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A history of coffee

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by Jemma

 

Appearance

Coffea Arabica is a an evergreen shrub that can reach up to 12 metres tall, though it is often trimmed to facilitate picking, and takes around 7 years to fully mature. The plant possesses foliage of broad, glossy, dark green leaves. It’s small, white flowers are not produced until 2-4 years after the shrub is planted. They are highly fragrant and often said to resemble the sweet smell of jasmine flowers. Over-flowering can lead to an inferior harvest of coffee beans, so the tree is often pruned to prevent this.

Coffea arabica with flowers in bloom. Image taken from http://commons.wikimedia.org/wiki/Coffea_arabica
Coffea arabica with flowers in bloom.
Image taken from http://commons.wikimedia.org/wiki/Coffea_arabica
Coffea arabica flowers.  Image taken from http://commons.wikimedia.org/wiki/Coffea_arabica
Coffea arabica flowers.
Image taken from http://commons.wikimedia.org/wiki/Coffea_arabica

Once Coffea Arabic reaches around 4-6 years old it begins to produce berries. These oval-shaped berries are drupes, meaning that they have a fleshy exterior surrounding the seeds. Most berries contain 2 seeds, which are frequently called coffee beans. It takes approximately 7-9 months before the berries ripen from green to yellow to red in colour. Since the berries can ripen at different times, it is possible for a single tree to possess both ripe and unripe fruit at the same time. For this reason, hand harvesting is vital for collecting good quality beans. After the plant begins to produce fruit, it can stay productive for over 30 years.

Ripe and unripe Coffea arabica berries. Image taken from http://commons.wikimedia.org/wiki/Coffea_arabica
Ripe and unripe Coffea arabica berries.
Image taken from http://commons.wikimedia.org/wiki/Coffea_arabica

History

The origin of Coffea Arabica is unclear, although it is believed that the plant was the first species of the genus Coffea to be cultivated for its beans. According to legend, cultivation began in Ethiopia after goats were seen mounting each other. Apparently they had become energetic after eating the leaves and fruit of the coffee tree. An herbal tea made from the plants leaves is still drunk in Ethiopia today.

Coffee beans Image taken from http://commons.wikimedia.org/wiki/Coffea_arabica
Coffee beans
Image taken from http://commons.wikimedia.org/wiki/Coffea_arabica

Early uses of the fruit did not actually involve the beans being drunk by themselves. African tribes originally crushed ripened berries and then mixed with animal fat, which allowed them to shape the mixture into balls that could be carried into battle for energy. Any early drinks would have probably been made with the juice of fermented berries rather than the beans themselves.

 

Coffee beans were soon exported to Yemen, who began to cultivate Coffea Arabica and spread the plant throughout Arabia. Coffee similar to how it is drunk today, i.e. with the plant’s beans, started to be served in coffeehouses by the middle of the 15th century. Coffee was then traded with Venetian merchants, who in turn introduced it to the European market. The drink steadily grew popular in Europe and in 1645 Venice opened its first coffeehouse.

Kahvihuone

At first, Arabs tried to keep monopoly on coffee trade. They boiled or dried any beans that were to be exported so as to prevent the seeds from germinating. However, their attempts were unsuccessful. Smugglers soon took seeds that had not been treated from the region and grew them elsewhere, particularly in India and Sri Lanka. Soon Dutch plantations in Java overtook the Arab nations as the leading exporter of coffee.

Materia Medica jar containing Coffea arabica beans
Materia Medica jar containing Coffea arabica beans

To distinguish between the competing beans, Arabian coffee was called Mocha (after the port on the Red Sea from where it was shipped) and beans from Dutch plantations became known as Java coffee. A drink that included both types of beans was, therefore, called Mocha Java. The Dutch managed to dominate the coffee market until the mid-19th century, when plant diseases and political disturbances ended their monopoly. However, trade continued from other plantations that had already become established around the world. The most notable was Brazil, which soon became the primary exporter of the bean.

 

There was a dark side associated with the high demand for coffee: its role in the slave trade. Between 1511 and 1886, millions of Africans were sold as slaves. Though they were primarily used as labourers in the sugar industry, a large number of slaves were used for the cultivation of C. Arabica. The use of slaves meant that, despite it being a labour intensive plant to harvest, coffee prices remained relatively low.

