Extraction of anthocyanin from mangosteen rind using ionic liquids and deep eutectic solvents

Anthocyanins is natural pigments found in many plants that not only impart colours but also have potential health benefits and used as natural colorant in food processing industries. Mangosteen rind, although rich in anthocyanins, is normally disposed of as waste after consuming the delicate pulp. Anthocyanins is stored within the membrane cell wall inside the mangosteen rind, and it is usually recovered from the rind using solvent. Hence, this study investigated potential alternative green solvents, e.g., ionic liquids and deep eutectic solvents in extracting anthocyanins from mangosteen rind. This study is designed in conjunction with Sustainable Development Goals (SDGs) outlined by the United Nations, particularly SDG3 where good health and well-being equalities are emphasized and SDG12 in which efficient management of natural resource is addressed. Anthocyanins yield was determined using pH-differential method and result was expressed in milligram of cyanidin-3-glucoside per gram of mangosteen rind (mg cy-3-glu/g). Results showed that mangosteen rind extracted using both ionic liquids e.g., 1-ethy-3metylimidazolium bromide (EMIM) and 1-butyl-3methylimidazolium bromide (BMIM) solutions gave higher anthocyanins yields of 0.72 mg cy-3-glu/g and 0.69 mg cy-3-glu/g, respectively, in comparison to the 50% ethanol and deep eutectic solvents. This study revealed that high viscosity of deep eutectic solvent was the main factor that hindered the penetration of the solvent into the cell membrane of mangosteen rind, as a result, lower anthocyanins yields were obtained. Hence, in bioactive compounds extraction from plant materials, deep eutectic solvent incorporated with ultrasound or microwave is recommended as it could enhance the penetration of solvent into the plant’s matrix.