Resorcinolic Lipids, the Natural Non-isoprenoid Phenolic Amphiphiles and Their Biological Activity

Dietary biomarkers-an update on their validity and applicability in epidemiological studies

The aim of this literature review was to identify and provide a summary update on the validity and applicability of the most promising dietary biomarkers reflecting the intake of important foods in the Western diet for application in epidemiological studies. Many dietary biomarker candidates, reflecting intake of common foods and their specific constituents, have been discovered from intervention and observational studies in humans, but few have been validated. The literature search was targeted for biomarker candidates previously reported to reflect intakes of specific food groups or components that are of major importance in health and disease. Their validity was evaluated according to 8 predefined validation criteria and adapted to epidemiological studies; we summarized the findings and listed the most promising food intake biomarkers based on the evaluation. Biomarker candidates for alcohol, cereals, coffee, dairy, fats and oils, fruits, legumes, meat, seafood, sugar, tea, and vegetables were identified. Top candidates for all categories are specific to certain foods, have defined parent compounds, and their concentrations are unaffected by nonfood determinants. The correlations of candidate dietary biomarkers with habitual food intake were moderate to strong and their reproducibility over time ranged from low to high. For many biomarker candidates, critical information regarding dose response, correlation with habitual food intake, and reproducibility over time is yet unknown. The nutritional epidemiology field will benefit from the development of novel methods to combine single biomarkers to generate biomarker panels in combination with self-reported data. The most promising dietary biomarker candidates that reflect commonly consumed foods and food components for application in epidemiological studies were identified, and research required for their full validation was summarized.

Human Intervention Study: Alkylresorcinol Metabolites as Potential Biomarkers for Grain Intake and the Occurrence of Alkylresorcinols in Commonly Consumed Foods in the German Retail Sector

Grains are one of the primary nutrients and are associated with many health benefits. To reflect the intake of grain-based products, two promising potential biomarkers are alkylresorcinol (AR) metabolites 3,5-dihydroxybenzoic acid (3,5-DHBA) and 3-(3,5-dihydroxyphenyl)-propanoic acid (3,5-DHPPA). The aim of this study was to validate the occurrence of AR in food samples and investigate the suitability of their metabolites as potential biomarkers in human intervention studies. In the first step, the AR content in different grain products from the German retail sector was analyzed by GC-MS. ARs were found in higher concentrations in whole grain products and in moderate contents in refined grains and quinoa. Based on these results, human intervention studies were performed in the next step, and the AR metabolites 3,5-DHBA and 3,5-DHPPA were analyzed by LC-MS/MS in urine samples. The intake of only whole grain products leads to an increasing level of both potential biomarkers, while a refined grain diet shows decreasing levels of the AR metabolites. The excretion of 3,5-DHBA after a whole grain-rich diet differs significantly (p = 0.043) from no grain intake.

Dissecting dietary alkylresorcinols: a compile of their distribution, biosynthesis, extraction and functional properties

Alkylresorcinols (ARs) are natural bioactive ingredients produced by: bacteria, fungi, sponges, and higher plants, possessing a lipophilic polyphenol structure with a myriad of biological properties. Focusing on the importance of ARs, several analogs can be extracted from different natural resources. Interestingly, the composition of ARs is usually reflective of their source, with structural differences to exist among ARs isolated from different natural sources. The identified compounds from marine are distinguished by sulfur atom and disulfide bond, while the alkyl chain of bacterial homologs are recognized for their saturated fatty acid chains. ARs occurrence in fungi is still poorly documented however most of the isolated fungal molecules are characterized by a sugar unit attached to their alkylated side chains. The biosynthetic pathway of ARs is postulated via a type III polyketide synthase in which the fatty-acyl chain is elongated and cyclized to generate ARs. The structure-activity relationship (SAR) has gained an increasing interest to mediate for ARs biological activities as discussed herein for the first time from their different resources. ARs extraction procedures showed much progress compared to classical methods compiling organic solvents with supercritical extraction appearing as a potential technique for producing highly purified food-grade of AR homologs. The current review also presents on the rapid qualitative and quantitative determination of ARs to increase accessibility for screening cereals as potential sources of these bioactives.

Antiprotozoal Activity of Plants Used in the Management of Sleeping Sickness in Angola and Bioactivity-Guided Fractionation of Brasenia schreberi J.F.Gmel and Nymphaea lotus L. Active against T. b. rhodesiense

Folk medicine is widely used in Angola, even for human African trypanosomiasis (sleeping sickness) in spite of the fact that the reference treatment is available for free. Aiming to validate herbal remedies in use, we selected nine medicinal plants and assessed their antitrypanosomal activity. A total of 122 extracts were prepared using different plant parts and solvents. A total of 15 extracts from seven different plants exhibited in vitro activity (>70% at 20 µg/mL) against Trypanosoma brucei rhodesiense bloodstream forms. The dichloromethane extract of Nymphaea lotus (leaves and leaflets) and the ethanolic extract of Brasenia schreberi (leaves) had IC50 values ≤ 10 µg/mL. These two aquatic plants are of particular interest. They are being co-applied in the form of a decoction of leaves because they are considered by local healers as male and female of the same species, the ethnotaxon "longa dia simbi". Bioassay-guided fractionation led to the identification of eight active molecules: gallic acid (IC50 0.5 µg/mL), methyl gallate (IC50 1.1 µg/mL), 2,3,4,6-tetragalloyl-glucopyranoside, ethyl gallate (IC50 0.5 µg/mL), 1,2,3,4,6-pentagalloyl-β-glucopyranoside (IC50 20 µg/mL), gossypetin-7-O-β-glucopyranoside (IC50 5.5 µg/mL), and hypolaetin-7-O-glucoside (IC50 5.7 µg/mL) in B. schreberi, and 5-[(8Z,11Z,14Z)-heptadeca-8,11,14-trienyl] resorcinol (IC50 5.3 µg/mL) not described to date in N. lotus. Five of these active constituents were detected in the traditional preparation. This work provides the first evidence for the ethnomedicinal use of these plants in the management of sleeping sickness in Angola.

