Wahid Herchi

Phytosterols accumulation in the seeds of Linum usitatissimum L.

A comparative study was performed to determine the free sterols content and composition during the development of three varieties of linseed (H52, O116 and P129). Seed samples were collected at regular intervals from 7 to 60 days after flowering (DAF). Ten compounds were identified: cholesterol, campesterol, brassicasterol, stigmasterol, beta-sitosterol, Delta5-avenasterol, cycloartenol; 24-methylene cycloartanol, obtusifoliol, citrostadienol. The maximum level of 4-desmethylsterols (1,515 mg/100g oil) was reached at 7 DAF in P129 variety. H52 had the highest level of 4-4 dimethylsterols (355 mg/100g oil) at 28 DAF. The greatest amount of 4-monomethylsterols (35 mg/100g oil) was detected in H52 at 14 DAF. During linseed development, beta sitosterol (830 mg/100g oil) was the major 4-desmethylsterols, followed by campesterol (564 mg/100g oil) and stigmasterol (265 mg/100g oil). Some of these compounds followed nearly the same accumulation pattern during linseed maturation.

Characterisation of the glycerophospholipid fraction in flaxseed oil using liquid chromatography–mass spectrometry

A high-performance liquid chromatographic method coupled with mass spectrometry was used to characterise the natural phospholipid (PL) classes and molecular species in flaxseed oils. The PL fraction included phosphatidylethanolamine (PE) (27-40%), phosphatidylinositol (PI) (29-32%), phosphatidylcholine (PC) (7-18%), lysophosphatidylcholine (LPC) (8-21%), phosphatidylglycerol (PG) (1-4%) and phosphatidic acid (PA) (1-9%). The distribution of fatty acids was found to differ between phospholipids. Stearic acid was mainly present in the form of PC and LPC. Palmitic acid was present in the most abundant molecular species in PI, PG and PA whereas linoleic acid formed the most abundant molecular species in PE.

Chemical composition and antibacterial activities of seven Eucalyptus species essential oils leaves

BackgroundIn this paper, we have studied the essential oils chemical composition of the leaves of seven Eucalyptus species developed in Tunisia. Eucalyptus leaves were picked from trees growing in different arboretums in Tunisia. Choucha and Mrifeg arboretums located in Sedjnene, region of Bizerte (Choucha: E. maideni, E. astrengens et E. cinerea; Mrifeg : E. leucoxylon), Korbous arboretums located in the region of Nabeul, North East Tunisia with sub-humid bioclimate, (E. lehmani), Souiniet-Ain Drahem arboretum located in region of Jendouba (E. sideroxylon, E. bicostata). Essential oils were individually tested against a large panel of microorganisms including Staphylococcus aureus (ATCC 6539), Escherichia coli (ATCC 25922), Enterococcus faecalis (ATCC29212), Listeria ivanovii (RBL 30), Bacillus cereus (ATCC11778).ResultsThe yield of essential oils ranged from 1.2% to 3% (w/w) for the different Eucalyptus species. All essential oils contain α-pinene, 1,8-cineol and pinocarveol-trans for all Eucalyptus species studied. The 1,8-cineol was the major compound in all species (49.07 to 83.59%). Diameter of inhibition zone of essential oils of Eucalyptus species varied from 10 to 29 mm. The largest zone of inhibition was obtained for Bacillus cereus (E. astrengens) and the lowest for Staphylococcus aureus (E. cinerea). The essential oils from E. maideni, E. astrengens, E. cinerea (arboretum of Bizerte), E. bicostata (arboretum of Aindraham) showed the highest antibacterial activity against Listeria ivanovii and Bacillus cereus.ConclusionThe major constituents of Eucalyptus leaves essential oils are 1,8-cineol (49.07 to 83.59%) and α-pinene (1.27 to 26.35%). The essential oils from E. maideni, E. astrengens, E. cinerea, E. bicostata showed the highest antibacterial activity against Listeria ivanovii and Bacillus cereus, they may have potential applications in food and pharmaceutical products.

