Marianna Usai

Composition and in vitro antimicrobial activity of the essential oil of Thymus herba-barona Loisel growing wild in Sardinia

Abstract Two samples of the essential oils from Thymus herba-barona Loisel (Labiatae) of Sardinian origin were chemically characterized and their antimicrobial activity evaluated, in comparison with T. vulgaris and T. serpyllum oils, on the basis of their minimum inhibitory concentrations (M.I.C.s) and of the contact times required to totally inhibit development of microorganisms. GC and GC/MS analysis showed that the main components of essential oils of T. herba-barona were carvacrol (75.4% and 73–0%), borneol (3.6% and 6.4%) and p-cymene (3.9% and 3.3%), while the percentage of thymol was very low (1.0% and 0.7%). Results of the antimicrobial investigation demonstrated that both oils possessed similar and relevant microbicidal activities, especially against Gram+ bacteria (M.I.C.s range 0.125–0.500 mg/mL) and mycetes (M.I.C.s 0.125–0.500 mg/mL). At inhibitory concentrations, times required to kill microbial inocula (5–10 min) are comparable with those of chlorhexidine gluconate, an antiseptic with a broad range of antimicrobial activities. The strong activity of T. herba-barona oils is very probably due to the presence of carvacrol, which was found from our screenings to exhibit a similar antimicrobial activity. Our findings provide for a rationale basis of a possible utilization of this oil in fields requiring safe and cheap compounds with antiseptic and preservative properties, such as cosmetic, pharmaceutical and food industries.

Fungitoxic activity of 12 essential oils against four postharvest citrus pathogens: chemical analysis of thymus capitatus oil and its effect in subatmospheric pressure conditions.

The fungitoxic activity against Penicillium digitatum, Penicillium italicum, Botrytis cinerea, and Alternaria citri of 12 essential oils (EOs) distilled from medicinal plants is reported. The results of the in vitro trials show strong fungitoxic activity of Thymus capitatus (L.) Hofmgg EOs, which inhibited the growth of the four fungi at a concentration of 250 ppm (vol/vol). The other 11 essences reduced the development of the fungi from 95 to 9% at 250 ppm (vol/vol). The fungitoxic activity of T. capitatus EOs (75, 150, and 250 ppm) on healthy orange fruits, inoculated with P. digitatum (10(8) conidia ml(-1)) by spraying and placed in 10-liter desiccators, was weak at atmospheric pressure (3 to 10% inhibition at all three concentrations), while in vacuum conditions (0.5 bar), conidial mortality on the exocarp was high (90 to 97% at all three concentrations). These data proved not to be statistically different from treatments with thiabendazole-TBZ (2,000 ppm). Scanning electron microscope observations showed that T. capitatus EO vapors altered the morphology of P. digitatum hyphae and conidia. The gas-chromatographic analyses of thyme EO indicated that carvacrol was present at 81 to 83%, p-cymene at 4.5 to 5%, gamma-terpinene at 2.6 to 3.3%, caryophyllene at 1.5 to 1.6%, beta-myrcene at 1.6%, and linalool at 1.1 to 1.2%. Carvacrol proved to be the most important fungitoxic compound among the thyme EO constituents, but, unlike thyme EO, it caused alterations to the fruit at the concentration of 75 ppm.

Solid Lipid Microparticles (SLM) Containing Juniper Oil as Anti-Acne Topical Carriers: Preliminary Studies

Solid lipid microparticles (SLM) were used as carriers of juniper oil and proposed for the topical treatment of acne vulgare. The formulations were obtained by the o/w emulsification method. Compritol and Precirol were employed as lipidic materials. Emulsions containing 1.5% (w/w) of lipophilic phase (lipid and oil) and two different lipid to oil ratios (1:1 and 2:1) were prepared. Blank particles were also prepared, as a comparison. The SLM were characterized in terms of encapsulation efficiency, size, and morphology. The particle size stability in aqueous dispersions was monitored over one month. Evaporation of volatile compounds of oil from microparticles by weight loss was investigated. The qualitative composition of Juniper oil before and after the encapsulation process was determined by gas chromatography (GC) and gas chromatography/mass spectrum (GC/MS) analyses. The antimicrobial activity of the oil encapsulated into the lipid microparticles against P. acnes was studied as contact time assay and compared to the activity of the oil not encapsulated. The emulsification method here described was a good technique for the encapsulation of essential oils. Percentage yields of production and encapsulation efficiencies were higher for Compritol preparations than for these prepared using Precirol. All preparations were characterized by similar particle size distributions (dvs about 3–4 µm) regardless of lipid type and lipid to oil ratios. Microscopy observations showed that the microparticles in aqueous dispersions had almost spherical shape, independently from their composition. The scanning electron microscopy (SEM) analyses showed that when the particles were dried, they had an irregular shape and a rough surface. The SLM dispersions based on Compritol revealed particle size stability over the investigated period of 30 days. In contrast, an increase of the mean dimensions in the preparations containing Precirol was observed. A low loss of volatile oil compounds owing to evaporation from dry particles was found in all preparations. This indicated that the microparticles were able to substantially maintain the oil loaded inside their lipidic structure, reducing its volatility. Some modifications of composition were found in the oil encapsulated in SLM with respect to the juniper oil raw material, but these modifications did not decrease the antibacterial activity of the oil. The SLM here described are promising carriers for the development of anti-acne topical formulations containing Juniper oil.