Chemotherapeutic Mechanism of Action of the Synthetic Resorcinolic Methyl 3,5-dimethoxy-2-octanoylbenzoate

Resorcinolic lipids are described as potential examples of selective chemotherapeutic adjuvants that can enhance the effects of cyclophosphamide (CYC) while promoting cell death without causing DNA damage. Therefore, the current study attempted to describe how the resorcinolic lipid methyl 3,5-dimethoxy-2-octanoylbenzoate (AMS35BB) interacted with DNA (DNA docking) and how this compound affected genetic toxicology models and other biological characteristics when combined with CYC. We observed that AMS35BB, used alone (7.5 and 10 mg/kg), increases the frequency of genomic damage (comet assay) but not chromosomal damage (micronuclei assay), lowers phagocytosis, and promotes cell death in Swiss male mice. When used in association with CYC, AMS35BB can reduce the risk of genomic damage by up to 33.8% as well as chromosomal damage, splenic phagocytosis, cell death, and lymphocyte frequency. Molecular docking showed that AMS35BB had a higher affinity than the active metabolite of CYC for binding to the DNA double helix major groove. As a result, AMS35BB has the potential to be both an adjuvant when used in association with CYC and a therapeutic candidate for the development of a selective chemotherapeutic drug.

Quercetin Enhances the Availability of 5-Heptadecylresorcinol by Inhibiting the Expression of P-gp

5-Heptadecylresorcinol (AR-C17), as the most important active monomer, is found in large quantities in wheat and triticale and plays a variety of health benefits, such as antidiabetic, anti-inflammatory, and antitumor. However, the low bioavailability of AR-C17 due to its low water solubility restricts its application. Moreover, the transport mechanism of AR-C17 is not fully understood. Here, we showed that the transport of AR-C17 in vitro was time- and concentration-dependent, and relatively higher temperature and lower pH obviously promoted the transport of AR-C17. Besides, transporters, especially P-glycoprotein (P-gp), markedly affected the transport of AR-C17 as well. Quercetin, a natural synergist in triticale bran (TB), was confirmed as an inhibitor of P-gp to promote the transport of AR-C17 in this study, and the bioavailability of AR-C17 reached the highest when the concentration ratio of quercetin to AR-C17 was 1:1.

Characteristic of the gene candidate SecARS encoding alkylresorcinol synthase in Secale

BACKGROUND

Alkylresorcinols (ARs) are compounds belonging to the class of phenolic lipids. A rich source of ARs are cereal grains such as rye, wheat, triticale or barley. ARs found in plants are characterized by a variety of biological properties such as antimicrobial, antifungal and cytotoxic activity. Moreover, they are proven to have a positive influence on human health. Here, we aimed to find and characterize the gene with ARs synthase activity in the species Secale cereale.

METHODS AND RESULTS

Using BAC library screening, two BAC clones containing the gene candidate were isolated and sequenced. Bioinformatic analyses of the resulting contigs were used to examine the structure and other features of the gene, including promoter, intron, 3'UTR and 5'UTR. Mapping using the FISH procedure located the gene on the 4R chromosome. Comparative analysis showed that the gene is highly similar to sequences coding for type III polyketide synthase. The level of gene expression in various parts of the plant was investigated, and the biochemical function of the gene was confirmed by heterologous expression in yeast.

CONCLUSIONS

The conducted analyses contributed to a better understanding of the processes related to ARs synthesis. Although the research concerned the rye model, the knowledge gained may help in understanding the genetic basis of ARs biosynthesis in other species of the Poaceae family as well.

Silver ion chromatography enables the separation of 2-methylalkylresorcinols from alkylresorcinols

Alkylresorcinols (∑ARs) is the generic term for a highly varied class of lipids found mainly in cereals. These bioactive compounds consist mainly of 5-alkylresorcinols (ARs), which differ in length, unsaturation, and substituents on the alkyl side chain on C-5. In addition, 2-methyl-5-alkylresorcinols (mARs) are scarcely studied minor compounds that are supposed to exist with the same structural diversity. In the first step, ∑ARs were enriched by solid-phase extraction from wheat grain and quinoa seed extracts. The subsequent application of silver ion chromatography (SIC), silica gel, coated with 20% AgNO3 , then deactivated with 1% water) enabled an unprecedented full separation of saturated mARs from conventional ARs. Specifically, saturated mARs were eluted with n-hexane/ethyl acetate (92:8, v/v), and conventional ARs with n-hexane/ethyl acetate (80:20, v/v). The unpreceded separation indicated that the SIC method could be useful not only for separations according to the degree of unsaturation, but also in the case of steric hindrance by additional (alkyl) substituents. Continued fractionation enabled the collection of unsaturated ARs in wheat and quinoa extracts. In this way, 35 ∑ARs (including five mARs) were detected by gas chromatography/mass spectrometry analysis in wheat and 45 ∑ARs (including 21 mARs) in quinoa. These included several low abundant and partly unknown ∑ARs such as 1,3-dihydroxy-5-tricosadienylbenzene.

Alkylresorcinols as New Modulators of the Metabolic Activity of the Gut Microbiota

Alkylresorcinols (ARs) are polyphenolic compounds with a wide spectrum of biological activities and are potentially involved in the regulation of host metabolism. The present study aims to establish whether ARs can be produced by the human gut microbiota and to evaluate alterations in content in stool samples as well as metabolic activity of the gut microbiota of C57BL, db/db, and LDLR (-/-) mice according to diet specifications and olivetol (5-n-pentylresorcinol) supplementation to estimate the regulatory potential of ARs. Gas chromatography with mass spectrometric detection was used to quantitatively analyse AR levels in mouse stool samples; faecal microbiota transplantation (FMT) from human donors to germ-free mice was performed to determine whether the intestinal microbiota could produce AR molecules; metagenome sequencing analysis of the mouse gut microbiota followed by reconstruction of its metabolic activity was performed to investigate olivetol's regulatory potential. A significant increase in the amounts of individual members of AR homologues in stool samples was revealed 14 days after FMT. Supplementation of 5-n-Pentylresorcinol to a regular diet influences the amounts of several ARs in the stool of C57BL/6 and LDLR (-/-) but not db/db mice, and caused a significant change in the predicted metabolic activity of the intestinal microbiota of C57BL/6 and LDLR (-/-) but not db/db mice. For the first time, we have shown that several ARs can be produced by the intestinal microbiota. Taking into account the dependence of AR levels in the gut on olivetol supplementation and microbiota metabolic activity, AR can be assumed to be potential quorum-sensing molecules, which also influence gut microbiota composition and host metabolism.

