Simultaneous determination of four phenolic components in citrus honey by high performance liquid chromatography using electrochemical detection

Phenolic profiles of Australian monofloral Eucalyptus, Corymbia, Macadamia and Lophostemon honeys via HPLC-DAD analysis

Australian honey samples from four botanical genera (Lophostemon, Eucalyptus, Macadamia and Corymbia) were investigated for their phenolic content. An improved phenolic extraction and high-performance liquid chromatography-diode array detection (HPLC-DAD) analysis method allowed for the rapid and reliable identification of phenolic compounds. A concentrated liquid-liquid extraction method with an acidified aqueous solution and acetonitrile was optimised to isolate phenolic compounds from the honey matrix. The concentrated extraction method improved sensitivity and permitted the identification of phenolics present at low concentrations (LOD: 0.012-0.25 mg/kg and LOQ: 0.040-2.99 mg/kg). The optimised HPLC-DAD chromatographic conditions gave stable retention times, improved peak separation and allowed for the inexpensive detection of each of the 109 phenolic compounds at their maximum absorbance wavelength. Out of the 109 phenolic compounds included in this study, 49 were identified in the Australian honeys tested. Furthermore, 25 of the 49 compounds were determined to be markers specific to honey floral origin.

Paper-Based Device for Phenolic Content Determination in Tea Extracts

INTRODUCTION

Phenolic compounds garner interest in developing medicines, nutraceuticals, and cosmeceuticals based on natural products. The quantity of phenolic compounds in a sample is commonly determined via spectrophotometry; however, this instrumented technique is relatively laborious and time consuming and requires a large amount of reagents.

OBJECTIVE

This work aimed to develop a simple, point-of-need colorimetric sensor to rapidly determine total phenolic content (TPC) in tea extracts.

METHODOLOGY

We developed a radial paper-based analytical device (PAD) for TPC determination based on the established colorimetric reaction between the Folin-Ciocâlteu reagent and phenols. The PAD was designed to enable quantitative (with image capturing device and color processing software) and semiquantitative (using a color palette reference card) determinations. Analytical performance and stability of the PAD were evaluated based on the color responses.

RESULTS

The PAD was successfully applied for the determination of phenolics in tea extracts obtained using several polar protic solvents, including water, methanol, and ethanol, with satisfactory accuracy (recovery of 95.5%-104%, 110%-116%, and 104%-110%, respectively) and precision (RSD < 9%). The obtained TPC values also agreed with those from visible spectrophotometry. Semiquantitative determination using the color reference card with three categories of TPC level (i.e., 0-100, 100-500, and 500-1000 mg gallic acid equivalent/L) provided > 95% accuracy. The devices were the most stable when stored at 4°C in a light-protected, vacuum-sealed container. The proposed PAD is promising for simple, rapid (~10-20 min), and accurate estimation of TPC in plant extracts.

Examining the Use of Polyphenols and Sugars for Authenticating Honey on the U.S. Market: A Comprehensive Review

The rise in honey production and imports into the United States necessitates the need for robust methods to authenticate honey origin and ensure consumer safety. This review addresses the scope of honey authentication, with a specific focus on the exploration of polyphenols and sugar markers to evaluate honeys in the U.S. In the absence of comprehensive federal standards for honey in the United States, challenges related to authenticity and adulteration persist. Examining the global landscape of honey authentication research, we observed a significant gap in the literature pertaining to U.S. honeys. While honeys from Europe, Australia, New Zealand, and Asia have been extensively studied, the decentralized nature of the U.S. honey market and the lack of comprehensive standards have limited the number of investigations conducted. This review consolidates the findings of global honey studies and emphasizes the need for further research studies on honey authenticity markers within the United States. We also explore previous studies on the U.S. that focused on identifying potential markers for honey authenticity. However, the inherent variability in polyphenol profiles and the lack of extensive studies of the sugar contents of honey on a global scale pose challenges to establishing universal markers. We conclude that by addressing these challenges, the field of research on polyphenols and sugars in honey can move toward more reliable and standardized methods. This advancement will enhance the use of polyphenols and other constituents like sugars as authenticity markers, ultimately benefiting both researchers and the honey industry in ensuring honey quality.

