Quantum mechanical and experimental oxidation studies of pentadecylresorcinol, olivetol, orcinol and resorcinol

Electrochemical Detection of Olivetol Based on Poly(L-Serine) Film Layered Copper Oxide Modified Carbon Paste Electrode (p-L-Serine/CuO/CPE)

Olivetol is an important polyphenol compound and intermediate in the synthesis of cannabinoids possessing many types of biological activities. A facile electrochemical sensor for olivetol was fabricated based on p-L-serine, and copper oxide (CuO) nanoparticles modified carbon paste electrode (p-L-serine/CuO/CPE). The proposed p-L-serine/CuO/CPE was applied to the electrochemical detection of olivetol by cyclic voltammetry (CV) and differential pulse voltammetric (DPV). Through the characterizations of materials and modified electrodes, the p-L-serine/CuO/CPE exhibited enhanced electrochemical signals for olivetol compared to bare CPE and CuO/CPE in both CV and DPV methods. Under the optimized conditions, the proposed p-L-serine/CuO/CPE showed a good quantitative analysis ability and a wide analysis range from 20 to 100 μmol L^-1 of olivetol with a limit of detection of 1.04 μmol L^-1. Based on the reproducibility, repeatability, and stability exhibited by this fabricated sensor and the cheap and accessible raw materials, the p-L-serine/CuO/CPE became a novel determination choice for olivetol in the electrochemical method with the advantages of being cost-effective and convenient.

The metabolite 5-methyl-1,3-benzenediol and its derivative methyl-2,4-dihydroxy-6-methylbenzoate from the lichen Parmotrema tinctorum with potent apoptotic and anti-angiogenesis effects

Nature has been a rich resource of novel anticancer agents, one such source being lichens, which represent the symbiosis between algae and fungi with diverse range of secondary metabolites having therapeutic significance. With respect to this, the present study evaluates the in vitro apoptogenic profile of secondary metabolites from the lichen Parmotrema tinctorum towards cancer cell lines. Treatment with TLC-purified fraction 1 from P. tinctorum resulted in significant reduction in the cell viabilities of cancer cells with IC50 values ranging between 1.2 and 12.8 μg/ml. The potential anticancer effect of the bioactive fraction was further supported by Trypan blue cell viability, LDH and DNA fragmentation assays. At the cellular level, induction of apoptosis was confirmed through the activation of the caspase cascade and apoptotic cells accumulating in the Sub-G1 phase of cell cycle. Angiogenesis being one of the major characteristics needed for cancer growth, the ability of the lichen fraction to inhibit angiogenesis was checked through in ovo Yolk Sac Membrane (YSM) assay and was found to be significant. The study also verified the non-toxic nature of the bioactive fraction towards normal human peripheral lymphocytes. HPLC analysis and GC-MS characterisation of the bioactive fraction indicated the presence of 5-methyl-1,3-benzenediol and its derivative methyl-2,4-dihydroxy-6-methylbenzoate.

Effect of alkyl chain length on the antioxidant activity of alkylresorcinol homologues in bulk oils and oil-in-water emulsions

The antioxidant cut-off theory details the importance of fine-tuning antioxidant hydrophobicity to optimize antioxidant effectiveness for a given food system; however, previous research has utilized synthetic antioxidant homologues which fail to align with the food industry's demand for natural ingredients. Alkylresorcinols represent a natural homologous series of phenolipid antioxidants. The antioxidant activities of individual alkylresorcinol homologues were investigated in bulk oils and oil-in-water emulsions. In oils, antioxidant activity decreased as alkyl chain length increased and there was no effect on rate of loss. In emulsions, optimum antioxidant activity was observed at intermediate alkyl chain length (C21:0) and longer homologues were lost more rapidly. Radical scavenging capacity decreased as alkyl chain length increased but alkylresorcinols were unable to chelate iron. This suggests that intrinsic properties (e.g. radical scavenging capacity) are responsible for the antioxidant activity of alkylresorcinols in oils while physicochemical phenomena (e.g. partitioning) drive antioxidant activity of alkylresorcinols in emulsions.

