Olfa Bachrouch

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.

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.

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.

Variations in composition and antioxidant activity of Tunisian Pistacia lentiscus L. leaf essential oil

In this study, the composition and antioxidant activity of Pistacia lentiscus L. leaf essential oil (EO) from four Tunisian localities were investigated. The EO yields (%, w/w) of P. lentiscus leaf were 0.009% in Oued El Bir, 0.02% in Jebel Mansour, 0.007% in Siliana and 0.01% in Tabarka. The main compounds of Oued El Bir EO were terpinene-4-ol (41.24%) and α-terpineol (7.31%), whereas those of Jebel Mansour were α-pinene (9.48%), limonene (19.11%) and α-phellandrene (3.20%). In Siliana samples, terpinene-4-ol (23.32%), β-caryophyllene (22.62%) and α-terpineol (7.12%) were the main compounds. For P. lentiscus L. from Tabarka, α-terpineol (9.79%) and β-caryophyllene (38.33%) were the major constituents. Three chemotypes of P. lentiscus EO were identified for the first time in Tunisia. P. lentiscus EOs were also screened for their antioxidant activities. The 1,1-diphenyl-2-picrylhydrazyl assay gives an IC50 range value of 60–110 μg/mL for all the samples studied. EOs from different Tunisian localities showed lower β-carotene bleaching activity than butylated hydroxytoluene and butylated hydroxyanisol. P. lentiscus EO presents a very low capacity to chelate ferrous irons (IC50 = 80.8–104 μg/mL) and no metal chelating activity was recorded.

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.

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.