Nabiha Bouzouita

Volatile Constituents and Antimicrobial Activity of Lavandula stoechas L. Oil from Tunisia

Abstract An oil obtained from the dried leaves of Lavandula stoechas L. in 0.77% yield was analyzed by capillary GC and GC/MS. Fenchone (68.2%) and camphor (11.2%) were the main components of the 28 identifed molecules. This oil has been tested for antimicrobial activity against six bacteria, and two fungi. The results showed that this oil was active against all of the tested strains; Staphylococcus aureus was the more sensitive strain.

Chemical Composition of Laurus nobilis Oil from Tunisia

Abstract An oil obtained from the dried leaves of Laurus nobilis (origin Tunisia) in 1.5% yield was analyzed by capillary GC and GC/MS. 1,8-Cineole (42.3%) and the α-terpinyl acetate (11.2%) were the main components of the 24 constituents identified.

Betalain and Phenolic Compositions, Antioxidant Activity of Tunisian Red Beet (Beta vulgaris L. conditiva) Roots and Stems Extracts

In the present study, betalains content, phenolic composition, and antioxidant activity of different parts of red beet (Beta vulgaris L. conditiva) (i.e., roots and stems) were compared. Crude extract of root showed the highest betalain content with a maximum of 53 ± 4 mg betanin eq and 46 ± 3 mg vulgaxantin I eq g−1 of extract stems showed higher total phenolic concentration than roots, ranging between 2.0 ± 0.4 and 14.6 ± 0.5 mg gallic acid eq−1 of extract. Chemical composition was analyzed using LC-MS. Betalains (vulgaxanthin I, betanin, and isobetanin) and phenolics (gallic acid, ferulic acid, chlorogenic acid, caffeic acid, vanillic acid, syringic acid, ellagic acid myricetin, quercetin, rutin, kampferol) were identified in roots and stems. Betalain extract obtained from roots showed higher antioxidant activity than extract obtained from stems.

Improvement of the composition of Tunisian myrtle berries (Myrtus communis L.) alcohol extracts.

Different extracts from myrtle berries were obtained using alcohol-water mixtures as an extraction medium in the range of 60-90% (v/v) to study the extraction efficiency in the preparation of myrtle liqueur. Flavonoids and anthocyanins were identified by high-performance liquid chromatography (HPLC) coupled with electrospray mass spectrometry and quantified during the maceration period by HPLC coupled with ultraviolet/visible detection. The antioxidant activity was tested by the 2,2-diphenyl-1-picrylhydrazyl assay. Dry matter, pH, and color parameters (L, a, b) were also analyzed. At the end of the maceration period, EE80 showed better anthocyanins stability and the highest total antioxidant activity (87.5%). These results suggest that the use of ethanol 80% provides the extract with the best characteristics for liqueur preparation. The present study contributes significantly to increase the marketing appeal of myrtle berries.

Phytochemical and Biological Investigation of Two Diplotaxis Species Growing in Tunisia: D. virgata & D. erucoides

A phytochemical investigation of Diplotaxis virgata D.C. and D. erucoides (L.) D.C. (Brassicaceae) offered to the isolation of two new flavonoids isorhamnetin-3-O-α-l-glucopyranoside (1) and rhamnetin-3,3ʹ-di-O-β-d-glucopyranoside (2), respectively. Their structures have been elucidated from the extended spectroscopic methods, including 1D- and 2D-NMR, UV and mass spectrometry analysis and by comparison with literature data. The fatty acid composition of the hexane extracts of the two species was also investigated by using GC-MS. The antioxidant activity of ethanol, ethyl acetate, n-butanol extracts and the isolated compounds from the two species was evaluated using DPPH and ABTS+ scavenging assays. All the tested samples showed an efficient radical scavenging ability, with IC50 values ranging from 16–40 µg/mL for the DPPH and from 17–44 µg/mL for the ABTS+ assays. In addition, the antibacterial activity of the prepared extracts and compounds 1 and 2, determined by well diffusion agar method against two Gram positive and five Gram negative bacteria, was evaluated and the results showed significant effects against all strains used.

