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Avaliação de propriedades biológicas em mel dos Açores – atividade antioxidante e antimicrobiana

Publication . Machado, Alexandra M.; Miguel, Maria da Graça; Vilas-Boas, Miguel; Faleiro, Maria Leonor; Figueiredo, Ana Cristina

O mel e os seus produtos derivados são geralmente consumidos devido às suas características nutricionais e terapêuticas, bem como igualmente empregues em fragrâncias ou cosméticos [1]. Em Portugal, existem nove denominações de origem protegida de mel reconhecidas, entre as quais a do mel dos Açores [2], cujas propriedades biológicas estão pouco estudadas. O objetivo deste trabalho consistiu no estudo de oito méis dos Açores, provenientes das ilhas de São Miguel, Santa Maria, Terceira e Pico, relativamente à quantificação do teor em compostos fenólicos totais e flavonoides, à determinação da atividade antioxidante e anti-inflamatória por métodos espetrofotométricos, bem como o controlo de qualidade microbiológico e a avaliação da atividade antimicrobiana. O teor de fenóis totais variou entre 12 μg e 460 μg equivalentes de ácido gálico (EAG)/g de mel e para os flavonóides entre 0,6 μg e 55 μg equivalentes de quercetina (EQ)/g de mel. A atividade antioxidante determinada pelo método ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) foi relativamente baixa nos oito méis, comparativamente ao padrão utilizado (Trolox), sendo apenas possível determinar o IC50 (concentração de amostra necessária para diminuir ou reduzir a concentração inicial do radical ABTS em 50%) de uma amostra, cujo valor foi 8 mg/mL. Relativamente à capacidade quelante de iões ferro(II), esta foi somente detetada em três amostras de mel, cujas percentagens de inibição variaram entre 5 e 18%. A captação do radical superóxido foi também avaliada. Os valores de IC50 variaram entre 23 e 73 mg/L. A capacidade de inibição da enzima xantina oxidase foi observada em cinco amostras de mel, sendo particularmente elevada numa delas. No que diz respeito ao controlo de qualidade microbiológico dos méis analisados, não foi observada contaminação microbiana. A atividade antimicrobiana dos oito méis foi testada contra Escherichia coli, Staphylococcus aureus, Candida albicans e Pseudomonas aeruginosa, tendo sido verificada ação inibitória dos oito méis para Escherichia coli, de quatro méis em Staphylococcus aureus e de três méis em Pseudomonas aeruginosa. Não foi observada atividade inibitória contra Candida albicans.

2018Conference object

Open access

Physicochemical characterization and antioxidant activity of honey with Eragrostis spp. pollen predominance

Publication . Aazza, Smail; Elamine, Youssef; El-Guendouz, Soukaïna; Lyoussi, Badiâa; Antunes, Maria Dulce; Estevinho, Leticia M.; Anjos, Ofélia; Carlier, Jorge D.; Costa, Maria Clara; Miguel, Maria da Graça

This study aimed to characterize the pollen and physicochemical profiles, and to evaluate the antioxidant capacity of six samples of Moroccan honey. The pollen grains of Eragrostis spp. were predominant in all samples (from a minimum of 46.58 ± 1.59% to 72.72 ± 2.43% as a maximum), exceeding the minimum (generally 45%) required for the monoflorality nomination of a honey sample, and suggestion a case of newly reported honey. The analyzed samples had low diastase activity and hydroxymethylfurfural (HMF) content. Potassium was the dominant element in practically all samples, except the sample with the highest Eragrostis spp. pollen percentage, which showed sodium predominance. The honey color ranged from water white to light amber, and positively correlated the concentrations of phenols, proline and the capacity for scavenging free radicals. However, great variability observed in all the analyzed parameters, and could not be explained by the variability of the Eragrostis spp. pollen percentage, which suggests a hypothesis of low concentrated nectar. Practical applications: The melissopalynological profile of honey is an important parameter for determining the type of honey (multifloral, monofloral, blossom, honeydew) and its relationship to the botanical and geographical provenance. There is generally a relationship between the pollen profile of honey and the biological properties. The physicochemical characterization, antioxidant activity and melissopalynological profile of Eragrostis honey was reported for the first time in this study. These data intend to contribute for the introduction of a new type of honey labeled as Eragrostis honey. At the same time, the evaluation of the antioxidant activity may also trigger the search of other biological properties with medicinal attributes for the new Eragrostis ssp. honey.

