Ultrasound-Assisted Extraction (UAE) of sappan wood (Caesalpinia sappan L.): Effect of solvent concentration and kinetic studies

Abstract

Sappan wood (Caesalpinia sappan L.) is a plant that contains many phytochemical constituents such as antioxidant, antimicrobial, antifungal and antiacne that have functional activities. Sappan woods have several phenolic compounds such as brazilin, xanthone, flavones and coumarin. In order to extract the phenolic compounds, Ultrasound-Assisted Extraction (UAE) is considered as green technology and gives better quality products with a higher extraction rate, shorter extraction time and less energy. The research investigated the effect of different ethanol concentrations on the sappan wood’s yield and studied the kinetic on its extraction process. Sappan wood was extracted using a type of UAE probe with ethanol concentrations of 50%, 60%, 70%, 80% and 90% (v/v). For the extract was analyzed its yield, Total Phenolic Content (TPC), antioxidant activity, Fourier Transform InfraRed (FTIR) spectroscopy and lees morphology. The kinetic study refers to Peleg’s model and was conducted for temperatures of 40 °C, 50 °C and 60 °C. The results showed that the increase of ethanol concentration increased the yield of extract until ethanol was 80% and decreased when the ethanol concentration is higher than 80%. While the TPC slowly decreased, when the ethanol concentration increased. Comparing the UAE and sohxlet methods, UAE gave a higher yield in a shorter time (10.33% in 20 min) than the Soxhlet method (9.67% in 180 min). All the extracts were categorized as high antioxidant material since the IC₅₀ points were lower than 50 ppm. FTIR spectroscopy showed that UAE did not change the functional group of the extract, while Scanning Electron Microscope (SEM) pictures showed the more obvious cracked and deep holes of UAE’s lees than the Soxhlet’s lees. Peleg’s model was suitable to describe the extraction kinetics with R² higher than 0.93. Regarding both yield and TPC, a mixture of ethanol-water with ethanol 60% (v/v) could be the optimum solvent concentration (10.33% yield with TPC 2.63 mg GAE/g) for UAE of sappan wood.

Keywords:
Ethanol; Phenolic compound; Antioxidant activity; Sonocapillary; Extraction rate; Extraction capacity

Highlights

Ultrasound-assisted extraction enhances the extraction process in a shorter time

Lees of ultrasound-assisted extraction has more cracks and deep holes

Peleg’s model is appropriates to describe the sappan wood’s UAE process