Majdi Hammami

Chemical Composition and Antioxidant and Antimicrobial Activities of Wormwood (Artemisia absinthium L.) Essential Oils and Phenolics

The aim of this study was to determine the chemical variability of wormwood extracts as affected by the growing region. Antioxidant and antimicrobial activities were also investigated. The essential oil composition variability of A. absinthium L. aerial parts collected from four different Tunisian regions was assessed by gas chromatography (GC/FID) and by gas chromatography mass spectrometry (GC/MS). In addition, total polyphenols, flavonoids, and condensed tannins as well as antioxidant, antibacterial, and antifungal activities of methanolic extract and essential oils were undertaken. Chromatographic analysis of wormwood essential oils showed the predominance of monoterpene hydrocarbons represented mainly by chamazulene. RP-HPLC analysis of wormwood methanolic extract revealed the predominance of phenolic acids. Antiradical activity was region-dependant and the methanolic extract of Bou Salem region has the strongest activity ( µg/mL). Concerning the reducing power, the methanolic extract of Bou Salem, Jerissa, and Boukornine regions was more active than the positive control. Obtained results of antimicrobial activities showed that wormwood essential oil is endowed with important antibacterial activity which was strongly related to the organoleptic quality of oil which appeared strongly region-dependant. A. absinthium L. EOs investigated are quite interesting from a pharmaceutical standpoint because of their biological activities.

Essential Oil Composition of Lavandula dentata, L. stoechas and L. multifida Cultivated in Tunisia

Abstract The chemical composition of the essential oils of dried aerial parts of Lavandula dentata L. stoechas and L. multifida were analyzed by GC and GC-MS. A total of 52 compounds were identified representing 89.62 ± 9.56, 99.94 ± 9.88 and 98.21 ± 10.23 in Lavandula dentata L. stoechas and L. multifida oil, respectively. Essential oil yield varied significantly (P < 0.05) among the three studied Lavandula species and there were (1.96 ± 0.22 %), (1.62 ± 0.15 %) and (1.04 ± 0.11 %) on dry weight basis in L. dentata, L. multifida and L. stoechas, respectively. Essential oil extracted from aerial parts of L. dentata was dominated by linalool (47.30 ± 5.34 %), linalyl acetate (28.65 ± 3.26 %), bicyclogermacrene (3.40 ± 0.41 %), camphor (2.32 ± 0.28 %) and δ-terpineol (1.47 ± 0.16 %). Linalyl acetate (64.30 ± 7.55 %), linalool (20.25 ± 3.21 %) and β-thujone (8.97 ± 0.99 %) were the predominant compounds in L. stoechas essential oil. L. multifida oil was characterized by the predominance of linalool (50.05 ± 6.52 %), camphene (10.06 ± 1.21 %), linalyl acetate (7.30 ± 0.65 %), α-thujene (3.83 ± 0.41 %), bornyl acetate (3.03 ± 0.41 %), β-caryophellene (2.13 ± 0.25 %), nerol (2.01 ± 0.22 %) and terpinolene (2.05 ± 0.23 %). This finding indicates that Lavender was rich in natural component which could be used as a source of natural antioxidants.

Fumigant and repellent potentials of Ricinus communis and Mentha pulegium essential oils against Tribolium castaneum and Lasioderma serricorne

ABSTRACT This work was aimed to investigate the chemical composition of pennyroyal (Mentha pulegium L.) aerial parts and castor (Ricinus communis L.) stems essential oils from Tunisia. Fumigant and repellent toxicities were assessed toward two major stored product beetles: Lasioderma serricorne and Tribolium castaneum. Pennyroyal essential oil was characterized by a clear predominance of the oxygenated monoterpenes fraction (97.10%) instead of phenol fraction (61.47%) in the castor essential oil. The major common compounds of Mentha pulegium were pulegone and isomenthone, whereas 2,4-bis (dimethylbenzyl)-6-t-butylphenol was the main volatile compound of castor essential oil. Pennyroyal essential oil showed a strong antiradical capacity (IC50 = 14 µg/mL) which is higher than synthetic standard. The effectiveness of pennyroyal essential oil against the coleopteran insects showed potential fumigant impact particularly against Lasioderma serricorne with LC50 = 8.46 µL/L air. Moreover, significant pest repellent activity was demonstrated with Ricinus communis and Mentha pulegium where the repellency effects reached 80 and 60% after 1 and 24h of exposure against Tribolium castaneum at doses of 0.31 µL/cm2 and 0.078 µL/cm2 respectively. Hence, these findings underlined the potential insecticidal effect of castor and pennyroyal essential oils and highlighted their use as valuable food and insecticide products instead of synthetic pesticides.