Phenolic lipids as unique bioactive compounds: a comprehensive review on their multifunctional activity toward the prevention of Alzheimer's disease

Phenolic lipids are multifunctional compounds which play an important biological role in the body. Their unique biologic functionality stems from their strong amphiphilic character which allows them to be incorporated in erythrocytes. Through membrane incorporation, these compounds exert their biological effects on neurons which are not modulated by hydrophilic compounds. These bioactive compounds are present in nature as secondary plant metabolites, and consequently their availability is limited, for dietary and medical purposes. In this review, the pathways and mechanisms associated with the pathogenesis of Alzheimer's disease will be described. In addition, the modulatory effects of phenolic lipids on these pathways and a list of several synthetic, semi synthetic and natural sources of phenolic lipids will be examined as having the potential to prevent or combat Alzheimer's disease.

Electrochemical oxidation of resorcinol: mechanistic insights from experimental and computational studies

This work investigates the mechanisms of resorcinol oxidation by density functional theory (DFT) calculation and cyclic voltammetry measurements. Complementary data from experimental and computational studies provide new insights into the reaction mechanisms. At both macro- and micro-electrodes, cyclic voltammetry of resorcinol is chemically and electrochemically irreversible over the whole pH range (1–14). Resorcinol molecules undergo a 1H⁺ 1e⁻ oxidation at pH < pK_a1 and a 1e⁻ oxidation at pH > pK_a2 to form radicals. The radicals then readily react to form dimers/polymers deposited on the electrode surface. All of the experimental findings are consistent with the proposed mechanisms, including the apparent transfer coefficient (β) of 0.6 ± 0.1, the slope of the peak potential (E_p) against pH of −54 mV pH⁻¹, the peak-shaped responses at micro-electrodes, and the fouling of the electrodes upon the oxidation of resorcinol. DFT calculation of the reaction energy of elementary steps and the eigenvalues of the highest occupied molecular orbital (HOMO) of the radical intermediates confirms that the (1H⁺) 1e⁻ oxidation is the energetically favorable pathway. In addition to mechanistic insights, an electrochemical sensor is developed for resorcinol detection at microelectrodes in low ionic strength samples with the sensitivity of 123 ± 4 nA μM⁻¹ and the limit of detection (3 s_B m⁻¹) of 0.03 μM.

Resorcinol oxidation mechanism was investigated by DFT calculation and cyclic voltammetry experiments at macro- and micro-electrodes (1 ≤ pH ≤ 14).

Characterization of the xanthine oxidase inhibitory activity of alk(en)yl phenols and related compounds

The inhibitory activity of xanthine oxidase (XO) is a combination of uric acid formation inhibition and superoxide anion (O₂^-) generation suppression. The inhibition of uric acid formation by XO is useful for the screening of natural compounds that prevent gout, while the suppression of O₂^- generation is useful for treating oxidative stress. Many edible plants contain abundant phenolic compounds and alk(en)yl phenols, and some of these compounds display XO inhibitory activity. This review focuses on XO inhibitory activity since this activity is used to characterize natural products. Recently, it was demonstrated that the inhibitory activity could be characterized using assays for XO inhibition, the suppression of O₂^- generation, DPPH radical scavenging and O₂^- radical scavenging. The inhibitory activity was divided three reaction types. The first is XO inhibition, the second O₂^- generation suppression by modification of enzyme molecules and the third two forms of O₂- scavenging. It was demonstrated that these three activities are related to both the hydroxy group arrangement in the phenol portion and the alk(en)yl chains. This characterization is useful for pursuing XO inhibitors and antioxidants in natural compounds.

Superoxide anion scavenging activity of alk(en)yl phenol compounds by using PMS-NADH system

Anacardic acid C_15:3 and cardol C_15:3 sigmoidally suppressed superoxide anion (O₂-) generation using xanthine oxidase. To study this suppression activity, anacardic acids, cardanols and cardols having different numbers of double bonds in alk(en)yl chains were prepared. The O₂- scavenging activity and H₂O₂ formation from O₂- using PMS-NADH were examined. Anacardic acids and cardols indicated sigmoidal O₂- scavenging activity but cardanols did not. The O₂- scavenging activity of anacardic acid C_15:3 was weaker than the suppression activity using xanthine oxidase, but the scavenging activity of cardol C_15:3 was quite similar to the suppression using xanthine oxidase. The H₂O₂ formation from O₂- decreased by the addition of anacardic acids, cardanols and cardols but increased by the addition of gallic and caffeic acids. From these results, we deduced that the O₂- suppression activity of xanthine oxidase reaction with cardols is the O₂- scavenging activity and that anacardic acids and cardols are O₂- scavengers having low prooxidant property.

