Selective Separation of Tocol Homologues by Liquid-Liquid Extraction Using Choline-Based Deep Eutectic Solvents

Abstract

In this paper we examined the potential of choline-based deep eutectic solvents (DESs) for selective extraction of tocol homologues from crude palm oil (CPO) through liquid-liquid extraction (LLE). Distribution of tocol homologues (α-tocopherol, α-, β, γ-, and δ-tocotrienol) presence in CPO when subjected to DES-assisted LLE has not been fully understood in the past. The effect of increasing the amount of DES on the distribution and selectivity of were investigated. It was found that tocol homologues were distributed in the order of their hydrophilic power, with tocols of higher polarity distributed more into the stripping phase compared to the less polar tocols. Distribution coefficients for α-tocopherol, α-, β, γ-, and δ-tocotrienol were 7.8, 13.1, 19.8, 22.1 and 29.6, respectively, when equal weight of CPO and choline chloride-malonic acid eutectic mixture (DES1) were used. The distribution of each tocol homologues also increased with increasing DES1, due to the increase in polarity of the stripping phase that attracted more tocols. Selectivity of δ-tocotrienol, which is the most polar tocol, was always higher than other homologues (α-tocopherol: 3.81, α-tocotrienol: 2.22, β-tocotrienol: 1.50, γ-tocotrienol: 1.34). Role of hydrophilic power of the tocols using selected DESs to selectively separate tocol homologues established in this paper has a potential for palm oil industry as tocotrienols are better antioxidants, thus more favorable, than α-tocopherol.
 HIGHLIGHTS
 
 Tocopherols and tocotrienols in palm oil products are usually extracted for nutritional capsules and dietary products formulations using high-end techniques which are costly. Liquid-liquid extraction is a cheap technique which can be carried out at ambient conditions but with low selectivity
 A series of choline-based eutectic solvents, a new generation of green chemicals, were formulated for targeted separation of, specifically five tocol homologues present in crude palm oil; α-tocopherol, α-, β-, γ-, and δ-tocotrienol
 Unique combination of the eutectic solvents and liquid-liquid extraction resulted in selective separation of tocol homologues depending on the polarity of the tocols. Tocotrienols, having higher polarity and better antioxidative power than tocopherols, can be selectively extracted with the right deep eutectic solvents made from choline chloride, malonic acid, and citric acid
 
 GRAPHICAL ABSTRACT