Marie-José Battesti

Chemical and genetic differentiation of Corsican subspecies of Teucrium flavum L.

Corsica Island exhibited the particularity to display Teucrium flavum subsp. glaucum and subsp. flavum on the same territory with the same bioclimatic conditions. For the first time, volatile components extracted from aerial parts and genetic diversity of both Corsican T. flavum L. subspecies have been investigated through (i) the characterization of the chemical composition of essential oils and (ii) the study of three polymorphic genetic markers. Chemical analysis were performed using combination of capillary GC/RI, GC-MS after fractionation on column chromatography and the definition of the genetic structure were carried out using two chlororoplast markers (RPL32-TRNL and TRNL-F) and ribosomal nuclear markers (ITS region). According to statistical analysis, both subspecies were clearly distinguished by the chemical and genetic studies. Chemical compositions of oils from both subspecies were qualitatively similar but they differed by the normalized% abundances of their major components; oils from subsp. flavum were dominated by large amounts of hydrocarbon monoterpenes while oils obtained from subsp. glaucum were characterized by higher amounts of oxygenated compounds. The genetic analysis divided T. flavum L. populations in two groups, the first displayed subsp. glaucum populations and the latter group exhibited subsp. flavum populations. The presence of two groups is weakly consistent with chemical differentiation. These data suggest that the differences in the volatile composition of the two T. flavum subspecies depends more on the genetic background and less on environmental factors.

Chemical and genetic differentiation of two Mediterranean subspecies of Teucrium scorodonia L.

Chemical and genetic diversity of Teucrium scorodonia L. subsp. scorodonia from Corsica and T. scorodonia L. subsp. baeticum from western Algeria were investigated. Diversity within and among the two populations of subspecies was assessed according to the chemical composition of their essential oils, and genetic diversity was evaluated using three polymorphic genetic markers. Chemical analysis was performed using a combination of capillary GC-RI and GC/MS after fractionation using column chromatography. Genetic structures were mapped using two chloroplast markers (RPL32-TRNL and TRNL-F) and ribosomal nuclear markers (ITS region). The statistical analysis showed that the two subspecies were clearly distinguished by these chemical and genetic markers. The chemical composition of oil differed qualitatively and quantitatively between the subspecies. Corsican oil samples contained germacrene B (4.2-8.8%) and γ-elemene (2.6-5.7%), which were not detected in Algerian oil samples. The oils of the scorodonia and baeticum subspecies were dominated by sesquiterpene hydrocarbon compounds (75.6-82.9% and 69.6-79.4%, respectively), but they differed in oxygenated sesquiterpene content (3.1-8.9% and 8.4-20.3%, respectively). Neighbor-joining trees constructed from chloroplast DNA and ITS region sequences showed the existence of two groups associated with taxonomic and chemical characteristics. One group consisted of T. scorodonia subsp. scorodonia and the other of T. scorodonia subsp. baeticum, indicating that variation in the essential oil composition of T. scorodonia subspecies depends more on genetic background than environmental characteristics.

Characterization of Botanical and Geographical Origin of Corsican “Spring” Honeys by Melissopalynological and Volatile Analysis

Pollen spectrum, physicochemical parameters and volatile fraction of Corsican “spring” honeys were investigated with the aim of developing a multidisciplinary method for the qualification of honeys in which nectar resources are under-represented in the pollen spectrum. Forty-one Corsican “spring” honeys were certified by melissopalynological analysis using directory and biogeographical origin of 50 representative taxa. Two groups of honeys were distinguished according to the botanical origin of samples: “clementine” honeys characterized by the association of cultivated species from oriental plain and other “spring” honeys dominated by wild herbaceous taxa from the ruderal and/or maquis area. The main compounds of the “spring” honey volatile fraction were phenylacetaldehyde, benzaldehyde and methyl-benzene. The volatile composition of “clementine” honeys was also characterized by three lilac aldehyde isomers. Statistical analysis of melissopalynological, physicochemical and volatile data showed that the presence of Citrus pollen in “clementine” honeys was positively correlated with the amount of linalool derivatives and methyl anthranilate. Otherwise, the other “spring” honeys were characterized by complex nectariferous species associations and the content of phenylacetaldehyde and methyl syringate.

