Physicochemical properties, total phenolic content, and antioxidant activity of chestnut, rhododendron, acacia and multifloral honey

Chemometric classification of chestnut honeys from different regions in Turkey based on their phenolic compositions and biological activities

The objective of this study was to investigate the phenolic composition and biological properties of chestnut honeys of 41 stations in Turkey's the Black Sea and Marmara regions. A total of sixteen phenolic compounds and organic acids were detected using HPLC-DAD and levulinic, gallic, protocatechuic, vanilic, trans-cinnamic acids and (4-hydroxyphenyl) ethanol were identified in all studied chestnut honeys. Antioxidant activities were measured by ABTS^•+, β-carotene-linoleic acid, CUPRAC, DPPH^•, and metal chelating assays. Antimicrobial activities were carried out against gram positive, gram negative bacteria and Candida species using well diffusion test. Anti-inflammatory activities were evaluated against COX-1 and COX-2 whereas enzyme inhibitory activities were assessed on AChE, BChE, urease, and tyrosinase. The chemometric classification of chestnut honeys were carried out using PCA and HCA and it was seen that some phenolic compounds contributed significantly to the classification of chestnut honeys from various geographical origin.

An Investigation into Chestnut Honeys from Artvin Province in Turkiye: Their Physicochemical Properties, Phenolic Profiles and Antioxidant Activities

The aim of this study was to investigate the physicochemical properties, phenolic compounds, and antioxidant activities of eight chestnut honey samples collected from Artvin province in Turkiye. The honey samples' phenolic profiles were analyzed using reverse phase high performance liquid chromatography (RP-HPLC). All honeys were monofloral, and the quantities of chestnut sativa pollen ranged from 56 % to 80 %. Total phenolic and flavonoid contents and ferric reducing/antioxidant power (FRAP) values were assessed. The pH and moisture values of the honeys ranged between 4.60 and 5.40 and between 17.60 % and 19.00 %, respectively. Electrical conductivity (EC) and Hunter color L values ranged between 0.56 and 1.12 mS/cm and between 43.16 and 67.60, respectively. Proline values ranged from 876 to 1246 mg/kg. The diastase activities of all honeys were high, ranging between 18.28 and 26.30 DU. The mean of total phenolic, total flavonoid and total antioxidant (FRAP) levels in the samples were 72.79±0.03 mg GAE/100 g, 2.25±00.03mg QE/100 g, and 312.67±2.85 μmol FeSO₄ /100 g, respectively. Almost all of the 19 phenolic standards studied were detected in the samples, with catechin, chrysin, caffeic acid, caffeic acid phenethyl ester (CAPE) and gallic acid being determined as major components. In conclusion, the honeys from the Artvin region were high-quality chestnut honeys, with high polyphenolic contents and diversity and high apitherapeutic potentials.

Risks for human health related to the presence of grayanotoxins in certain honey

The European Commission asked EFSA for a scientific opinion on the risks for human health of the presence of grayanotoxins (GTXs) in 'certain honey' from Ericaceae plants. The risk assessment included all structurally related grayananes occurring with GTXs in 'certain' honey. Oral exposure is associated with acute intoxication in humans. Acute symptoms affect the muscles, nervous and cardiovascular systems. These may lead to complete atrioventricular block, convulsions, mental confusion, agitation, syncope and respiratory depression. For acute effects, the CONTAM Panel derived a reference point (RP) of 15.3 μg/kg body weight for the sum of GTX I and III based on a BMDL₁₀ for reduced heart rate in rats. A similar relative potency was considered for GTX I. Without chronic toxicity studies, an RP for long-term effects could not be derived. There is evidence for genotoxicity in mice exposed to GTX III or honey containing GTX I and III, showing increased levels of chromosomal damage. The mechanism of genotoxicity is unknown. Without representative occurrence data for the sum of GTX I and III and consumption data from Ericaceae honey, acute dietary exposure was estimated based on selected concentrations for GTX I and III reflecting concentrations measured in 'certain' honeys. Applying a margin of exposure (MOE) approach, the estimated MOEs raised health concerns for acute toxicity. The Panel calculated the highest concentrations for GTX I and III below which no acute effects would be expected following 'certain honey' consumption. The Panel is 75% or more certain that the calculated highest concentration of 0.05 mg for the sum of GTX I and III per kg honey is protective for all age groups regarding acute intoxications. This value does not consider other grayananes in 'certain honey' and does not cover the identified genotoxicity.

