Giuseppe Ruberto, Maria T Baratta, Antioxidant activity of selected essential oil components in two lipid model systems. Food Chemistry 2000;

69 (2): 167-174

About 100 pure components of essential oils have been tested for their antioxidant effectiveness. The main classes of compounds, namely monoterpene hydrocarbons, oxygenated monoterpenes, sesquiterpene hydrocarbons, oxygenated sesquiterpenes, benzene derivatives, and non isoprenoid components comprising alcohols, aldehydes, ketones, which are the most common constituents of essential oils, have been analysed. Two model systems for the antioxidant efficacy have been used; the first exploiting the thiobarbituric acid reactive species (TBARS) method using egg yolk as oxydable substrate, the second measuring the formation of hydroperoxydienes from linoleic acid in a micellar system, using in both cases 2,2′-azobis (2-amidinopropane) dihydrochloride (ABAP) as a radical initiator, and α-tocopherol as a reference compound. From a general point of view phenols were confirmed to possess the highest antioxidant activity. In particular some monoterpene hydrocarbons, namely, terpinolene, α- and γ-terpinene showed a significant protective action, whereas among the oxygenated components, beside the aforesaid phenols, allylic alcohols manifested an appreciable activity. Sesquiterpene hydrocarbons and non isoprenoid components subjected to this study showed a low, if any, antioxidant effect. The role of the different model systems and the relationship between structure and antioxidant effectiveness are discussed.

 

 

Gianni Sacchetti, Silvia Maietti, Mariavittoria Muzzoli, Martina Scaglianti, Stefano Manfredini, Matteo Radice, Renato Bruni, Comparative evaluation of 11 essential oils of different origin as functional antioxidants, antiradicals and antimicrobials in foods. Food Chemistry 2005; 91, (4): 621–632

Eleven essential oils, namely, Cananga odorata (Annonaceae), Cupressus sempervirens (Cupressaceae), Curcuma longa (Zingiberaceae), Cymbopogon citratus (Poaceae), Eucalyptus globulus (Myrtaceae), Pinus radiata (Pinaceae), Piper crassinervium (Piperaceae), Psidium guayava (Myrtaceae), Rosmarinus officinalis (Lamiaceae), Thymus x citriodorus (Lamiaceae) and Zingiber officinale (Zingiberaceae), were characterized by means of GC and GC–MS and evaluated for their food functional ingredient related properties. These properties were compared to those of Thymus vulgaris essential oil, used as a reference ingredient. Antioxidant and radical-scavenging properties were tested by means of 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay, β-carotene bleaching test and luminol-photochemiluminescence (PCL) assay. In the DPPH assay, C. odorata, C. citratus, R. officinalis and C. longa showed major effectiveness, with a radical inhibition ranging from 59.6 ± 0.42–64.3 ± 0.45%. In the β-carotene bleaching test, C. odorata (75.5 ± 0.53%), R. officinalis (81.1 ± 0.57%) and C. longa (72.4 ± 0.51%) gave the best inhibition results. Similar results were obtained for the same essential oils in the PCL assay. Antimicrobial properties were obtained on five food-spoilage yeasts: Candida albicans ATCC 48274, Rhodotorula glutinis ATCC 16740, Schizosaccharomyces pombe ATCC 60232, Saccharomyces cerevisiae ATCC 2365, Yarrowia lypolitica ATCC 16617 . C. citratus and T. x citriodorus were the most effective against the tested strains. Suggestions on relationships between chemical composition and biological activities are outlined.

All the biological activities of the tested essential oils were compared to those achieved from a commercial essential oil of Thymus vulgaris in order to have a reference with a product reputed for its antioxidant (Dang, Takacsova, Nguyen, & Kristianova, 2000), and antimicrobial properties (Dorman & Deans, 2000; Zambonelli, Zechini D_Aulerio, Bianchi, & Albasini, 1996). Antioxidant activity was assessed by 1,1-diphenyl-2-picrylhydrazyl (DPPH), b-carotene bleaching tests and luminol-photochemiluminescence (PCL) assay, while antimicrobial activities were determined on five American Type Culture Collections (ATCC) yeast strains. The culture media and conditions employed were in accordance with ATCC protocols. All the data collected for each assay are the averages of three determinations of three independent experiments.

