Abstract
Concern for the long-term toxicology of commonly used synthetic antioxidants such as butylated hydroanisole (BHA) butylated hydroxytoluene (BHT) and propyl gallate (PG) has increased the demand for natural antioxidants. That has motivated extensive research into methods of extracting natural anti-oxidants. The herb Rosmarinus Officinalis has proved to be a rich source of natural antioxidants, in particularly that of carnosic acid. The aim of this project was to compare conventional solvents, novel low-pressure solvents and ultrasonic methods for the extraction of carnosic acid and rosmarinic acid from the fresh and dried leaves of the Rosemary herb.The conventional extraction method using ethanol, butanone and ethyl acetate as solvents was compared with ultrasonic extraction in the same solvents. Under conventional conditions butanone extraction gave the maximum yields of the known anti-oxidant carnosic acid. Extracts obtained by ultrasonic butanone extraction showed similar results to the conventional method. However ethanol proved to be a poor solvent for conventional carnosic extraction but when ultrasound was applied a significantly improved yield of carnosic acid was obtained.
The higher yields obtained from conventional extraction in butanone compared with ethanol are attributed to the much greater solubility of carnosic acid in butanone. The increase in yield when ultrasound is applied to the ethanol extraction is believed to be due to increased disruption of cell walls by cavitational effects permitting greater access of the solvent to cell contents.
Extraction of carnosic acid from dried rosemary leaves gave better results then fresh rosemary. On the other hand the extraction of rosmarinic acid was more efficient from fresh rosemary.
The poor yields obtained from extractions using the low boiling tetraflurocarbon solvent are ascribed to the low solubility both carnosic and rosmarinic acid in this solvent.
| Date of Award | 2003 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Timothy Mason (Supervisor) & Larysa Paniwnyk (Supervisor) |