Analytical method for urinary homovanillic acid and 5-hydroxyindoleacetic acid levels using HPLC with electrochemical detection applied to evaluate children environmentally exposed to manganese

Homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) are the urinary metabolites of dopamine (DA) and serotonin (5-HA), respectively. We aimed to develop an extraction method for the determination of HVA and 5-HIAA, using strong anionic exchange cartridges combined with HPLC with electrochemical detection, and apply it to measure the levels of HVA and 5-HIAA in children living near a ferro-manganese alloy plant in Simões Filho, Brazil. The validated method showed good selectivity, sensitivity, precision, and accuracy. The limits of detection (LOD) were 4 and 8 μmol/L for 5-HIAA and HVA, respectively, in urine. Recoveries ranged from 85.8 to 94%. The coefficients of determination (R2 ) of the calibration curves were greater than 0.99. Spot urine samples of 30 exposed children and 20 nonexposed ones were processed accordingly. The metabolite levels in exposed and reference children were within the physiological ranges. The medians (range) for 5-HIAA and HVA of the exposed ones were 36.4 μmol/L (18.4-58.0) and 32.9 μmol/L ( Collapse

Key Words

• 5-HIAA
• HPLC-ECD
• HVA
• dopamine
• manganese exposure
• serotonin

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MESH Headings

• Humans
• Child
• Homovanillic Acid/urine
• Hydroxyindoleacetic Acid
• Chromatography, High Pressure Liquid/methods
• Manganese
• Dopamine/metabolism

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Grants

• JCB0029/2015 Fundação de Amparo à Pesquisa do Estado da Bahia

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Affiliation(s)

Mariana Silva Cardoso Graduate Program in Pharmacy, College of Pharmacy, Federal University of Bahia, Salvador, Brazil
Andrea Rebouças Rocha Graduate Program in Food Science, College of Pharmacy, Federal University of Bahia, Salvador, Brazil
José Antônio Souza-Júnior Laboratory of Toxicology, College of Pharmacy, Federal University of Bahia, Salvador, Brazil
José Antonio Menezes-Filho Graduate Program in Pharmacy, College of Pharmacy, Federal University of Bahia, Salvador, Brazil Graduate Program in Food Science, College of Pharmacy, Federal University of Bahia, Salvador, Brazil Laboratory of Toxicology, College of Pharmacy, Federal University of Bahia, Salvador, Brazil

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Citrus Honeys from Three Different Regions of Turkey: HPLC-DAD Profiling and in Vitro Enzyme Inhibition, Antioxidant, Anti-Inflammatory and Antimicrobial Properties with Chemometric Study

The objectives of the present study are to compare the phenolic profiles and biological activities of 15 citrus honey samples from three different locations in Turkey using a chemometric approach. The HPLC-DAD analysis was used to determine phenolic profiles. Nineteen phenolic compounds were identified. Gallic acid (107.14-717.04 μg/g) was recorded as the predominant compound. AF (Antalya-Finike) had the highest antioxidant activity in ABTS⋅+ (IC50 : 18.01±0.69 mg/mL), metal chelating (IC50 : 6.20±0.19 mg/mL) and CUPRAC (A0.50 : 12.05±0.68 mg/mL) assays, while it revealed the best anti-inflammatory activity against COX-2 (17.28±0.22 %) and COX-1 (43.28±0.91 %). AM (Antalya-Manavgat) was the most active in β-carotene-linoleic acid (IC50 : 10.05±0.19 mg/mL), anti-urease (38.90±0.69 %), anti-quorum sensing and antimicrobial activities. AKO1 (Adana-Kozan-1) in DPPH⋅ (IC50 : 34.25±0.81 mg/mL) assay, AKU1 (Antalya-Kumluca-1) in tyrosinase inhibition activity (37.73±0.38 %) assay, AKU2 (Antalya-Kumluca-2) in AChE (10.55±0.63 %) and BChE (9.18±0.45 %) inhibition activity assays showed the best activity. Chemometric tools were applied to the phenolic compositions and biological properties. PCA and HCA ensured that 15 citrus honey samples were grouped into 3 clusters. The results showed that myricetin, kaempferol, vanillin, protocatechuic acid, rosmarinic acid, rutin, vanillic acid, gallic acid, catechin and p-hydroxyphenyl acetic acid are phenolic compounds that can be used in the classification of citrus honeys.

Volatile markers as a reliable alternative for the correct classification of citrus monofloral honey

The pollen analysis to classify monofloral honey is an unresolved challenge specially when the pollen is under-represented as the case of citrus honey. Thus, this study assesses the validity of the volatile fraction to differentiate types of honey, with special attention to markers compounds of citrus honey that could permit their distinction. Unsupervised analysis (PCA and HCA) showed that the volatile fraction of honey containing Citrus sp. pollen, undoubtedly differentiates it from other types of honey. An OPLS model focused on citrus honey selected 5 volatile compounds (of the 123 found in all samples by GC-MS) as significant predictors of the currently used value of methyl anthranilate obtained by HPLC. The joint detection of 4 lilac-aldehydes and the volatile methyl-anthranilate has the advantage of providing more precise information. Therefore, it could be proposed as a consistent marker to ensure the correct classification of citrus honey, fostering its labelling reliability.

