Total phenolic content and antioxidant capacity of Greek medicinal and aromatic plant extracts using pulsed electric field followed by ultrasounds extraction process

Optimization of Four Different Rosemary Extraction Techniques Using Plackett-Burman Design and Comparison of Their Antioxidant Compounds

Rosemary has many medicinal and therapeutic properties and therefore it is important to study how to maximize the recovery of its bioactive compounds. In the present study, four different extraction techniques were used, namely stirring extraction (STE), pulsed electric field-assisted extraction (PEF), ultrasound probe-assisted extraction (UPAE), and ultrasound bath-assisted extraction (UBAE). First, some primary experiments were carried out in order to optimize each technique individually through the Plackett-Burman design. Then, each technique was applied under optimal conditions and the results were compared with each other. The optimal total polyphenol content (TPC) of STE is ~19 mg gallic acid equivalents per gram of dry weight (dw), while the antioxidant activity of the extract is 162 μmol ascorbic acid equivalents (AAEs) per gram of dw via FRAP and ~110 μmol AAE per gram of dw via DPPH. As for PEF, the optimal TPC is ~12 mg GAE/g dw, and the FRAP and DPPH values are ~102 and ~70 μmol AAE per gram of dw, respectively. When it comes to UPAE, the optimal TPC is ~16 mg GAE/g dw and the antioxidant capacity of the extract is ~128 μmol AAE/g dw through FRAP and ~98 μmol AAE/g dw through DPPH. UBAE optimal extract yielded ~17 mg GAE/g dw TPC, ~146 μmol AAE/g dw for FRAP, and ~143 μmol AAE/g dw for DPPH. The highest flavonoid content (~6.5 mg rutin equivalent/g dw) and DPPH (~143 μmol ascorbic acid equivalent/g dw) is obtained through UBAE. UPAE has been shown to be more efficient in recovering ascorbic acid (~20 mg/g dw). Additionally, the chlorophyll-to-carotenoid ratios of UPAE and UBAE were 2.98 and 2.96, respectively, indicating that the extracts had a generally positive impact on health. Considering the environmental impact of each extraction technique but also which antioxidant factor needs to be maximized, the most suitable extraction technique will be chosen.

Ultrasonic-assisted extraction to enhance the recovery of bioactive phenolic compounds from Commiphora gileadensis leaves

The "ultrasonic-assisted extraction (UAE)" method was utilized in this work to assess how different process parameters affected the yield and recovery of phenolic compounds from the leaf of Commiphora gileadensis, which is one of the medicinal plants with a variety of biological functions. Its leaf is used for a various of therapeutic applications, such as the treatment of bacterial infections, inflammation, and wound healing. The "One-Factor-At-a-Time (OFAT)" approach was employed to examine the impacts of various UAE process parameters on the process of extraction, which include time of extraction, sample/solvent ratio, ultrasonic frequency, and solvent (ethanol) concentration. The extracts were then investigated for the presence of several phytochemicals using analytical techniques such as "Gas Chromatography-Mass Spectroscopy (GC-MS)" and "Fourier Transform Infrared Spectroscopy (FTIR)" studies. The findings showed that the maximum extraction yield, the total phenolic content (TPC), and the total flavonoids content (TFC) of the ethanolic extract of the leaves of C. gileadensis using the UAE method were at 31.80 ± 0.41 %, 96.55 ± 2.81 mg GAE/g d.w. and 31.66 ± 2.01 mg QE/g d.w. accordingly under a procedure duration of 15 min, ultrasonic frequency of 20 kHz, solvent/sample ratio of 1:20 g/mL, and solvent concentration of 40 % v/v. The leaves extract of C. gileadensis included 25 phenolic compounds that were previously unreported, and GC-MS analysis confirmed their presence. Hence, it follows that the UAE technique can successfully extract the phytochemicals from C. gileadensis for a variety of therapeutic uses.

Polyphenol Extraction from Food (by) Products by Pulsed Electric Field: A Review

Nowadays, more and more researchers engage in studies regarding the extraction of bioactive compounds from natural sources. To this end, plenty of studies have been published on this topic, with the interest in the field growing exponentially. One major aim of such studies is to maximize the extraction yield and, simultaneously, to use procedures that adhere to the principles of green chemistry, as much as possible. It was not until recently that pulsed electric field (PEF) technology has been put to good use to achieve this goal. This new technique exhibits many advantages, compared to other techniques, and they have successfully been reaped for the production of extracts with enhanced concentrations in bioactive compounds. In this advancing field of research, a good understanding of the existing literature is mandatory to develop more advanced concepts in the future. The aim of this review is to provide a thorough discussion of the most important applications of PEF for the enhancement of polyphenols extraction from fresh food products and by-products, as well as to discuss the current limitations and the prospects of the field.