Antifungal mechanism of the combination of Cinnamomum verum and Pelargonium graveolens essential oils with fluconazole against pathogenic Candida strains

The present study aimed to investigate the anti-Candida activity of ten essential oils (EOs) and to evaluate their potential synergism with conventional drugs. The effect on secreted aspartic protease (SAP) activity and the mechanism of action were also explored. The antifungal properties of essential oils were investigated using standard micro-broth dilution assay. Only Cinnamomum verum, Thymus capitatus, Syzygium aromaticum, and Pelargonium graveolens exhibited a broad spectrum of activity against a variety of pathogenic Candida strains. Chemical composition of active essential oils was performed by gas chromatography-mass spectrometry (GC-MS). Synergistic effect was observed with the combinations C. verum/fluconazole and P. graveolens/fluconazole, with FIC value 0.37. Investigation of the mechanism of action revealed that C. verum EO reduced the quantity of ergosterol to 83%. A total inhibition was observed for the combination C. verum/fluconazole. However, P. graveolens EO may disturb the permeability barrier of the fungal cell wall. An increase of MIC values of P. graveolens EO and the combination with fluconazole was observed with osmoprotectants (sorbitol and PEG6000). Furthermore, the combination with fluconazole may affect ergosterol biosynthesis and disturb fatty acid homeostasis in C. albicans cells as the quantity of ergosterol and oleic acid was reduced to 52.33 and 72%, respectively. The combination of P. graveolens and C. verum EOs with fluconazole inhibited 78.31 and 64.72% SAP activity, respectively. To our knowledge, this is the first report underlying the mechanism of action and the inhibitory effect of SAP activity of essential oils in synergy with fluconazole. Naturally occurring phytochemicals C. verum and P. graveolens could be effective candidate to enhance the efficacy of fluconazole-based therapy of C. albicans infections.

Chemical Composition and Antioxidant Activities of Tunisian Thymus capitatus L. Methanolic Extract

Thymus capitatus has traditionally been considered as an anthelmintic, antispasmodic, carminative, emmenagogue, expectorant, rubefactient, sedative, stimulant, and tonic. This work was carried out to determine total polyphenol and total flavonoids chemical composition of phenolics and to evaluate the antioxidant activities of the methanolic extract. Total phenolic contents were assayed using the Folin–Ciocalteu reagent, total flavonoid content was measured spectrophotometrically and phenolics were analyzed by reverse phase–high performance liquid chromatography. The 1,1-diphenyl-2-picrylhydrazyl and reducing power were calculated. Total phenols and total flavonoids varied significantly among the studied regions. Chromatographic analysis by reverse phase–high performance liquid chromatography showed that phenolic acids: tannic, gallic, chlorogenic hemihydrate, caffeic, syringic, ferulic, p-coumaric acid, and trans-cinnamic rosmarinic were the main compounds. The anti-radical activity was region-dependent and could be summarized as follows in ascending order: Boukornine > Kef > Bizerte > Grombelia. Reducing power in the four studied regions was stronger than positive control (ascorbic acid). From these results we have conclude that thyme methanolic extract may have a role in pharmaceutical preparations and preservatives as an antioxidant.

Chemical composition and insecticidal activity of essential oil from coriander fruit against Tribolium castaenum, Sitophilus oryzae, and Lasioderma serricorne

ABSTRACT Gas chromatography and gas chromatography–flame ionization detector analysis of essential oil of Coriandrum sativum fruit showed a high percentage of linalool (79.22%) γ-terpinene (6.26%), camphor (2.63%), α-pinene (2.32%), geranyl acetate (1.75%), and p-cymene (1.70%). Significant differences in insect mortality were observed within insect species, oil concentrations, and exposure time. Fumigant treatments have shown that three insect mortality rate increased with the increase in essential oils concentration. Complete insect mortality was detected at the highest concentration within 24 h of exposure for the single compound against Tribolium castaneum and Lasioderma serricorne. Probit analysis showed that LC50 values of coriander essential oil against L. serricorne than Sitophilus oryzae and T. castaneum were 5.25 µL/L air, and 145.49 µL/L air and 276.29 µL/L air, respectively. Among the test compound, linalool demonstrated strong fumigant toxicity against L. serricorne. These result could be important in order to the efficacy of essential oil of coriander and could be potential for use in the insecticidal activities.

Variations in Tunisian borage essential oil profiles and their antioxidant activities during flowering

This study was conducted to examine the chemical composition and antioxidant activity of the essential oils (EOs) of Borago officinalis stem during its flowering stage. The EO composition was characterised by high proportions of E,E-decadienal, the main compound of monoterpene hydrocarbon class, with values varying from 47.08% to 55.28% in two Tunisian regions. The region of Korba exhibited the highest scavenging activity (2.05 mg/mL) by comparison with Beja region. In all tests, the fructification stage showed the best antioxidant activity of all flowering stages.