Effect of Liquefaction of Honey on the Content of Phenolic Compounds

Thermal liquefaction at low temperature is very time consuming and microwaves or an ultrasonic bath can be used to accelerate the process of dissolving sugar crystals. Phenolic compounds, such as phenolic acids or flavonoids, are an important group of secondary metabolites of plants and become honey from the nectar of blossoms. In this study, how the content of phenolic acids and flavones in honey were affected by liquefaction of honey using a microwave oven was studied. The concentration of tested compounds in untreated honey and in honey liquefied in a hot water bath, ultrasonic bath and microwave oven at four microwave power levels were determined by reversed phase liquid chromatography combined with multichannel electrochemical detection. A significant decrease in the content of all compounds was observed for all melting treatments. The phenolic compounds concentration decreased on average by 31.1-35.5% using microwave at intensities 270, 450 and 900 W and the time required for the sugar crystal melting was more than 20 times less than in the case of the 80 °C water bath. The temperature of samples after the end of microwave liquefaction was 76-89 °C. Significantly higher losses of phenolic compounds were observed during ultrasound treatment (48.5%), although the maximum temperature of honey was 45 °C, and at the lowest microwaves power (50.6%).

Chemical Composition and the Anticancer, Antimicrobial, and Antioxidant Properties of Acacia Honey from the Hail Region: The in vitro and in silico Investigation

In consideration of the emergence of novel drug-resistant microbial strains and the increase in the incidences of various cancers throughout the world, honey could be utilized as a great alternative source of potent bioactive compounds. In this context, this study pioneers in reporting the phytochemical profiling and the antimicrobial, antioxidant, and anticancer properties of Acacia honey (AH) from the Hail region of Saudi Arabia, assessed using in vitro and molecular docking approaches. The phytochemical profiling based on high-resolution liquid chromatography-mass spectrometry (HR-LCMS) revealed eight compounds and three small peptide-like proteins as the constituents. The honey samples exhibited promising antioxidant activities (DPPH-IC₅₀ = 0.670 mg/mL; ABTS-IC₅₀ = 1.056 mg/mL; β-carotene-IC₅₀ > 5 mg/mL). In the well-diffusion assay, a high mean growth inhibition zone (mGIZ) was observed against Staphylococcus aureus (48.33 ± 1.53 mm), Escherichia coli ATCC 10536 (38.33 ± 1.53 mm), and Staphylococcus epidermidis ATCC 12228 (39.33 ± 1.15 mm). The microdilution assay revealed that low concentrations of AH could inhibit the growth of almost all the evaluated bacterial and fungal strains, with the minimal bactericidal concentration values (MBCs) ranging from 75 mg/mL to 300 mg/mL. On the contrary, high AH concentrations were required to kill the tested microorganisms, with the minimal bactericidal concentration values (MBCs) ranging from approximately 300 mg/mL to over 600 mg/mL and the minimal fungicidal concentration values (MFCs) of approximately 600 mg/mL. The AH exhibited effective anticancer activity in a dose-dependent manner against breast (MCF-7), colon (HCT-116), and lung (A549) cancer cell lines, with the corresponding IC₅₀ values of 5.053 μg/mL, 5.382 μg/mL, and 6.728 μg/mL, respectively. The in silico investigation revealed that the observed antimicrobial, antioxidant, and anticancer activities of the constituent compounds of AH are thermodynamically feasible, particularly those of the tripeptides (Asp-Trp-His and Trp-Arg-Ala) and aminocyclitol glycoside. The overall results highlighted the potential of AH as a source of bioactive compounds with significant antimicrobial, antioxidant, and anticancer activities, which could imply further pharmacological applications of AH.

A Comprehensive Survey of Phenolic Constituents Reported in Monofloral Honeys around the Globe

The aim of this review is to provide a comprehensive overview of the large variety of phenolic compounds that have to date been identified in a wide range of monofloral honeys found globally. The collated information is structured along several themes, including the botanical family and genus of the monofloral honeys for which phenolic constituents have been reported, the chemical classes the phenolic compounds can be attributed to, and the analytical method employed in compound determination as well as countries with a particular research focus on phenolic honey constituents. This review covers 130 research papers that detail the phenolic constituents of a total of 556 monofloral honeys. Based on the findings of this review, it can be concluded that most of these honeys belong to the Myrtaceae and Fabaceae families and that Robinia (Robinia pseudoacacia, Fabaceae), Manuka (Leptospermum scoparium, Myrtaceae), and Chestnut (Castanea sp., Fagaceae) honeys are to date the most studied honeys for phenolic compound determination. China, Italy, and Turkey are the major honey phenolic research hubs. To date, 161 individual phenolic compounds belonging to five major compound groups have been reported, with caffeic acid, gallic acid, ferulic acid and quercetin being the most widely reported among them. HPLC with photodiode array detection appears to be the most popular method for chemical structure identification.

