Phenolic Content, Antioxidant, Antibacterial, and Anti-Acetylcholinesterase Activities of Biosynthesized and Characterized Silver Nanoparticles from Tunisian Medicinal Lichen Species.

Lichens produce a myriad of bioactive compounds that can be exploited as reducing and capping agents in the green process of synthesizing nanoparticles. In this study, we exploit a simple, environmentally safe method for synthesizing silver nanoparticles (AgNPs), using aqueous extracts of three lichen species (Lobaria pulmonaria, Ramalina farinacea, and Evernia prunastri) for the first time. Characterization showed that the three lichen species selected could be perfectly suitable as reducing agents to produce AgNPs. First, ultraviolet-visible spectroscopy confirmed the presence of metallic silver with a maximum absorbance at 425 nm. Second, Fourier transform infrared spectroscopy analysis confirmed the chemical compounds involved in reduction. Third, the elemental composition of AgNPs was illustrated by energy dispersive X-ray spectroscopy. Finally, scanning electron microscopy images displayed the size and shape of biosynthesized particles. The prepared extracts containing AgNPs showed high contents of phenolic compounds and high antioxidant activities on three assays (DPPH, ferric reducing power, and chelating power). Moreover, since bacteria are developing resistance to many common antibiotics, AgNPs produced in an environmentally safe method are an interesting replacement. The antibacterial assessment revealed more effective activity against Gram-negative than Gram-positive bacteria and a bactericidal effect against all strains tested. In this study, we present a pioneering evaluation of acetylcholinesterase inhibition by lichen-based AgNPs. The three extracts exhibited strong enzyme inhibition, with IC50 values of 3.46 ± 0.09, 3.59 ± 0.02, and 4.34 ± 0.03 mg/mL for L. pulmonaria, R. farinacea, and E. prunastri, respectively. The green approach presented would encourage the nontoxic production of AgNPs, suggesting pharmaceutical applications.

Tunisian Native Mentha pulegium L. Extracts: Phytochemical Composition and Biological Activities.

Mint species (Lamiaceae family) have been used as traditional remedies for the treatment of several diseases. In this work, we aimed to characterize the biological activities of the total phenolic and flavonoid contents of Mentha pulegium L. extracts collected from two different regions of Tunisia. The highest amounts of total phenols (74.45 ± 0.01 mg GAE/g DW), flavonoids (28.87 ± 0.02 mg RE/g DW), and condensed tannins (4.35 ± 0.02 mg CE/g DW) were found in the Bizerte locality. Methanolic leaf extracts were subjected to HPLC-UV analysis in order to identify and quantify the phenolic composition. This technique allowed us to identify seven phenolic compounds: two phenolic acids and five flavonoid compounds, such as eriocitrin, hesperidin, narirutin, luteolin, and isorhoifolin, which were found in both extracts with significant differences between samples collected from the different regions (p < 0.05). Furthermore, our results showed that the methanolic extract from leaves collected from Bizerte had the highest antioxidant activities (DPPH IC50 value of 16.31 µg/mL and 570.08 µmol Fe2+/g, respectively). Both extracts showed high radical-scavenging activity as well as significant antimicrobial activity against eight tested bacteria. The highest antimicrobial activities were observed against Gram-positive bacteria with inhibition zone diameters and MIC values ranging between 19 and 32 mm and 40 and 160 µg/mL, respectively. Interestingly, at 10 µg/mL, the extract had a significant effect on cell proliferation of U87 human glioblastoma cells. These findings open perspectives for the use of Mentha pulegium L. extract in green pharmacy, alternative/complementary medicine, and natural preventive therapies for the development of effective antioxidant, antibacterial, and/or antitumoral drugs.

Mycochemical Contents and Biological Activities of Three Wild Mushrooms from Tunisia.

The objective of the current study was to compare the mycochemical composition and biological activities of two extracts (aqueous extracts and ground materials prepared with the QUENCHER approach) of three wild Basidiomy-cetes, Agaricus vaporarius, Lactarius deliciosus, and Lycoperdon pyriforme, collected from a region located in the north of Tunisia. Mycochemical analysis in terms of total phenolic compounds, flavonoids, flavanols, proanthocyanidins, and tannin contents were determined. In addition, the antioxidant activities of the mushrooms were evaluated using three assays (2,2-di-phenyl-1-picrylhydrazyl free radical scavenging, ferric reducing antioxidant power assay, and metal chelating assay). Their antimicrobial activities were assessed against seven bacterial species. The obtained data revealed the presence of significant differences between secondary metabolites and the biological activities of the different tested extracts. Extracts of Basidiomy-cetes prepared with the QUENCHER approach had higher total phenolic content and antimicrobial activity against the evaluated strains. Antioxidant activity showed that the water extract had the greatest activity. The water extracts were analyzed with high-performance liquid chromatography, and the results showed that these three wild macromycetes contain a wide variety of antioxidant compounds in addition to many other bioactive compounds of nutritional and therapeutic interest.

Screening of Bioactive Compounds of Medicinal Mushrooms Collected on Tunisian Territory.