 

Today, the plant is still tended and harvested by hand. It has become an immensely important industry that employs around 30 million people worldwide. Coffee is now one of the world’s most popular beverages and is drunk is almost every country.

Dried coffee berries in small Materia Medica jar
Dried coffee berries in small Materia Medica jar

There are two species of coffee plant that are commercially grown: Coffea Arabica and Coffea robusta. Arabica is the more subtle of the two as it contains less caffeine. It is also the more expensive variety that accounts for around 75% of the world’s coffee production. The higher caffeine content in robusta gives it a harsher and bitter flavour compared to Arabica.

Saffron: the world’s most expensive spice (Part 2)

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by Jemma

This two-part blog post has looked at Crocus sativus, also known as saffron. Part 1 focused on the plant’s history in Europe (https://herbologymanchester.wordpress.com/2015/04/27/saffron-the-worlds-most-expensive-spice-part-1/). Part 2 will now focus on its genetics, harvest and uses.

 

Appearance

Saffron is a species of autumn-flowering plant that can grow up to 20-30 cm and produces around 4 flowers. These light- to dark-purple flowers each possess 3 bright crimson stigmas from which the spice saffron is obtained.

Saffron flowers.  Image taken from http://www.herbalencounter.com/2010/12/07/medicinal-spices-saffron-crocus-sativus/
Saffron flowers.
Image taken from http://www.herbalencounter.com/2010/12/07/medicinal-spices-saffron-crocus-sativus/

Genetics

Crocus sativus is a monomorphic clone, which means that almost every saffron plant is identical both physically and genetically. It is unknown in the wild and probably descends from Crocus cartwrightianus (also known as ‘wild saffron’), though Crocus thomasii and Crocus pallasii have also been suggested as saffron precursors. The species sativus probably arose through extensive selective breeding by growers after longer stigmas during Bronze Age Crete.

Crocus cartwrightianus - the plant from which the saffron crocus might be descended  Image taken from: http://commons.wikimedia.org/wiki/Category:Crocus_cartwrightianus
Crocus cartwrightianus – the plant from which the saffron crocus might be descended
Image taken from: http://commons.wikimedia.org/wiki/Category:Crocus_cartwrightianus

The saffron crocus is a triploid (possess 3 sets of each chromosome) that is male sterile and incapable of reproduction. Thus, the majority of propagation of Crocus sativus takes place by asexual reproduction.

 

Harvest

As mentioned previously, the plants crimson stigmas are the source of the popular spice. Due to the few produced per plant and the difficulty involved in manually extracting the minute stigmas, the saffron spice is the world’s most expensive spice by weight. Large quantities of flowers are required in order for marketable amount of saffron to be produced. Approximately 75,000 flowers, which give around 225,000 stigmas, are required to obtain a single pound (0.5 kg) of the spice. Each of these stigmas must be collected by hand and then immediately dried to prevent decomposition or mould from damaging them.

 

Medicinal uses

For as long as it has been cultivated by Homo sapiens, the saffron crocus has been used extensively for medicinal purposes. Even the paintwork by the Minoans hinted at the possibility of its use as a drug. Ancient Egyptian healers used Crocus sativus to treat a wide range of gastrointestinal problems; from stomach ache to internal bleeding. They also viewed it as an aphrodisiac, poison antidote and cure for measles. Alexander the Great was noted for having baths with saffron to help heal wounds after a battle. With its medieval revival, the medicinal uses of the crocus increased further. It was used to treat everything from coughs to smallpox, insomnia to heart diseases, and from stomach ache to gout. Saffron was even believed to be able to cure the Black Death.

Materia Medica jar containing saffron.
Materia Medica jar containing saffron.

Today, saffron is still used frequently in both alternative and modern medicine. Crocus sativus is included in the hematoxylin-phloxine-saffron (HPS) stain and Movat’s pentachrome stain, both of which are tissue stains used to make structures more visible under a microscope. This is because saffron stains collagen (most abundant protein and the main structural protein) yellow.