Monofloral Honeys as a Potential Source of Natural Antioxidants, Minerals and Medicine

Background: vegetative diversity is based on different climate and geographical origins. In terms of beekeeping, herbal diversity is strongly correlated to the production of a wide variety of honey. Therefore, based on the existing plant diversity in each country, multiple honey varieties are produced with different health characteristics. While beekeeping potential and consumption preferences are reflected in products’ variety, this leads to an increase in the region’s economy and extensive export. In the last years, monofloral honey has gained interest from consumers and especially in the medicinal field due to the presence of phytochemicals which are directly linked to health benefits, wound healing, antioxidant, anticancer and anti-inflammatory activities. Scope and approach: this review aims to highlight the physicochemical properties, mineral profiles and antioxidant activities of selected monofloral honeys based on their botanical and geographical origin. Moreover, this review focuses on the intercorrelation between monofloral honey’s antioxidant compounds and in vitro and in vivo activities, focusing on the apoptosis and cell proliferation inhibition in various cell lines, with a final usage of honey as a potential therapeutic product in the fight towards reducing tumor growth. Key findings and conclusions: multiple studies have demonstrated that monofloral honeys have different physicochemical structures and bioactive compounds. Useful chemical markers to distinguish between monofloral honeys were evidenced, such as: 2-methoxybenzoic acid and trimethoxybenzoic acid are distinctive to Manuka honey while 4-methoxyphenylacetic acid is characteristic to Kanuka honey. Furthermore, resveratrol, epigallocatechin and pinostrobin are markers distinct to Sage honey, whereas carvacrol and thymol are found in Ziziphus honey. Due to their polyphenolic profile, monofloral honeys have significant antioxidant activity, as well as antidiabetic, antimicrobial and anticancer activities. It was demonstrated that Pine honey decreased the MDA and TBARS levels in liver, kidney, heart and brain tissues, whereas Malicia honey reduced the low-density lipoprotein level. Consumption of Clover, Acacia and Gelam honeys reduced the weight and adiposity, as well as trygliceride levels. Furthermore, the antiproliferative effect of chrysin, a natural flavone in Acacia honey, was demonstrated in human (A375) and murine (B16-F1) melanoma cell lines, whereas caffeic acid, a phenolic compound found in Kelulut honey, proves to be significant candidate in the chemoprevention of colon cancer. Based on these features, the use of hiney in the medicinal field (apitherapy), and the widespread usage of natural product consumption, is gaining interest by each year.

The Use of Right Angle Fluorescence Spectroscopy to Distinguish the Botanical Origin of Greek Common Honey Varieties

The standardization of the botanical origin of honey reflects the commercial value and quality of honey. Nowadays, most consumers are looking for a unifloral honey. The aim of the present study was to develop a novel method for honey classification using chemometric models based on phenolic compounds analyzed with right angle fluorescence spectroscopy, coupled with stepwise linear discriminant analysis (LDA). The deconstructed spectrum from three-dimensional-emission excitation matrix (3D-EEM) spectra provided a correct classification score of 94.9% calibration and cross-validation at an excitation wavelength (λex) of 330 nm. Subsequently, a score of 81.4% and 79.7%, respectively, at an excitation wavelength (λex) of 360 nm was achieved. Each chemometric model confirmed its power through the external validation with a score of 82.1% for both. Differentiation could be correlated with hydroxycinnamic and hydroxybenzoic acids, which absorb in this region of the spectrum. Fluorescence spectroscopy constitutes a rapid and sensitive technique, which, when combined with the stepwise algorithm and LDA method, can be used as a reliable and predictive authentication tool for honey. This study indicates that the developed methodology is a promising technique for determination of the botanical origin of common Greek honey varieties. Our long-term ambition is to support producers and suppliers to remain in a competitive national and international market.

