Extraction of Phenolic Compound using Natural Deep Eutectic Solvent from Biomass Waste

Abstract

Phenolic compounds are aromatic compounds known for their bioactive substances which can be found in plants. It has been widely used in various applications due to its antibiotics, anti-inflammatory, anti-allergic, and other benefits. There are various methods to extract the phenolic compounds from plants including ionic liquid, liquid-liquid extraction as well as supercritical extraction. However, all of these methods requires energy extensive, laborious processes, advanced technology, and generate toxic waste. Therefore, there is a growing need to find an alternative green extraction method to reduce the environmental impact while improving the efficiency of the extraction process. Thus, natural deep eutectic solvents (NADES), a combination of two or more components that comes from primary metabolites like organic acids, choline chloride, or sugar, are able to form liquids upon mixing with lower melting point of individual constituents due to hydrogen bond interactions were proposed as alternatives to conventional extraction methods. Therefore, this research determined the suitable combination of NADES solvents (hydrogen bond acceptor/donor ratio) for extraction of phenolic compounds from biomass waste which included young and mature coconut shells and coconut husk, banana peel, empty fruit bunch, and palm oil fruit husk. The extracted compound was analysed using fourier-transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS) to identify the functional groups and type of phenolic compounds present. The best biomass waste was coconut shell and the best NADES combination was choline chloride and ascorbic acid at 1:2 molar ratio. The FTIR analysis of coconut shell extracted by NADES showed peaks at 3404 cm−1 and 3523 cm−1 indicating OH stretching followed by 2915 cm−1, 1388 cm−1 to 1473 cm−1, and 1674 cm−1 showing C-H stretching, sp3 C-H band and C=C stretch respectively. As for GC-MS analysis, 26 compounds were detected and four phenolic compounds were identified at peaks 2, 13, 22, and 25. The research was successful in determining the best biomass waste and NADES combination for highest total phenol. The use of NADES was able to extract more phenolic compound from coconut shell than water due to the hydrogen bond between the choline chloride and ascorbic acid.