Effect of Solvent, Preheating Temperature, and Time on the Ultrasonic Extraction of Phenolic Compounds from Cold‐Pressed Hempseed Cake

Abstract

AbstractThe effect of different solvents (aqueous methanol [70%, v/v], aqueous acetone [80%, v/v], and a solvent mixture [MA] of aqueous methanol [70%, v/v] and aqueous acetone [70%, v/v] in a ratio of 1:1 [v/v]), preheating temperatures (140, 160, and 180°C), and times of exposure (5, 15, and 30 min) on the ultrasonic extraction of the main phenolic compounds from hempseed cake (Cannabis sativa) was investigated. A simplified new high‐performance liquid chromatography (HPLC) method was developed to identify and quantify the main phenolics (namely, N‐trans‐caffeoyltyramine and cannabisin B) in the extracts. Two other main compounds, numbered 3 and 4, were also detected. The results showed that the nature of the extracting solvent had a significant (P < 0.05) impact on the ultrasonic extraction of phenolic compounds. The acetone extracts exhibited the highest total phenolic content (TPC), followed by MA and methanol. The preheating temperature and time of exposure enhanced the TPC for all solvents examined. The main phenolics, N‐trans‐caffeoyltyramine, cannabisin B, and compound 3, were positively affected by the temperature and time of exposure, irrespective of the solvents used. In sharp contrast, compound 4 appeared to be thermally sensitive: increasing preheating time and temperature decreased the yields of this compound. This study demonstrated that acetone was the most effective extracting solvent and that preheating enhanced the yield of the main phenolics.