Quality, composition and health-protective properties of citrus honey: A review

Citrus honey is one of the most important monofloral honeys produced and consumed worldwide. This honey has pleasant sensorial characteristics, which include light color and typical aroma and flavor. Besides that, several constituents such as minerals, phenolic and volatile compounds, amino acids, sugars, enzymes, vitamins, methylglyoxal and organic acids are found in citrus honey. Moreover, potential biological properties have been associated with citrus honey. All these factors make it highly desired by consumers, increasing its market value, which can stimulates the practice of fraud. Also, citrus honey is susceptible to contamination and to inadequate processing. All these factors can compromise the quality, safety and authenticity of citrus honey. In this sense, this review aims to update and to discuss, for the first time, the data available in the literature about the physicochemical and the sensorial characteristics, composition, health properties, contamination, authenticity and adulteration of citrus honey. With this background, we aim to provide data that can guide future researches related to this honey.

Magnetic dual-template molecularly imprinted polymer based on syringe-to-syringe magnetic solid-phase microextraction for selective enrichment of p-Coumaric acid and ferulic acid from pomegranate, grape, and orange samples

Magnetic dual-template molecularly imprinted polymer (Fe3O4@SiO2-MDMIP) was prepared to enrich and determine both p-Coumaric acid (p-CA) and ferulic acid (FA) based on syringe-to-syringe magnetic solid-phase microextraction (SS-MSPME). The obtained MDMIP was characterized and recognized, and then its adsorbing performance was studied. Based on the results, the Fe3O4@SiO2-MDMIP indicated selective recognition towards p-CA and FA with large adsorption capacity. The optimization of MDMIP-SS-MSPME conditions (pH, Fe3O4@SiO2-MDMIP mass, NaCl concentration, number of cycle, and elution volume) were conducted using the central composite design (CCD). Under the optimum conditions, an effectual and a convenient method was established to determine p-CA and FA in pomegranate, grapes, and orange samples based on SS-MSPME coupling with high-performance liquid chromatography-ultraviolet (HPLC-UV). Our developed method showed the limit of detection (LOD) of 0.08 ng mL-1 for p-CA and 0.07 ng mL-1 for FA. The method also indicated good linearity with R2 > 0.99 and good recoveries of 85.12-94.96% with RSDs ≤ 5.58% spiked at three various concentration levels in pomegranate, grapes, and orange samples.

Profiling of phenolic flavorings using core-shell reversed-phase liquid chromatography with electrochemical detection at a boron-doped diamond electrode

A high-performance liquid chromatography (HPLC) method equipped with a boron-doped diamond (BDD) electrode was established for the simultaneous determination of phenol, 4-ethylphenol (4-EP), guaiacol, 4-ethylguaiacol (4-EG), 4-vinylguaiacol (4-VG), eugenol, and o-, m- and p-cresol. The separation was performed on a reversed-phase HALO C₁₈ core-shell column (3.0 × 50 mm, 2.7 µm) with a mobile phase comprising 10 mM formate, pH 3, and 15% acetonitrile (ACN) (v/v), a flow rate of 1.5 mL/min, corresponding to a total run time of 9 min. The electrochemical detection (ECD) was set at +1.5 V vs. Pd/H₂ in oxidative mode. Under optimized operating conditions, good linearity was obtained for the nine phenolics with corresponding coefficients of determination (R²) above 0.998. The limits of detection (LODs, S/N = 3) were 10 nM-1 µM, with an 80-fold increase in sensitivity for guaiacol achieved with ECD over ultraviolet (UV) detection. The sensitive and selective HPLC-ECD method was successfully applied for the identification and quantification of the nine phenolics in Islay, Irish, Scotch, and Highland whiskey samples, with significantly higher concentrations of the flavorings determined in Islay whiskey.

Determination of Phenolic Acids in Sugarcane Vinasse by HPLC with Pulse Amperometry

A reversed-phase liquid chromatographic separation with pulsed amperometric detection of phenolic acids at a glassy carbon electrode is described. Chromatographic separation was carried out in isocratic conditions using 0.20 mol·L^-1 acetic acid (pH 5.0)/water (80 : 20, v/v) as mobile phase under constant working potential mode of 0.80 V. Chromatographic peaks presented high resolution and separation. Calibration curves exhibited excellent correlation coefficients, above 0.995. Linear ranges of the analytes, in mg L^-1, were of 0.018-18 (gallic acid), 0.146-19 (vanillic acid), 0.13-17 (caffeic acid), 0.016-16 (ferulic acid), and 0.008-17 (p-coumaric acid), respectively. Limits of detection ranged from 1.6 to 97 μg·L^-1 and precision varied in 1.73-3.78% interval. Concentrations of 19 ± 0.51 mg·L^-1 and 7.8 ± 2.5 mg·L^-1 were found for vanillic and caffeic acids, respectively, in a sugarcane vinasse sample. Gallic, ferulic, and p-coumaric acids were not detected. Recovery results demonstrated that the proposed method is accurate, and it can be used to detect and quantify phenolic acids in sugarcane vinasse without any influence of interferents.