Anxiolytic effects of orcinol glucoside and orcinol monohydrate in mice

CONTEXT

Anxiety is a common psychological disorder, often occurring in combination with depression, but therapeutic drugs with high efficacy and safety are lacking. Orcinol glucoside (OG) was recently found to have an antidepressive action.

OBJECTIVE

To study the therapeutic potential of OG and orcinol monohydrate (OM) as anxiolytic agents.

MATERIALS AND METHODS

Anxiolytic effects in mice were measured using the elevated plus-maze, hole-board, and open-field tests. Eight groups of mice were included in each test. Thirty minutes before each test, mice in each group received one oral administration of OG (5, 10, or 20 mg/kg), OM (2.5, 5, or 10 mg/kg), the positive control diazepam (1 or 5 mg/kg), or control vehicle. Each mouse underwent only one test. Uptake of orcinol (5 mg/kg) in the brain was qualitatively detected using the HPLC-MS method.

RESULTS

OG (5, 10, and 20 mg/kg) and OM (2.5 and 5 mg/kg) increased the time spent in open arms and the number of entries into open arms in the elevated plus-maze test. OG (5 and 10 mg/kg) and OM (2.5 and 5 mg/kg) increased the number of head-dips in the hole-board test. At all tested doses, OG and OM did not significantly affect the locomotion of mice in the open-field test. Orcinol could be detected in the mouse brain homogenates 30 min after oral OM administration, having confirmed that OM is centrally active.

DISCUSSION AND CONCLUSION

The results demonstrated that OG and OM are anxiolytic agents without sedative effects, indicating their therapeutic potential for anxiety.

Comprehensive study of valuable lipophilic phytochemicals in wheat bran

Wheat bran, the major side-stream generated in the milling of wheat grains in the production of white flour, contains significant quantities of carbohydrate and proteins. While not interfering with flour utilization, the bran could be considered as an important feedstock within a biorefinery concept. Wheat bran also contains some amounts of lipids that can be used as a source of valuable phytochemicals. Gas chromatography and mass spectrometry analysis of the lipid composition of destarched wheat bran demonstrated that the predominant lipids found in wheat bran were free fatty acids (ca. 40% of total lipids), followed by acylglycerols (40%). Additionally, important amounts of alkylresorcinols (13% of total lipids) and steroid compounds (hydrocarbons, ketones, free sterols, sterol glycosides, sterol esters, and sterol ferulates) (7% of total lipids) were also present among the lipids of wheat bran. The use of wheat bran as a valuable source of phytochemicals of interest in the context of a wheat bran biorefinery is discussed.

Irreversible competitive inhibitory kinetics of cardol triene on mushroom tyrosinase

Cardol triene was first purified from cashew (Anacardium occidentale L.) nut shell liquid and identified by gas chromatography coupled to mass spectroscopy and nuclear magnetic resonance. The effects of this compound on the activity of mushroom tyrosinase were studied. The results of the kinetic study showed that cardol triene was a potent irreversible competitive inhibitor and the inactivation was of the complexing type. Two molecules of cardol triene could bind to one molecule of tyrosinase and lead to the complete loss of its catalytic activity. The microscopic rate constants were determined for the reaction of cardol triene with the enzyme. The anti-tyrosinase kinetic research of this study provides a comprehensive understanding of inhibitory mechanisms of resorcinolic lipids and is beneficial for the future design of novel tyrosinase inhibitors.

Comparative antioxidant activity of an extract of Lithraea molleoides and an isolated 5-alkyl resorcinol derivative. Effects on the proliferation of normal and tumoral lymphocytes

