark chocolate, milk chocolate, cocoa, and chocolate-containing cereals by RP-HPLC-fluorescence and HPLC-MS. For each THbetaC, the concentration ranges were determined: 6OHMTHbetaC (0.16-3.92 microg/g), THCA (0.01-0.85 microg/g), 1S,3S-MTCA (0.35-2 microg/g), 1R,3S-MTCA (0.14-0.88 microg/g), and MTHbetaC (nd-0.21 microg/g). The highest content was generally found in chocolates and cocoas, but cereals containing chocolate also showed an appreciable amount of THbetaCs. The possible biological implications of this novel group of alkaloids in chocolate are discussed.

A possible link between beta -carboline metabolism and infantile autism

Benzodiazepine receptors and abnormal hepatic metabolism have been suggested to participate in several neuropsychiatric disorders including autism. Neuropsychoactive beta-carboline alkaloids as the potent ligands for benzodiazepine receptors are endogenously produced and exogenously supplied much more than benzodiazepines. 1-Methyl-1,2,3,4-tetrahydro-beta-carboline, a predominant alkaloid in humans and foodstuffs, is metabolically hydroxylated in liver. Although its in vivo levels show no difference between autistic and healthy children, the metabolic 6-hydroxylation is significantly decreased in autistic subjects. Therefore, it could be hypothesized that the reduced hepatic metabolism of 1-methyl-1,2,3, 4-tetrahydro-beta-carboline to 6-hydroxyl metabolite may be linked to the pathogenesis of infantile autism as suggested for autistic occurrence to involve the pathology similar to hepatic encephalopathy.