The influence of different extraction conditions and extraction techniques on antioxidant activity of wild thyme extracts

Abstract

The aim of the present study was the investigation of the impact of different extraction conditions (particle size of plant material, solvent-to-solid ratio and solvent type) and extraction techniques (maceration, heat- and ultrasound-assisted extractions) on the antioxidant activity of wild thyme (Thymus serpyllum L.) extracts. Liquid wild thyme extracts were obtained in maceration (in shaker at 25°C), in heat-assisted extraction (in incubator shaker at 80°C) and in ultrasound-assisted extraction (by ultrasound probe at amplitude of 80%) using three particle sizes (0.3, 0.7, and 1.5 mm), three solvent-to-solid ratios (10:1, 20:1, and 30:1), and three ethanol concentrations (0, 30 and 50 % ethanol). Antioxidant potential of the obtained extracts was determined using ABTS and DPPH assays. The statistical analysis was performed by using statistical software, STATISTICA 7.0 (analysis of variance and Duncan’s post-hoc test); the difference was considered statistically significant at p<0.05. According to the results, higher degree of herbal drug disintegration resulted with better antioxidant activity, but this effect was statistically significant for heat- and ultrasound-assisted extractions according to ABTS assay, and for maceration and heat-assisted extraction according to DPPH assay. According to the influence of solvent-to-solid ratio, the increase in ratio from 10:1 to 30:1 resulted in the extracts with higher antioxidant potential regardless of the type of extraction method. Furthermore, in comparison to aqueous wild thyme extracts the antioxidant activity of ethanol extracts was higher, particularly in the case of 50 % ethanol extracts. In ABTS assay, there were no differences between antioxidant activity of the extracts obtained by different extraction procedures, while in neutralization of DPPH radicals, the extracts obtained using ultrasonic probe had statistically significantly higher antioxidant potential. Due to the antioxidant properties shown in the present study, wild thyme ethanol extract may be used in the formulations in food, pharmaceutical, and cosmetic industries.