Rosemary Oil and Distillation Time

Zheljazkov, Astatkia, Zhalnov, and Georgieva (2015) decided to compare extraction techniques using both dried and fresh rosemary leaves to determine if one technique was better to treat one ailment while another technique is more suited for a second ailment.  In this case, they specifically looked at the length of distillation.  These times were 1.25, 2.5, 5, 10, 20, 40, 80, and 160 minutes.  They grew the plants from the exact same species and in the same soil using raised beds to control soil content.  The dried leaves produced more oil but the yield was not increased after the 10-minute mark. 

The amount of verbenone was not seemingly affected by the length of boiling while camphor and borneol were more prevalent in the 80- and 160-minute samples. 

Myrcene and linalool were not affected by time but the dried material produced more.  Myrcene was most prevalent in the dried herb. 

The short boiling time had more a-pinene, camphene, eucalyptol (1,8-cineole), and b-pinene.

Camphene was not affected by whether the leaves were dry or not dry but eugenol was more prevalent in the oil made from the fresh leaves, as was eucalyptol. 

Borneol and b-caryophyllene were more prevalent from the dried herb at 40 minutes.

Bornyl acetate was more prevalent in the fresh samples. 

A-pinene, camphene, b-pinene, myrcene, eucalyptol, camphor had differing results between the dry and fresh herb. 

The highest amount of a-pinene was at the 2.5-minute mark from dry leaves. 

For b-pinene, it was fresh leaves at the 2.5-minute mark. 

Camphor was the highest at the 160-minute mark from fresh leaves while b-caryophyllene was the most at the 80-minute mark with dried leaves.

They tested some of the oils against various microbes and the oils were not effective.  In the discussion portion, they discuss the optimal time for distilling the oil is 20 minutes but all of the studies they refer to are between 2 and 4 hours. 

The study they conducted didn’t go longer than 2 hours.  The distillation methods for these studies were not necessarily the same (some didn’t mention the method).  They also mention the distillation time had a direct relationship to the concentration of the chemicals in the oil, more so than harvesting stage (not further described). 

They mention the studies where the oil worked against various microbes used a much higher concentration of the oil that that used in this study.  The chemical profile was also different for this study. 
 
Have a Great Day!

Zheljazkov, V. D., Astatkia, T., Zhalnov, I., and Georgieva, T. D. (2015). Method for attaining Rosemary Essential Oil with Differential Composition from Dried or Fresh Material.  Journal of Oleo Science, 64(5):485-496.  doi: 10.5650/jos.ess14258.