Hichem Ben Jannet

Comparison of chemical composition and antimicrobial activities ofMentha longifolia L. ssp.longifolia essential oil from two Tunisian localities (Gabes and Sidi Bouzid)

This study was conceived to evaluate the difference in the chemical composition of the essential oil ofMentha longifolia ssp.longifolia from two ecotypes (Sidi Bouzid and Gabes) as well as the difference of the composition of the oils extracted from the leaves and stems. The antimicrobial activity was also tested against 16 human pathogenic microorganisms. The chemical composition of the hydrodistilled essential oils ofMentha longifolia ssp.longifolia were analysed by GC and GC/MS system. Remarkable differences were recorded between the percentages of the few constituents from leaves and stems and between plants from the two geographical provinces. The chemical analysis of the essential oil obtained from leaves and stems showed the presence of 34 compounds. The most important ones were consecutively: 1,8-cineole (5.6–10.8%), menthone (20.7–28.8%), terpineol-4 (3.1–4.9%), menthol (19.4–32.5%), pulegone (7.8–17.8%) and piperitone (2.2–3.3%). These major components occur in different amounts depending on the organs (leaves or stems) and the geographical origin of the plant. The antimicrobial activity of the essential oil was tested using the disc-diffusion assay and minimal inhibition concentration (MIC) values were estimated according to the microdilution method. The results showed that the essential oil ofMentha longifolia ssp.longifolia had great potential of antimicrobial activity against all 8 bacteria and 8 yeast species tested. The (MIC) for bacteria was ranging from 0.195 to 3.12 × 103 μg/ml.

Isolation and Structure Elucidation of a Flavanone, a Flavanone Glycoside and Vomifoliol from Echiochilon Fruticosum Growing in Tunisia

A flavanone and a flavanone glycoside, together with vomifoliol, have been isolated for the first time from the aerial parts of the plant Echiochilon fruticosum and identified. Their structures were established on the basis of spectroscopic measurements, mainly 2D NMR using COSY, HMQC and HMBC experiments.

Antioxidant, 5-Lipoxygenase Inhibitory and Cytotoxic Activities of Compounds Isolated from the Ferula lutea Flowers

A phytochemical investigation of the Ferula lutea (Poir.) Maire flowers has led to the isolation of a new compound, (E)-5-ethylidenefuran-2(5H)-one-5-O-β-d-glucopyranoside (1), designated ferunide, 4-hydroxy-3-methylbut-2-enoic acid (2), reported for the first time as a natural product, together with nine known compounds, verbenone-5-O-β-d-glucopyranoside (3), 5-O-caffeoylquinic acid (4), methyl caffeate (5), methyl 3,5-O-dicaffeoylquinate (6), 3,5-O-dicaffeoylquinic acid (7), isorhamnetin-3-O-α-l-rhamnopyranosyl(1→6)-β-d-glucopyranoside, narcissin (8), (−)-marmesin (9), isoimperatorin (10) and 2,3,6-trimethylbenzaldehyde (11). Compounds 3–10 were identified for the first time in Ferula genus. Their structures were elucidated by spectroscopic methods, including 1D and 2D NMR experiments, mass spectroscopy and X-ray diffraction analysis (compound 2), as well as by comparison with literature data. The antioxidant, anti-inflammatory and cytotoxic activities of isolated compounds were evaluated. Results showed that compound 7 exhibited the highest antioxidant activity with IC50 values of 18 ± 0.5 µmol/L and 19.7 ± 0.7 µmol/L by DPPH radical and ABTS radical cation, respectively. The compound 6 exhibited the highest anti-inflammatory activity with an IC50 value of 5.3 ± 0.1 µmol/L against 5-lipoxygenase. In addition, compound 5 was found to be the most cytotoxic, with IC50 values of 22.5 ± 2.4 µmol/L, 17.8 ± 1.1 µmol/L and 25 ± 1.1 µmol/L against the HCT-116, IGROV-1 and OVCAR-3 cell lines, respectively.