A tissue sample stained with HPS stain. Collagen is dyed yellow whilst muscle and cytoplasm are both pink. Image taken from http://en.wikipedia.org/wiki/HPS_stain
A tissue sample stained with HPS stain. Collagen is dyed yellow whilst muscle and cytoplasm are both pink. Image taken from http://en.wikipedia.org/wiki/HPS_stain

Use as a dye

For millennia saffron has been used to colour textiles and other items. It was traditionally reserved for nobles, political elites and important religious figures to emphasise their social standing. Even in small amounts, the sativus stamens produced a bright yellow-orange dye but with increasing amounts of saffron used, a richer shade of red was achieved. This led to these richer shades indicating those who were of particular importance. However, saffron is an unstable colouring agent over long periods of time, resulting in the vibrant colours to fade quickly. Over time there have been numerous attempts to replace saffron with a cheaper dye. Crocin, the main chemical in saffron that imparts the colour, has been discovered in other plants and is now extracted cheaper and easier from species in the Gardenia genus.

 

Culinary uses

Another use for saffron that dates back thousands of years is for cooking. A popular addition worldwide, saffron imparts a bright yellow-orange hue onto dishes and is included in everything from curies and soups to cheeses and baked goods. It is also sometimes added to liquors for flavour and colour. However, due to its high price, saffron is often substituted or combined with other spices in order to reduce the cost. Safflower (Carthamus tinctorius) and turmeric (Curcuma longa) are the most common replacements as they mimic the colour imparted by saffron. Though they can produce a similar colour to the pricey Crocus sativus spice neither safflower nor turmeric can replicate its distinctive taste (which is mainly due to the compound picrocrocin).

Safflower is sometimes used as a cheaper alternative to saffron
Safflower is sometimes used as a cheaper alternative to saffron

Other uses

In addition to the uses mentioned already, saffron was also a popular ingredient in perfumes in ancient Greece and Rome. They also included Crocus sativus in cosmetics, wine and potpourri. It was even considered a worthy offering for the gods. Queen Cleopatra of Egypt added saffron to her bathwater as she considered it an aphrodisiac.

Saffron: The world’s most expensive spice (part 1)

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by Jemma

 

This two-part blog post is going to focus on Crocus sativus, also known as saffron. Part 1 is going to focus on the plant’s history in Europe and part 2 (https://herbologymanchester.wordpress.com/2015/04/27/saffron-the-worlds-most-expensive-spice-part-2/) will focus on its genetics, harvest and uses.

 

Ancient Times

The cultivation and trade of the saffron crocus by humans has persisted for around 4 millennia; spanning cultures, continents and civilisations. The first recorded image of saffron appears in Minoan paintings. Though there is no written record of what they used the crocus for, suggestions have been made (mentioned in part 2) and it is clear that the plant held some significance for them. A powerful earthquake followed by a volcanic eruption resulted in the loss of this early settlement around 1,500 BCE. The Minoan herbal paintings survived over the next few millennia through being entombed by the volcanic ash, which preserved these early frescoes.

Minoan fresco depicting a saffron gatherer.  Image taken from: http://en.wikipedia.org/wiki/Wall_Paintings_of_Thera
Minoan fresco depicting a saffron gatherer.
Image taken from: http://en.wikipedia.org/wiki/Wall_Paintings_of_Thera

Saffron again became popular during the time of the ancient Greeks, when early documentation shows that they cultivated and harvested the plant for its spice. During this time, saffron began to be widely traded across the Mediterranean. The plant even had its own origin legend: the story of Crocus and Smilax. Crocus, a handsome young man, falls for the nymph (a female nature deity) Smilax. At first Smilax is flattered but she soon tires of his advances and turns Crocus into a saffron plant; the bright stigmas of the flower representing the glow of the undying and unrequited passion of Crocus. Possibly for this reason, saffron was widely associated with the class of professional courtesans and entertainers called the hetaerae. Though it remained a popular spice and medicine for many centuries, Crocus sativus cultivation in Europe went into decline following the fall of the Roman Empire.

 

It should be noted, however, that Crocus sativus cultivation was not limited to Europe. Whilst its popularity was still spreading, saffron began to be grown further and further from Greece. By the 3rd century AD, it had spread to China and was incorporated into their traditional medicinal practices.

