Effects of γ-Irradiation of Wild Thyme (Thymus serpyllum L.) on the Phenolic Compounds Profile of Its Ethanolic Extract

The presented study revealed that there were changes in the phenolic compounds profile of extract of wild thyme (Thymus serpyllum L.) after γ-irradiation at the dose of 5 kGy. Ethanolic extracts of irradiated and non-irradiated herb were prepared and their compounds were analyzed by RP-HPLC-DAD technique. Between thirty two detected constituents, twelve phenolic compounds classified as hydroxybenzoic and hydroxycinnamic acids derivatives, flavones and flavanones were identified. Among them, caffeic acid derivatives and flavones predominated with the highest content of rosmarinic acid and luteolin-7-O-glucoside, respectively. Additionally, thymol was recognized in the analyzed extracts. γ-Irradiation slightly affected the quantitative profile of phenolic compounds of a wild thyme ethanolic extract. Only four constituents differed significantly (P<0.05) in terms of their content in the irradiated and non-irradiated samples. The content of phenolic acids (p-coumaric and caffeic acids) decreased and that of flavonoid aglycons (luteolin and eriodictyol) increased after the γ-ray treatment

Protective effects of new antioxidant compositions of 4-methylcoumarins and related compounds with dl-α-tocopherol and l-ascorbic acid

Coumarin derivatives possess a wide range of biological activities. By functionalization of the parent coumarin skeleton that has neither antioxidant nor biological activity, a series of new bio-antioxidants has been designed

Structure-activity relationship of dihydroxy-4-methylcoumarins as powerful antioxidants: Correlation between experimental & theoretical data and synergistic effect

The chain-breaking antioxidant activities of eight coumarins [7-hydroxy-4-methylcoumarin (1), 5,7-dihydroxy-4-methylcoumarin (2), 6,7-dihydroxy-4-methylcoumarin (3), 6,7-dihydroxycoumarin (4), 7,8-dihydroxy-4-methylcoumarin (5), ethyl 2-(7,8-dihydroxy-4-methylcoumar-3-yl)-acetate (6), 7,8-diacetoxy-4-methylcoumarin (7) and ethyl 2-(7,8-diacetoxy-4-methylcoumar-3-yl)-acetate (8)] during bulk lipid autoxidation at 37 degrees C and 80 degrees C in concentrations of 0.01-1.0 mM and their radical scavenging activities at 25 degrees C using TLC-DPPH test have been studied and compared. It has been found that the o-dihydroxycoumarins 3-6 demonstrated excellent activity as antioxidants and radical scavengers, much better than the m-dihydroxy analogue 2 and the monohydroxycoumarin 1. The substitution at the C-3 position did not have any effect either on the chain-breaking antioxidant activity or on the radical scavenging activity of the 7,8-dihydroxy- and 7,8-diacetoxy-4-methylcoumarins 6 and 8. The comparison with DL-alpha-tocopherol (TOH), caffeic acid (CA) and p-coumaric acid (p-CumA) showed that antioxidant efficiency decreases in the following sequence: TOH > CA > 3 > 4 > 6 > 5 > 2 > 1 = 7 = 8 = p-CumA. Theoretical calculations and the "Lipinski's Rule of Five" were used for explaining the structure activity relationships and pharmacokinetic behavior. A higher TGSO oxidation stability was observed in the presence of equimolar (1:1) binary mixtures of coumarins with TOH (1 + TOH, 3 + TOH and 5 + TOH). However, the synergism (14%) was observed only for the binary mixture of 5 + TOH. (C) 2010 Elsevier Masson SAS. All rights reserved