Analysis of Polyphenols in Honey: Extraction, Separation and Quantification Procedures

Differential in vitro cytotoxic effects and metabolomic insights into raw and powdered Manuka honey through UPLC-Q-TOF-MS

Manuka honey (MH) has garnered much attention due to its remarkable antimicrobial, anticancer, immunomodulatory and wound-healing properties. This study compared the antiproliferative effects of raw and powdered MH (pMH) on various human and murine cancer cell lines. A detailed metabolomics analysis was also carried out using untargeted ultrahigh-performance liquid chromatography-quadrupole-time-of-flight-mass spectrometry (UPLC-Q-TOF-MS) to compare the constituents in raw MH and pMH. The results of the viability studies showed that both raw MH and pMH caused a dose-dependent inhibition of tumor cell growth at concentrations of > 1% w/v (equivalent to ~ 10 mg/ml). A differential susceptibility to MH was observed among the cell lines with the human MDA-MB-231 and A549 cells and murine B16.F10 cells being relatively resistant to MH while the murine MC38 colorectal adeno-carcinoma cells showing the most sensitivity. The effect of raw MH and pMH on cell viability was validated using 2 indepndent assays. Metabolomics analysis detected 2440 compounds, out of which 833 were successfully identified. Among these, 90 phytochemical compounds, predominantly comprising terpenoids, flavonoids, coumarins and derivatives, and phenylpropanoic acids, and 79 lipids were identifiable. Significant differences in 5 metabolite classes, including flavonoids, phenols, terpenoids, carbohydrates, and organic acids were observed between the raw and pMH. Moreover, several altered metabolic pathways were identified in pMH compared to raw MH, such as energy metabolism, amino acid metabolism, and various other pathways that collectively influence biological functions associated with cellular growth, signaling, and stress response.

Biochemical Profile and Antioxidant Properties of Propolis from Northern Spain

The antioxidant, anti-inflammatory, and antimicrobial characteristics of propolis, a bioactive compound collected from hives, have prompted its use in the food sector in recent times. This study investigated the physicochemical characteristics, phenolic profile, and antioxidant capacity of 31 propolis extracts collected from Northern Spain. The physicochemical composition (resins, waxes, ashes mineral content, and heavy metals) was within the allowable regulatory limits. The analysis of bioactive compounds enabled the identification of 51 constituents: flavonoids (apigenin, catechin, chrysin, quercetin, and pinocembrin) and phenolic acids (caffeic, ferulic, and coumaric). The mean value of total polyphenols was 42.72 ± 13.19 Pinocembrin-Galangin Equivalents/100 g, whereas a range between 1.64 ± 0.04 and 4.95 ± 0.36 Quercetin Equivalents (QE) g/100 g was found for total flavonoids content. The determination of bioactivities revealed significant antioxidant capacity using DPPH (1114.28 ± 10.39 µM Trolox Equivalents and 3487.61 ± 318.66 µM Vitamin C Equivalents). Resin content in propolis samples was positively and significantly correlated with both polyphenols (rho = 0.365; p = 0.043) and flavonoid composition (rho = 0.615; p = 0.000) as well as the antioxidant capacity TEAC DPPH (rho = 0.415; p = 0.020). A multiple regression analysis modeled the correlation between resin composition, flavonoids, and TEAC DPPH values, yielding a significant regression equation (R2 = 0.618; F (2,28) = 22.629; p < 0.000; d = 2.299). Therefore, evaluating physicochemical parameters and biological activities provides a promising framework for predicting propolis' quality and antioxidant properties, thus suggesting its potential as a functional and bioactive compound for the food industry.

The Development and Application of a HPTLC-Derived Database for the Identification of Phenolics in Honey

This study reports on the development and validation of a HPTLC-derived database to identify phenolic compounds in honey. Two database sets are developed to contain the profiles of 107 standard compounds. Rich data in the form of Rf values, colour hues (H°) at 254 nm and 366 nm, at 366 nm after derivatising with natural product PEG reagent, and at 366 nm and white light after derivatising with vanillin–sulfuric acid reagent, λ max and λ min values in their fluorescence and λ max values in their UV-Vis spectra as well as λ max values in their fluorescence and UV-Vis spectra after derivatisation are used as filtering parameters to identify potential matches in a honey sample. A spectral overlay system is also developed to confirm these matches. The adopted filtering approach is used to validate the database application using positive and negative controls and also by comparing matches with those identified via HPLC-DAD. Manuka honey is used as the test honey and leptosperine, mandelic acid, kojic acid, lepteridine, gallic acid, epigallocatechin gallate, 2,3,4-trihydroxybenzoic acid, o-anisic acid and methyl syringate are identified in the honey using the HPTLC-derived database.