Lipids, proteins, phenolic composition, antioxidant and antibacterial activities of seeds of peanuts (Arachis hypogaea l) cultivated in Tunisia

Fatty acid composition of peanut seed oil in four varieties cultivated in Tunisia showed that linoleic (C18:2), oleic (C18:1) and palmitic (C16) acids account for more than 84% for Chounfakhi and Massriya and for more than 85% of the total fatty acids of Trabilsia and Sinya seed oil respectively. Seed oil contents were significantly different (P ≤ 0.05) and did not exceed 48%. The study of total phenolics revealed that Chounfakhi contained more total phenolics (2.1 mg GAE/g DW), followed by the Massriya and Sinya cultivars (1.35 mg GAE/g DW for each); Trabilsia presented the lowest total phenolic content with 1 mg GAE/g DW. Considerable antiradical ability was found, especially in the Trabilsia peanut seed cultivar (IC50 = 1550 μg/ml), the Massriya and Sinya cultivars had, respectively, 720 and 820 mg/ml IC50. In the Massriya variety the sterol fraction showed antibacterial activity against Listeria ivanovii, Listeria inocua, Pseudomonas aeruginosa, Staphylococus aureus, Enterococcus hirae and Bacillus cereus.

A review of the methods used in the determination of flaxseed components

Flaxseed ( Linum usitatissimum L.) is a multi-purpose crop and its consumption is beneficial for human health. The nutritional components of flaxseed are oil, protein, lignans, fiber and vitamin. The determination of the minor components is of great importance in establishing the flaxseed oil quality and their genuineness. The qualitative and quantitative determination of its constituents has been carried out by using several analytical techniques most of which are based on gas chromatography and some being based on high-performance liquid chromatography. In the present work, the different methods used for the determination of flaxseed components are revised. Keys words : Methods, chromatography, flaxseed, food, fiber, protein, oil, lignans.

Characterization and quantification of the aliphatic hydrocarbon fraction during linseed development ( Linum usitatissimum L.).

Changes in hydrocarbon composition were investigated during maturation of three varieties of linseed (H52, O116, and P129) cultivated in Tunisia. The hydrocarbon fraction of the three linseed oil samples was found to contain mainly n-alkanes and squalene. The greatest decrease of these components occurred between 7 and 21 days after flowering (DAF); thereafter, the changes were slight. At 7 DAF, P129 had a significantly higher level of squalene (27.24 mg/100 g of oil) than H52 (3.36 mg/100 g of oil), but from this date until 21 DAF squalene decreased much more actively in P129, resulting in similar levels in H52 (0.57 mg/100 g of oil) and P129 (0.52 mg/100 g of oil) at full maturity. In three varieties of linseed, 13 n-alkanes were detected ranging from C(22) to C(34) carbon atoms. The n-alkane composition of linseed oil was influenced by the ripening stage of seeds. At 7 DAF, C29 was the most predominant hydrocarbon (19.84 mg/100 g of total oil), followed by C(27) (11.82 mg/100 g) and C(25) (11.28 mg/100 g). C(29) exhibited the most significant decrease from 7 to 21 DAF, as a result C(27) being the most significant n-alkane component for the remainder of the period. At full maturity, the content of total n-alkanes in three varieties of linseed ranged from 4.0 to 4.26 mg/100 g of oil.

Germination kinetics and seed reserve mobilization in two flax (Linum usitatissimum L.) cultivars under moderate salt stress

Because of its high contents of protein, α-linolenic-rich oil, lignans, and fiber, demand is increasing for flax(Linum usitatissi-mum L.) and flax seed oil as a food source. In this comparative survey, we examined germination and the mobilization of seed storage products (lipids and soluble proteins) of 3-d-old seedlings from two flax cultivars (N 51 and H 52) challenged with moderate salinity (up to 200 mM NaCl). At the highest salt concentration, germination appeared to be cultivar-dependent, with that of ‘N 51’ being less impaired and delayed than in ’H 52’. Sodium chloride inhibited germination via osmotic and toxic effects, so that seed viability was altered, especially in ‘H 52’. At 200 mM NaCl, lipid mobilization was delayed in the earliest germination phases. This response was associated with increased proportions of linolenic acid contents in both cultivars and more linolenic acid-rich molecular species of TAGs. Irrespective of the salt level, soluble protein contents in both cultivars decreased over time, although a salt-related precocity of protein degradation occurred at 200 mM NaCl.

