Essential oils extracted by hydrodistillation from the aerial parts of 23 samples of Algerian Origanum glandulosum Desf. were analysed by gas chromatography (GC) and GC-mass spectrometry (MS). Overall, 30 components have been fully characterized. However, all the oils were characterized by the predominance of four components, thymol (18.5-73.1%), carvacrol (7.6-72.6%), p-cymene (1.7-18.5%) and γ γ γ γ γ -terpinene (1.1-18.7%). Cluster analysis of the identified components allowed us to establish the presence of three main groups, characterized by carvacrol, thymol and comparable amounts of both compounds, respectively. The free radical scavenging activity of essential oils was determined by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) model system. The SC 50 (scavenging concentration) values were in the range 16.2-26.7 µ µ µ µ µg/ml, representing a good antioxidant effectiveness. The roles of thymol and carvacrol, the main components of all oils, were estimated by measuring their stoichiometric factors. The essential oils were also evaluated for their antimicrobial activity by the agar disc diffusion method and the determination of minimum inhibitory concentration (MIC) against six standard strains (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Enterococcus hirae, Candida albicans, Candida tropicalis). All microbial strains employed (Gram-positive and Gram-negative bacteria and yeasts) showed a fairly similar degree of susceptibility to the essential oils under investigation, although no evident difference was observed in their sensitivity. Furthermore, a similar level of toxicity was observed for all oils examined, with MIC values of 31.25-125.00 µ µ µ µ µg/ml. Finally, the addition of the emulsifier Tween 80 to the oil or to the agar markedly decreases the antimicrobial activity of the essential oils against all microbial strains employed, thus suggesting that the antimicrobial activity of the essential oils is dependent on the physicochemical characteristics of their components and also on the microbial strains employed.

The essential oils obtained from Origanum glandulosum Desf., collected in four different localities of the Sètif region (north-eastern Algeria), were analysed by GC-MS and assayed for their antioxidative effectiveness. The antioxidant capacity of the oils was measured by the modified thiobarbituric acid reactive species (TBARS) assay, using egg yolk as oxidizable substrate in presence of the radical inducer 2,2 0 -azobis-(2-amidinopropane) dihydrochloride (ABAP). The activity was compared with those of˛-tocopherol and 2,6-ditertbutyl-4-methyl phenol (BHT, butylated hydroxytoluene). The four oils were also endowed with a high degree of activity at the lowest concentration (100 ppm). This activity is to be ascribed to the high content of phenol components, viz. thymol and carvacrol, which strongly characterize the composition of these oils.

Genista species are sources of antioxidant phenolic compounds such as O-and C-glycosylflavonoids and isoflavonoids. A combination of a DPPH scavenging assay with HPTLC-MS, a fast and efficient method for identification of bioactive compounds, has been applied for evaluation of the radical scavenging activity of metabolites from Genista saharae Coss. & Dur. Different organs collected at various periods have been compared. Identification of antioxidant compounds was obtained by elution of the major DPPH-inhibition zones. The resulting HPTLC-MS analysis under moderately polar conditions, coupled to the DPPH results led to the putative identification of two antioxidant isoflavone aglycones: 3',4',5,7-tetrahydroxyisoflavone (1) and ficuisoflavone (3), whereas polar migration conditions led to the identification of the glycosides 5-methoxy-4',7-trihydroxy-8-glucopyranosylisoflavone (4) and 4',5-dihydroxy-7-methoxyisoflavone-4'-O-β-D-glucopyranoside (5). Evaluation of percentage of inhibition of DPPH radical by the purified isoflavone 4 from the root extract showed that it affords a moderate contribution to the total radical scavenging activity of the extract.

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