 

Medieval Revival

For several centuries the cultivation of Crocus sativus was, for the most part, none-existent throughout Europe. This changed after the Moorish civilisation spread from North Africa around the 8th century and began reintroducing the spice. Saffron was rare, expensive and in high demand right up until the 14th century, when its use soared due to the medicinal applications of the plant in attempted treatments for the Black Death. However, many of the farmers that grew Crocus sativus had died from the disease and the demand far outstripped the supply. Thus large quantities of non-European saffron began to be heavily imported. The trade of saffron became of such significance that those found guilty of adulterating supplies were fined, imprisoned and even executed.

An image from La Francescina manuscript (1474) showing Black Death victims being treated. Image taken from http://commons.wikimedia.org/wiki/Category:Medieval_miniatures_of_plague?uselang=en-gb#/media/File:Plague-st-francis-la-francescina-jacopo-oddi-c1474.jpg
An image from La Francescina manuscript (1474) showing Black Death victims being treated. Image taken from http://commons.wikimedia.org/wiki/Category:Medieval_miniatures_of_plague?uselang=en-gb#/media/File:Plague-st-francis-la-francescina-jacopo-oddi-c1474.jpg

The Saffron War

As already mentioned, the Black Death during the 14th century drastically increased the demand for saffron in central and northern Europe to a level that local suppliers could not meet. The only other major producers at the time were Arab sources, who were unwilling to trade due to hostilities over the crusades. This left Greece as Europe’s primary supplier.

 

The sale of saffron quickly made merchants extremely wealthy and powerful, which disturbed the declining aristocracy. In an attempt to regain control, a group of nobles seized a large saffron shipment heading to Basel in Switzerland. The stolen cargo would be worth over £300,000 in today’s market. The theft triggered a 14 week long war, named the ‘Saffron War’ that lasted until the shipment was returned. Though the cargo was returned in this instance, the saffron trade was plagued with thieves for the majority of the 13th century. Pirates would target saffron bound for Europe, often ignoring ships loaded with gold in preference for this profitable spice.

 

Decline and Modern Revival

Trade of Crocus sativus began to dwindle for a second time during the 18th century. There have been a number of causes suggested for this decline, including fungal diseases destroying crops, cold winters and to traders offering steadily lower prices in an attempt to outcompete their rivals. By the middle of the 20th century, the crocus started to become primarily grown for ornamental purposes. The use of saffron as a spice fell out of fashion and the only areas in which it endured were southern France, Italy and Spain.

Materia Medica jar containing saffron.
Materia Medica jar containing saffron.

Since the turn of the millennia in 2000, saffron has been making a comeback. Today, rather than being predominantly grown in Greece and Europe, the majority of C. sativus is now grown in Iran and North America.

Mallorcan orchids

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Ophrys lutea

 

There’s still time for one final post before it’s time to say goodbye to the Mallorca field course for another year. With two orchid fans on the staff, it’s not surprising that a good few hours each day were spent orchid spotting, but this year we had an up-and-coming orchid specialist amongst the students too. Head over to the FrogBlog to check out Tom’s thoughtful account of his Mallorcan orchid-hunting experiences.

 

Sunset over the port of Alcudia
Sunset over the port of Alcudia

 

 

Sea squill, sea squill on the sea shore

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by Jemma

Earlier in the month Rachel went on a trip to Mallorca, with a group of 1st year undergraduates from the University of Manchester (for more information see her blog post: https://herbologymanchester.wordpress.com/2015/04/07/surviving-salt-and-waterlogging-on-the-albuferita-mallorca/). During her time there she saw a number of sea squills (Drimia maritima) so I thought I would write a post about this interesting plant.

Sea squill from Albuferita, Mallorca
Sea squill from Boquer Valley, Mallorca

Drimia maritima is a poisonous plant that grows in rocky coastal habitats across southern Europe, western Asia and northern Africa. It grows from a large bulb that can be up to 20 cm wide and a kilogram in weight. In the spring, the bulb produces a rosette of dark green, leathery leaves that can reach up to a metre long. The leaves die away by autumn, when a shoot containing the flowers grows from the bulb. This flower-bearing shoot can achieve a height of up to 2 metres. Pollination of the Drimia maritima flowers occurs by both insects (specifically the western honey bee, the Oriental hornet, and the paper wasp) and wind.

