Extraction of triterpenic acids from wet olive pomace by using closed microwave extraction system

In this study, triterpenic acids (maslinic and oleanolic acid) were extracted from wet olive pomace (51.5 moisture content/100 g wet pomace) under pressure by using closed vessel microwave extraction system with a nonpolar solvent, hexane. Effects of microwave power (150-300 Watt), extraction time (4-20 min) and solvent to solid ratio (5:1-10:1) on extraction efficiency were examined. Optimum conditions which provide the highest efficiency were found as 250 Watt, 12 min and 10:1 for microwave power, time and solvent to solid ratio, respectively. Total amount of triterpenic acid extract which obtained under optimum conditions was 26 mg/g dry pomace. The identification and quantification of obtained triterpenic acids were performed by using HPLC, TLC and ESI-MS. The percentages of the acids present in the extract were 80% maslinic acid and 20% oleanolic acid. The acids present in the extract was separated from each other by using column chromatography with hexane:ethyl ether:acetic acid (65:34:1) mixture. The antioxidant and antimicrobial activity for extract and acid fractions were determined. According to the DPPH (% inhibition 22.87) and FRAP (263.087 μM TE) results the maslinic acid fraction had shown the highest antioxidant activity. In addition, it was observed that the maslinic acid fraction had almost as much antimicrobial effect on the studied microorganisms as amoxicillin. Key words: microwave assisted extraction, maslinic acid, oleanolic acid, olive pomace