Antioxidant Activity and Phenolic Compound Identification and Quantification in Western Australian Honeys

This study reports on the total phenolic content and antioxidant activity as well as the phenolic compounds that are present in Calothamnus spp. (Red Bell), Agonis flexuosa (Coastal Peppermint), Corymbia calophylla (Marri) and Eucalyptus marginata (Jarrah) honeys from Western Australia. The honey's total phenolic content (TPC) was determined using a modified Folin-Ciocalteu assay, while their total antioxidant activity was determined using FRAP and DPPH assays. Phenolic constituents were identified using a High Performance Thin-Layer Chromatography (HTPLC)-derived phenolic database, and the identified phenolic compounds were quantified using HPTLC. Finally, constituents that contribute to the honeys' antioxidant activity were identified using a DPPH-HPTLC bioautography assay. Based on the results, Calothamnus spp. honey (n = 8) was found to contain the highest (59.4 ± 7.91 mg GAE/100 g) TPC, followed by Eucalyptus marginata honey (50.58 ± 3.76 mg GAE/100 g), Agonis flexuosa honey (36.08 ± 4.2 mg GAE/100 g) and Corymbia calophylla honey (29.15 ± 5.46 mg GAE/100 g). In the FRAP assay, Calothamnus spp. honey also had the highest activity (9.24 ± 1.68 mmol Fe²⁺/kg), followed by Eucalyptus marginata honey (mmol Fe²⁺/kg), whereas Agonis flexuosa (5.45 ± 1.64 mmol Fe²⁺/kg) and Corymbia calophylla honeys (4.48 ± 0.82 mmol Fe²⁺/kg) had comparable FRAP activity. In the DPPH assay, when the mean values were compared, it was found that Calothamnus spp. honey again had the highest activity (3.88 ± 0.96 mmol TE/kg) while the mean DPPH antioxidant activity of Eucalyptus marginata, Agonis flexuosa, and Corymbia calophylla honeys were comparable. Kojic acid and epigallocatechin gallate were found in all honeys, whilst other constituents (e.g., m-coumaric acid, lumichrome, gallic acid, taxifolin, luteolin, epicatechin, hesperitin, eudesmic acid, syringic acid, protocatechuic acid, t-cinnamic acid, o-anisic acid) were only identified in some of the honeys. DPPH-HPTLC bioautography demonstrated that most of the identified compounds possess antioxidant activity, except for t-cinnamic acid, eudesmic acid, o-anisic acid, and lumichrome.

Enhancement of the Antioxidant Capacity of Thyme and Chestnut Honey by Addition of Bee Products

Honey consumption and imports have increased in recent years, and it is considered by consumers to be a healthy alternative to more commonly used sweeteners. Honey contains a mixture of polyphenols and antioxidant compounds, and the botanical origin and geographical area of collection play an important role on its chemical composition. The present study investigated the physicochemical properties, total phenolic content and antioxidant capacity of Spanish thyme honey and chestnut honey, and their mixtures with royal jelly (2% and 10%) and propolis (2% and 10%). The analysis of the physicochemical parameters of both honey samples showed values within the established limits. Propolis showed the highest value of total phenolic content (17.21–266.83 mg GAE/100 g) and antioxidant capacity (DPPH, ORAC and ABTS assays; 0.63–24.10 µg eq. Tx/g, 1.61–40.82 µg eq. Tx/g and 1.89–68.54 µg eq. Tx/g, respectively), and significantly reduced ROS production in human hepatoma cells. In addition, mixtures of honey with 10% of propolis improved the results obtained with natural honey, increasing the value of total phenolic content and antioxidant capacity. A significant positive correlation was observed between total phenolic compounds and antioxidant capacity. Therefore, the antioxidant capacity could be attributed to the phenolic compounds present in the samples, at least partially. In conclusion, our results indicated that thyme and chestnut honey supplemented with propolis can be an excellent natural source of antioxidants and could be incorporated as a potential food ingredient with biological properties of technological interest, added as a preservative. Moreover, these mixtures could be used as natural sweeteners enriched in antioxidants and other bioactive compounds.

Antimicrobial and Antioxidant Activity of Different Honey Samples from Beekeepers and Commercial Producers

Honey contains compounds with antioxidant and antibacterial capacities, such as phenolic compounds and carotenoids. The current analysis evaluates the antioxidant and antibacterial activity of 100 honey samples from beekeepers from Slovakia and commercially purchased ones. Honey samples were diluted to 50%, 25%, 12.5%, and 6.25% concentrations. The antimicrobial activity of honey samples was evaluated against three Gram-positive, three Gram-negative bacteria, and four Candida spp. by well diffusion method. The highest antimicrobial effect of all honey concentrations was expressed as the size of the inhibition zone and was found against Pseudomonas aeruginosa among Gram-negative bacteria, Bacillus subtilis among Gram-positive bacteria, and Candida tropicalis among yeasts. Antibiotics used in the study showed the highest antimicrobial effect compared to all concentrations of honey samples. Slovakian honey from beekeepers and commercial honey samples from the Slovak market showed variable inhibitory effectiveness against microorganisms. The honey concentration of 50% was found the most effective. Lower concentrations of honey exhibited no effect against yeasts. The best antioxidant activity was found in a sample of buckwheat honey yielding 70.83% of DPPH inhibition and 2373.85 μg/g TEAC. Overall, better antioxidant activity was evaluated in honeydew honey.