Analysis of pecan nut (Carya illinoinensis) unsaponifiable fraction. Effect of ripening stage on phytosterols and phytostanols composition

Changes in 4-desmethylsterol, 4-monomethylsterol, 4,4-dimethylsterol and phytostanol composition were quantitatively and qualitatively investigated during the ripening of three varieties of Tunisian-grown pecan nuts (Mahan, Moore and Burkett). These components have many health benefits, especially in lowering LDL-cholesterol and preventing heart disease. The phytosterol composition of whole pecan kernel was quantified by Gas Chromatography-Flame Ionisation Detection (GC-FID) and identified by Gas Chromatography-Mass Spectrometry (GC-MS). Fifteen phytosterols and one phytostanol were quantified. The greatest amount of phytosterols (2852.5mg/100g of oil) was detected in Mahan variety at 20 weeks after the flowering date (WAFD). Moore had the highest level of phytostanols (7.3mg/100g of oil) at 20 WAFD. Phytosterol and phytostanol contents showed a steep decrease during pecan nut development. Results from the quantitative characterisation of pecan nut oils revealed that β-sitosterol, Δ5-avenasterol, and campesterol were the most abundant phytosterol compounds at all ripening stages.

Triacylglycerols and aliphatic alcohols from fruits of three Tunisian Pistacia lentiscus populations.

BACKGROUND The search for other sources of vegetable oils by the exploitation and the enhancement of other oil plants will be needed to meet the demands of the international market. This study aims to determine the triacylglycerol (TAG) molecular species and aliphatic alcohol compositions of unexploited fruits of three Tunisian Pistacia lentiscus (lentisc) populations from the Korbous, Tebaba and Rimel areas of Tunisia. RESULTS Results show that the content of total TAG varies from 738.32 mg g(-1) of total lipid in the Tebaba population to 981.15 mg g(-1) of total lipid in the Korbous population. Furthermore, 14 species of TAG were detected in the three studied populations. In addition, 13 aliphatic compounds were identified and classified into two groups: (1) aliphatic alcohols with fewer than 20 carbon atoms (hexadecanol, heptadecanol, (Z)-octadec-9-en-1-ol, octadecanol and nonadécanol); and (2) the policosanol group (eicosenol, docosenol, docosanol tetracosanol, hexacosanol octacosanol and triacontanol). The Tebaba population showed a distinct composition compared to Korbous and Rimel where heptadecanol is the major compound. CONCLUSION Quantitatively, the most abundant TAG species are those constituted by palmitic, oleic and/or linoleic acid. Furthermore, the significant difference observed at the oil composition is associated with a remarkable station effect.

Changes in the triacylglycerol content of flaxseeds during development using liquid chromatography- atmospheric pressure photoionization-mass spectrometry (LC-APPI-MS)

Changes in the composition of triacylglycerols (TAGs) of three varieties of flaxseeds (H52, O116 and P129) during development were investigated using non-aqueous reversed phase liquid chromatography coupled to atmospheric pressure photoionization-mass spectrometry (LC-APPI-MS). 17 species of triacylglycerols were found and their fatty acyl composition was confirmed by fragment ions in the mass spectra. The major forms observed were LnLnLn, LnLLn, LnOLn, LLLn, LnLnP, OOLn and OLLn. The highest change in these compounds occurred in the early development period for most TAGs. The most active period of triacylglycerol synthesis was between 7 and 35 days after flowering (DAF). LnLnLn exhibited the most significant increase during flaxseed development. At maturity, similar TAG profiles were found for the three samples.