Profiling and Isolation of Ten Rare Branched-Chain Alkylresorcinols in Quinoa

Alkylresorcinols (∑ARs) are bioactive lipid compounds predominantly found in cereals. These amphiphilic compounds exist in a high structural diversity and can be divided into two main groups, i.e., 5-alkylresorcinols (ARs) and 2-methyl-5-alkylresorcinols (mARs). The pseudocereal quinoa has a very unique AR profile, consisting not only of straight-chain alkyl chains but also iso- and anteiso-branched isomers. Here, we describe a method for the isolation of such methyl-branched ARs and mARs from quinoa. The enrichment of the ∑AR fraction from the lipid extracts by centrifugal partition chromatography (CPC) was followed by ∑AR profiling using countercurrent chromatography (CCC) and GC/MS analysis of CCC fractions. A total of 112 ∑ARs could be detected, 63 of which had not been previously described in quinoa. Due to this high number of ∑ARs, the direct isolation of individual ARs was not possible using conventional CCC. Instead, the more powerful heart-cut mode was applied to enrich the target compounds. A final purification step-the separation of CCC-co-eluting mARs from ARs -was performed via silver ion chromatography. Altogether, ten rare branched-chain ∑ARs (five iso-branched mARs and five anteiso-branched ARs, including mAR19:0-i and AR20:0-a) were isolated with purities up to 98% in the double-digit mg range.

Estimated dietary intake of polyphenols from cereal foods and associated lifestyle and demographic factors in the Melbourne Collaborative Cohort Study

Cereal foods are consumed globally and are important sources of polyphenols with potential health benefits, yet dietary intakes are unclear. We aimed to calculate the dietary intakes of polyphenols from cereal foods in the Melbourne Collaborative Cohort Study (MCCS), and describe intakes by demographic and lifestyle factors. We estimated intakes of alkylresorcinols, lignans and phenolic acids in n = 39,892 eligible MCCS participants, using baseline dietary data (1990-1994) from a 121-item FFQ containing 17 cereal foods, matched to a polyphenol database developed from published literature and Phenol-Explorer Database. Intakes were estimated within groups according to lifestyle and demographic factors. The median (25th-75th percentile) intake of total polyphenols from cereal foods was 86.9 mg/day (51.4-155.8). The most consumed compounds were phenolic acids, with a median intake of 67.1 mg (39.5-118.8), followed by alkylresorcinols of 19.7 mg (10.8-34.6). Lignans made the smallest contribution of 0.50 mg (0.13-0.87). Higher polyphenol intakes were associated with higher relative socio-economic advantage and prudent lifestyles, including lower body mass index (BMI), non-smoking and higher physical activity scores. The findings based on polyphenol data specifically matched to the FFQ provide new information on intakes of cereal polyphenols, and how they might vary according to lifestyle and demographic factors.

Whole grain metabolite 3,5-dihydroxybenzoic acid is a beneficial nutritional molecule with the feature of a double-edged sword in human health: a critical review and dietary considerations

Nonprocessed foodstuffs of plant origin, especially whole-grain cereals, are considered to be health-promoting components of the human diet. While most of their well-studied effects derive from their high fiber content and low glycemic index, the presence of underrated phenolic phytonutrients has recently been brought to the attention of nutritionists. In this review, we report and discuss findings on the sources and bioactivities of 3,5-dihydroxybenzoic acid (3,5-DHBA), which is both a direct dietary component (found, e.g., in apples) and, more importantly, a crucial metabolite of whole-grain cereal-derived alkylresorcinols (ARs). 3,5-DHBA is a recently described exogenous agonist of the HCAR1/GPR81 receptor. We concentrate on the HCAR1-mediated effects of 3,5-DHBA in the nervous system, on the maintenance of cell stemness, regulation of carcinogenesis, and response to anticancer therapy. Unexpectedly, malignant tumors take advantage of HCAR1 expression to sense 3,5-DHBA to support their growth. Thus, there is an urgent need to fully identify the role of whole-grain-derived 3,5-DHBA during anticancer therapy and its contribution in the regulation of vital organs of the body via its specific HCAR1 receptor. We discuss here in detail the possible consequences of the modulatory capabilities of 3,5-DHBA in physiological and pathological conditions in humans.

In Vitro Pro-Apoptotic and Anti-Migratory Effects of Marantodes pumilum (syn. Labisia pumila) Extracts on Human Prostate Cancer Cell Lines: Bioguided Isolation of 5-Henicosene-1-yl-resorcinol

This study aims to evaluate the in vitro cytotoxic and anti-migratory effects of Marantodes pumilum Blume Kuntze plant extracts on prostate cancer cells, identify the active compound/s, and characterize their mechanism of action. The crude methanolic extract was partitioned into n-hexane (MPh), chloroform (MPc), and aqueous (MPa) extracts. Antiproliferative fractions (IC50 < 30 μg/mL based on SRB staining of LNCaP and PC3 cell lines) were further fractionated. Active compound/s were identified using spectroscopic methods. In vitro mechanistic studies on PC3 cells included: annexin V-FITC staining, mitochondrial membrane potential (MMP) depolarization measurements, the activity of caspases 3 and 7, nuclear DNA fragmentation, cell cycle analysis, modulation of Bax, Bcl-2, Smac/Diablo, Alox-5, VEGF-A, CXCR4, and CXCL12 mRNA gene expression via RT-PCR, 2D migration (scratch assay), and 3D invasion (Boyden chamber). MPc extract was the most active, inducing cell death (p < 0.05) via apoptosis, as evidenced by nuclear DNA fragmentation and an increase in MMP depolarization (p < 0.05) as well as the activation of caspases 3/7 (MPc p < 0.01) in both PC3 and LNCaP cell lines. In addition, MPc upregulated Bax and Smac/DIABLO, downregulated Bcl-2 (p < 0.05), and inhibited ALOX-5 mRNA gene expression (p < 0.001). MPc was not cytotoxic against normal human fibroblast cells (HDFa) at the tested concentrations. Moreover, MPc inhibited migration and invasion of PC3 cells (p < 0.01). These effects were accompanied by the downregulation of both VEGF-A and CXCL-12 gene expressions (p < 0.001). A monounsaturated 5-alkyl resorcinol was isolated as the active compound in the MPc extract and identified as 5-henicosene-1-yl-resorcinol.