NMR Metabolite Profiling in the Quality and Authentication Assessment of Greek Honey—Exploitation of STOCSY for Markers Identification

Honey is a natural, healthy commodity and is probably among the most complex foods produced by nature. It is the oldest recorded and certainly the only natural sweetener that can be used by humans without any further processing. Nowadays, the increase in honey’s value, along with its growing list of healthy attributes, has made the present raw material a prime target for adulteration. In the current study, NMR-based metabolite profiling in combination with chemometrics was applied in the quality control of Greek honeys from northeastern Aegean islands. Moreover, statistical total correlation spectroscopy (STOCSY) was employed for the first time as a dereplication and structural elucidation tool in the honey biomarker identification process. A total of 10 compounds were successfully identified in honey total extracts via 1H NMR spectroscopy. Compounds such as 5-(hydroxymethyl)furfural, methyl syringate, a mono-substituted glycerol derivative and 3-hydroxy-4-phenyl-2-butanone, among others, were identified as potential biomarkers related to the botanical and geographical origin of the samples. High-Resolution Mass Spectrometry (HRMS) was used as an additional verification tool on the identified compounds.

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.

Determination of the Carbohydrate Profile and Invertase Activity of Adulterated Honeys after Bee Feeding

The higher demand for honey from consumers, combined with its limited availability, has led to different types of honey adulteration, causing substantial economic as well as negative impacts on consumers’ nutrition and health. Therefore, a need has emerged for reliable and cost-effective quality control methods to detect honey adulteration to ensure both the safety and quality of honey. To simulate the process with those applied by beekeepers in real-time, bee colonies were fed with different types of bee feeding (sugar syrup, candy paste and commercial syrup). The produced samples were analyzed for their carbohydrate profile and their invertase activity with the aim to find the effects of bee feeding on the quality of the final product. Honey samples produced after feeding with commercial syrup presented low fructose (22.9 %) and glucose (31.7 %) concentrations and high content of maltose (20.1%), while the samples that came from bee feeding with sugar syrup and candy paste had high concentrations of sucrose (6.2 % and 3.2 %, respectively), exceeding in some cases the legislative limits. Moreover, the samples coming from sugar feeding had lower values of invertase activity, while the group with inverted syrup was clearly discriminated through multi-discriminant analysis. The invertase activity of control samples was found at 153.7 U/kg, which was significantly higher compared to the other groups. The results showed that bee feeding during honey production might lead to adulteration, which can be detected through routine analyses, including the carbohydrate profile and the invertase activity.

Antioxidant Properties and Characterization of Heterotrigona itama Honey from Various Botanical Origins according to Their Polyphenol Compounds

Stingless bee honey is a good source of antioxidants, which is attributed to the phenolic compounds. The type and concentration of phenolic compounds in honey can be affected by botanical origin. Therefore, in this study, Heterotrigona itama honey from three botanical origins (gelam, acacia, and starfruit) was evaluated for its antioxidant activity and profile of phenolic compounds. Apis mellifera honey was used as a comparison. Antioxidant activity and profile of phenolic compounds in honey were determined using spectrophotometric and chromatographic methods, respectively. The total phenolic content (TPC), total flavonoids content (TFC), free radical scavenging activity (IC50), and ferric reducing antioxidant power (FRAP) of H. itama were ranged between 52.64 and 74.72 mg GAE/100 g honey, 10.70–25.71 mg QE/100 g honey, 11.27–24.09 mg/mL, and 77.88–164.88 µmol FeSO4.7H2O/100 g honey, respectively. The findings showed that the antioxidant activity and phenolic and flavonoid contents in H. itama honey were significantly higher than Apis honey. Benzoic acid and taxifolin were found as the predominant phenolic acid and flavonoid in all samples. However, chrysin was significantly highest in Apis honey than stingless bee honey. This result suggested that chrysin can be used as a chemical marker to distinguish Apis honey from stingless bee honey. Gallic acid and ellagic acid were found as the chemical marker for gelam honey, salicylic acid, benzoic acid, and 4-hydroxybenzoic acid for starfruit honey while ferulic acid for acacia honey.

Evaluating the Presence and Contents of Phytochemicals in Honey Samples: Phenolic Compounds as Indicators to Identify Their Botanical Origin

Honey is a natural product well known for its beneficial properties. It contains phytochemicals, a wide class of nutraceuticals found in plants, including compounds with highly demonstrated antimicrobial and antioxidant capacities as phenolic compounds and flavonoids. The main goal of this work is the development of a miniaturized and environmentally friendly methodology to obtain the phenolic profile of Galician honeys (Northwest Spain) from different varieties such as honeydew, chestnut, eucalyptus, heather, blackberry and multi-floral. The total phenolic content (TPC) and antioxidant activity (AA) were also evaluated. As regards sample preparation, miniaturized vortex (VE) and ultrasound assisted extraction (UAE) employing aqueous-based solvents were performed. Individual quantification of 41 target phenolic compounds was carried out by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Results revealed the presence of 25 phenolic compounds in the 91 analyzed samples, reaching concentrations up to 252 µg g⁻¹. Statistical tools such as analysis of variance (ANOVA) and principal component analysis (PCA) were employed to obtain models that allowed classifying the different honeys according to their botanical origin. Obtained results, based on TPC, AA and ∑phenolic compounds showed that significant differences appeared depending on the honey variety, being several of the identified phenol compounds being responsible of the main differentiation.

