Gamal S. El-Baroty

Bio: Gamal S. El-Baroty is an academic researcher from Cairo University. The author has contributed to research in topics: DPPH & Antioxidant. The author has an hindex of 23, co-authored 47 publications receiving 2207 citations. Previous affiliations of Gamal S. El-Baroty include Texas Southern University.

Antioxidant activity of some spice essential oils on linoleic acid oxidation in aqueous media

Abstract: Some spice essential oils (caraway, clove, cumin, rosemary, sage and thyme) and their major constituents were added to emulsified linoleic acid in aqueous media to examine their antioxidant activity. The methods used for measuring linoleic acid oxidation were coupled oxidation ofβ-carotene, conjugated diene formation and thiobarbituric acid test. The essential oils under study possess an antioxidant effect and this phenomenon was increased by increasing their concentration. Generally, the effectiveness of the various essential oils on linoleic acid oxidation was in the following descending order: caraway >sage>cumin>rosemary>thyme>clove. It appears that there was a relationship between the antioxidant effect and the chemical composition of the oils.

Characterization of antioxidant and antimicrobial compounds of cinnamon and ginger essential oils

Abstract: Essential oils obtained from the bark of Cinnamomum zeylanicum (cinnamon) and the rhizomes of Zingiber officinale (ginger) were characterized by analytical TLC and GC/MS, and their antimicrobial and antioxidant compounds were detected by TLC-bio-autography assays. Essential oil of cinnamon bark (CEO) was found to be a unique aromatic monoterpene-rich natural source, with trans-cinnamaldehyde (45.62%) as the major constituents. Ginger oil (GEO) was characterized by high content of sesquiterpene hydrocarbons, including β-sesquiphellandrene (27.16%), caryophyllene (15.29%), zingiberene (13.97%), α-farnesene (10.52%) and ar-curcumin (6.62%). CEO and GEO oils showed significant inhibitory activity against selected strains of bacteria and pathogenic fungi, with MIC values ranging from 20 to 120 µg/ml depending upon the microbial species. Cinnamaldehyde (CA) and eugenol in cinnamon bark oil and β-sesquiphellandrene, caryophyllene and zingiberene in ginger rhizome oil were identified as the most active antibacterial components, with the aid of bioautography on TLC and GC-MS. Also, both oil exhibited appreciable in vitro antioxidant activity as assessed by 2, 2'-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and β-carotene bleaching methods, compared to α-tocopherol, BHT and BHA. Guided isolation through TLC-autography using 0.05% DPPH and β-carotene/linoleic acid as a detection reagent led to identified CA and eugenol as main active antioxidant compounds in CEO. The significant antimicrobial and antioxidant activities of both oils suggest that it could serve as a source of compounds with preservative phenomenon. Key words: Antimicrobial, bioautographic assay, antioxidant, essential oils, ginger, cinnamon.

The influence of phenolic extracts obtained from the olive plant (cvs. Picual and Kronakii), on the stability of sunflower oil

Abstract: Summary The phenolic compounds of olive cultivars (Picual and Kronakii) were extracted. The total phenolic content of the extracts was estimated and their ability to reduce the oxidation of sunflower oil was tested at 100 °C by using a Rancimat®. The fruits, leaves and pomaces were extracted separately with ethanol. Portions of the fruits were crushed to produce an oil/aqueous mixture, which was separated and the two fractions further processed. The oil fraction was extracted with 60% aqueous methanol and was separated further, by the method of Dabrowski & Sosulski (1984), into three major fractions. These contained mainly free phenols, soluble phenolic esters or bound phenolic acids, respectively. The phenolic concentrations were measured in all the fractions and were in accordance with expected amounts. When tested at 100, 200 or 400 ppm for their ability to stabilize sunflower oil the results showed that the vast majority of the anti-oxidant activity found in the ‘total phenols’ fraction was because of a ‘free phenolic’ group. The free phenolics, at a 400-ppm level, exhibited remarkable anti-oxidant activity and were superior to that of butylated hydroxy toluene (BHT) in retarding sunflower oil oxidative rancidity. The mode of action is discussed.

Antimicrobial properties of plant essential oils and essences against five important food-borne pathogens

Abstract: The antimicrobial properties of 21 plant essential oils and two essences were investigated against five important food-borne pathogens, Campylobacter jejuni, Salmonella enteritidis, Escherichia coli, Staphylococcus aureus and Listeria monocytogenes. The oils of bay, cinnamon, clove and thyme were the most inhibitory, each having a bacteriostatic concentration of 0.075% or less against all five pathogens. In general, Gram-positive bacteria were more sensitive to inhibition by plant essential oils than the Gram-negative bacteria. Campylobacter jejuni was the most resistant of the bacteria investigated to plant essential oils, with only the oils of bay and thyme having a bacteriocidal concentration of less than 1%. At 35 degrees C, L. monocytogenes was extremely sensitive to the oil of nutmeg. A concentration of less than 0.01% was bacteriostatic and 0.05% was bacteriocidal, but when the temperature was reduced to 4 degrees, the bacteriostatic concentration was increased to 0.5% and the bacteriocidal concentration to greater than 1%.

In‐vitro antimicrobial activity and chemical composition of Sardinian Thymus essential oils

Abstract: Essential oils and their components are becoming increasingly popular as naturally occurring antimicrobial agents. In this work the chemical composition and the antimicrobial properties of Thymus essential oils and of their main components were determined. Three essential oils obtained from different species of Thymus growing wild in Sardinia and a commercial sample of Thymus capitatus oil were analysed. The essential oil components were identified by GC/MS analysis. The antimicrobial activity of the oils and components was determined against a panel of standard reference strains and multiple strains of food-derived spoilage and pathogenic bacteria, using a broth microdilution method. The GC/MS analysis showed that the major constituents of the oils were monoterpene hydrocarbons and phenolic monoterpenes, but the concentration of these compounds varied greatly among the oils examined. The results of the antimicrobial assay showed that essential oils extracted from Sardinian Thymus species have an antimicrobial activity comparable to the one observed in other thyme oils. It seems also confirmed that the antimicrobial properties of thyme essential oils are mainly related to their high phenolic content. Among the single compounds tested carvacrol and thymol turned out to be the most efficient against both reference strains and food-derived bacteria. The results of this study confirmed the possibility of using thyme essential oils or some of their components in food systems to prevent the growth of foodborne bacteria and extend the shelf-life of processed foods.