2018Journal article

Open access

Insight into the sensing mechanism of an impedance based electronic tongue for honey botanic origin discrimination

Publication . Elamine, Youssef; Inácio, Pedro M.C.; Lyoussi, Badiâa; Anjos, Ofélia; Estevinho, Leticia M.; Miguel, Maria da Graça; Gomes, Henrique L.

Animpedance based electronictongue was developed and used to discriminate honey of diﬀerent botanic origin. The e-tongue presented here is based on the small-signal frequency response of the electrical double-layer established between the honey solution and an array of four diﬀerent sensing units composed by gold, carbon, indium-tin-oxide, and doped silicon. The ability of the e-tongue to discriminate honey of diﬀerent ﬂoral origins was demonstrated by distinguishing honey from Bupleurum and Lavandula pollen prevalence. The honey ﬁngerprint obtained with the e-tongue was validated by parallel melissopalenogical analysis and physico-chemical methods. It is demonstrated that the e-tongue is very sensitive to changes on the honey electrical conductivity. Small diﬀerences in electrical conductivity are introduced by the presence of ionisable organic acids and mineral salts. Moreover, we propose that the sensitivity of the tongue to changes in electrical conductivity can be explored to probe other complex liquid substances.

2019Journal article

Open access

Zantaz honey “monoflorality”: chemometric applied to the routinely assessed parameters

Publication . Elamine, Youssef; Lyoussi, Badiâa; Anjos, Ofélia; Estevinho, Leticia M.; Aazza, Smail; Carlier, Jorge D.; Costa, Maria Clara; Miguel, Maria da Graça

The comparison of Zantaz honey samples harvested in Morocco in two different years was performed through chemometric analysis of routinely assessed parameters. The objective was to study how the pollen profile of this newly reported honey shapes its physicochemical characteristics as well as to determine its monoflorality threshold, which has not yet been defined. The predominance of B. spinosum pollen was confirmed in the majority of samples reaching 45%, generally requested for monoflorality declaration. The principal component analysis (PCA) was used for clustering and variables correlations. Pollen qualitative and quantitative differences could discriminate the samples belonging to both seasons when combined with the sugar analysis (59.44%) better than the combination with physicochemical parameters (pH, acidity, ash content, electrical conductivity and color) (60.62%). Positive correlation between the presence of B. spinosum pollen and melanoidins, color, fructose, moisture, trehalose, melezitose, iron, manganese and calcium could be seen. Integrating all the parameters except the pollen data allowed distinguishing two groups with significant differences (P < 0.05) in B. spinosum representability (58 ± 11.24% against 40 ± 15.98%). This may suggest that 40% is the monoflorality threshold of the Moroccan Zantaz honey, although a confirmation with sensorial analysis is required.

2019Journal article

Open access

Volatile characterization of different commercial honeys types from the Azores (Portugal)

Publication . Machado, Alexandra M.; Miguel, Maria da Graça; Vilas-Boas, Miguel; Figueiredo, Ana Cristina

Honey and beekeeping products are usually consumed due to their nutritional and therapeutic properties, being also used in fragrances or cosmetics [1]. The Azores have a specific endemic flora as well as climate and soil conditions that allow the production of a unique honey classified as Protected Designation of Origin (PDO), with multifloral or Pittosporum undulatum Vent. (“incenso”) botanical origin [2]. As part of a research program aiming to evaluate the existence of specific honey volatile markers, this work reports the volatile profile of eight commercial honeys from the Azores (São Miguel, Santa Maria, Terceira and Pico). The volatiles were isolated by hydrodistillation for 1 h and analysed by gas chromatography and gas chromatography-mass spectrometry. The acyclic hydrocarbons n-nonadecane, n-heneicosane, n-tricosane, n-pentacosane, n-heptacosane and n-nonacosane dominated in all samples. Saturated fatty acids were also identified, namely decanoic and hexadecanoic acids. 2-Furfural, benzaldehyde, phenylacetaldehyde, phenylethyl alcohol, limonene and oxygen-containing terpenes, cis- and trans-linalool oxides, linalool, α-terpineol and α-, β- and Y-eudesmol, were detected in lower amounts. Although no previous studies described the volatiles of Pittosporum flowers from the Azores, a comparison with the volatiles isolated from the mainland Pittosporum flowers [3] showed that limonene, linalool, α-terpineol and α-eudesmol were present both in the Azorean honey samples (0.05-0.5%) and in the mainland flowers (0.05-2.2%). Further studies will aim at evaluating both the volatiles of honey from the main botanical origin, and well as the honey‟s biological properties.

2018Conference object

Open access