Chedia Aouadhi

Antidiarrhoeal, antimicrobial and antioxidant effects of myrtle berries (Myrtus communis L.) seeds extract

The present study was carried out to determine the antidiarrheal effects of myrtle (Myrtus communis L.) berries seeds aqueous extract (MBSAE) from Tunisia as well as the involvement of its antimicrobial and antioxidant properties in such protection.

Fatty acids composition of Tunisian Ziziphus lotus L. (Desf.) fruits and variation in biological activities between leaf and fruit extracts

This study was conceived to evaluate the essential fatty acids, secondary metabolites, antiradical and antimicrobial activities of unexploited Tunisian Ziziphus lotus L. The obtained results indicated that the major components of fatty acids were oleic acid (88.12%) and elaidic acid (7.88%). Leaves contained higher amount of total phenols, flavonoids and tannins than fruits, although both methanolic extracts had significant antioxidant activities. Significant correlations were observed between the total phenol or flavonoid contents in methanolic extracts and antioxidant activity estimated by using both 2,2′-diphenyl-1-picrylhydrazyl and 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulfonic radical-scavenging methods. In addition, both methanolic extracts exhibited strong antibacterial and antifungal activities. The inhibition zone diameters and the minimal inhibition concentration values were in the range of 10–17 mm and 3.1–50 mg/mL, respectively.

Optimization of nutrient-induced germination of Bacillus sporothermodurans spores using response surface methodology

Spores of Bacillus sporothermodurans are known to be contaminant of dairy products and to be extremely heat-resistant. The induction of endospore germination before a heat treatment could be an efficient method to inactivate these bacteria and ensure milk stability. In this study, the nutrient-induced germination of B. sporothermodurans LTIS27 spores was studied. Testing the effect of 23 nutrient elements to trigger an important germination rate of B. sporothermodurans spores, only D-glucose, L-alanine, and inosine were considered as strong independent germinants. Both inosine and L-alanine play major roles as co-germinants with several other amino acids. A central composite experimental design with three factors (L-alanine, D-glucose, and temperature) using response surface methodology was used to optimize the nutrient-induced germination. The optimal rate of nutrient-induced germination (100%) of B. sporothermodurans spores was obtained after incubation of spore for 60 min at 35 °C in presence of 9 and 60 mM of D-glucose and L-alanine, respectively. The results in this study can help to predict the effect of environmental factors and nutrients on spore germination, which will be beneficial for screening of B. sporothermodurans in milk after induction their germination. Moreover, the chosen method of optimization of the nutrient-induced germination was efficient in finding the optimum values of three factors.

In vitro antimicrobial activity of Pistacia lentiscus L. edible oil and phenolic extract

Pistacia lentiscus L. is known in some Tunisian forest area by its fixed oil used in traditional medicine as an antiseptic product. This investigation is the first to study the antimicrobial activity of P.lentiscus edible oil and its phenolic extract. Oil was extracted from fruits harvested from six provenances located in Tunisia. The antimicrobial activity was tested using disc diffusion assay and the broth dilution method. Kbouch and Sidi Zid oils were most efficient (p < 0.003) against, respectively, Staphylococcus aureus and Aspergillus niger with an inhibition zone of 9.33 mm. The phenolic extract had the largest spectrum of sensitive microorganisms. The minimum inhibitory concentration and minimum bactericidal concentration results showed that all strains were inhibited by both oil and extract.

Phenolic content, antioxidant capacity and antimicrobial activity of leaf extracts from Pistacia atlantica

Abstract The aim of this study was to investigate the secondary metabolites related to Pistacia atlantica Desf as well as their biological activities. Results show that using ethanol as a solvent exhibited the highest content of total phenolics and flavonoids (68.23 mg GAE g−1 of DW and 44 mg RE g−1 of DW), followed by aqueous one (20.07 mg GAE g−1 of DW and 15 mg RE g−1 of DW). Good correlation (Data not shown) was obtained between the DPPH radical-scavenging activities and total phenolics contents. Many similarities were observed between the results of the DPPH (IC50 = 32 and 200 μg mL−1) and ABTS (IC50 = 42 and 300 μg mL−1) assays. All tested extracts contained phenolic compounds exhibited an antimicrobial effect against Gram-positive and Gram-negative bacteria. Further, researches for identification and purification of phenolic compounds are required.

