Optimization of methods used to extract polyphenols from dried rosemary leaves

In this study, researchers from the Academic Center for Education, Culture and Research and Islamic Azad University in Iran optimized conditions used in heat- and ultrasound-assisted extraction of polyphenols from rosemary leaves through response surface methodology. The results of their study were published in the Journal of Food Processing and Preservation.

• Rosemary leaves are known to have antioxidant properties hence rosemary extracts are the only accepted natural food antioxidants in the EU.
• Heat-assisted extraction (HAE) is the conventional method generally used to extract active compounds from rosemary. However, the use of sustainable new technologies like ultrasound-assisted extraction (UAE) is also recommended.
• The researchers reported that a maximum total extraction yield (TEY) of 17.8 percent or total polyphenol content (TPC) of 147.56 milligrams gallic acid equivalent per gram of extract dry weight (mg GAE/g of extract DW) and a minimum half maximal inhibitory concentration (IC50) of 994.68 microgram per milliliter (mcg/mL) can be achieved using the following optimum conditions for HAE:
  • Extraction time: 132.80 minutes
  • Temperature: 70 C temperature
  • Liquid-to-solid ratio: 20:1
• For UAE, a maximum TEY of 20.82 percent or TPC of 185.16 mg GAE/g of extract DW and a minimum 1C50 of 805.84 mcg/mL can be achieved using the following optimum conditions:
  • Extraction time: 12.60 minutes
  • Power: 200 W
  • Solvent concentration: 56.26 percent ethanol
• For HAE, the researchers recorded the lowest IC50 value of 787.70 mcg/mL using a solvent mixture of water and 56 percent ethanol. This was similar to the value obtained for the antioxidant butylated hydroxytoluene (BHT, 714.79 mcg/mL), which confirmed the efficiency of the extraction procedure.

The researchers concluded that these optimal conditions will allow researchers to obtain maximum extraction efficiency of polyphenols from rosemary leaves.

Hosseini H, Bolourian S, Hamgini EY, Mahababadi EG. OPTIMIZATION OF HEAT- AND ULTRASOUND-ASSISTED EXTRACTION OF POLYPHENOLS FROM DRIED ROSEMARY LEAVES USING RESPONSE SURFACE METHODOLOGY. Journal of Food Processing and Preservation. 17 October 2018;42(11). DOI: 10.1111/jfpp.13778