The Fragrant Compounds in Rose Oil
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We will now look at the components of rose oil extracted from Damask rose, which has light pink blooms. This rose is renowned for its fine fragrance, so much so, that the flowers are commercially harvested and the resulting rose oil is used in perfumery.
Rose Oil Analysis
Analysis of rose oil from the Damask rose has resulted in the isolation of more than 100 organic compounds, whose structures have been elucidated using spectroscopic techniques including mass spectrometry.
Citronellol is the major component of rose oil – interestingly, almost entirely as the (S)‐enantiomer. Next comes geraniol followed by nerol – the only difference between these two alcohols is the arrangement of groups around one of the C=C double bonds. In geraniol, the methyl (CH3) and CH2OH groups are on the same side of the C=C bond, and it is called the E isomer. In nerol, the methyl (CH3) and CH2OH groups are on the opposite sides of the C=C bond, and it is called the Z isomer. (The E/Z system is a general notation used to define and name alkene isomers.)
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This means these alcohols have different shapes and while they both smell rose‐like, geraniol smells more flowery, and nerol more fresh. Reducing the E or Z C=C bond in geraniol or nerol, by adding hydrogen to it, forms citronellol. Next on the list is β‐ionone, containing both a six-membered ring and a ketone group. It has a similar aroma to that of violets. Finally, there is cis‐ and trans‐ rose oxide, which is discussed in detail in the accompanying pdf in the downloads section below.
Smell the Roses
The heady scent of a perfumed rose is one of life’s great pleasures. Sadly it has been bred out of many commercially available rose flowers in favour of longevity and colour. But, in 2015, researchers unlocked the secret of the rose’s scent… and how to get it back. It was found that a gene, called RhNUDX1, produces an enzyme that is responsible for triggering the production of geraniol (as we have seen, a key ingredient in rose oil) in the petals. This discovery will make it easier for rose breeders to select plants for their fragrance. We could even see the gene inserted into existing roses to create genetically modified variants with all the existing vase life/strong stem characteristics, but with added perfume (just like the creation of genetically modified blue roses).
Plant Fragrance Uses Pushy Proteins
It now appears that plants like petunias actively emit their fragrances and smells thanks to transporter proteins inside plant cells rather than just releasing them passively (i.e. the scent molecules ‘hitch a ride’ on a particular protein to escape the flower). This was demonstrated when genetically engineered flowers containing more of the protein were found to release more of the scent molecules. This new discovery means that plants use energy to smell the way they do, offering a new insight into the importance of plant communication.
Rose Fragrance Boosts Intelligence!
An experiment involving over fifty students showed that studying close to a rose-scented incense improved their test performance. The results showed a link between rose-scented studying and higher information retention, with an overall average increase in learned information of around 30% for students who used the incense during studying and sleeping. So, can sleeping with rose-scented incense nearby give your brain a learning boost, allowing you to retain more information that you may have learned during the course of the day? Further studies will be needed, but you may also be interested to know that it is not just the smell of roses that could aid learning. In 2013, a study found that pupils working in a room with the aroma of rosemary, in the form of an essential oil, achieved 5% to 7% better results in memory tests!
Fragrances can trigger powerful feelings and memories. Perhaps the smell of a rose-scented soap reminds you of your childhood? Or a favourite old book whose pages remind you of whiling away the hours in libraries? This ‘aromatherapy’ works because you have past emotional associations with the scent you are smelling. It has been explained by the intimate connection between the area of the brain that processes smell and those that process emotion and emotional memory – the amygdala and hippocampus. This may be why smell, more than any other sense, is so successful at triggering emotions and memories.
Are there any scents that conjure up positive memories for you?
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