Comparison of phytochemical composition and biological activities of Rubus ulmifolius extracts originating from four regions of Tunisia.

In the current study, the phenolic composition, antioxidant and antimicrobial activities of extracts from Rubus ulmifolius Schott leaves harvested in four localities (Sejnen, Tabarka, Faija and Ain drahem) in Tunisia were investigated for the first time. Great differences were found for the chemical composition, total phenol contents and biological activities among the evaluated extracts. HPLC analysis of methanolic extracts showed that the dominant compounds were kaempferol 3‐O‐rutinoside and naringenine. In addition, significant correlations were observed between antioxidant activities and phenolic contents. In fact, leaves collected from Sejnen presented higher total phenol content (53.32 mg GAE/g DW) and antioxidant activities (IC50 = 39.40 mg/l) than the others samples. All extracts showed significant antimicrobial activity against six used bacteria with the inhibition zones diameters and minimal inhibitory concentration values were in the range of 8 – 16 mm and 6.25 – 25 mg/ml, respectively. The highest antimicrobial activities were recorded in Sejnen extract against Gram‐positive bacteria.

Chemical Composition, Antioxidant Potential, and Antibacterial Activity of Essential Oil Cones of Tunisian Cupressus sempervirens

The extraction yield of the essential oil (EO) extracted by hydrodistillation from the cones of Tunisian Cupressus sempervirens L. was of 0.518%. The chemical composition was analyzed by GC-MS. Results showed that this essential oil was mainly composed of monoterpene hydrocarbons (65%) with α-pinene as the major constituent (47.51%). Its antioxidant activity was ascertained by evaluating the total antioxidant capacity and also by evaluating its inhibitory effect against DPPH and ABTS radicals. In addition, it showed a strong antioxidant power against the DPPH (IC50 = 151 µg/mL) and ABTS (IC50 = 176.454 µg/mL) radicals scavenging. Moreover, its antibacterial activity was tested against different species of pathogenic bacteria (three Gram-positive and eight Gram-negative bacteria). The bacterial strains susceptible to the evaluated oil were Bacillus subtilis, Escherichia coli, Klebsiella oxytoca, Morganella morganii, Shigella, and Vibrio cholerae.

Chemical Composition of Ruta chalepensis Leaves Essential Oil and Variation in Biological Activities between Leaves, Stems and Roots Methanolic Extracts

Abstract: To our knowledge, this study is the first to investigate the biological activities of the methanolic extracts of leaves, roots and stems of Ruta chalepensis L. (Rutaceae) in Tunisia. The chemical composition of the essential oil extracted from R. chalepensis leaves was determined by GC-MS. The antioxidant activities of tested essential oil and the methanolic extracts of leaves, stems and roots of R. chalepensis were evaluated using DPPH and ABTS radicals scavenging tests. Their antimicrobial activities were achieved by disc diffusion method and broth dilution assay. The main components of the selected essential oil were menthol (43.92 %) and linalool (42.10 %). Significant differences were found between the total phenol contents and biological activities of the different parts of R. chalepensis. In addition, significant correlations were observed between antioxidant activities and phenolic contents for methanol extracts. In fact, leaves extract presented higher total phenol content than stems and roots extracts. The tested oil showed better antioxidant activity than methanolic extracts. The highest antioxidant activity was recorded in leaves methanolic extract. The latter showed strong antibacterial activity against tested microorganisms, whereas the evaluated oil remained almost inactive. The inhibition zones diameters and minimal inhibitrice concentration values for tested bacteria, which were sensible to different methanolic extracts, were in the range of 8-35 mm and 0.78-25 mg/ml, respectively. This study demonstrated that the R. chalepensis extract can be regarded as promising candidate for natural plant source of antioxidant and antimicrobial agents.