It has been determined by history that the rose itself is a man-made phenomenon. What we call “roses” are actually man-made cultivars of representatives of the biological genus Briar or Wild rose (Rosa), a plant of the Rosaceae family. The vast majority of varieties of roses are obtained through breeding: by crossing and selection. There are about 400 species of Briar and, according to various estimates, from 10 to 50 thousand varieties of roses.
There is a theory that says that roses were grown in the countries of the Middle East more than five thousand years ago. Even before the Common Era, roses were cultivated in India and China. Roses are depicted on the walls of the palaces in Crete (2000 years BC) and on the tombs of the pharaohs in Egypt (about 1000 years BC). Clay tablets found in the palace of Nestor in Crete tell us about the fragrant rose oil; Confucius wrote about the cultivation of roses in China; and dozens of varieties of roses are mentioned in the works of Roman writers. In the Middle Ages, roses were quite ubiquitous in Europe, and at the beginning of the 17th century they came to America with the first English colonists.
In all likelihood, the rose came to Kievan Russia in the Byzantine period; the first mention of the cultivation and selection of roses in this country belongs to the beginning of the 17th century, the period of the reign of Mikhail Fyodorovich. Roses were brought from Germany and remained the royal court's property. Only since the reign of Peter the Great were roses planted in gardens, and the mass distribution of them could be seen only under Catherine II. By the end of the 19th century, roses began to grow in the whole European part of Russia.
The most common roses, those that are grown to be cut for the creation of beautiful bouquets, are most often tea-hybrid tetraploid varieties that were bred not so long ago – in the second half of the 19th century. Many selectors aim to get varieties that have a strong vivid scent, so among the most fragrant varieties of roses are: Aida, Captain Harry Stebbings, Dublin, Folklore, Fragrant Cloud, Limelight, Royal Highness, and Tiffany.
Decorative variety "Fragrant Cloud"
Despite the diversity of species and varieties of roses, only two of them are of interest from the point of view of perfumery: the Damascus Rose (Rosa Damascena) and the Cabbage Rose or Rose de Mai (Rosa Centifolia).
The Damascus Rose has been known in the Middle East for ages. In the 7th century, the Arabs knew the principle of distillation and were able to get from flowers both rose oil and rose water. In the 19th century, this species of rose came from Syria to Europe.
At the moment, it is the most important type of roses for perfumery and it is grown in the Bulgarian Kazanlak (about 70%). Learn more by reading How to Buy Bargain Bulgarian Rose Perfumes Online. In the Crimea, specific frost-resistant hybrids of the Damascus Rose are cultivated, since the climate is too cold for the rose there; Earlier in the Nikitsky Botanical Garden the grade "Red Crimean" of the Rosa Gallica species was introduced, which for a long time was the main industrial grade on the peninsula. Damascus Rose is also grown in Syria, Turkey, Iran, India, China and Saudi Arabia.
The process of extraction of the rose by petroleum ether results in concrete or an essential oil which is produced on an industrial scale only in Bulgaria and Turkey. In Bulgaria the concrete is later extracted via ethanol in order to get an absolute (with an output of about 50%), but some manufacturers prefer to buy concrete and carry out the extraction independently, therefore some of the absolutes of the Damascus Rose are formally "produced in France". To produce 1 kg of the absolute of the rose, 3-4 tons of flowers are required, one kilogram of the rose absolute from Bulgaria costs about $5000.
The essential oil of rose or so-called "otto of rose" is obtained via steam distillation in Bulgaria, Turkey, Crimea and other places, in the total amount of about 2500 kg per year.
Rose de Mai is grown in France, Egypt, Tunisia and other countries of North Africa, Eastern Europe, Italy and China, but most actively it is cultivated in Morocco: every year more than 2000 kilograms of the Rose de Mai concrete are produced there by extraction with petroleum ether.
Later, the concrete is extracted by ethyl alcohol in order to get the Rose de Mai absolute with the result of 67%. The aroma of the absoluteis deep, honey sweet and very rich. Unlike the absolute of the Damascus Rose, its spicy and phenolic aspects are less pronounced.
Some of the flowers of the Moroccan rose are also used in the production of the essential oil. There is another rather exotic product obtained from this plant: In the south of France, the absolute of the leaves of the Rose de Maiis obtained by extraction with chlorocarbons (trichlorethylene, dichloromethane). It is a semi-liquid green mass with a leafy, slightly woody odor. Steffen Arctander calls this material a "selling note" in his book. Some perfumers list it in the "pyramid" as an indisputable advantage of their compositions, however, the effect of its presence is very little if any. According to Arctander, if perfumers were interested in this material, then it would be produced in much larger quantities.
Over the years, chemists have tried to identify and separate the components of the oil and the absolute of the rose. In the first half of the twentieth century all the key components were known: substances whose content in natural rose materials exceeds 1% (in total they are more than 80%). These are the so-called "rose alcohols": citronellol (30-40%), geraniol (10-20%), nerol, linalool, eugenol and its methyl ether, phenylethyl alcohol (PEA), as well as esters of these alcohols, primarily acetates.