Lithraea molleoides (Vell.) Engl. (Anacardiaceae), is known in South America for its medicinal properties: antiarthritic, haemostatic, diuretic, tonic and useful for the treatment of respiratory diseases. Previously the isolation of a new cytotoxic 5-alkyl resorcinol derivative, 1,3-dihydroxy-5-(tridec-4',7'-dienyl) benzene, from a dichloromethane extract (DM) was reported. The aim of this work was to determine and to compare the antioxidant activity of DM and the isolated compound, 1,3-dihydroxy-5-(tridec-4',7'-dienyl) benzene. Moreover, the activity of both on the proliferation of tumoral and normal lymphocytes was determined. The compound was isolated and quantified by HPLC. The compound represented 0.036% of DM. The extract and the compound exerted antioxidant activity by DPPH and FTC methods. On tumoral cells, both exerted antiproliferative action but the compound was more active (EC(50) : 17.4 ± 1 µg/mL). On normal lymphocytes, both exerted a stimulatory effect on cell proliferation inversely related to concentration, the extract was more active than the compound (maximum effect: 300 ± 20% of stimulation). Most of the effects observed with the extract were independent of the isolated compound. DM could be an important source of antioxidant and immunomodulatory compounds to be studied on cancer diseases.

Biological activity of phenolic lipids

Phenolic lipids are a very diversified group of compounds derived from mono and dihydroxyphenols, i.e., phenol, catechol, resorcinol, and hydroquinone. Due to their strong amphiphilic character, these compounds can incorporate into erythrocytes and liposomal membranes. In this review, the antioxidant, antigenotoxic, and cytostatic activities of resorcinolic and other phenolic lipids are described. The ability of these compounds to inhibit bacterial, fungal, protozoan and parasite growth seems to depend on their interaction with proteins and/or on their membrane-disturbing properties.

Disturb or stabilize? A molecular dynamics study of the effects of resorcinolic lipids on phospholipid bilayers

Resorcinolic lipids, or resorcinols, are commonly found in plant membranes. They consist of a substituted benzene ring forming the hydrophilic lipid head, attached to an alkyl chain forming the hydrophobic tail. Experimental results show alternative effects of resorcinols on lipid membranes. Depending on whether they are added to lipid solutions before or after the formation of the liposomes, they either stabilize or destabilize these liposomes. Here we use atomistic molecular dynamics simulations to elucidate the molecular nature of this dual effect. Systems composed of either one of three resorcinol homologs, differing in the alkyl tail length, interacting with dimyristoylphosphatidylcholine lipid bilayers were studied. It is shown that resorcinols preincorporated into bilayers induce order within the lipid acyl chains, decrease the hydration of the lipid headgroups, and make the bilayers less permeable to water. In contrast, simulations in which the resorcinols are incorporated from the aqueous solution into a preformed phospholipid bilayer induce local disruption, leading to either transient pore formation or even complete rupture of the membrane. In line with the experimental data, our simulations thus demonstrate that resorcinols can either disturb or stabilize the membrane structure, and offer a detailed view of the underlying molecular mechanism.

Enzymatic polymerization of natural anacardic acid and antibiofouling effects of polyanacardic acid coatings

Anacardic acid, separated from cashew nut shell liquid, is well known for its strong antibiotic and antioxidant activities. Recent findings indicate that phenolic compounds from plant sources have an effect on Gram-negative bacteria biofilm formation. In this work, a polyphenolic coating was prepared from anacardic acid using enzymatic synthesis and tested for its effects on biofilm formation of both Gram-negative and Gram-positive bacteria. Natural anacardic acid was enzymatically polymerized using soybean peroxidase. Hydrogen peroxide and phenothiazine-10-propionic acid were used as an oxidizing agent and redox mediator, respectively. Nuclear magnetic resonance and Fourier transform infrared (FTIR) analyses showed the formation of oxyphenylene and phenylene units through the phenol rings. No linkage through the alkyl chain was observed, which proved a high chemo-selectivity of the enzyme. Aqueous solvents turned out to play an important role in the polymer production yield and molecular weight. With 2-propanol, the highest production yield (61%) of polymer (molecular weight = 3,900) was observed, and with methanol, higher-molecular-weight polymers (5,000) were produced with lower production yields (43%). The resulting polyanacardic acid was cross-linked on a solid surface to form a permanent natural polymer coating. The FTIR analysis indicates that the cross-linking between the polymers took place through the unsaturated alkyl side chains. The polyanacardic acid coating was then tested for its antibiofouling effect against Gram-negative and Gram-positive bacteria and compared with the antibiofouling effects of polycardanol coatings reported in the literature. The polyanacardic acid coating showed more reduction in biofilm formation on its surface than polycardanol coatings in the case of Gram-positive bacteria, while in the case of Gram-negative bacteria, it showed a similar reduction in biofilm formation as polycardanol.