Alkyl aromatic derivatives from the endophytic fungus Cytospora rhizophorae

Two new alkylresorcinols named herein 5'-methoxy-integracins A-B (1-2), two new monomeric alkyl aromatic derivatives 3-(7-hydroxyheptyl)-5-methoxyphenol (5) and 7-(3,5-dihydroxyphenyl) heptyl acetate (6), along with four known compounds including integracins A-B (3-4), 2,4-dihydroxy-6-(8-hydroxyoctyl) benzene (7), and cytosporone B (8) were isolated from the endophytic fungus Cytospora rhizophorae A761. The structures of the four new compounds were elucidated by NMR, HRESIMS data, and electronic circular dichroism (ECD) calculations, whereas the compounds 1 and 2 were disclosed as a class of the natural rare-occurring dimeric alkylresorcinol derivatives. Moreover, the bioassays of the new compounds clarified that compound 1 was a potent inhibitor for the α-glucosidase, and compound 2 showed relatively good activity against the tumor cell lines. It is worth mentioning that the known compound integracin B (4) was first reported to display significant antibacterial activity against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) with MIC values of 6.25 μg ml^-1.

Wheat bran layers: composition, structure, fractionation, and potential uses in foods

Wheat bran, the main by-product of dry milling of wheat, is currently mainly used in the animal feed industry, but has attracted attention as a food ingredient owing to its high dietary fiber and phytochemical contents, providing excellent physiological effects. The bran layers (aleurone layer, outer pericarp and intermediate layer) contain different compositions, structures, and nutrients, and have different properties. Each layer, when separated and isolated, potentially could find more extensive applications in foods. This triggered interest in isolating the bran layers using milling and wet- or dry-fractionation techniques based on their chemical or physical properties. The recent progress has allowed the production of commercial products from wheat bran layers, particularly aleurone-rich products, enhancing the value of wheat bran layers and their applications in food. The present review highlights the recent advances in studying the chemical composition including distribution of chemical components, physical structure, biopolymer matrix, and physicochemical properties of each wheat bran layer. Technologies to fractionate wheat bran layers and utilization of different bran layers in foods are discussed and reviewed, providing new strategies for improving the value of wheat bran and utilization of wheat bran in foods.

Mucilaginibacter straminoryzae sp. nov., isolated from rice straw used for growing periphyton

A rod-shaped, non-motile, Gram-negative bacterium, strain RS28^T, was isolated from rice straw used as material for periphyton growth. Phylogenetic analysis of the 16S rRNA gene sequence revealed that strain RS28^T was affiliated with the genus Mucilaginibacter and had the highest sequence similarity to Mucilaginibacter ginkgonis HMF7856^T (96.47 %) and Mucilaginibacter polytrichastri DSM 26907^T (96.12 %). Strain RS28^T was found to grow at pH 5.5-8.0, 17-40 °C and in the presence of 0-1.5 % (w/v) NaCl. Strain RS28^T contained summed feature 3 (comprising C_16 : 1  ω7c and/or C_16 : 1  ω6c), iso-C_15 : 0 and iso-C_17 : 0 3-OH as the major fatty acids (> 10.0 %). The major polar lipids were phosphatidylethanolamine, two unidentified phospholipids, two unidentified aminophospholipids, three unidentified aminolipids and one unidentified lipid. The respiratory quinone was menaquinone 7. The genomic DNA G+C content was 44.7 mol%. Strain RS28^T possessed six putative secondary metabolite gene clusters involved in the synthesis of resorcinol, NRPS-like, terpene, lassopeptide, T3PKS and arylpolyene. On the basis of the phenotypic, chemotaxonomic, and phylogenetic characteristics, strain RS28^T represents a novel species of the genus Mucilaginibacter, for which the name Mucilaginibacter straminoryzae sp. nov. is proposed. The type strain is RS28^T (=KCTC 92039^T=LMG 32424^T).

Resorcinol Derivatives as Novel Aldose Reductase Inhibitors: In Silico and In Vitro Evaluation

Background:

The polyol pathway, an alternative way of carbohydrate metabolism, is activated by hyperglycemia. Aldose reductase (AR), the first and rate-limiting enzyme of the polyol pathway, is responsible for the reduction of glucose to sorbitol. Inhibiting the aldose reductase enzyme and reducing the polyol pathway is considered an effective method to prevent and postpone the onset of diabetic complications.

Objective:

Therefore, in this work, we investigate the inhibition effects of certain resorcinol derivatives and the positive control compound quercetin on the AR enzyme in vitro and in silico. These phenolic compounds, whose inhibitory effects on the AR enzyme were investigated, were also compared with known drugs in terms of their drug-like characteristics.

Methods:

Three methods were used to determine the inhibitory effects of resorcinol derivatives on recombinant human AR enzyme. After the in vitro inhibition effects were determined spectrophotometrically, the binding energy and binding modes were determined by molecular docking method. Finally, the MM-GBSA method was used to determine the free binding energies of the inhibitors for the AR enzyme.

Results:

5-pentylresorcinol compound showed the strongest inhibition effect on recombinant human AR enzyme with an IC50 value of 9.90 μM. The IC50 values of resorcinol, 5-methylresorcinol, 4- ethylresorcinol, 4-hexylresorcinol, 2-methylresorcinol, and 2,5-dimethylresorcinol compounds were determined as 49.50 μM, 43.31 μM, 19.25 μM, 17.32 μM, 28.87 μM, 57.75 μM, respectively.

Conclusion:

The results of this research showed that resorcinol compounds are effective AR inhibitors. These findings are supported by molecular docking, molecular mechanics, and ADME investigations undertaken to corroborate the experimental in vitro results.

Variation on a theme: the structures and biosynthesis of specialized fatty acid natural products in plants

Plants are able to construct lineage-specific natural products from a wide array of their core metabolic pathways. Considerable progress has been made toward documenting and understanding, for example, phenylpropanoid natural products derived from phosphoenolpyruvate via the shikimate pathway, terpenoid compounds built using isopentyl pyrophosphate, and alkaloids generated by the extensive modification of amino acids. By comparison, natural products derived from fatty acids have received little attention, except for unusual fatty acids in seed oils and jasmonate-like oxylipins. However, scattered but numerous reports show that plants are able to generate many structurally diverse compounds from fatty acids, including some with highly elaborate and unique structural features that have novel bioproduct functionalities. Furthermore, although recent work has shed light on multiple new fatty acid natural product biosynthesis pathways and products in diverse plant species, these discoveries have not been reviewed. The aims of this work, therefore, are to (i) review and systematize our current knowledge of the structures and biosynthesis of fatty acid-derived natural products that are not seed oils or jasmonate-type oxylipins, specifically, polyacetylenic, very-long-chain, and aromatic fatty acid-derived natural products, and (ii) suggest priorities for future investigative steps that will bring our knowledge of fatty acid-derived natural products closer to the levels of knowledge that we have attained for other phytochemical classes.