The principal difference of the product of distillation (essential oil, otto) from the product of extraction (concrete, absolute) is in the content of phenylethyl alcohol. Essential oil of primary distillation hardly contains any phenylethyl alcohol at all for the reason that it is freely soluble in water and remains in the hydrolate. However, often manufacturers make a repeated distillation of the hydrolyte (so-called cohobation) and attach the regenerated phenylethyl alcohol to the oil.
Attempts to reconstruct rose oil or the absolute, using only rose alcohols, did not lead to success – such mixtures resembled the smell of natural materials only fractionally, so it was obvious that something very important in them was absent. Among the minor components undiscovered at that time, there clearly were compounds that made a serious contribution to the overall aroma of the rose.
Nevertheless, perfumers always show miracles of ingenuity: the Wardia base, created by the company Firmenich in the early 30s of the last century, was conceived as a substitute for the absolute of the Rose de Mai. It consists mainly of rose alcohols and their acetates, a small amount of hydroxycitronellal, traces of citral, diphenyloxide, undecene, syringaldehyde and some other compounds. Rose ketones and other micro-components of the rose, which will be discussed below, were not used in this base. However, this product proved to be very popular and sought-after, so the Wardia family bases are produced even in our time.
The first breakthrough in the analysis of minor rose odorants occurred in 1959 when Casimir F. Seidel and Max Stoll discovered rose oxide. This compound was found in the essential oil of the Bulgarian rose in an amount of 0.5%. Its penetrating, bright smell is responsible for the green, slightly metallic starting note of the rose's fragrance.
Later, rose oxide was found in many other natural sources: more than 1% of it can be found in geranium oil; rose oxide is an important aspect of the flavor of the Gewürztraminer wine, tea, blackcurrant, lychee and passion fruit. It is even found in fauna: the musk beetle (Aromia moschata) uses this compound as a chemical weapon. So one should be careful with it, this is a substance with a very intense odor and it is best to highly dilute it for perfume purposes.
The discovery of rose oxide was one of the most important events in the study of rose aromachemistry. In many respects, the 4th International Congress on Essential Oils held in Tbilisi in 1968 was dedicated to the chemistry of minor rose odorants. The event was so large that it was awarded a postage stamp on which one can see the formula of rose oxide.
Twenty years later, with the help of gas chromatography, nerol oxide was detected in the smell of the rose. It can be found in quantities of approximately 0.09%. Nerol oxide is often an aromatic component of some varieties of wine as well: shoirebe, a variety of grape, contains a lot of nerol oxide.
Ervin Kováts, a pioneer of gas chromatography from Hungary, completed a titanic work identifying 127 compounds contributing to the smell of the rose. Rose furan and perillene form the fresh citrusy top note.
Decorative variety "Dioressence" (Delbard, 1984)
However, even more important was the discovery of β-damascenone and β-damascone. These substances have a hypnotic, fruity-floral and sweet aroma reminiscent of dried fruits (raisins, prunes), black currant, plum, with nuances of honey and tobacco. Together with traces of a similarly structured β-ionone and rose oxide, β-damascenone and β-damascone make up less than 1% of all the fragrant components of the rose essential oil, but at the same time make a decisive contribution to the overall smell of the rose.
Damascones are ubiquitous in nature as the components of the smell of raspberries, roman chamomile, tobacco, honey, some wines, tea, coffee and even beer. The sweet honey aspect is also supported by the esters contained in the rose, in particular, phenylethyl alcohol esters and benzyl tiglate.
Decorative variety "Lolita Lempicka'"(Meilland, 2002)
A few words about the relatively recently discovered, not even micro, but rather nano-components. Sulfur compounds are present in natural essential oils and absolutes in miniscule amounts: A fraction of a million, or ppm, in quantities of approximately 0.0001%.
For clarity, it's like one drop in comparison with a fifty-liter (13 gallon) barrel of water or like 30 seconds a year. Nevertheless, these compounds have a very intense smell and even in such quantity have a definite influence on the absolute, essential oil, and the aroma of a living, flowering rose.
The studies of such small quantities require precise modern equipment, so technically they became possible around the 1980s of the last century. By that time, there were already more than 300 compounds forming the fragrance of the rose, of which only three were known to contain sulfur: dimethyl sulfide, dimethyl disulphide and β-mint sulfide.
In the course of further delving into the microcomponents of rose oil, scientists found a number of low molecular weight sulfurous compounds with a marine odor; butyl methyl disulfide, hexyl methyl disulfide, dimethyl trisulfide and other alkyl sulfides with a penetrating odor reminiscent of onion; dibenzothiophene and its methyl substituted analogues (currently found only in rose), 3-(4-methylenepent-3-yl) thiophene and 3-methyl-2-(3-methylpenten-3-yl) thiophene which are responsible for the starting green spicy-powder note of the rose oil and give a certain effect of naturalness, which recalls the smell of a living plant and rose petals.
Heavier compounds, 4-(4-methylpenten-3-yl-1)-1, 2-dithiacyclohexene-4, 1,2-epithiohumulene, 4,5-epithiohumulene, and 4,5-epithiocaryophyllene have a persistent green smell with smoky-woody and powdery nuances; they considerably determine the base note of essential oil roses.
