Extraction Kinetics of Phenolic Antioxidants from the Hydro Distillation Residues of Rosemary and Effect of Pretreatment and Extraction Parameters

Abstract

Rosemary residue, remaining after the distillation of essential oil, is currently unexploited, while it is a source of phenolic antioxidant components. This raw material was used for the extraction of phenolic compounds by aqueous ethanol or acetone in a continuously stirred reactor. The experimental results were fitted with a two-stage diffusion model. The highest extraction rates, total phenolic content (TPC) recovery, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity were obtained by acetone 60% and ethanol 60%. Grinding of the raw material enhanced the extraction rate and increased TPC yield and antioxidant capacity as the particle size decreased. Pre-treatment by maceration in water (4 h) dissolved a high amount of TPC and shortened the extraction time, while the combination with the pulsed electric field process did not provide further improvement. The use of ultrasound increased the efficiency of the extraction.

Six Common Herbs with Distinctive Bioactive, Antioxidant Components. A Review of Their Separation Techniques

“…The presence of triterpenoid acids, i.e., ursolic and oleanolic has been also reported [ 18 ]. The main flavonoids of the plant are apigenin, luteolin and other flavones, found mostly as glucosides [ 17 , 19 , 20 , 21 ]. All the identified compounds reported in the literature are presented in supplementary material (Table S1) .…”

“…Carnosic acid and carnosol are compounds of medium polarity and therefore are effectively extracted with acetone or ethanol [ 21 , 22 , 23 , 24 , 25 ]. Other non-polar solvents like hexane and butanone proved also effective [ 24 , 25 ].…”

“…The extraction of carnosic acid in a shaking bath was enhanced with temperature (25–50 °C) and time (30–180 min), while butanone was more effective than ethanol, due to lower polarity [ 24 ]. The presence of water in mixtures with organic solvents decreases the extraction yield [ 21 ]. Confirming this observation, the fresh plant material presented lower carnosic acid extraction yield than the dried material due to the presence of water that combined with ethanol, which was used as solvent, resulting in a more polar solvent [ 24 , 26 ].…”

“…Comparing ethanol and methanol as solvents, it was found that the less polar ethanol is effective for the extraction of carnosic acid, while methanol for rosmarinic acid [ 26 ]. Water is an excellent solvent for rosmarinic acid, while increasing the organic solvents concentration in water decreases its extraction yield [ 21 ].…”

Environmentally Friendly Techniques and Their Comparison in the Extraction of Natural Antioxidants from Green Tea, Rosemary, Clove, and Oregano

“…Even this technique allows the extraction of polyphenolic compounds from rosemary, even when the raw material has already been used for the extraction of essential oils, obtaining polyphenols with 77.5 ± 1.2 mg GAE/g dw with an antioxidant capacity of 37.8 ± 1.1 mg GAE/g dw and 47.4 ± 1.1 (mg/g dw) of total phenolic diterpenes for UAE with 60% ethanol with a frequency of 37 kHz at 22 °C [ 57 ].…”