The Role of Resorcinolic Lipids of Caryopsis Surface in the Process of Cereal Infection by Rhizoctonia solani and Fusarium culmorum

Cereal caryopses are rich in 5-n-alk(en)ylresorcinols, antimicrobial compounds. In this paper, the correlation between the presence of resorcinolic lipids on the surface of cereal grains and the susceptibility of their seedlings to infection by Rhizoctonia solani or Fusarium culmorum was evaluated. The declines in length of both the roots and coleoptiles were observed in barley seedlings of Scarlett and Rabel cultivars grown from the wax-impoverished seeds infected with F92 and F93 strains of Rhizoctonia solani, respectively. Regarding wheat, R. solani F93 significantly reduced only the coleoptile growth. Resorcinolic lipids, being the mixture of homologues with C17–C25 carbon chains, were the only compounds washed off wheat caryopses by chloroform. Moreover, the better anti-Rhizoctonia solani F93 activity of 5-n-alk(en)ylresorcinols of wheat grains than that of rye caryopsis lipids was proven by the poisoned medium technique. Two saturated homologues (C21:0 and C23:0) were the most effective inhibitors of the mycelial growth of this fungus. Thus, the susceptibilities of barley and wheat seedlings to some fungal pathogens have been found to be related to the content and composition of 5-n-alk(en)ylresorcinols in the waxy layer of cereal grains, confirming the protective role of these compounds, during the early stages of cereal development.

Online hyphenation of centrifugal partition chromatography with countercurrent chromatography (CPC-CCC) and its application to the separation of saturated alkylresorcinols

Centrifugal partition chromatography (CPC) and countercurrent chromatography (CCC) are two preparative techniques mainly used for the isolation and purification of natural products. While CPC benefits from a larger sample capacity, CCC typically provides better peak resolutions and hereby higher purities. In this study, we aimed to combine both advantages by the direct linking of CPC and CCC which was achieved by installation of switching valves and connection tube. The hyphenated CPC-CCC setup was tested with major alkylresorcinols which were obtained from a transesterified and hydrogenated rye extract. Injections of 1- and 5-g samples into the individual CCC system confirmed the limited sample capacity because of immediate flooding with the 5-g sample (total loss of stationary phase). In comparison, the CPC system was stable with 5- and 10-g samples but the peak resolution with 1-g sample was poorer than with the CCC system. Injections of 5- and 10-g samples into the CPC-CCC system were successful. However, a sample load of 10 g resulted in lower purities of the alkylresorcinols (80% or less) due to peak tailing. By contrast, injection of 5-g sample provided high amounts of ~ 1.2 g alkylresorcinols with purities of > 95%.

(2'-Oxo)alkylresorcinols restore dehydration tolerance in a knockout line of PpORS, a bryophyte-specific type III polyketide synthase in Physcomitrium (Physcomitrella) patens

PpORS-produced 2'-oxo-5-pentacosylresorcinol (2'-oxo-C₂₅-RL) restored dehydration tolerance in ors-3, a knockout mutant of PpORS. Feeding experiments with [¹⁴C]-2'-oxo-C₂₅-RL suggested the role of PpORS products in cuticular polymer that confer dehydration resistance. 2'-Oxoalkylresorcinol synthase from the moss Physcomitrium (Physcomitrella) patens (PpORS) is the earliest diverged member of plant type III polyketide synthases, and produces very-long-chain 2'-oxoalkylresorcinols in vitro. Targeted knockouts of PpORS (ors) exhibited an abnormal phenotype (increased susceptibility to dehydration), and a defective cuticle in ors was suggested (Li et al., Planta 247:527-541, 2018). In the present study, we investigated chemical rescue of the ors phenotype and also metabolic fates of the PpORS products in the moss. Using C₂₄-CoA as substrate, 2'-oxo-5-pentacosylresorcinol (2'-oxo-C₂₅-RL) and two minor pyrones were first enzymatically prepared as total in vitro products. When a knockout mutant (ors-3) and control strains were grown in the presence of the total in vitro products or purified 2'-oxo-C₂₅-RL, the ability of ors-3 and the control to survive dehydration stress increased in a dose-dependent manner. Structurally analogous long-chain alkylresorcinols also rescued the ors phenotype, although less efficiently. When the moss was grown in the presence of ¹⁴C-radiolabeled 2'-oxo-C₂₅-RL, 96% of the radioactivity was recovered only after acid hydrolysis. These findings led us to propose that 2'-oxoalkylresorcinols are the functional in planta products of PpORS and are incorporated into cuticular biopolymers that confer resistance to dehydration. In addition, the earliest diverging ORS clade in phylogenetic trees of plant type III PKSs exclusively comprises bryophyte enzymes that share similar active site substitutions with PpORS. Further studies on these bryophyte enzymes may shed light on their roles in early plant evolution and offer a novel strategy for improving dehydration tolerance in plants.

General Health Benefits and Pharmacological Activities of Triticum aestivum L

Common wheat (Triticum aestivum), one of the world's most consumed cereal grains, is known for its uses in baking and cooking in addition to its medicinal uses. As this plant's medical benefits are enormous and scattered, this narrative review was aimed at describing the pharmacological activities, phytochemistry, and the nutritional values of Triticum aestivum. It is a good source of dietary fiber, resistant starch, phenolic acids, alkylresorcinols, lignans, and diverse antioxidant compounds such as carotenoids, tocopherols and tocotrienols. These constituents provide Triticum aestivum with a wide range of pharmacological properties, including anticancer, antimicrobial, antidiabetic, hypolipemic, antioxidant, laxative, and moisturizing effects. This review summarized the established benefits of wheat in human health, the mode of action, and different clinical, in vitro and in vivo studies for different varieties and cultivars. This review also gives an insight for future research into the better use of this plant as a functional food. More clinical trials, in vivo and in vitro studies are warranted to broaden the knowledge about the effect of Triticum aestivum on nutrition-related diseases prevention, and physical and mental well-being sustenance.