The chemistry of synthetic rose odorants is extremely diverse, complex and intriguing. It is impossible to mention all substances with a descriptor "rose" within the framework of one entertaining article, for this purpose the format of a weighty monograph would be more suitable. I will focus only on the most popular and sought-after.
As for synthetic rose odorants, one can illustrate a technique used by chemists when they need to create a substance with a similar smell, but longer lasting. Often "long-lasting" equals to a higher molecular weight. Therefore, the aim is to make the molecule heavier, while retaining its spatial shape.
It is known that the prenyl group, a fragment of many terpenic compounds, is similar in shape and size to the phenyl group, the latter being much heavier. The replacement of the first one by the second one makes the compound heavier, hence more long-lasting, while the basic olfactory profile of the substance remains the same.
A substance called Doremox is a "weighted" analog of the rose oxide, both have a similar smell, but Doremox has a less pronounced metallic aspect and a certain fruity pear nuance.
Rosyrane is close to the structure to Doremox and is characterized by the presence of a double bond in the oxygen-bearing ring and is an analog of neroloxide. Dihydro-roseoxide or Dihydrorosan, is produced by BASF and has a geranium-metallic odor characteristic of the rose oxide.
Phenoxanol is an analogue of citronellol and has a calmer and deeper odor with fruity nuances. Phenoxanol in the quantity of 2.5% is contained in Bvlgari EDP. In this fragrance the rose theme is supported by the natural absolute. Birmane Van Cleef & Arpels contains 0.6% of Phenoxanol. Rosaphen is an alcohol which is structurally close to it and both of these substances can be considered distant relatives of phenylethyl alcohol.
Peomosa is a rather popular material among the synthetic "rose" alcohols, it differs from phenylethyl alcohol by an additional methyl substituent in the benzene ring, due to which this compound acquires the powdery nuances of peony and mimosa. Phenylpropyl alcohol is an "older brother" of phenylethyl alcohol – with its more pronounced character of hyacinth and cinnamon, and also there is a popular rose odorant among its derivatives – Centifolether.
Decorative variety "d'Ornano" (Jean-Marie Gaujard, 1967), its fragrance was an inspiration for Sisley Izia
Cyclohexyl ethyl alcohol, a saturated "variant" of phenylethyl alcohol, is much more muguet-like, waxy and green. Coranol is close to the mentioned substances and has some resemblance to linalool, both in terms of olfactory profile and its structure, it is actively used as a substantive "floralizer" (for a long time it was a Firmenich captive material).
Coranol has an interesting fresh "hygienic" character, reminiscent of dihydromyrcenol, so often this material can be found in large quantities in men's fragrances, for example, in L'Eau d'Issey pour Homme (8%), Dior Dune Homme(8%), L'Eau par Kenzo Homme (7%).
The unsaturated alcohol 9-decen-1-ol, Trepanol or Rosalva, has a specific aldehyde-wax, fresh smell reminiscent of the luscious rose petals covered with dew. The acetic ester of this alcohol, called Roseate or Rose Petal Acetate has the citrus nuances of magnolia, peony and the musky shade of ambrette seeds.
Damascones, as well as the similar in structure damascenones and ionons, are often theoretically combined into a group called "rose ketones". Compounds of natural origin, having a similar structure, are most often products of oxidative degradation of carotenoids. In addition to the large number of compounds found in nature, there are a number of synthetic substances with a similar structure, in particular, δ-damascone, which has a bright, diffusive, fruity apple-black-chestnut note with a pronounced rose tone and interesting earthy-tobacco nuances.
Firascone, Romsacone (Firmenich) and Givescone (Givaudan) are similar in structure to damascons - they have a damascone-like odor, but can be used to create perfume compositions without any limits, up to multiples of ten percent if necessary.
Somewhat different in structure, Rosamusk (IFF) has a rose-geranium smell with musky, fruity-pear and violet aspects. Floramat, also having some structural resemblance to damascons, has the spicy-woody, rose-fruity smell that's common to such substances.
Structurally close to damascons, β-cyclocitral, from the chemical point of view being an aldehyde and at the same time a fairly light compound, is virtually free of rose and dried fruit aspects common to damascons and has a green herbaceous citrus smell.
Particularly I would like to mention Pomarose (Givaudan), a material with a damascone-like structure. This substance was synthesized in 2001 by the Swiss chemist Philip Kraft and his colleagues. Pomarose has an extremely intense (0.5 ng/l threshold) fruity-rose smell with aspects of apple, plum and dried fruits. At the moment, the substance is patented and is "captive" but the perfumers of Givaudan are willingly using it.
It is impossible not to mention the substance with the romantic name Rose Crystals, with its deep and heavy powdery-rosy smell. Rose crystals are also noteworthy because it is one of the few (if not the only) perfume compounds that contains chlorine. It would also be appropriate to mention another exotic odorant containing bromine: Bromarosa, which was produced by Firmenich in the middle of the last century and, you guessed it, also had the smell of a rose. Nowadays it is no longer used