Ismahen Essaidi

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.

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.

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.