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Bioactive potential of medicinal plant extracts obtained by employing combined conventional and innovative extraction techniques

Extraction and product recovery are the most imperative steps in evaluation of valuable biologically active compounds from different plant substrates and ensuring availability of high-quality herbal products to consumers worldwide. With the growing interest in phytochemicals that exhibit positive health effects, for use in the production of functional food products, a need arises for the development of an efficient, simple, selective, environmentally friendly and economically feasible extraction technique, which will provide extracts prepared with non-toxic solvents. As the result of growing interest in innovative extraction techniques for the extraction of bioactive compounds, conventional extraction techniques that use water as the extraction media, such as infusion, decoction and maceration have been neglegted in recent years. Innovative extraction techniques including Microwave-Assisted Extraction (MAE) and Ultrasonic-Assisted Extraction (UAE) are much faster and efficient, and have significant advantages over conventional methods in terms of reduction in organic solvent consumption, process duration, minimizing sample degradation and elimination of undesirable and insoluble components from the extract. In this study the extraction efficiency of polyphenols from three traditional, widely used medicinal plants ; nettle (Urtica dioica L.), hawthorn (Crateagus oxycantha L.) and olive leaf (Olea europaea L.) by employing conventional and innovative extraction techniques was evaluated. In order to obtain an extract for use in food purposes, the application of organic solvents for the extraction of polyphenols was avoided by using water as the extraction solvent. Three conventional (infusions, maceration and decoction) and one innovative extraction technique (Ultrasonic-Assisted Extraction (UAE)) of medicinal plants, as well as their combination were employed. Bioactive potential of the obtained extracts was evaluated in terms of their polyphenolic profile and antioxidant properties by using spectrophotometric methods and high performance liquid chromatography (HPLC). According to the obtained results, among conventional extraction techniques, infusions of all three medicinal plants provided the highest and macerates the lowest polyphenolic yield, while the high temperature maintained during preparation of decoctions led to degradation of polyphenols when compared to infusions. Ultrasonically prepared extracts were more abundant in polyphenols than conventinally prepared extracts. The combination of ultrasonic-treatment prior to maceration and infusion revealed to be highly efficient for the extraction of polyphenols from all medicinal plants. The highest extraction efficiency of polyphenols was observed in ultrasound-pretreated and infused extracts. The extraction efficiency of specific polyphenols from different medicinal plants was dependant on the employed extraction technique, as well as the antioxidant properties of extracts which did not correlate well with total phenols, thus implying on the selective effect of employed techniques.

Antioxidant capacity; Extraction; Medicinal plants; Polyphenols; Ultrasound

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