Honey Extracted Polyphenolics Reduce Experimental Hypoxia in Human Keratinocytes Culture

Hypoxic assault affects fundamental cellular processes and generates oxidative stress on healthy cells/molecules. Honey extracted polyphenolics (HEP) as a natural antioxidant reduced hypoxic cytotoxicity in this study. Different honey samples were physicochemically characterized to identify preferred (jamun) honey [pH 3.55 ± 0.04, conductivity (μs/cm) = 6.66 ± 0.14, water content % (w/w) = 14.70 ± 0.35, total solid content % (w/w) = 85.30 ± 0.35, phenol content (mg GAE/100 g) = 403.55 ± 0.35, flavonoid content (mg QE/100 g) = 276.76 ± 4.10, radical scavenging activity (% 500 μL) = 147.75 ± 3.13, catalase activity (absorbance at 620 nm) = 0.226 ± 0.01]. HEP was tested in different doses on hypoxic and normoxic cells (HaCaT) using viability and antioxidant assays. Cardinal molecular expressions such as cadherin-catenin-cytoskeleton complex (namely, E-cadherin, β-catenin, and F-actin), hypoxia marker (Hif 1 α), proliferation marker (Ki67), and epithelial master regulator (p63) were studied by immuno-cytochemisty (ICC) and qRT-PCR. The 0.063 mg/mL HEP demonstrated better vitality and functionality of HaCaT cells as per viability assay (*, P < 0.01) even under hypoxia. ICC and qRT-PCR observations indicated restoration of cellular survival and homeostasis under 0.063 mg/mL HEP after hypoxic assault. Furthermore, major spectral changes for nucleic acid and membrane phospholipid reorganizations by Fourier transform infrared spectroscopy illustrated a positive impact of 0.063 mg/mL HEP on hypoxic cells considering proliferation and cellular integrity. It was concluded that a specific dose of jamun HEP reduces hypoxic cytotoxicity.

Antioxidant and hepatoprotective activity of vitex honey against paracetamol induced liver damage in mice

Fourteen vitex honeys from China were investigated to evaluate its antioxidant and hepatoprotective activity against paracetamol-induced liver damage. All honey samples exhibited high total phenolic content (344-520 mg GAE per kg), total flavonoid content (19-31 mg Rutin per kg), and strong antioxidant activity in DPPH radical scavenging, ferric reducing antioxidant power and Ferrous ion-chelating ability. Nine phenolic acids were detected in vitex honey samples, in which caffeic acid was the main compound. Honey from Heibei Zanhuang (S2) ranked the highest antioxidant activity was orally administered to mice (5 g kg(-1), 20 g kg(-1)) for 70 days. In high-dose (20 g kg(-1)), vitex honey pretreatment resulting in significant increase in serum oxygen radical absorbance capacity (15.07%) and decrease in Cu(2+)-mediate lipoprotein oxidation (80.07%), and suppression in alanine aminotransferase (75.79%) and aspartate aminotransferase (74.52%), enhancement in the superoxide dismutase and glutathione peroxidase activities and reduction in malondialdehyde (36.15%) and 8-hydroxy-2'-deoxyguanosine (19.6%) formation compared with paracetamol-intoxicated group. The results demonstrated the hepatoprotection of vitex honey against paracetamol-induced liver damage might attribute to its antioxidant and/or perhaps pro-oxidative property.

Recent Advances in the Analysis of Phenolic Compounds in Unifloral Honeys

Honey is one of the most renowned natural foods. Its composition is extremely variable, depending on its botanical and geographical origins, and the abundant presence of functional compounds has contributed to the increased worldwide interest is this foodstuff. In particular, great attention has been paid by the scientific community towards classes of compounds like phenolic compounds, due to their capability to act as markers of unifloral honey origin. In this contribution the most recent progress in the assessment of new analytical procedures aimed at the definition of the qualitative and quantitative profile of phenolic compounds of honey have been highlighted. A special emphasis has been placed on the innovative aspects concerning the extraction procedures, along with the most recent strategies proposed for the analysis of phenolic compounds. Moreover, the centrality of validation procedures has been claimed and extensively discussed in order to ensure the fitness-for-purpose of the proposed analytical methods. In addition, the exploitation of the phenolic profile as a tool for the classification of the botanical and geographical origin has been described, pointing out the usefulness of chemometrics in the interpretation of data sets originating from the analysis of polyphenols. Finally, recent results in concerning the evaluation of the antioxidant properties of unifloral honeys and the development of new analytical approaches aimed at measuring this parameter have been reviewed.