Fibre concentrate from artichoke (Cynara scolymus L.) stem by-products: Characterization and application as a bakery product ingredient

The potential of fibre concentrate from artichoke stem by-product in bakery application was investigated. The elaboration of fibre concentrate was characterized by an extraction yield of 48.5%. The chemical composition showed high total dietary fibre (85 g/100 g d.m) and low lipid contents (0.5 g/100 g d.m). The fibre concentrate showed good water holding capacity (8.17 g/g) and high oil holding capacity (16.17 g/g). The effect of fibre concentrate incorporation to wheat dough, at level of 2%, on the rheological properties and physical characteristics of bread was also evaluated. The results showed that the addition of fibre concentrate in wheat flour significantly improved (P < 0.05) dough properties inducing an increase of water absorption, stability and tenacity, and a reduction of extensibility and softening in comparison to the dough without fibre. The colour values of the crust and crumb were significantly (P < 0.05) altered by the addition of fibre concentrate. It was also found that incorporation of fibre concentrate to bread produced a comparable specific volume and enhanced the shelf life, as textural studies revealed.

Chemical Composition of Cyperus rotundus L. Tubers Essential Oil from the South of Tunisia, Antioxidant Potentiality and Antibacterial Activity against Foodborne Pathogens

Abstract The chemical composition of Cyperus rotundus L. tubers essential oil from the South of Tunisia was analyzed using GC-FID and GC-MS. Fifty compounds were identified representing 84.6% of the total oil. A new chemotype was found in Tunisia. This essential oil was characterized by sesquiterpenes abundance (78.3%) mainly represented by cyperene (15.2%) and cyperotundone (19.7%). The essential oil (EO) was further fractionated into three fractions (F1: n-pentane, F2: n-pentane/diethyl ether (95/5) and F3: diethyl ether). The antioxidant activity of the EO and its fractions was tested using the1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging test and β-carotene bleaching method. Results showed that the whole EO was more active than the fractions with an effective concentration (EC) of 0.85 ± 0.03 mg/mL and an antioxidant activity coefficient (AAC) of 396.0 ± 2.4. The antimicrobial activity of the EO and its fractions was evaluated using the disc diffusion method against six foodborne pathogens and results showed that Staphylococcus aureus was the most inhibited bacterium with an inhibition diameter of 15.2 ± 0.8 mm for the whole EO.

Chemical Composition and Antioxidant Activity of Myrtus communis L. Floral Buds Essential Oil

Abstract The essential oil of Mytrus communis L. floral buds from Tunisia was analyzed by GC and GC/MS. Thirty-seven compounds were identified, representing 98.7% of the total oil. The major constituents were described as α-pinene (48.9%) and 1,8-cineole (15.3%). The antioxidant activity of the obtained essential oil was investigated by means of β-carotene bleaching (BCB) test and free radical scavenging assay using 2,2-diphenyl-1-picrylhydrazyl radical (DPPH). Results showed that Myrtus communis L. floral buds essential oil has a significant antioxidant effect when tested by each method respectively. The strong antioxidant activity of the studied oil can be attributed to the high content in hydrocarbon monoterpenes and oxygenated monoterpenes.

Effect of acid hydrolysis on alizarin content, antioxidant and antimicrobial activities of Rubia tinctorum extracts

Purpose The paper aims to analyse the effect of acid hydrolysis on the chemical composition and the biological activities of Rubia tinctorum collected from the south of Tunisia. It proposes to clarify the relationship between alizarin content and the antioxidant and antimicrobial activities of Rubia extract. Design/methodology/approach The paper opted for analytical tools (HPLC) and the in-vitro study of biological activities, namely, the antioxidant activity which is evaluated using the radical scavenging assay (ABTS) and ferric reducing power assay (FRAP); the antimicrobial activity is tested using the wells agar diffusion method. Findings The paper provides information about the positive effect of acid hydrolysis, namely, the enhancement of alizarin content in the extract which has increased its antioxidant and antimicrobial activities. Originality/value This paper fulfils an identified need to study the relationship between the chemical composition, biological activities and colour enhancement.

Detection of Organo-Sulphur Volatiles in Allium sativum by FactorialDesign

The influence of temperature and time of heating on the production and composition of organosulfur compounds (OSC) in Allium sativum were investigated in a two-level design with two factors. The organosulfur compounds were identified by Headspace-GC-MS. It was established that temperature plays an important role in the regulation of the production of monosulfides and trisulfides. The effect of both negative and positive temperatures on the production and decomposition of OSC were showed. Although, monosulfides and trisulfides were totally absent at the beginning of incubation, several mono- and trisulfides were detected in high proportions at 120°C, during the 30 minutes incubation period. It appears that high temperature reduces the amount of disulfides, which are converted to monosulfides and trisulfides.