Determination of diterpene esters in green and roasted coffees using direct ultrasound assisted extraction and HPLC–DAD combined with spectral deconvolution

Abstract

In recent decades, attraction towards the green extraction techniques has persuaded researchers to find an alternative for traditional extraction techniques. Here, the application of ultrasound assisted extraction (UAE) followed by chromatographic analysis using high performance liquid chromatography combined with diode array detection and spectral deconvolution (HPLC–DAD/SD) were investigated to quantify the main eight diterpene esters (cafestol and kahweol linoleates, oleates, palmitates and stearates) in green and roasted coffees. Factors employed were time of ultrasonication (0, 10, 20 and 30 min) and extraction solvent volume (10, 15 and 20 mL). The UAE was successfully optimized (20 min and three times extraction with diethyl ether equivalent to 15 mL) and resulted in the extraction of the considerable portion of the diterpene esters from ground coffee, representing cafestol palmitate in larger amount in green (201–739 mg/100 g) and the respective roasted ones (154–670 mg/100 g). Whereas, kahweol linoleate presented slightly higher content than kahweol palmitate either in green or roasted samples. In general, the diterpene esters content slightly decreased from green to roasted coffees, although it was not statistically significant (p > 0.05). Likewise, the profile of diterpene esters was not affected by the roasting process. The analytical method was also validated as good intra- and inter-day precisions ( 0.98) was acquired. We concluded that as a rapid and accurate approach, the UAE combined with HPLC–DAD/SD is an economic approach that can be used for monitoring of diterpene esters in either green or roasted coffee.