Nectar Attracts Foraging Honey Bees with Components of Their Queen Pheromones

Floral nectar often contains chemicals that are deterrent to pollinators, presenting potential challenges to outcrossing plant species. Plants may be able to co-opt pollinator chemical signals to mitigate the negative effects of nectar deterrent compounds on pollination services. We found that buckwheat (Fagopyrum esculentum) and Mexican sunflower (Tithonia diversifolia) produce nectar with abundant phenolics, including three components of the Apis honeybee queen mandibular pheromone (QMP). In addition, these nectars contain a non-pheromonal phenolic, chlorogenic acid (CA), which was toxic to honeybees, and T. diversifolia nectar also contained isochlorogenic acid (IA). Fresh nectar or solutions containing nectar phenolics reduced Apis individual feeding compared to sucrose solutions. However, freely foraging bees preferred solutions with QMP components to control solutions, and QMP components over-rode or reversed avoidance of CA and IA. Furthermore, prior exposure to the presence or just the odor of QMP components removed the deterrent effects of CA and IA. By mimicking the honey bee pheromone blend, nectar may maintain pollinator attraction in spite of deterrent nectar compounds.

Buckwheat Honey Attenuates Carbon Tetrachloride-Induced Liver and DNA Damage in Mice

Buckwheat honey, which is widely consumed in China, has a characteristic dark color. The objective of this study was to investigate the protective effects of buckwheat honey on liver and DNA damage induced by carbon tetrachloride in mice. The results revealed that buckwheat honey had high total phenolic content, and rutin, hesperetin, and p-coumaric acid were the main phenolic compounds present. Buckwheat honey possesses super DPPH radical scavenging activity and strong ferric reducing antioxidant power. Administration of buckwheat honey for 10 weeks significantly inhibited serum lipoprotein oxidation and increased serum oxygen radical absorbance capacity. Moreover, buckwheat honey significantly inhibited aspartate aminotransferase and alanine aminotransferase activities, which are enhanced by carbon tetrachloride. Hepatic malondialdehyde decreased and hepatic antioxidant enzymes (superoxide dismutase and glutathione peroxidase) increased in the presence of buckwheat honey. In a comet assay, lymphocyte DNA damage induced by carbon tetrachloride was significantly inhibited by buckwheat honey. Therefore, buckwheat honey has a hepatoprotective effect and inhibits DNA damage, activities that are primarily attributable to its high antioxidant capacity.

Identification of monofloral honeys using HPLC-ECD and chemometrics

A total of 77 jujube, longan and chaste honey samples were collected from 18 different areas of China. Thirteen types of phenolic acids in the honey samples were analysed using high-performance liquid chromatography with electrochemical detection (HPLC-ECD). Moreover, HPLC-ECD fingerprints of the monofloral honey samples were established. From the analysis of the HPLC-ECD fingerprints, common chromatography peak information was obtained, and principal component analysis and discriminant analysis were performed using selected common chromatography peak areas as variables. By comparing with phenolic acids as variables, using a chemometric analysis which is based on the use of common chromatography peaks as variables, 36 honey samples and 41 test samples could be correctly identified according to their floral origin.

Analysis of 10 metabolites of polymethoxyflavones with high sensitivity by electrochemical detection in high-performance liquid chromatography

Polymethoxyflavones (PMFs) have been known as a type of bioactive flavones that possess various beneficial biological functions. Accumulating evidence demonstrated that the metabolites of PMFs, that is, hydroxyl PMFs (OH-PMFs), had more potent beneficial biological effects than their corresponding parent PMFs. To facilitate the further identification and quantification of OH-PMFs in biological samples, the aim of this study was to develop a methodology for the simultaneous determination of 10 OH-PMFs using high-performance liquid chromatography (HPLC) coupled with electrochemistry detection. The HPLC profiles of these 10 OH-PMFs affected by different chromatographic parameters (different organic composition in mobile phases, the concentration of trifluoroacetic acid, and the concentration of ammonium acetate) are fully discussed in this study. The optimal condition was selected for the following validation studies. The linearity of calibration curves, accuracy, and precision (intra- and interday) at three concentration levels (low, middle, and high concentration range) were verified. The regression equations were linear (r > 0.9992) over the range of 0.005-10 μM. The limit of detection for 10 OH-PMFs was in the range of 0.8-3.7 ng/mL (S/N = 3, 10 μL injection). The recovery rates ranged from 86.6 to 108.7%. The precisions of intraday and interday analyses were less than 7.37 and 8.63% for relative standard deviation, respectively. This validated method was applied for the analysis of a variety of samples containing OH-PMFs. This paper also gives an example of analyzing the metabolites of nobiletin in mouse urine using the developed method. The transformation from nobiletin to traces of 5-hydroxyl metabolites has been discovered by this effective method, and this is the first paper to report such an association.