The flowers and bulb of Drimia maritima Image taken from http://en.wikipedia.org/wiki/Drimia_maritima
The flowers and bulb of Drimia maritima
Image taken from http://en.wikipedia.org/wiki/Drimia_maritima
Drimia maritimia flowers Image taken from http://www.xericworld.com/forums/attachment.php?attachmentid=6344&stc=1&thumb=1&d=1341359115
Drimia maritima flowers
Image taken from http://www.xericworld.com/forums/attachment.php?attachmentid=6344&stc=1&thumb=1&d=1341359115

Drimia maritima has been mentioned as far back as the 16th century BCE in the Ebers Papyrus (an ancient Egyptian medicinal text). In the 6th century BCE the Greek philosopher Pythagoras wrote about the uses of squill and, along with Dioscorides (1st century ACE and author of De Materia Medica), recommended hanging the bulb to protect against evil spirits.

Materia Medica jar containing sea squill bulb
Materia Medica jar containing sea squill bulb

One of the earliest medical applications of the sea squill came from the Greek physician Hippocrates (4th century BCE), who advocated its use to treat jaundice (yellowing of the skin), convulsions and asthma. Over the centuries, Drimia maritima was used as a common treatment for dropsy (abnormal accumulation of fluid in tissues) before the more effective foxglove (Digitalis sp.) became the standard treatment during the 18th century.  The plant has also been used in folk medicine as a laxative and to clear mucus build-up.

Materia Medica jar containing sea squill
Materia Medica jar containing sea squill

In addition to its medicinal use, squill has been employed as a poison. All parts of the plant contain toxic chemicals. Once such compound, called Scilliroside, was shown in 1942 to be an effective rodenticide that is avoided by most other animals. In the 20th century, Drimia maritima began to be experimented on to develop highly toxic varieties for use in rat poison. Though not the most common rodenticide, interest in squill’s rat killing abilities has increased dramatically since many rats became resistant to the coumarin-based poisons previously used.

Palm oil: The Good, the Bad and a History

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by Jemma

 

Elaeis guineensis is a single-stemmed palm tree in the Arecaceae family that can reach up to 20 metres in height. It is native to West and Southwest Africa and thrives on open, flat land with plenty of water. The palm’s plum-sized palm fruit grow in bunches of around 1,000 and are reddish in colour. The fruit is a drupe, which means it has a fleshy outer layer surrounding a single seed. Both the flesh and seed are rich in oil, which can be extracted. Elaeis guineensis is the primary source of palm oil and is closely related to the American species Elaeis oleifera.

The parts of an Elaeis guineensis plant (African palm oil). Image taken from http://en.wikipedia.org/wiki/Elaeis_guineensis
The parts of an Elaeis guineensis plant (African palm oil).
Image taken from http://en.wikipedia.org/wiki/Elaeis_guineensis

History

In the late 1800s, archaeologists showed that humans have used Elaeis guineensis for the past 5,000 years. They found the plant in a tomb dating from 3,000 BCE in the ancient Egyptian city of Abydos. It is widely believed that Arab traders brought the palm to Egypt from Africa.

Fruit and seeds of Elaeis guineensis oil palm
Fruit and seeds of Elaeis guineensis oil palm

Europeans were introduced the palm sometime during the 16th-17th centuries. They originally traded for palm oil in the ‘palm oil coast’ (the southern coast of Nigeria) before growing the plant in their colonies. One such colony was the British-occupied Malaysia. Elaeis guineensis became established in Malaysian plantations in the early 1900s. For the most part, these plantations were owned and run by the British until the late 1900s when the Malaysian government took control.

Materia Medica jar containing Elaeis guineensis seeds
Materia Medica jar containing Elaeis guineensis seeds

The government set up the Federal Land Development Authority (Felda) in 1956 to operate their plantations. The main aim of Felda was to use the plantations as a means of eradicating poverty in the area. Those wishing to be involved were given 10 acres of land in which to plant oil palms or rubber plants and 20 years in which to pay off the debt for the land. In the 1960-70s, the Malaysian government expanded the project to include other crops so that they had an economic ‘cushion’ for when the price of rubber fell. Soon the land dedicated to rubber became more palm oil plantations. By the end of the 20th century, Felda had given rise to other organisations, such as the Federal Land Consolidation and Rehabilitation Authority (FELCRA) and the Sarawak Land Consolidation and Rehabilitation Authority (SALCRA). These additional organisations had the same primary aim as Felda; to eliminate poverty through the cultivation of crops. Today Felda is the world’s largest palm oil producer, with around 900,000 hectares dedicated to growing the palm.