Antimicrobial activity

The biological activity against yeasts was determined by employing the standard discs diffusion technique (Benson, 1990; Okeke, Iroegbu, Eze, Okoli, & Esimone, 2001). Antifungal activity was assessed on the yeasts Candida albicans ATCC 48274, Rhodotorula glutinis ATCC 16740, Schizosaccharomyces pombe ATCC 60232, Saccharomyces cerevisiae ATCC 2365, and Yarrowia lypolitica ATCC 16617. Mother cultures of each micro-organism were set up 24 h before the assays in order to reach the stationary phase of growth. The tests were assessed by inoculating Petri dishes from the mother cultures with proper sterile media, with the aim of obtaining the micro-organism concentration of 105 colony forming units (CFU)/ml. An aliquot of dimethylsulfoxide (DMSO; Sigma–Aldrich) was added to the essential oils in order to obtain a 0.01–0.75 mg/ ml concentration range. Serial dilutions of the DMSO/essential oil solution were deposited on sterile paper discs (6 mm diameter, Difco) which were subsequently placed in the centre of the inoculated Petri dishes. Therefore, the Petri dishes were then incubated at 37 _C for 24 h and the growth inhibition zone diameter (IZD) was measured to the nearest mm. The lowest concentration of each DMSO/essential oil solution deposited on the sterile paper disc showing a clear zone of inhibition was taken as the minimum inhibitory concentration (MIC) (Okeke et al., 2001). Controls were set up with DMSO in amounts corresponding to the highest quantity present in the test solution.

 

Fig. 1. Free radical-scavenging activity percentage of 11 essential oils evaluated by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay and comparison with that of the references (trolox; Thymus vulgaris esential oil). Different letters mean significant differences (P < 0.001) among the DPPH scavenging activities based on LSD post hoc tests.

 

 

Rossi D, Guerrini A, Paganetto G, Bernacchia G, Conforti F, Statti G, Maietti S, Poppi I, Tacchini M, Sacchetti G. Croton lechleri Müll. Arg. (Euphorbiaceae) stem bark essential oil as possible mutagen-protective food ingredient against heterocyclic amines from cooked food. Food Chem. 2013;139(1-4):439-47

Dipartimento di Scienze della Vita e Biotecnologie (SVeB)-LT Terra&Acqua Tech UR7, Università degli Studi di Ferrara, Italy.

The Amazonian Croton lechleri stem bark essential oil was tested for its anti-mutagenic potential by performing the Ames test against heterocyclic amines (HCAs), in continuing research on applicative functional profile of this phytocomplex as food ingredient (Rossi et al., 2011). Salmonella typhimurium strain TA98 was used with and without metabolic activation (S9 mix). The anti-mutagenic properties was assayed with the following HCAs: 2-amino-3-methylimidazo-[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo-[4,5-f]quinoline (MeIQ), 2-amino-3,8-dimethylimidazo-[4,5-f]quinoxaline (MeIQx), the imidazoles 2-amino-6-methyldipyrido-[1,2-a:3',2'-d]imidazole (Glu-P-1) and 2-aminodipirydo-[1,2-a:3',2'-d]imidazole (Glu-P-2). All HCAs with S9 induced mutagenicity at 10(-10) mol/plate. Without S9, IQ and MeIQ showed mutagenicity at 10(-8) mol/plate, MeIQx and Glu-P-1 at 10(-5) mol/plate, while Glu-P-2 was inactive. In presence of HACs (10(-9) mol/plate), C. lechleri essential oil was tested for mutagen-protective properties (concentration range: 0.01-0.10 mg/plate) taking the Highest Uneffective Dose (HUD) as threshold reference. With S9 mix, C. lechleri essential oil displayed a significant reduction of revertants at 0.05 mg/plate, from 21% to 34%. The essential oil showed mutagen-protective efficacy against IQ and MeIQ tested as direct mutagens (10(-7) mol/plate), with a revertants percentage reduction of 39% and 40%, respectively. No anti-mutagen capacity was noted for MeIQx and Glu-P-1 (10(-5) mol/plate). Since HACs are known as possible colon and liver cancer inducers, C. lechleri essential oil was tested for its cytotoxicity and anti-proliferative capacity against LoVo and HepG2 cancer cell lines showing IC50 of 74.95±0.05 μg/ml (LoVo) and 82.28±0.03 μg/ml (HepG2), displaying a promising role of this essential oil as a functional food ingredient with interesting mutagen preventing properties.