Volatiles, phenolic compounds, antioxidant and antibacterial properties of kohlrabi leaves.

This work presents the volatile compounds and phenolic profile investigation of the leaves of Brassica oleracea L. growing in Tunisia, together with antioxidant and antibacterial properties. Volatile constituents were determined by HS-SPME coupled to GC/MS, and the results showed that α-pinene (31.6%) and limonene (16.9%) were the main volatiles. The phenolic profile was determined by HPLC analysis, the methanol extract revealed the presence of four hydroxycinnamic acids (chlorogenic, ferulic, p-coumaric and sinapic acids), two hydroxybenzoic acids (syringic and gallic acids), and four flavonoids (catechol, catechin hydrate, epigallocatechin and epicatechin 3-O-gallate). The methanol extract showed the best significantly antiradical activity by DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS ((2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) antioxidant assays, with EC50 of 0.32 and 0.45 mg/mL, respectively. For antibacterial activity, the methanol extract inhibits all the tested strains. It can be concluded that kohlrabi leaves are rich in bioactive compounds and are a potential source of natural antioxidants and antibacterials.

Profiles of the Essential Oils and Headspace Analysis of Volatiles from Mandragora autumnalis Growing Wild in Tunisia.

Mandragora autumnalis Bertol. (Solanaceae family), synonym of M. officinalis Mill., occurs in North Africa and grows natively in Northern and Central Tunisia, in humid to sub-arid climates. The ripe fruits of mandrake are odiferous with a particular, indescribable, specific odor, shared, to a lesser extent, by the leaves and roots. We carried out an investigation of the essential oils (EOs) and of the aromatic volatiles emitted by fresh leaves, roots and ripe fruits of M. autumnalis growing wild in Central Tunisia. The EOs were obtained from freshly collected plant material by hydrodistillation, while the volatile emissions from the powdered M. autumnalis tissues were sampled by headspace solid phase microextraction (HS-SPME); both types of samples were analyzed by gas chromatography-mass spectrometry (GC/MS). Fifty-one compounds representing 96.2-98.6 % of the total oil compositions were identified in the three tissues and belonged to different chemical classes specifically in 16 esters, 12 alcohols, 12 hydrocarbons, 6 ketones, 3 aldehydes and 3 acids. The main constituents were pentadecanoic acid (34.2 %) and hexadecanol (26.3 %). A total of 78 volatile compounds emanating from M. autumnalis tissues, representing 94.1-96.4 % of the total volatile compositions, were identified: 22 esters, 11 alcohols, 9 aldehydes, 14 ketones, 7 nitrogen, 10 hydrocarbons, 2 lactones, 1 sulfur and 2 ethers. Ethyl hexanoate (12.3 %) and 1,3-butanediol (12.3 %) were at the highest relative percentages. This study characterizes and distinguishes M. autumnalis from Tunisia and attributes the compounds responsible for the intoxicating and particular odor of fruits. Chemosystematic of Mandragora autumnalis based on the identification of essential oils and headspace volatiles of each of its organ can be used to characterize this species according to its geographic distribution.

Valorization of the Green Waste from Two Varieties of Fennel and Carrot Cultivated in Tunisia by Identification of the Phytochemical Profile and Evaluation of the Antimicrobial Activities of Their Essentials Oils.

The purpose of this study was to identify the chemical composition and the antibacterial activity of the essential oils (EOs) extracted from the green tops of Daucus carota L. subsp. sativus (Hoffm.) Arcang. plants producing yellow roots (DcsYR) and those producing orange roots (DcsOR) and from two varieties of Foeniculum vulgare subsp. vulgare cultivated in Tunisia. Analyses revealed that the EOs from the two D. carota varieties were rich in constituents belonging to sesquiterpenes. Phenylpropanoids and non-terpene derivatives were the most abundant classes of compounds in the EOs from the two varieties of F. vulgare, of which compositions were predominated by (E)-anethole and p-acetonylanisole. All the tested EOs were significantly more effective against Gram-negative bacteria, and that obtained from var. azoricum was more active against the yeast Candida albicans than the reference drug. The EOs obtained from these by-products showed indeed interesting potential to be promoted as natural antimicrobials in food preservation systems, as well as the possibility to be used in flavor industries.

Chemical Composition and Activity of Essential Oils of Carissa macrocarpa (Eckl.) A.DC. Cultivated in Tunisia and Its Anatomical Features.

This is the first study investigating the chemical composition of essential oils (EOs) isolated from different tissues of Carissa macrocarpa (Eckl.) A.DC., their antimicrobial activity and the anatomical characters of the aerial organs and the fruits. The main EO components were pentadecanal and tetradecan-1-ol (31.9 and 16.5% in fresh leaf EO, respectively), (E)-nerolidol and caryophyllene oxide (27.3 and 15.0% in fruit EO, respectively), linalool and hexahydrofarnesyl acetone (30.9 and 24.9% in stem EO, respectively), benzyl benzoate (24.3% in flower EO). The fruit EO was more active against Candida albicans (MIC = 0.46 mg/mL) compared to the reference antibiotic (17.66 mg/mL). Furthermore, at this concentration it inhibited all the Gram-positive bacteria. Concerning the anatomical features, it is noteworthy to mention the presence of a large cluster of calcium oxalate crystals inside some parenchymatous cells. Large ducts corresponding to non articulated laticifers were identified in the cortex of leaf, stem and fruit pericarp. The laticifers categories and their distribution are taxonomically important to discriminate this species from others acclimated in different countries. Considering the obtained results, EOs of C. macrocarpa can be a good source of antimicrobial compounds, contributing to solve the problem of microbial resistance to antibiotics.