Inhibitory Effect of Bovine Lactoferrin on Catechol-O-Methyltransferase

Identification of human in vitro metabolites of the haemoglobin S polymerization inhibitor voxelotor for doping control purposes

Voxelotor (GBT440) is a haemoglobin S polymerization inhibitor used to treat anaemia in sickle cell disease. Due to an increase of arterial oxygen saturation as well as serum erythropoietin and haemoglobin, the World Anti-Doping Agency included voxelotor in the list of prohibited substances and methods in 2023. The objective of the present study was to identify and characterize metabolites of voxelotor to detect a potential misuse by athletes. The biotransformation was studied in vitro using the human hepatocellular cell line HepG2 and pooled human liver microsomes. The metabolites were analysed using high-performance liquid chromatography (high-resolution) mass spectrometry. In total, three phase I metabolites and six phase II metabolites (resulting from glucuro-conjugation and O-methylation) were formed by the HepG2 cells in a time-dependent manner, and two phase I metabolites were generated by the liver microsomes, among them one also found in the HepG2 incubations. A reduced metabolite and the glucuro-conjugate of a reduced metabolite were the most abundant formed by HepG2 cells. In addition, metabolites resulting from mono-hydroxylation, reduction and O-methylation in different combinations were identified. Voxelotor was also found as glucuro-conjugate with a low abundance. With the spectrometric behaviour of voxelotor and its in vitro metabolites described herein, an implementation in doping control screening and, consequently, a detection of an abuse in an athlete urine sample might be possible.

Catechol-O-methyltransferase Inhibitors from Calendula officinalis Leaf

Calendula officinalis is commonly known as marigold and its flowers are used in herbal medicines, cosmetics, perfumes, dyes, pharmaceutical preparations, and food products. However, the utility of its leaves has not been studied in depth. The purpose of the present study was to identify the major compounds in C. officinalis leaves and to determine the inhibitory properties of the isolated compounds toward human catechol-O-methyltransferase (COMT), a key neurotransmitter involved in Parkinson's disease and depression. We isolated and identified ten compounds, including two phenylpropanoids and seven flavonoids, from C. officinalis leaf extracts, of which four flavonoids were identified from C. officinalis leaves for the first time. Eight compounds exhibited COMT inhibitory activities with IC₅₀ values of less than 100 μM. Our results indicate that compounds in C. officinalis leaves are potentially effective for preventing Parkinson's disease and depression. Thus, C. officinalis leaves may hold promise as dietary supplements.

Thermostability and catechol-O-methyltransferase inhibitory activity of acylated anthocyanins from purple yam

The thermostability of purple yam was investigated to be used as natural colorants. In addition, the inhibitory properties of purple yam and its isolated anthocyanins toward human catechol-O-methyltransferase (COMT), a key neurotransmitter involved in Parkinson's disease and depression, were also investigated. The thermostability of purple yam was higher than that of the reference samples (purple sweet potato and purple potato). Quantitative HPLC analysis revealed that alatanin A (2) contributed to the thermostability of purple yam. Methanol extracts of purple yam exhibited the highest COMT inhibitory activity of the tested samples. Alatanin D (1) showed the highest inhibitory activity of the anthocyanins in purple yam (IC50 19 µM). This study revealed the thermostability and COMT inhibitory activity of purple yam and may lead to its use not only as a thermostable natural source of colorants, but also for the prevention and treatment of Parkinson's disease and depression.

Chemical Profiles of Korean Bee Pollens and Their Catechol-O-methyltransferase Inhibitory Activities

Bee pollen is an apicultural product collected by honeybees from flower stamens and is consumed to help maintain a healthy diet. In this study, the chemical profiles of 11 Korean bee pollens were investigated using molecular networking analysis. This analysis elucidated the presence of two major clusters, hydroxycinnamoyl acid amides (HCAAs, molecular network 1 (MN₁)) and flavonoid glycosides (MN₂), in the bee pollen samples. The inhibitory properties of the bee pollens and the isolated HCAAs toward human catechol-O-methyltransferase (COMT), a key neurotransmitter involved in Parkinson's disease and depression, were determined. N¹,N⁵,N¹⁰-(E)-tricaffeoylspermidine ((E,E,E)-1) exhibited the highest activity of the four compounds isolated, with an IC₅₀ value 16 μM, and inhibited COMT competitively. Quantitative analysis of HCAAs showed that the amounts of N¹,N¹⁰-dicaffeoyl-N⁵-p-coumaroylspermidine (2) and N¹⁰-caffeoyl-N¹,N⁵-di-p-coumaroylspermidine (3) contributed to the observed differences in the COMT inhibitory activities of Korean bee pollens. This study may lead to the prevention and treatment of Parkinson's disease and depression using bee pollens.

