Saša S. Stojičević

Comparison of Antioxidant and Antimicrobial Activities of Methanolic Extracts of the Artemisia sp. Recovered by Different Extraction Techniques

Abstract The polyphenol content, antioxidant and antimicrobial activities of the extracts obtained by classical, ultrasonic and Soxhlet extractions from dry aerial parts of two Artemisia species (Artemisia vulgaris and Artemisia campestris) were compared. Ultrasound positively affected the yield of extractive substance and the kinetics of extraction, but the extract obtained by the classical extraction showed the highest antioxidant activities and contained higher total contents of phenolic compounds and flavonoids than the extracts obtained by two other extraction techniques. Both flavonoid aglycones (apigenin, quercetin, quercetin 3,37prime;-dimethyl ether) and flavonoid glycosides (rutin, hyperoside and kaempferol 3-rhamnoside) were identified by thin layer chromatograph (TLC) analysis in the extracts from both species. A. campestris extracts were richer in quercetin than A. vulgaris and its antimicrobial activity was also better than A. vulgaris. Extracts obtained from both species were found to be more effective on the tested yeasts than bacteria. The kinetics of the total extractive substances, such as phenolic, flavonoids and quercetin extraction, was successfully described by the model of unsteady-state diffusion.

Antioxidant and Antimicrobial Activities of Echinacea （Echinacea purpurea L.） Extracts Obtained by Classical and Ultrasound Extraction

Abstract Antioxidant and antimicrobial activities of Echinacea purpurea L. ( Asteraceae ) extracts obtained by classical and ultrasound solvent extraction were compared. The dry aerial part of plant was extracted by 70% ethanol at a solid-to-liquid ratio of 1:10 (m/v) and 25°C. The extract obtained by classical solvent extraction contained 29% larger amounts of phenolic compounds and 20% higher content of flavonoids. 2,2-diphenyl-1-picril hydrazyl radical (DPPH) scavenging reached 93.6% and the values of EC50 were (34.16±0.65) μg·ml −1 and (65.48±1.12) μg·ml −1 for the extracts obtained by the classical and ultrasound extractions, respectively. The extracts, independent of the extraction technique applied, showed a considerable growth inhibition on Candida albicans and Saccharomyces cerevisiae , while no growth inhibition zones were observed for Aspergillus niger . The diameters of inhibition zone observed for all the microorganisms were larger for extracts obtained by classical extraction than those by ultrasound extraction.

Optimization of Microwave-Assisted Extraction of Cherry Laurel Fruit

Response surface methodology was used to optimize the influence of microwave power (300–600 W), plant material-to-solvent ratio (0.05–0.2 g/cm3), and extraction time (10–30 min) on the efficiency of microwave-assisted extraction of the cherry laurel (Prunus laurocerasus L.) fruit. From experimental data, a quadratic polynomial mathematical model (R2 = 0.9949) was developed to predict the extract yield. All considered factors were statistically significant for extraction efficiency, while the most important factor was extraction time. Microwave power of 550 W, plant material-to-solvent ratio of 0.05 g/cm3, and time of 25 min were determined as optimal conditions with a maximum yield of 9.36 g/100 g fresh plant material, which was confirmed through laboratory experiments (9.12 ± 0.61 g/100 g fresh plant material). An economic condition for simultaneous maximum extract yield (7.58 g/100 g fresh plant material) with minimal energy and solvent consumption was determined by the desirability function method (18.2 min, 300 W, and 0.2 g/cm3). Additionally, the total phenol and flavonoid quantification and antioxidant activity of both extracts were tested. There is no statistically significant difference in the total flavonoid content in the extracts obtained under both proposed conditions, while the total phenolic content and antioxidant activity of the extract obtained under economic conditions were slightly lower.