4-Hexylresorcinol: pharmacologic chaperone and its application for wound healing

4-Hexylresorcinol (4HR) is amphiphilic organic chemical and auto-regulator for micro-organism. As 4HR administration induces the stress on the endoplasmic reticulum, 4HR changes protein folding. The application of 4HR inhibits NF-κB signal pathway and TNF-α production. In addition, 4HR administration increases VEGF, TGF-β1, and calcification associated proteins. As a consequence, 4HR administration increases angiogenesis and bone formation in wounded area. Strong anti-inflammatory reaction and capillary regeneration in diabetic model demonstrate that 4HR can be applied on many types of surgical wound.

An Overview of Alkylresorcinols Biological Properties and Effects

The investigation of alkylresorcinols has drawn an increasing interest recently. Alkylresorcinols (ARs) are natural chemical compounds synthesized by bacteria, fungi, sponges, and higher plants, possessing a lipophilic polyphenol structures and a myriad of biological properties. Human takes ARs as a component of a whole grain diet (from whole grain rye, wheat, and barley products), and thus, alkylresorcinols are frequently used as whole grain intake markers. Besides, ARs are considered as promising bioregulators of metabolic and immune processes, as well as adjuvant therapeutic agents for antimicrobial and anticancer treatment. In this review, we attempted to systematize the accumulated information concerning ARs origin, metabolism, biological properties, and their effect on human health.

Short and efficient synthesis of alkylresorcinols: a route for the preparation of cannabinoids

In this work, we describe a general and efficient method for the preparation of alkylresorcinols (ARs), also in deuterated form.

Unexpected Role of pH and Microenvironment on the Antioxidant and Synergistic Activity of Resveratrol in Model Micellar and Liposomal Systems

Experimental and theoretical studies indicate that resveratrol (RSV, dietary polyphenol that effectively reduces cellular oxidative stress) is a good scavenger of hydroxyl, alkoxyl, and peroxyl radicals in homogeneous systems. However, the role of RSV as a chain-breaking antioxidant is still questioned. Here, we describe pH dependent effectiveness of RSV as an inhibitor of peroxidation of methyl linoleate in Triton X-100 micelles and in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) liposomes, with the best effectiveness at pH 6 (stoichiometric factors, n, are 4.9 and 5.6, and the rate constants for reaction with peroxyl radicals, k_inh, are 1200 and 3300 M^–1 s^–1 in micellar and liposomal systems, respectively). We propose the mechanism in which RSV-derived radicals are coupled to dimers with recovered ability to trap lipidperoxyl radicals. The formation of such dimers is facilitated due to increased local concentration of RSV at the lipid–water interface. Good synergy of RSV with α-tocopherol analogue in micelles and liposomes is in contrast to the previously reported lack of synergy in non-polar solvents; however, the increased persistency of tocopheroxyl radicals in dispersed lipid/water systems and proximal localization of both antioxidants greatly facilitate the possible recovery of α-TOH by RSV.

The effect of 4-hexylresorinol administration on NAD+ level and SIRT activity in Saos-2 cells

Background

4-hexylresorcinol (4HR) has been shown to have anti-oxidant activity similar to that of resveratrol. As resveratrol increases sirtuin (SIRT) activity, 4HR might behave similarly to resveratrol.

Method

In this study, the expression levels of SIRT1, SIRT3, and SIRT6 were evaluated after 4HR administration (1–100 μM). As NAD+ is a substrate for SIRTs, its levels with SIRT activity were also studied.

Results

In the results, SIRT3 (100 μM at 24 h) and SIRT6 (1–100 μM at 24 h and 10 μM at 8 h) were shown to have significantly higher expression levels compared to untreated control (p < 0.05). Pan-SIRT activity and the NAD+ level was significantly increased compared to that of the untreated control (p < 0.05; 10 and 100 μM at 24 h).

Conclusion

4HR administration increased SIRT activity and the NAD+ level in Saos-2 cells.

Tailored Functionalization of Natural Phenols to Improve Biological Activity

Phenols are widespread in nature, being the major components of several plants and essential oils. Natural phenols' anti-microbial, anti-bacterial, anti-oxidant, pharmacological and nutritional properties are, nowadays, well established. Hence, given their peculiar biological role, numerous studies are currently ongoing to overcome their limitations, as well as to enhance their activity. In this review, the functionalization of selected natural phenols is critically examined, mainly highlighting their improved bioactivity after the proper chemical transformations. In particular, functionalization of the most abundant naturally occurring monophenols, diphenols, lipidic phenols, phenolic acids, polyphenols and curcumin derivatives is explored.

New Antiproliferative Compounds against Glioma Cells from the Marine-Sourced Fungus Penicillium sp. ZZ1750

Seven novel compounds, namely peniresorcinosides A–E (1–5), penidifarnesylin A (6), and penipyridinone A (7), together with the 11 known ones 8–17, were isolated from a culture of the marine-associated fungus Penicillium sp. ZZ1750 in rice medium. The structures of the new compounds were established based on their high-resolution electrospray ionization mass spectroscopy (HRESIMS) data, extensive nuclear magnetic resonance (NMR) spectroscopic analyses, chemical degradation, Mosher’s method, ¹³C-NMR calculations, electronic circular dichroism (ECD) calculations, and single crystal X-ray diffraction. Peniresorcinosides A (1) and B (2) are rare glycosylated alkylresorcinols and exhibited potent antiglioma activity, with IC₅₀ values of 4.0 and 5.6 µM for U87MG cells and 14.1 and 9.8 µM for U251 cells, respectively.

