Subcritical Water for Recovery of Polyphenols from Comfrey Root and Biological Activities of Extracts

Abstract

In the present study, subcritical water was used for extraction of bioactive compounds of Symphytum officinale root. Temperature (120-200 °C), extraction time (10-30 min) and HCl concentration in extraction solvent (0-1.5%) were investigated as independent variables in order to obtain the optimal conditions for extraction and to maximize the yield of total phenols, flavonoids and antioxidant activity of obtained extracts. The application of optimal conditions (200 °C, 25.6 min and 0.0075%) provided extracts rich in total phenols and flavonoids and high antioxidant activity. Results also demonstrated that subcritical water extraction showed significant advantages for recovery of comfrey root bioactive compounds comparing to maceration and ultrasound-assisted extraction techniques. In addition, subcritical water extracts of S. officinale root are the promising sources of compounds with antioxidant, ACE inhibition, and antiproliferative properties and could potentially be used for production of new pharmacologically-active formulations.

Valorization of Yarrow (Achillea millefolium L.) By-Product through Application of Subcritical Water Extraction

“…In present study, pressure exerted an insignificant impact. Similar findings were determined in a study by Vladic et al [21], where HCl addition did not demonstrate a significant effect on TPH yield, which was also the case in a study by Pavlic et al [12], where that effect was only moderately significant. Finally, the efficiency of the recovery of phenolics depends on the nature of the material and their distribution in matrix, as well as stability.…”

“…Higher temperatures consequentially led to lowering surface tension, which further allows better pore filling and solubilization of phenols [21,35]. Similar findings, which state that only temperature exhibits an important influence, were determined in studies where SWE was used for the extraction of bioactive compounds from Satureja montana, Symphytum officinale, Coriandrum sativum, and Allium ursinum [20,21,36,37]. the nature of the material and their distribution in matrix, as well as stability.…”

“…TPH content was increased with the increase of temperature owing to the increased polyphenol solubility and mass transfer coefficient between the matrix and media [18,19]. Higher temperatures consequentially led to lowering surface tension, which further allows better pore filling and solubilization of phenols [21,35]. Similar findings, which state that only temperature exhibits an important influence, were determined in studies where SWE was used for the extraction of bioactive compounds from Satureja montana, Symphytum officinale, Coriandrum sativum, and Allium ursinum [20,21,36,37].…”

“…The same findings were recorded by Singh and Saldana [28], who discovered that a higher yield of phenolics was extracted from potato peel at temperatures ranging from 140 to 180 • C. A further rise in temperature up to 240 • C affected the efficiency of the extraction and produced a lower yield of phenols [28]. In addition, in a previous study in which winter savory, purple coneflower, and comfrey root were used as a sources of polyphenols, the optimal SWE process parameters were as follows: 200 • C and 20.8 min [20]; 148 • C and 17.8 min [29]; 200 • C, 25.6 min, and 0.0075% HCl [21], respectively.…”

“…In SWE, temperature represents the most significant influencing factor because an increase in temperature leads to better mass transfer between the matrix and media, solubility of solutes, and diffusion rate at a lower solvent viscosity and surface tension [18][19][20][21]. Extraction time is also an important factor that can significantly impact the quality of extracts, because long-term exposure to high temperature can cause degradation of bioactive components or formation of new antioxidants [20,22,23].…”