Characterization of major and minor alk(en)ylresorcinols from mango (Mangifera indica L.) peels by high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry

5-Alkyl- and 5-alkenylresorcinols, as well as their hydroxylated derivatives, were extracted from mango (Mangifera indica L.) peels, purified on polyamide and characterized by high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (HPLC/APcI-MS) for the first time. Among the 15 compounds analyzed, 3 major and 12 minor C(15)-, C(17)-, and C(19)-substituted resorcinols and related analogues, showing varying degrees of unsaturation, were characterized by their specific fragmentation patterns in collision-induced dissociation experiments. This marks the first report on the occurrence of mono-, di-, and triunsaturated C(15)-homologues, saturated and triunsaturated C(17)-homologues, and mono- and diunsaturated C(19)-homologues in mango peels. Additionally, several hydroxylated C(15)- and C(17)-homologues, also not yet described in mango, and a C(14)-monoene, unique because of its even-numbered side chain, were tentatively identified on the basis of their fragmentation patterns. The results obtained in the present study indicate that HPLC-DAD-APcI-MS(n), combined with the newly developed solid-phase extraction, is a powerful tool for the analysis of alk(en)ylresorcinols and could therefore be used for their determination in various matrices.

Dietary alkylresorcinols: absorption, bioactivities, and possible use as biomarkers of whole-grain wheat- and rye-rich foods

The biologic and chemical properties of alkylresorcinols (ARs) have been reviewed previously, but there has been relatively little research or focus on the importance of ARs in food and diet. ARs represent a significant proportion of the phytochemicals present in wheat and rye, in which they normally exist in concentrations between 300 and 1500 microg/g. ARs are concentrated in the bran fraction of these cereals, and are therefore a significant component of food products rich in whole grain wheat and rye but not in products containing only refined cereal flour. In this review, we discuss the presence of ARs in food, methods of analysis, their absorption and role in the diet in light of their in vitro bioactivities, and their possible use as biomarkers of whole-grain wheat and rye intake.

Gas chromatographic-mass spectrometric method for the determination of alkylresorcinols in human plasma

Alkylresorcinols can be found in high amounts in whole grain cereals, especially in rye. Previously it has not been possible to measure alkylresorcinols in plasma. In this paper a validated gas chromatographic-mass spectrometric method for the quantitative determination of alkylresorcinols with chain lengths of C15:0, C17:0, C19:0, C21:0, and C23:0 in human plasma samples is presented. Other alkylresorcinols may be measured with the method as well, but their assay was not validated in this work. In this work also the amount of alkylresorcinol C25:0 was measured. The pretreatment of plasma samples consists of a simple incubation, an extraction with diethyl ether and a chromatographic purification before the GC-MS analysis. As internal standard an alkylresorcinol C20:0 was used. The validation of the method showed that it fulfilled the reliability criteria. Calibration graphs were linear over the range of 4.1-660pg per injection. The mean recovery percentage was 112+/-10.8%. Our results show that the alkylresorcinols are found in plasma in the same ratio, as found in rye grains, according to literature. The alkylresorcinols were in the unconjugated form. The total amounts of alkylresorcinols in two plasma samples analyzed here were 333 and 381nmol/L.

Synthesis and biological evaluation of CX-659S and its related compounds for their inhibitory effects on the delayed-type hypersensitivity reaction

In order to find novel nonsteroidal compounds possessing an inhibitory activity against delayed-type hypersensitivity (DTH) reactions, we conducted random screening using a picryl chloride (PC)-induced contact hypersensitivity reaction (CHR) in mice, and found compound 1 as a lead compound. Then we synthesized and evaluated an extensive series of 5-carboxamidouracil derivatives focused on both the uracil and the antioxidative moieties. Among them, we found that the hindered phenol moiety was necessary to exhibit the activities; especially, compounds 28a-28c having the partial structure of vitamin E were found to exert potent activities against the DTH reaction by both oral and topical administration. And compound 28c showed antioxidative activity against lipid peroxidation with an IC50 of 5.9 microM. Compound 28c (CX-659S) was chosen as a candidate drug for the treatment of cutaneous disorders such as atopic dermatitis and allergic contact dermatitis.