Effects of 4-Hexylresorcinol on Craniofacial Growth in Rats

4-Hexylresorcinol (4HR) has been used as a food additive, however, it has been recently demonstrated as a Class I histone deacetylase inhibitor (HDACi). Unlike other HDACi, 4HR can be taken through foods. Unfortunately, some HDACi have an influence on craniofacial growth, therefore, the purpose of this study was to evaluate the effects of 4HR on craniofacial growth. Saos-2 cells (osteoblast-like cells) were used for the evaluation of HDACi and its associated activities after 4HR administration. For the evaluation of craniofacial growth, 12.8 mg/kg of 4HR was administered weekly to 4 week old rats (male: 10, female: 10) for 12 weeks. Ten rats were used for untreated control (males: 5, females: 5). Body weight was recorded every week. Serum and head samples were collected at 12 weeks after initial administration. Craniofacial growth was evaluated by micro-computerized tomography. Serum was used for ELISA (testosterone and estrogen) and immunoprecipitation high-performance liquid chromatography (IP-HPLC). The administration of 4HR (1-100 μM) showed significant HDACi activity (p < 0.05). Body weight was significantly different in male rats (p < 0.05), and mandibular size was significantly smaller in 4HR-treated male rats with reduced testosterone levels. However, the mandibular size was significantly higher in 4HR treated female rats with increased growth hormone levels. In conclusion, 4HR had HDACi activity in Saos-2 cells. The administration of 4HR on growing rats showed different responses in body weight and mandibular size between sexes.

The effect of 4-hexylresocinol administration on SCC-9 cells: mass spectrometric identification of proteins and cDNA microarray analysis

BACKGROUND

In stress situations, bacteria produce dormancy-inducing factors to stop cell growth. The dormancy-inducing factors may have an inhibitory effect on tumor cell growth. Here we analyzed the differentially expressed protein profiles after 4-hexylresorcinol (4HR), one of the dormancy-inducing factors, administration using in vitro oral squamous carcinoma cells (SCC-9).

METHOD

The control group was SCC-9 cells culture without 4HR administration. The experimental group received 10 μg/mL of 4HR. Collected proteins from each group were loaded for 2D electrophoresis. Among the separated proteins, 20 differentially expressed proteins were selected and processed for LC-MS/MS.

RESULTS

In proteomic analysis, the expression of keratin 1, keratin 10, and histone H2B were increased. In cDNA microarray assay, the genes related to the cellular differentiation (involucrin, keratin 13, 14) were highly expressed in the 4HR treated group (fold ratio > 2.0; Table 2). Interestingly, histone family was upregulated in the cDNA microarray assay.

CONCLUSION

The administration of 4HR on SCC-9 cells increased epithelial cell differentiation markers and histone.

Discovery of anti-infective adipostatins through bioactivity-guided isolation and heterologous expression of a type III polyketide synthase

Antibiotic resistance and emerging viral pandemics have posed an urgent need for new anti-infective drugs. By screening our microbial extract library against the main protease of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the notorious ESKAPE pathogens, an active fraction was identified and purified, leading to an initial isolation of adipostatins A (1) and B (2). In order to diversify the chemical structures of adipostatins toward enhanced biological activities, a type III polyketide synthase was identified from the native producer, Streptomyces davawensis DSM101723, and was subsequently expressed in an E. coli host, resulting in the isolation of nine additional adipostatins 3-11, including two new analogs (9 and 11). The structures of 1-11 were established by HRMS, NMR, and chemical derivatization, including using a microgram-scale meta-chloroperoxybenzoic acid epoxidation-MS/MS analysis to unambiguously determine the double bond position in the alkyl chain. The present study discovered SARS-CoV-2 main protease inhibitory activity for the class of adipostatins for the first time. Several of the adipostatins isolated also exhibited antimicrobial activity against selected ESKAPE pathogens.

4-Hexylresorcinol Inhibits Class I Histone Deacetylases in Human Umbilical Cord Endothelial Cells

Histone deacetylases (HDACs) are key enzymes for post-translational modification and influence on various cellular activities. Thus, HDACs are associated with many diseases and their inhibitors have clinical significance. Here, 4-Hexylresorcinol (4HR) was studied as an inhibitor for class I HDACs using the HDAC inhibitor (HDACi) Trichostatin-A as a positive control. The 4HR was administered 1–100 μM to human umbilical endothelial cells (HUVECs) and the HDAC expression and activity were examined. The 4HR decreased the expression level of HDAC1, 3, 4, and 5 in a time and dose-dependent manner. The 4HR also increased acetylated lysine and decreased HDAC activity significantly (p < 0.05). Collectively, 4HR was a new class I HDAC inhibitor that reduced the expression and activity of HDAC in HUVECs.

Alkyl-Resorcinol Derivatives as Inhibitors of GDP-Mannose Pyrophosphorylase with Antileishmanial Activities

Leishmaniasis is a vector-borne disease caused by the protozoan parasite Leishmania found in tropical and sub-tropical areas, affecting 12 million people around the world. Only few treatments are available against this disease and all of them present issues of toxicity and/or resistance. In this context, the development of new antileishmanial drugs specifically directed against a therapeutic target appears to be a promising strategy. The GDP-Mannose Pyrophosphorylase (GDP-MP) has been previously shown to be an attractive therapeutic target in Leishmania. In this study, a chemical library of 5000 compounds was screened on both L. infantum (LiGDP-MP) and human (hGDP-MP) GDP-MPs. From this screening, oncostemonol D was found to be active on both GDP-MPs at the micromolar level. Ten alkyl-resorcinol derivatives, of which oncostemonols E and J (2 and 3) were described for the first time from nature, were then evaluated on both enzymes as well as on L. infantum axenic and intramacrophage amastigotes. From this evaluation, compounds 1 and 3 inhibited both GDP-MPs at the micromolar level, and compound 9 displayed a three-times lower IC₅₀ on LiGDP-MP, at 11 µM, than on hGDP-MP. As they displayed mild activities on the parasite, these compounds need to be further pharmacomodulated in order to improve their affinity and specificity to the target as well as their antileishmanial activity.

Isolation of saturated alkylresorcinols from rye grains by countercurrent chromatography

Alkylresorcinols (5-alkyl-1,3-dihydroxybenzenes) are amphiphilic phenolic lipid compounds that are abundant in cereals with highest contents in rye. Alkylresorcinols are suspected to show a wide range of favourable biological activities. For such and further testing, highly pure alkylresorcinol standards are required. Especially, purities >> 98% were partly difficult to obtain in the past. Here, we aimed to isolate the most abundant (saturated) alkylresorcinols from rye using countercurrent chromatography. To achieve very high purity, alkylresorcinol-containing extract (∼7.14 g) of rye grains (cold extracts with cyclohexane/ethyl acetate (46/54, w/w)) were preparatively transesterified followed by a preparative hydrogenation. Countercurrent chromatography separation of ∼1 g hydrogenated and transesterified rye grain extract using the solvent system n-hexane-ethyl acetate-methanol-water (9:1:9:1, v/v/v/v) yielded 51.8 mg AR17:0, 77.4 mg AR19:0, 57.2 mg AR21:0, 28.8 mg AR23:0 and 11.5 mg AR25:0 with purities >99% in either case. The isolated alkylresorcinol homologues can be used for subsequent bioassays.