Catechol-O-Methyltransferase Inhibitors Isolated From Thai Propolis

Propolis is an aggregate of functional components found in plant resins and has been reported to exhibit a variety of valuable biological activities. This study investigated the inhibitory properties of propolis from Thailand toward human catechol- O-methyltransferase (COMT), a key neurotransmitter involved in Parkinson's disease and depression. Samples collected from Chanthaburi and Chiang Mai exhibited relatively high inhibitory activity against COMT. γ-Mangostin (1) and 6-prenyleriodictyol (3) were identified as COMT inhibitors with IC50 values of 62 and 75 μM, respectively. In an enzyme inhibition assay, 1 exhibited mixed inhibition toward COMT. The results suggest that both 1 and propolis have potential applications in the prevention and treatment of psychological illness.

Comparative examination of levodopa pharmacokinetics during simultaneous administration with lactoferrin in healthy subjects and the relationship between lipids and COMT inhibitory activity in vitro

Background: Lactoferrin (bLF) is an iron-binding multifunctional protein that is abundant in milk. In mice, it inhibits catechol-O-methyltransferase (COMT) activity and increases blood levodopa levels. However, the clinical effects are unknown.Objective: The objective of this study was to determine the effect of bLF on the kinetics of levodopa in blood.Design: The effects of the concomitant administration of a combined formulation of levodopa and an aromatic amino acid decarboxylase inhibitor and bLF on the concentration of levodopa in blood and its metabolism were assessed in eight healthy subjects. In addition, we analyzed the association with clinical factors and evaluated whether clinical factors affected the COMT inhibitory activity of bLF in vitro.Results: Although not statistically significant, the peak plasma concentration (C_max) of levodopa increased by 18.5%. From the results of the stratified analysis of total cholesterol, a relationship with ΔC_max was predicted. Therefore, bLF was reacted with cholesterol in the presence of lecithin and sodium deoxycholate in vitro to evaluate COMT inhibitory activity, and an increase in inhibitory activity was observed. By contrast, the ester compound cholesteryl oleate had no effect. The inhibitory activity of free fatty acids, which are known to interact with bLF, was also enhanced.Conclusion: The COMT inhibitory activity of bLF is not effective in elevating blood levodopa levels. However, in humans with high lipid levels, such as cholesterol, interactions may enhance the inhibitory effect, resulting in the enhanced absorption of levodopa.Trial registration: ID, UMIN000026787, registered 30 March 2017; URL, https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000030749Trial registration: UMIN Japan identifier: UMIN000026787.

Effects of bovine lactoferrin on l-DOPA absorption and metabolism in mice

Bioactive natural products, habitually ingested with milk or its derivative nutrients, have been studied for their bioavailability. In this study, we investigated the effects of the co-administration of bovine milk-derived lactoferrin (bLF) and bioactive products, with a focus on catechol-O-methyltransferase (COMT), an enzyme in the catechol metabolism. bLF showed inhibitory activity on COMT in vitro, and acidic pretreatment of bLF enhanced its inhibitory activity. Moreover, partially digested products of bLF by pepsin retained inhibitory activity. Based on these results, bLF was co-administered with levodopa (l-DOPA), which is a catechol compound and a precursor of dopamine, and the effect of bLF on l-DOPA absorption and metabolism was investigated in a mouse model. The co-administration of l-DOPA and bLF alone showed no effect on the concentration of l-DOPA in plasma. However, with the additional administration of carbidopa, the concentration of l-DOPA was significantly enhanced. Furthermore, the ratio of l-DOPA/3-O-methyldopa significantly increased. On the other hand, casein, which is a major milk protein, was not effective. In addition, COMT activity in the intestines was lowered with bLF administration. We concluded that the co-administration of bLF and carbidopa enhances the concentration of l-DOPA.