Flower and Root Oils of the Tunisian Daucus carota L. ssp. maritimus (Apiaceae): Integrated Analyses by GC, GC/MS, and 13C‐NMR Spectroscopy, and in vitro Antibacterial Activity

The essential oils from flowers and roots of Daucus carota L. ssp. maritimus were obtained by hydrodistillation and analyzed by combination of GC, GC/MS, and (13)C-NMR. The chemical composition of the flower and root oils of this subspecies is reported here for the first time. Thirty-two and six compounds were identified in flower and root oils, respectively. A remarkable difference was found between the constituent percentages of the two organs. The chemical composition of the essential oil from flowers was characterized by a high proportion of monoterpene hydrocarbons (68.4%) and belonged to the sabinene (4; 51.6%) chemotype. The oxygenated monoterpenes represented the second major fraction of the same oil among which terpinen-4-ol (11.0%) was the predominant compound. Root oil exhibited a surprisingly different composition. Phenolic derivatives (76.3%), myristicin (31; 29.7%), and dillapiole (32; 46.6%) constituted the main fraction. The antibacterial effect resulted in the inhibition of a series of common human pathogenic bacteria, and of some clinically and environmentally isolated strains with significant MIC and MBC values.

Chemical composition and antimicrobial and allelopathic activity of Tunisian Conyza sumatrensis (Retz.) E.WALKER essential oils.

Conyza sumatrensis (Retz.) E.Walker (Asteraceae) is a spontaneous annual herb, fairly widespread throughout Tunisia, which has rarely been studied or valued in any sector. Essential oils were obtained by hydrodistillation of different parts (flower heads, leaves, stems, and roots) of C. sumatrensis plants, which were collected in autumn (November 2007) at the flowering stage in the area of Monastir, Tunisia. In total, 98 compounds, representing 88.1–99.3% of the oil composition, were identified by GC‐FID and GC/MS analyses. The root essential oil was distinguished by its high content in acetylenes (matricaria ester, 4; 74.3%), while those from flower heads and leaves were dominated by oxygenated sesquiterpenes (61.1 and 50.3%, resp.). The oils of C. sumatrensis from Tunisia belonged to a matricaria ester/caryophyllene oxide chemotype. All the oils were evaluated for antibacterial, antifungal, and allelopathic activities. The results indicate that the leaf oil exhibited significant in vitro antibacterial activity against Enterococcus faecalis, Staphylococcus aureus, and Proteus mirabilis and that the C. sumatrensis oils isolated from the aerial parts presented high mycelia‐growth inhibition of Candida albicans and the filamentous fungi tested. Moreover, the essential oils of the different plant parts inhibited the shoot and root growth of Raphanus sativus (radish) seedlings. Indeed, the inhibition of the hypocotyl growth varied from 28.6 to 90.1% and that of the radicle from 42.3 to 96.2%.

Synthesis of new isoxazoline derivatives from harmine and evaluation of their anti-Alzheimer, anti-cancer and anti-inflammatory activities

Abstract In our study, a series of new harmine derivatives has been prepared by cycloaddition reaction using various arylnitrile oxides and evaluated in vitro against acetylcholinesterase and 5-lipoxygenase enzymes, MCF7 and HCT116 cancer cell lines. Some of these molecules have been shown to be potent inhibitors of acetylcholinesterase and MCF7 cell line. The greatest activity against acetylcholinesterase (IC50 = 10.4 µM) was obtained for harmine 1 and cytotoxic activities (IC50 = 0.2 µM) for compound 3a. Two derivatives 3e and 3f with the thiophene and furan systems, respectively, showed good activity against 5- lipoxygenase enzyme (IC50 = 29.2 and 55.5 µM, respectively).

New bioactive dihydrofuranocoumarins from the roots of the Tunisian Ferula lutea (Poir.) Maire.