Monitoring of changes in 5-n-alkylresorcinols during wheat seedling development

For seven days of wheat growth, caryopsis remained the main source of 5-n-alkylresorcinols with C19 and/or C21 homolog as a main compound. Shoot contained small amount of these phenolic lipids; their average content was 3.23% of level obtained in the whole seedling. Moreover, 41.38% of resorcinolic lipids of seven-day-old shoot was accumulated in part of leaf covered by coleoptile. Interestingly, a removal of 1.07% of the primary pool of kernel alkylresorcinols by short-term washing (10 s) of wheat seed with acetone before planting decreased their level only in seed of seven-day old seedling. Compared to the respective controls, this treatment did not affect the amount of these lipids in the green part of seedling that proved that de novo synthesis of 5-n-alkylresorcinols takes place in shoots. The very similar homolog profiles of these lipids in four- and seven-day-old shoots turned out to be markedly less diversified than those found in respective seed samples. Compared to the mature wheat caryopsis, the rise in the content of very-long-chain homologs was observed only in the oldest shoot. Their increased accumulation was probably connected with formation of cuticular layer providing the defensive barrier against various phytopathogens.

4-hexylresorcinol-induced protein expression changes in human umbilical cord vein endothelial cells as determined by immunoprecipitation high-performance liquid chromatography

4-Hexylresorcinol (4HR) is used as a food preservative and an ingredient of toothpaste and cosmetics. The present study was performed using 233 antisera to determine the changes in protein expression induced by 4HR in human umbilical cord vein endothelial cells (HUVECs), and evaluated the 4HR-induced effects in comparison with previous results (Kim et al., 2019). Similar to RAW 264.7 cells, 4HR-treated HUVECs showed decreases in the expression of the proliferation-related proteins, cMyc/MAX/MAD network proteins, p53/RB and Wnt/β-catenin signaling, and they showed inactivation of DNA transcription and protein translation compared to the untreated controls. 4HR upregulated growth factors (TGF-β1, β2, β3, SMAD2/3, SMAD4, HGF-α, Met, IGF-1) and RAS signaling proteins (RAF-B, p38, p-p38, p-ERK-1, and Rab-1), and induced stronger expression of the cellular protection-, survival-, and differentiation-related proteins in HUVECs than in RAW 264.7 cells. 4HR suppressed NFkB signaling in a manner that suggests potential anti-inflammatory and wound healing effects by reducing M1 macrophage polarization and increasing M2 macrophage polarization in both cells. 4HR-treated HUVECs tended to increase the ER stress mediators by upregulating eIF2AK3, ATF4, ATF6, lysozyme, and LC3 and downregulating eIF2α and GADD153 (CHOP), resulting in PARP-1/AIF-mediated apoptosis. These results indicate that 4HR has similar effects on the protein expression of HUVECs and RAW 264.7 cells, but their protein expression levels differ according to cell types. The 4HR-treated cells showed global protein expression characteristic of anticancer and wound healing effects, which could be alleviated simultaneously by other proteins exerting opposite functions. These results suggest that although 4HR has similar effects on the global protein expression of HUVECs and RAW 264.7 cells, the 4HR-induced molecular interferences in those cells are complex enough to produce variable protein expression, leading different cell functions. Moreover, HUVECs have stronger wound healing potential to overcome the impact induced by 4HR than RAW 264.7 cells.

Bioactive Components and Health Beneficial Properties of Whole Wheat Foods

Epidemiological studies have found that whole wheat consumption is inversely associated with the risk of chronic diseases, such as obesity, type 2 diabetes, cardiovascular diseases, and cancer. The health benefits of whole wheat foods are attributed to their bioactive components, including phytochemicals and dietary fiber. In this review, the current studies regarding bioactive components and their health-promoting roles and the underlying mechanisms were summarized and discussed. The current research advances in processing technologies capable of potentially enhancing the nutritional quality of wheat and wheat-based foods were also included. This review may promote the research, development, and consumption of whole wheat foods in reducing the risk of human chronic diseases.

The Strong Anti-Kinetoplastid Properties of Bee Propolis: Composition and Identification of the Active Agents and Their Biochemical Targets

The kinetoplastids are protozoa characterized by the presence of a distinctive organelle, called the kinetoplast, which contains a large amount of DNA (kinetoplast DNA (kDNA)) inside their single mitochondrion. Kinetoplastids of medical and veterinary importance include Trypanosoma spp. (the causative agents of human and animal African Trypanosomiasis and of Chagas disease) and Leishmania spp. (the causative agents of the various forms of leishmaniasis). These neglected diseases affect millions of people across the globe, but drug treatment is hampered by the challenges of toxicity and drug resistance, among others. Propolis (a natural product made by bees) and compounds isolated from it are now being investigated as novel treatments of kinetoplastid infections. The anti-kinetoplastid efficacy of propolis is probably a consequence of its reported activity against kinetoplastid parasites of bees. This article presents a review of the reported anti-kinetoplastid potential of propolis, highlighting its anti-kinetoplastid activity in vitro and in vivo regardless of geographical origin. The mode of action of propolis depends on the organism it is acting on and includes growth inhibition, immunomodulation, macrophage activation, perturbation of the cell membrane architecture, phospholipid disturbances, and mitochondrial targets. This gives ample scope for further investigations toward the rational development of sustainable anti-kinetoplastid drugs.

New Alkenylresorcinols with Cytotoxic and Antimicrobial Activities from the Leaves of Embelia schimperi

A phytochemical study of the methanol extract of the leaves of Embelia schimperi resulted in the isolation of three new alkenylresorcinols, 1:  - 3: , together with the known analogs 4:  - 7: . Their structures were established by a combination of spectroscopic techniques. Compounds 1:  - 7: exhibited moderate cytotoxic activity against human cervical cancer cells HeLa-S3 and more pronounced antimicrobial properties towards bacteria and filamentous fungi. The present study falls into an ongoing research project on the characterization of bioactive phenolic lipids from plants of the family Primulaceae.