Antioxidant properties of jujube honey and its protective effects against chronic alcohol-induced liver damage in mice

The antioxidant potential of jujube honey, one of the most widely consumed honeys in China, has never been determined fully. In this study, jujube honey from six geographical origins in China was analyzed for individual phenolic acid, total phenolic content, and the antioxidant effect in chronic alcohol-related hepatic disease in mice. The results showed that jujube honey from Linxian of Shanxi province contained higher phenol levels, exhibited DPPH antioxidant activity, ferric ion reducing antioxidant power (FRAP) and protective effects against DNA damage. Treatment with jujube honey (Shanxi Linxian) for 12 weeks significantly inhibited serum lipoprotein oxidation, reduced the impact of alcoholism on aspartate aminotransferase (AST) and alanine aminotransferase (ALT). It also inhibited the generation of 8-hydroxy-2-deoxyguanosine (8-OHdG), lowered the levels of malondialdehyde (MDA) and increased the activity of hepatic glutathione peroxidase (GSH-Px). The study indicates that jujube honey exerts potent antioxidant activity and significant protection in hepatic disorders associated with chronic alcoholism. The protective effect is attributed to its antioxidant mechanisms and inhibition of oxidative degradation of lipids.

Dispersive liquid-liquid microextraction for the determination of flavonoid aglycone compounds in honey using liquid chromatography with diode array detection and time-of-flight mass spectrometry

A rapid approach for the determination of eight flavonoid aglycone compounds, baicalein, hesperitin, fisetin, naringenin, chrysin, myricetin, quercetin and kaempferol, in honey samples and related products has been optimized and validated. The enriched extracts obtained by dispersive liquid-liquid microextraction (DLLME) were analyzed by liquid chromatography with diode array detection coupled to electrospray ionization and time-of-flight mass spectrometry (LC-DAD-ESI-ToFMS). For DLLME, using acetonitrile and chloroform as disperser and extractant solvents, respectively, a Taguchi experimental method was applied to find the optimal combination of following six factors: disperser and extractant solvent volumes, sodium chloride concentration, pH of the aqueous phase, honey mass and centrifugation time. The sedimented organic phase obtained after centrifugation was evaporated, reconstituted in acetonitrile and submitted to LC. The matrix effect was evaluated, and it was concluded that sample quantification can be carried out against aqueous external standards when using DAD and by matrix-matched calibration in the case of ToFMS. Detection limits in the ranges of 0.4-4 and 0.01-0.5 ng g(-1) were obtained for DAD and ToFMS, respectively. Satisfactory recovery values between 80 and 111% were obtained for three spiked samples. Honeys and related products were analyzed and flavonoids were found within a wide range.

Analysis of flavonoids in honey by HPLC coupled with coulometric electrode array detection and electrospray ionization mass spectrometry

The analysis of flavonoids in unifloral honeys by high-performance liquid chromatography (HPLC) coupled with coulometric electrode array detection (CEAD) is described. The compounds were extracted by a nonionic polymeric resin (Amberlite XAD-2) and then separated on a reversed phase column using gradient elution. Quercetin, naringenin, hesperetin, luteolin, kaempferol, isorhamnetin, and galangin were detected in a coulometric electrode array detection system between +300 and +800 mV against palladium reference electrodes, and their presence was additionally confirmed by HPLC coupled with electrospray ionization mass spectrometry. The method was applied to analysis of 19 honeys of different varieties and origin. The limits of detection and quantitation ranged between 1.6 and 8.3 μg/kg and 3.9 and 27.4 μg/kg, respectively. The recoveries were above 96% in fluid and above 89% in creamy honeys. Some of these honeys (melon, pumpkin, cherry blossom, dandelion, maple, and pine tree honey) were investigated for their flavonoid content and profile for the first time. Differences between honeys were observed both in flavonoid concentrations and in the flavonoid profiles. The flavonoid concentrations ranged from 0.015 to 3.4 mg/kg honey. Galangin, kaempferol, quercetin, isorhamnetin, and luteolin were detected in all investigated honeys, whereas hesperetin occurred only in lemon and orange honeys and naringenin in lemon, orange, rhododendron, rosemary, and cherry blossom honeys.