Chemical composition and biological activities of essential oils of Salvia officinalis aerial parts as affected by diurnal variations

Abstract The main objective of this work is to evaluate the impact of the diurnal variation on the essential oil (EO) of Salvia officinalis and on their antioxidant, antifungal and insecticidal potentials. Obtained results showed that the chemical composition of EOs of sage varied significantly during the day. For the EO, the 7 am extract was characterized by the most significant antiradical activity. The EOs of 12 and 5 pm used at a dose of 10 μL were found to have the most effective potential to inhibit the growth of Botrytis cinerea whereas, the EO of 5 pm used at the same dose (10 μL) was the most effective against Fusarium sambucinum. For the fumigant test, the EO from 7 am had the highest activity against Spodoptera littoralis. The EO of 12 pm had the largest repellency activity against Trogoderma granarium. In addition, the EO from 7 am belongs to the repulsive class III, those of 12 and 5 pm belong to the repulsive class IV. The results of this study indicate how to optimize the best harvesting hour to obtain extracts characterized by the best yield of active compounds and by the more effective biological activity.

Phytochemical characterisation and bioactive properties of Solanum sodomaeum L. fruits at two stages of maturation

Summary Introduction: Solanum sodomaeum L. has been observed to have several medicinal properties, in particular, in the treatment of several types of human skin cancer. Objective: The influence of the maturation stage of S. sodomaeum fruits on the total lipid contents, fatty acid profiles, essential oil yields and compositions, as well as the antibacterial and antioxidant activities of the essential oils, was investigated. Methods: The fatty acid and essential oil constituents were identified using gas chromatography (GC) and GC–mass spectrometry (GC–MS). The antioxidant properties of essential oil and vegetal oil were assessed using 1,1-diphenyl-2-picryl-hydrazyl (DPPH) scavenging and reducing power assays. The antibacterial activity of essential oil was tested using the disc diffusion assay for resistance in human pathogenic bacteria. Results: Mature fruits showed higher total lipid content (17%) and were characterised by polyunsaturated fatty acids (53.87%), represented mainly by linoleic acid (53.11%). Similar yields of essential oils were detected for immature (0.43%) and mature (0.45%) fruits. Tetrahydronaphthalene (41.79%) was detected as the major essential oil component at the immature stage versus dihydrocoumarin pentane (18.27%), hexadecanoic acid (17.43%) and 2-undecanone (13.20%) in mature fruits. The DPPH test showed that essential oils had better antioxidant properties; however, the vegetal oils showed better performance in the reducing power assay. Moreover, the essential oil of S. sodomaeum mature fruits was active against bacterial strains. Conclusions: S. sodomaeum fruits could be a valuable source of natural antioxidants and antibacterial agents.

Phenological stage effect on phenolic composition and repellent potential of Mentha pulegium against Tribolium castaneum and Lasioderma serricorne

Objective: To elucidate for the first time the phenological stage effect on polyphenol, flavonoid and proanthocyanidin contents of pennyroyal (Mentha pulegium) as well as their antioxidant capacities and insecticidal potentials against Tribolium castaneum and Lasioderma serricorne. Methods: Crude methanol extracts from pennyroyal (Mentha pulegium) aerial parts were evaluated for their antiradical, reducing power activities and repellent potentials against selected coleopteran insects during different phenological stages. Results: Phenolic contents of pennyroyal aerial parts and their antioxidant effects were significantly dependent on maturity stage of the plant. The maximum of phenol production was reached during the full flowering stage. Apigenin was the major phenol in Mentha pulegium with an amount of 6.01 mg/g of dry vegetable matter during this period. Nevertheless, at fructification stage, the highest antioxidant activity was not related to high phenolic content. The repulsive effect of pennyroyal extract showed that Lasioderma serricorne was more susceptible to pennyroyal extract than Tribolium castaneum with corresponding median repellent dose values of 0.124 and 0.006 mg/mL respectively. Moreover, great differences in insect repulsion depending on extract concentrations, exposure time and developmental stage was observed. For the lowest concentration (0.125 mg/mL), the repellent effect against Tribolium reached its maximum (90%) during the fructification stage (after 24 h of exposure) while this repellent effect was 80% during the vegetative stage. Conclusions: Due to the strong insecticidal potential of pennyroyal extracts, this study highlights the therapeutic properties of this plant and encourages its use as a safer, environmental-friendly and efficient insecticide in food industry.