Pollen Diversity and Volatile Variability of Honey from Corsican Anthyllis hermanniae L. Habitat

Melissopalynological, physicochemical, and volatile analyses of 29 samples of Corsican ‘summer maquis’ honey were performed. The pollen spectrum was characterized by a wide diversity of nectariferous and/or polleniferous taxa. The most important were Anthyllis hermanniae and Rubus sp., associated with some endemic taxa. Castanea sativa was also determined in these honeys with a great variation. The volatile fraction was characterized by 37 compounds and dominated by phenolic aldehydes and linear acids. The major compounds were phenylacetaldehyde, benzaldehyde, and nonanoic acid. Statistical analysis of pollen and volatile data showed that 18 samples were characterized by a high abundance of phenylacetaldehyde, which might relate to the high amount of A. hermanniae and Rubus sp. Eleven other samples displayed a higher proportion of phenolic ketones and linear acids, which characterized the nectar contribution of C. sativa and Thymus herba‐barona, respectively.

Investigating the antibacterial action of Corsican honeys on nosocomial and foodborne pathogens

Honey is known for its medicinal uses, with compounds such as hydrogen peroxide or phenolic compounds. For the first time, the antibacterial activity of protected designation of origin (PDO) “Miel de Corse – Mele di Corsica” commercial Corsican honeys was investigated. According to the PDO recommendation, melissopalynological analysis were used to classify 11 Corsican honeys. They have been tested for antimicrobial action on seven foodborne and nosocomial bacterial strains by Minimum Inhibitory Concentration (MIC90) then statistical analyses helped to correlate their action on the different strains. The varietal range of honey samples were obtained by melissopalynological analysis leading to 2: “Spring”, 3 “Chestnut grove”, 1 “Summer maquis”, 2 “Honeydew maquis” and 1 “Autumn maquis” and 2 samples classified as “generic” Corsican honeys. 29 MIC values determined were under 10%. Only Enterococcus faecalis didn’t seem sensitive to the action of the honey. However, “Honeydew maquis”, “generic” Corsican honeys and 2 “Chestnut grove” honeys appeared as the most effective (MIC values ranging from under 5 to 9% on Pseudomonas aeruginosa and Staphylococcus aureus). The antimicrobial activity of PDO “Miel de Corse – Mele di Corsica” honeys demonstrate bacterial growth inhibition on 6 of the 7 bacterial strains. Now, an in-depth study must be performed to identify the mode of action of the active honeys.

Key role of hydrogen peroxide in antimicrobial activity of Spring, Honeydew maquis and Chestnut grove Corsican honeys on Pseudomonas aeruginosa DNA

In honeys, several molecules have been known for their antibacterial or wound healing properties. Corsican honeys just began to be tested for their antimicrobial activity with promising results on Pseudomonas aeruginosa. So, identification of active molecules and their mode of action was determined. Hydrogen peroxide concentrations were evaluated and, in parallel, the minimal inhibitory concentrations (MIC) values were performed with and without catalase. More, the quantity of phenolic compounds and ORAC assay were measured. Observation of antibacterial action was done using scanning electron microscopy (SEM) followed by plasmidic DNA extraction. MIC values of chestnut grove and honeydew maquis honeys vary between 7 and 8%, showing a strong antimicrobial capacity, associated with a plasmidic DNA degradation. When catalase is added, MIC values significatively increase (25%) without damaging DNA, proving the importance of H2O2. This hypothesis is confirmed by SEM micrographies which did not show any morphological damages but a depletion in bacterial population. Although, such low concentrations of H2O2 (between 23 μmol l−1 and 54 μmol l−1) cannot explain antimicrobial activity and might be correlated with phenolic compounds concentration. Thus, Corsican honeys seem to induce DNA damage when H2O2 and phenolic compounds act in synergy by a putative pro‐oxidant effect.