A phytochemical investigation of the roots of Ferula lutea (Poir.) Maire led to the isolation of new dihydrofuranocoumarins as two inseparable isomers, (-)-5-hydroxyprantschimgin 1 and (-)-5-hydroxydeltoin 2, together with eight known compounds, (-)-prantschimgin 3, (-)-deltoin 4, psoralen 5, xanthotoxin 6, umbelliferone 7, caffeic acid 8, β-sitosterol 9 and stigmasterol 10. Their structures were elucidated on the basis of extensive spectroscopic methods, including 1D and 2D NMR experiments and mass spectroscopy analysis, as well as by comparison with literature data. The anti-acetylcholinesterase and cytotoxic effects of the isolates and antioxidant activities of the mixture (1+2) were also evaluated in this work. Results showed that the mixture (1+2) has the most cytotoxic activity with IC50 values 0.29±0.05 and 1.61±0.57μM against the cell lines HT-29 and HCT 116, respectively. The greatest acetylcholinesterase inhibitory activity (IC50=0.76±0.03) was exhibited by the xanthotoxin 6. In addition, the mixture (1+2) was investigated for its antioxidant activity and showed IC50 values 18.56, 13.06, 7.59, and 4.81μM towards DPPH free radical scavenging, ABTS radical monocation, singlet oxygen and hydrogen peroxide, respectively.

Chemical Composition, Biological and Cytotoxic Activities of Plant Extracts and Compounds Isolated from Ferula lutea

The present work describes the phytochemical study on Ferula lutea flowers. Total phenolics and flavonoids of the n-butanol and ethyl acetate extracts were quantified (phenolics [40.68–52.29 mg gallic acid equivalent/g of dry weight], flavonoids [12.38–14.72 mg quercitin/g dry weight]). Two diastereoisomers were isolated and identified using spectroscopic techniques (1D, 2D NMR and GC-MS). The extracts and diastereoisomers were tested for antioxidant, antiacetylcholinesterase, antimicrobial, antidiabectic, cytotoxic (leukemia cell line) activities and allelopathic potentialities. The strongest antioxidant activity was obtained for the ethyl acetate extract (IC50 = 12.8 ± 1.29 µg/mL). The two extracts exhibited high antidiabetic activity (54.1 and 52.1% at 40 µg/mL).

Two new sesquiterpene derivatives from the Tunisian endemic Ferula tunetana Pom.

A new sesquiterpene ester, tunetanin A (1), a new sesquiterpene coumarin, tunetacoumarin A (2), together with eight known compounds, i.e., coladin (3), coladonin (4), isosmarcandin (5), 13‐hydroxyfeselol (6), umbelliprenin (7) propiophenone (8), β‐sitosterol (9), and stigmasterol (10), were isolated from the roots of Ferula tunetana. Their structures were elucidated on the basis of extensive spectroscopic methods, including 1D‐ and 2D‐NMR experiments and MS analysis, as well as by comparison with published data. The cytotoxicity of compounds 1–7 towards two human colon cancer cell lines, HT‐29 and HCT 116, was evaluated. Compounds 3, 4, and 6 showed weak cytotoxic activities.

Semi-synthesis of new antimicrobial esters from the natural oleanolic and maslinic acids

In this article, we report an effective procedure for the selective isolation of oleanolic acid 1 and maslinic acid 2 (3.4 and 8.5mg/g DW, respectively) from pomace olive (Olea europaea L.) using an ultrasonic bath, and the synthesis of a series of new triterpenic acid esters. The compounds were characterized by their spectral data and were evaluated for their antimicrobial activity. Among the compounds tested, those having sulfur and chlorine atoms were found to be antibacterial. They showed activity against two Gram-positive bacteria Staphylococcus aureus and Enterococcus faecalis and two Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa (MICs within a range of 5-25μg/mL). The fungus Penicillium italicum was found to be the most sensitive to both sulfur derivatives: (3β)-3-((thiophene-2-carbonyl)oxy)-olean-12-en-28-oic acid (1a) (IZ=22mm) and (2α,3β-2,3-bis((thiophene-2-carbonyl)oxy)olean-12-en-28-oic acid (2a) (IZ=24mm).