This study is, to our knowledge, the first to investigate the pharmacological importance of wild Tunisian mushrooms. Ethanolic extracts of 5 Tunisian mushrooms-Phellinus torulosus, Fomes fomentarius, Trametes versicolor, Pisolithus albus, and Fomitopsis pinicola-were collected from the Kroumirie Region (North Tunisia). The dry basidomes of mushrooms were extracted using ethanol and evaluated for total polyphenol, flavonoid, flavonol, tannin, proanthocyanidin, and anthocyanin content. In addition, their antioxidant activities were determined using 3 assays (testing 2,2-diphenyl-1-picrylhydrazyl [DPPH] radical scavenging, the reducing power of iron, and the iron-chelating power). Their antimicrobial activities were assessed against 8 bacterial species. The results revealed the presence of significant differences between the secondary metabolites and biological activities of the different tested extracts. In addition, significant correlations were observed between antioxidant activities and phenolic contents. Crude ethanol extracts prepared from basidomes of F. fomentarius and Ph. torulosus have higher total phenolic content and antioxidant activity per the DPPH and metal-chelating activity assays. The reducing power assay showed that the ethanolic extract of F. pinicola had the highest activity. Ethanolic extracts of the 5 mushrooms have antibacterial activity against the evaluated strains.

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

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.

Evaluation of the anti-diarrheal activity of the hydromethanolic root extract of Rhus tripartita (Ucria) (Anacardiacae).

INTRODUCTION: Rhus tripartita (Anacardiacae) is a plant which is traditionally used for the treatment of ulcer and diarrhea in Tunisia. However, the scientific basis for this usage has not been well established. The core aim of the present study is to evaluate the antidiarrheal activity of Rhus tripartita root methanolic extract (RRE). MATERIAL AND METHODS: The antidiarrheal activity of RRE oral doses (50, 100, 200 and 300mg/kg) was evaluated using the castor oil-induced diarrhea, the intestinal fluid emptying method and the normal intestinal transit test. The antibacterial activity was tested against four pathogenic bacteria using two methods. The RRE was also phytochemical studied. RESULTS: Diarrhea experiments showed a protective effect of the RRE which produced a significant (p<0.05) and dose-dependent reduction of all the diarrhea parameters. It delayed the onset of diarrhea, produced a significant decrease in the frequency of defecation and the diarrhea score severity and decreased the volume of intestinal fluid induced by castor oil as well as the propulsion intestinal transit. The effect of the extract at the highest dose (300mg/kg) was similar to that of loperamide, the standard anti-diarrheal drug (10mg/kg). The anti-bacterial activity test showed that RRE exhibited a great inhibition activity against four pathogenic bacteria strains (Esherichia coli, Salmonella typhimurium, Salmonella argenosa, Staphylococcus aureus). Oral administration of the extract up to 3g/kg did not produce any acute toxicity in rats. The preliminary phytochemical screening of the RRE revealed the presence of flavonoids, tannins, and polyphenols. CONCLUSION: Results showed that RRE at 300mg/kg possesses the highest anti-diarrheal activity possibly mediated by the inhibitory effects on gastrointestinal propulsion and intestinal fluid accumulation.

Barks Essential Oil, Secondary Metabolites and Biological Activities of Four Organs of Tunisian Calligonum azel Maire.

This study is the first to investigate the chemical composition of barks essential oil (EO), secondary metabolites and biological activities of the MeOH and infusions extracts of seeds, leaves, barks and roots of Calligonum azel Maire (Polygonaceae) harvested from Tunisian desert. The gas chromatography/mass spectrometry (GC/MS) results showed the presence of fifty-four compounds in barks EO. The major components were: viridiflorol (14.6%), α-eudesmol (8.65%), trans-caryophyllene (6.72%), elemol (6.63%), ß-eudesmol (6.21%). The obtained results showed that C. azel is a very rich plant in secondary metabolites. High contents in polyphenols, flavonoids and tannins were observed in both extracts of all studied organs. Significant differences were found between both extracts of the four organs. Thus, polyphenols and tannins were more abundant in leaves infusion extract, while, flavonoids showed a high level in barks extract. The antioxidant activity data demonstrated that all extracts showed strong antioxidant and radical scavenging activities. The MeOH extracts presented potential for antibacterial and antifungal activities against all tested microorganisms. The inhibition zones diameters and minimal inhibitrice concentration values were in the range of 9 - 15 mm and 2.5 - 20 µg/ml, respectively. This study demonstrated that C. azel can be regarded as an excellent plant source for natural antimicrobial agents.

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

OBJECTIVES: 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. METHODS: Adult male wistar rats were used and divided into six groups of ten each: control, Castor oil, Castor oil + Loperamide and Castor oil + various doses of MBSAE. Animals were per orally (p.o.) pre-treated with MBSAE for one hour and intoxicated by castor oil acute oral administration. KEY FINDINGS: Our results demonstrated that the MBSAE is rich in total and condensed tannins and exhibited a broad spectrum of antibacterial activity. In vivo, we found that MBSAE administration induced a significant dose-dependent protection against diarrhoea and intestinal fluid accumulation. Castor oil-induced intestinal hypersecretion was accompanied by an oxidative stress status in the intestine. More importantly, we showed that acute diarrhoea was accompanied by an increase in intestinal mucosa hydrogen peroxide (H2 O2 ), calcium and free iron levels while MBSAE pre-treatment reversed all castor oil-induced intracellular mediators disturbances. CONCLUSIONS: We suggest that MBSAE had a potent protective effects against castor oil-induced acute diarrhoea due in part to its antioxidant and antimicrobial properties.