The effect of temperature and methanol–water mixture on pressurized hot water extraction (PHWE) of anti-HIV analogoues from Bidens pilosa

Abstract

BackgroundPressurized hot water extraction (PHWE) technique has recently gain much attention for the extraction of biologically active compounds from plant tissues for analytical purposes, due to the limited use of organic solvents, its cost-effectiveness, ease-of-use and efficiency. An increase in temperature results in higher yields, however, issues with degradation of some metabolites (e.g. tartrate esters) when PHWE is conditioned at elevated temperatures has greatly limited its use. In this study, we considered possibilities of optimizing PHWE of some specific functional metabolites from Bidens pilosa using solvent compositions of 0, 20, 40 and 60 % methanol and a temperature profile of 50, 100 and 150 °C.ResultsThe extracts obtained were analyzed using UPLC-qTOF-MS/MS and the results showed that both temperature and solvent composition were critical for efficient recovery of target metabolites, i.e., dicaffeoylquinic acid (diCQA) and chicoric acid (CA), which are known to possess anti-HIV properties. It was also possible to extract different isomers (possibly cis-geometrical isomers) of these molecules. Significantly differential (p ≤ 0.05) recovery patterns corresponding to the extraction conditions were observed as recovery increased with increase in methanol composition as well as temperature. The major compounds recovered in descending order were 3,5-diCQA with relative peak intensity of 204.23 ± 3.16 extracted at 50 °C and 60 % methanol; chicoric acid (141.00 ± 3.55) at 50 °C and 60 % methanol; 4,5-diCQA (108.05 ± 4.76) at 150 °C and 0 % methanol; 3,4-diCQA (53.04 ± 13.49) at 150 °C and 0 % methanol; chicoric acid isomer (40.01 ± 1.14) at 150 °C and 20 % methanol; and cis-3,5-diCQA (12.07 ± 5.54) at 100 °C and 60 % methanol. Fitting the central composite design response surface model to our data generated models that fit the data well with R2 values ranging from 0.57 to 0.87. Accordingly, it was possible to observe on the response surface plots the effects of temperature and solvent composition on the recovery patterns of these metabolites as well as to establish the optimum extraction conditions. Furthermore, the pareto charts revealed that methanol composition had a stronger effect on extraction yield than temperature.ConclusionUsing methanol as a co-solvent resulted in significantly higher (p ≤ 0.05) even at temperatures as low as 50 °C, thus undermining the limitation of thermal degradation at higher temperatures during PHWE.

Subcritical Water Extraction and Its Prospects for Aflatoxins Extraction in Biological Materials

“…It is in line with this that we propose the adoption of SWE as an alternative to conventional extraction methods for AFs, particularly with respect to improved recovery and selectivity, reduced organic solvent consumption and extraction time, at a lower cost. SWE has been in the spotlight as an efficacious and highly promising alternative to traditional techniques of extraction, whose successful applications in the biochemical, pharmaceutical and chemical engineering fields have been well documented in the literature [14,[90][91][92][93][94][95][96]. A brief description of this method of extraction is presented in the proceeding sections of this chapter.…”

“…Cosolvents and solvent modifiers are often used to enhance the extractability of SWE. Cosolvents are secondary solvents (usually organic solvents) that are added to subcritical water to enhance its solvation power [95,110]. The incorporation of methanol during SWE was observed to significantly (p < 0.05) increase yield of flavonoids and di-acylated cinnamic acids from Bidens pilosa [95,111].…”

“…Cosolvents are secondary solvents (usually organic solvents) that are added to subcritical water to enhance its solvation power [95,110]. The incorporation of methanol during SWE was observed to significantly (p < 0.05) increase yield of flavonoids and di-acylated cinnamic acids from Bidens pilosa [95,111]. Solvent modifiers such as salts and other reagents can alter important physicochemical properties of water such as polarity, surface tension, and hydrogen bonding strength, which results in an enhanced extractability [13,112].…”

“…When the temperature and pressure of water are extremely high (i.e., above 374°C and 221 bar), there is also the risk that water can become very reactive and could oxidize or catalyze the hydrolysis of some compounds [13]. However, optimization by means of the adoption of a cosolvent or modifier could ameliorate or eliminate these issues [95].…”

“…Although issues with thermal degradation of some analytes have been a major limiting factor of SWE, it is interesting to know that AFs and most other mycotoxins are relatively thermally stable [31,62]. Moreover, optimization using cosolvents has been found effective in ameliorating this setback [95,127]. Accordingly, in our recent study [125] described in the beginning of this section (Section 3.7), we observed a clear positive enhancement on the recovery of AFB 1 by means of a cosolvent (methanol).…”