 

Uses

Palm oil can be extracted either from the flesh of the fruit or from the seed. As mentioned previously, some of the earliest findings of Elaeis guineensis were in Egyptian tombs. The vast quantities of oil found have suggested that they used it for culinary rather than cosmetic purposes. The unrefined oil is still a common cooking ingredient in West Africa today, but elsewhere is always refined before use. Palm oil is high in saturated fats, making it solid at room temperature and able to withstand higher temperatures compared to many other cooking oils. For these reasons, as well as a rise in popularity for naturally saturated fats, palm oil has become a cheap and popular substitute for butter. Due to its ability to withstand high temperatures, palm oil is second only to the soybean in its use as vegetable cooking oil. Oil from Elaeis guineensis is often also included in many other foods, such as ice cream, crisps and chocolate.

Materia Medica jars containing palm oil
Materia Medica jars containing palm oil

Although around 90% of palm oil is used in food, its use is not limited to culinary purposes. It is also added to cosmetics, shampoos and soaps. In recent years, palm oil has become a popular biofuel. Traditional African medicine have used Elaeis guineensis as a laxative, to stimulate the production of urine, as a poison antidote, to cure gonorrhoea and to treat skin infection – to name but a few uses. However, it may not be entirely harmless as some studies have linked palm oil with cardiovascular diseases.

 

Materia Medica jar containing palm oil
Materia Medica jar containing palm oil

 

Social and environmental concerns

Despite its wide range of uses, there are many social and environmental impacts of cultivating the palm. Growing the plant is a source of income for governments – particularly in Malaysia – as well as a major provider of employment. However, there have been many unfavourable social effects of this. Many palm oil plantations have appropriated lands for cultivation without consulting or compensating the local residents. In some cases, the plantations do not even employ the locals but rather import labour or illegal immigrants.

Elaeis guineensis in palm oil plantation. Image taken from http://en.wikipedia.org/wiki/Elaeis_guineensis
Elaeis guineensis in palm oil plantation.
Image taken from http://en.wikipedia.org/wiki/Elaeis_guineensis

Along with the social concerns that accompany the plantations, there are also substantial environmental impacts. Cultivation of the plants has caused irreversible damage, including deforestation, habitat loss and increased greenhouse gas emissions. Large areas of tropical rainforests have been cleared for plantations and the resulting biodiversity loss could result in the extinction of species of potential medicinal importance. In some areas where enforcement of environmental legislations is lax, plantations have had little regulation to stop tem encroaching into protected areas and releasing pollutants into the environment.

 

Other states have implemented environmentally-friendly practices to try to limit the damage. These have included the use of waste products as sources of ‘renewable’ methane production to generate electricity. However, palm oil plantations are still environmentally damaging as many rainforest are above peat bog that store vast amounts of carbon. The deforestation and bog draining involved in setting up the plantations releases this carbon into the atmosphere, contributing to greenhouse gas emissions and global warming. Many environmental groups have pointed out that the environmental impacts of running plantations are far more damaging to the climate than the benefits gained by the biofuel produced.

Specimen of the day – Amyl salicylate

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by Jemma

Amyl salicylate

Materia Medica jar containing Amyl salicylate
Materia Medica jar containing Amyl salicylate

Amyl salicylate is the registered trade name of the chemical pentyl ortho hydroxy benzoate, also known as pentyl salicylate, and has the formula C6H4(OH)COOC5H11. This colourless liquid is frequently used in perfumes for its ability to counteract and/or mask unpleasant smells. Amyl salicylate has often been referred to as having an odour similar to orchids. It has also been included in perfumes to help fix floral fragrances to the skin. In addition to perfumes, the chemical is often included in shampoo, soaps, deodorant, hair sprays and fabric softeners. Amyl salicylate is produced from salicylic acid by an esterification reaction (mentioned in later section).