Continuous and pulsed ultrasound-assisted extraction of carob's antioxidants: Processing parameters optimization and identification of polyphenolic composition

Polyphenols in carobs have recently attracted great attention due to their wide range of biological and health promoting effects. A comprehensive study was conducted to find an optimum method for the extraction, purification and characterization of these valuable bioactive substances. Under this framework, the ultrasound-assisted extraction (UAE) of polyphenols from carob pulp was optimized by the maximization of the yield in total phenolics using response surface methodology. In particular, the effects of solid-solvent ratio, solvent concentration, extraction time, sonication amplitude, and sonication mode were investigated and optimized using a complete experimental design. In comparison to conventional extraction techniques, UAE offered a higher yield of antioxidants and a shorter processing time. Solid-phase extraction was evaluated as a clean-up strategy prior to the electrophoretic analysis of extracts. The results from the analysis of real samples revealed the predominance of gallic acid and highlighted the great influence of the ripening stage on carobs composition.

Classification of Unifloral Honeys from SARDINIA (Italy) by ATR-FTIR Spectroscopy and Random Forest

Nowadays, the mislabeling of honey floral origin is a very common fraudulent practice. The scientific community is intensifying its efforts to provide the bodies responsible for controlling the authenticity of honey with fast and reliable analytical protocols. In this study, the classification of various monofloral honeys from Sardinia, Italy, was attempted by means of ATR-FTIR spectroscopy and random forest. Four different floral origins were considered: strawberry-tree (Arbutus Unedo L.), asphodel (Asphodelus microcarpus), thistle (Galactites tormentosa), and eucalyptus (Eucalyptus calmadulensis). Training a random forest on the infrared spectra allowed achieving an average accuracy of 87% in a cross-validation setting. The identification of the significant wavenumbers revealed the important role played by the region 1540-1175 cm-1 and, to a lesser extent, the region 1700-1600 cm-1. The contribution of the phenolic fraction was identified as the main responsible for this observation.

Recent Trends in the Application of Chromatographic Techniques in the Analysis of Luteolin and Its Derivatives

Luteolin is a flavonoid often found in various medicinal plants that exhibits multiple biological effects such as antioxidant, anti-inflammatory and immunomodulatory activity. Commercially available medicinal plants and their preparations containing luteolin are often used in the treatment of hypertension, inflammatory diseases, and even cancer. However, to establish the quality of such preparations, appropriate analytical methods should be used. Therefore, the present paper provides the first comprehensive review of the current analytical methods that were developed and validated for the quantitative determination of luteolin and its C- and O-derivatives including orientin, isoorientin, luteolin 7-O-glucoside and others. It provides a systematic overview of chromatographic analytical techniques including thin layer chromatography (TLC), high performance thin layer chromatography (HPTLC), liquid chromatography (LC), high performance liquid chromatography (HPLC), gas chromatography (GC) and counter-current chromatography (CCC), as well as the conditions used in the determination of luteolin and its derivatives in plant material.

Phenolic compounds profile and biochemical properties of honeys in relationship to the honey floral sources

INTRODUCTION

Honey has been considered to have therapeutic properties since ancient times and among the factors responsible for such activity are phenolic compounds including phenolic acids and flavonoids from different natural sources.

OBJECTIVE

This study investigated the phenolic compounds profile and bioactive properties of different honey types from Romanian flora in order to develop reliable tools for honey floral origin, thus contributing to the honey traceability in the European Union context.

MATERIAL AND METHODS

Thirty-three honey samples were examined, including unifloral (acacia and rape), polyfloral, honeydew honeys and mixture honeys. Phenolic acids and flavonoids were isolated from the water soluble honey matrix using a solid-phase extraction (SPE) method and analysed by ultra-high-performance liquid chromatography diode array detector electrospray ionisation mass spectrometry (UHPLC-DAD-ESI/MS). Honey bioactive properties were measured in honey dissolved in 80% ethanol using UV-visible spectrophotometric methods. Multivariate statistical tools (principal component analysis and hierarchical clustering analysis) were used for honey classification.

RESULTS

The results of this study confirm that honey samples had similar, but quantitatively different, phenolic acids and flavonoids profiles and bioactive properties, related with honey floral source. Coloured honeys, such as honeydew honey, show high phenolic composition and bioactive properties and implicitly a high therapeutic potential compared with the other floral honeys.

CONCLUSION

Distinctive clusters obtained by principal component analysis enabled us to consider that honeydew and polyfloral honeys could be distinguished from acacia and rape honey with the analytical methods developed. Based on this study, the methods might be promising tools for honey traceability, which needs to be explored on a larger set of samples with different regional floral origins in future studies.