Comparative palynological, physicochemical, antioxidant and antibacterial properties of Romanian honey varieties for biomedical applications

The aim of this study was to investigate the melissopalynology, physicochemical characteristics, antioxidant and antibacterial activity of seven honey samples harvested from different geographical regions and climates of Romania. The melissopalynological analysis revealed that monofloral and multifloral samples contained a wide diversity of minor pollen types from Romanian flora. The moisture, pH and free acidity values were within international limit. HPLC analysis indicated high content of fructose and glucose and low content of sucrose. Bioactive compounds including proteins, phenolics, flavonoids and ascorbic acid were present in variable quantities, according to the botanical origin and geographical area. The highest phenolics and ascorbic acid content was in multifloral honeys from Crisana mountain and meadow and the extrafloral honeydew honey. The same honey samples have exerted free radical scavenging and antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa. The free radical scavenging activity was strongly correlated to phenolics and ascorbic acid content, while the antimicrobial activity was medium correlated only to phenolics content. In conclusion, the selected Romanian honey samples with best antioxidant and antimicrobial activity could be further tested for the development of novel biomedical products.

Plasticizing effect of Apis mellifera honey on whey protein isolate films

The aims of this study were to analyze the plasticizing effect of Apis mellifera honey on the mechanical, physicochemical and optical properties of whey protein isolate (WPI) films and to compare the results collected with the plasticizing effect of glycerol on WPI-films. Response surface was applied to optimize the amounts of WPI and glycerol in order to obtain films with higher tensile strength (TS), moderate elongation, and lower water vapor permeability so that they could be used as reference films. Honey was added at different concentrations (60%, 80%, and 100%) of g honey/100 g WPI, as a plasticizer to the WPI-films. In comparison to glycerol-plasticized films, an increase in the percentage of honey produced a reduction of 20 ± 10 to 48 ± 0.5% of TS, a 66 ± 0.5% lower in Young's modulus (WPI-films with 100% honey), and an increase of 186 ± 11% in elongation at break in the WPI-films with 100% honey. Honey-plasticized WPI-films were from 29 ± 11 to 43 ± 3% less permeable to water vapor than glycerol-plasticized WPI films. The mechanical characteristics of the 80% honey formulation did not differ significantly from those of the reference film (p > 0.05). Findings from this study indicate that honey has great potential as a plasticizer in WPI-films.

Physicochemical Characterization and Biological Properties of Pine Honey Produced across Greece

Pine honey is a honeydew honey produced in the East Mediterranean region (Greece and Turkey) from the secretions of the plant sucking insect Marchalina hellenica (Gennadius) (Coccoidea: Marchalini-dae) feeding on living parts of Pinus species. Nowadays, honeydew honey has attracted great attention due to its biological activities. The aim of this study was to study unifloral pine honey samples produced in Greece regarding their physicochemical parameters and antioxidant and antibacterial activity against five nosocomial and foodborne pathogens. These honeys showed physicochemical and microscopic characteristics within the legal limits, except for diastase activity, a parameter known to be highly variable, depending on various factors. Substantially higher levels of H₂O₂ were estimated compared to other types of honeydew honey, whereas protein content was similar. The total phenolic content was 451.38 ± 120.38 mg GAE/kg and antiradical activity ranged from 42.43 to 79.33%, while FRAP values (1.87 to 9.43 mmol Fe⁺²/kg) were in general higher than those reported in the literature. Various correlations could be identified among these parameters. This is the first attempt to investigate in depth the antibacterial activity of pine honey from Greece and correlate it with honey quality parameters. All tested honeys exerted variable but significant antibacterial activity, expressed as MIC and MBC values, comparable or even superior to manuka honey for some tested samples. Although honey antibacterial activity is mainly attributed to hydrogen peroxide and proteins in some cases (demonstrated by elevated MICs after catalase and Proteinase K treatment, respectively), no strong correlation between the antibacterial activity and hydrogen peroxide concentration or total protein content was demonstrated in this study. However, there was a statistically significant correlation of moisture, antioxidant and antibacterial activity against Klebsiella pneuomoniae, as well as antioxidant and antibacterial activity against Salmonella ser. Typhimurium. Interestingly, a statistically significant negative correlation has been observed between diastase activity and Staphylococcus aureus antibacterial activity. Overall, our data indicate multiple mechanisms of antibacterial activity exerted by pine honey.

Phenolic Compounds in Honey and Their Relationship with Antioxidant Activity, Botanical Origin, and Color

Honey has been employed since antiquity due to its sensory, nutritional, and therapeutic properties. These characteristics are related to its physical and chemical composition. For example, phenolic compounds are substances that can determine antioxidant activity, as well as sensory characteristics, and can be employed as biomarkers of floral and geographical origin. This has generated a growing interest in the study of phenolic compounds and their influence in the intrinsic properties of this beekeeping product. This review aims to summarize, analyze, and update the status of the research that demonstrates the role of phenolic compounds in antioxidant activity, botanical-geographical origin, and the sensory characteristics of honey. These phenolic compounds, according to various results reported, have great relevance in honey's biological and functional activity. This leads to research that will link phenolic compounds to their floral, geographical, productive, and territorial origin, as well as some sensory and functional characteristics.