Analytical study of the reduction of chromium(VI) by D- galacturonic acid

Abstract The reduction of chromium (VI) to chromium(III) by d -galacturonic acid takes place to a significant extent only in the presence of metal ions such as copper(II) or chromium(III) itself. These metals can form stable complexes in which the opening of the sugar ring leads to a reducing free aldehydic group. The stoichiometry of the reaction, the dependence of the yield on the nature of the metal ion and the pH of the solution and the products formed, were studied. Stoichiometries and stability constants of the complexes present in the system chromium(III)- d -galacturonic acid were evaluated.

Essential Oil Composition of Hypericum perforatum L. var. angustifolium DC Growing Wild in Sardinia (Italy)

Abstract The oil from inforescences of Hypericum perforatum var. angustifolium growing wild and harvested in Sardinia (Italy) was analyzed by GC and GC/MS. The major compounds in the oil were 2-methyloctane (21.1%), germacrene D (17.6%) and α-pinene (15.8%).

Chemical Composition and Variation of the Essential Oil of Wild Sardinian Helichrysum Italicum G. Don subsp. Microphyllum (Willd.) Nym from Vegetative Period to Post-blooming

Abstract The essential oils obtained by water distillation from the aerial parts of Helichrysum italicum G. Don subsp. microphyllum (Willd.) Nym. were analyzed by gC and gC/MS. Three different populations growing at different elevations and under different weather conditions were studied from their vegetative period to post-blooming time. Forty-eight constituents accounting for between 96.5% and 83.0% of total oils have been identified and quantified. Among the identified constituents those present in the highest percentage were neryl acetate (17.6–35.6%), nerol (3.7–14.4%) and eudesmen-5-en-11-ol (6.4–23.5%). Among them, the neryl acetal percentage decreased when 5-eudesmen-11-ol percentage increased, and limonene reached 7% relative composition. The main fraction of the oil consisted of oxygenated compounds present in higher concentrations in June.

Cardenolides content in wild Sardinian Digitalis purpurea L. populations

In order to quantify the amounts of digitoxigenin and gitoxigenin in wild Sardinian Digitalis purpurea L. an easy extraction method and an high performance liquid chromatography (HPLC) analytical technique have been set up. The analyzed samples, stemming from six different locations, showed a great variability in glycoside content. The HPLC analyses carried out on 2-year-old plants of D. purpurea showed that the amounts of digitoxigenin and gitoxigenin ranged between 11.34 and 240.59 mg kg−1 and 4.05 and 178.07 mg kg−1, respectively, calculated on fresh material. Chemometric analyses, carried out considering different morphological characters, showed that correlations between morphological variations and glycoside content are poor.

Influence of Cultivar on the Composition of Lemon Peel Oil

ABSTRACT Forty constituents (accounting for 99.96-94.96 wt% of total volatile constituents) have been identified in the oils of twelve lemon cultivars grown in Sardinia. A statistical analysis of data was performed using Principal Component Analysis (PCA) method; through this analysis most lemon cultivars could be clustered into two groups. The nucellar cv. Santa Teresa (165 and ICAS 146) and Internodato, which possess different essential oil compositions, could not be clustered into either of the two groups, in fact they were even differentiated from one another.

Essential Oil Composition of Different Aerial Parts of Pistacia terebinthus L. Growing Wild in Sardinia

Abstract Essentials oils from different aerial parts of Pistacia terebinthus L. growing wild in Sardinia were analyzed in a single GC and GC/MS run. The oil yields obtained from the different parts range from 0.01–1.5%. α-Pinene was the main constituent of each of the P. terebinthus oils with the twig oil containing the highest concentration of 66.0%. In fruitful twigs the α-pinene concentration was 54.8% while in the leaf oil it was 16.4%. The other major component was β-pinene, the level of which in the oils of fruitful twigs and leaves was 22.5% and 13.5%, respectively.

Annual changes in the composition of the unsaponifiable oil of Euphorbia characias

Abstract The qualitative and quantitative variations in the acetone extracts of Euphorbia characias growing in Sardinia were studied throughout one year (May 1986 to April 1987) by capillary column GC and GC-MS. The composition of the triterpene alcohols as well as the sterol fraction was investigated.