The chemical structure of the ester amyl salicylate.  Image taken from http://pubchem.ncbi.nlm.nih.gov/compound/Amyl_salicylate#section=Top

The chemical structure of the ester amyl salicylate.
Image taken from http://pubchem.ncbi.nlm.nih.gov/compound/Amyl_salicylate#section=Top

 

Isoamyl salicylate

The term ‘amyl salicylate’ is not solely used for pentyl salicylate as it is sometimes used to refer to its chemical isomer. An isomer is a substance with the same molecular formula that differs in the way that its atoms are arranged. In this case, the molecular formula is still C12H16 O3 but the structural formula is C6H4(OH)COOCH2CH­­2CH(CH)2 (see image below). In fact, the amyl salicylate used commercially is often the isomer form of the compound. The isomer form of amyl salicylate is a clear liquid that is insoluble in water and has an orchid-like scent. The commercial use of the isomer is similar to that of the above substance, as both are used for the same purpose. Though not used particularly for medicinal applications, studies into the two isomers have also suggested that they can reduce pain, fever and inflammation.

The chemical structure of isoamyl salicylate.  Image taken from http://www.chemspider.com/Chemical-Structure.6612.html
The chemical structure of isoamyl salicylate.
Image taken from http://www.chemspider.com/Chemical-Structure.6612.html

 

Salicylic acid and aspirin

Salicylic acid has a chemical formula of C6H4(OH)COOH and is the precursor of both isomers of amyl salicylate. For a long time, this acid was obtained from the bark of the willow tree in the genus Salix. Medicinally useful in its own right, salicylic acid has been used for pain relief, reducing fevers and as an anti-inflammatory. Due to its fungicidal properties, the acid is sometimes included in treatments for fungal skin infections, such as tinea (commonly called ringworm). Salicylic acid is also effective at breaking down keratin. Keratin is one of the key structural materials found in the body, including in the outer layer of human skin, hair and nails. By breaking down keratin, the acid can be used to treat a number of disorders, such as hyperkeratosis (abnormal levels of keratin), dandruff and ichthyosis (dry, thickened, scaly or flaky skin). Salicylic acid and many of its derivatives are used in pharmaceuticals to fight viral infections (like the flu), in dyes, as a flavouring and as a preservative. Unlike its amyl salicylate derivatives, the acid is not a liquid. It is a white, crystalline powder that possesses a sweet taste.

The structure of salicyclic acid.  Image taken from http://en.wikipedia.org/wiki/Salicylic_acid
The structure of salicyclic acid.
Image taken from http://en.wikipedia.org/wiki/Salicylic_acid

As mentioned above, salicylic acid is a precursor for the production of many chemical compounds including amyl salicylate. Two other derivatives of note are aspirin (also known as acetylsalicylic acid) and methyl salicylate, which is used to sooth joint and muscle pain. Aspirin, methyl salicylate and amyl salicylate are all produced through esterification of the precursor acid. Esterification reactions are those in which an –OH (hydroxyl) group is replaced by an –O–R group, where R is any alkyl group. An alkyl is a hydrocarbon consisting only of carbon and hydrogen atoms. The basic equation for this reaction is shown below. In the case of amyl salicylate synthesis, the R group is C5H11.

General esterification reaction for salicylate.  Image adapted from http://www.scielo.cl/scielo.php?pid=S0717-97072009000100009&script=sci_arttext
General esterification reaction for salicylate.
Image adapted from http://www.scielo.cl/scielo.php?pid=S0717-97072009000100009&script=sci_arttext

Though the synthesis of aspirin is also an esterification reaction, it takes place on a different hydroxyl group to amyl salicylate. Aspirin production also involves the R group being donated not from an alcohol, like with amyl salicylate, but from acetic anhydride (two acetic acids already joined by an esterification reaction). The esterification of salicylic acid by acetic anhydride results in two products: aspirin and acetic acid.

Synthesis of aspirin from salicylic acid and acetic anhydride.  Image taken from http://en.wikipedia.org/wiki/Aspirin
Synthesis of aspirin from salicylic acid and acetic anhydride.
Image taken from http://en.wikipedia.org/wiki/Aspirin