The power of plants by Ola Stepien

THE POWER OF PLANTS THE IMPACT OF PLANT-DERIVED CHEMICALS ON HUMAN HEALTH by Aleksandra Stępień

Biological Photography and Imaging Summer Project C14206 Aleksandra Stepien 4214412

With special thanks to : Anita and Krzysztof StÄ&#x2122;pieĹ&#x201E;, Alice Fillan and Paul Phillips for your help and support.

August 2014

THE POWER OF PLANTS THE IMPACT OF PLANT-DERIVED CHEMICALS ON HUMAN HEALTH

CONTENTS 1. Introduction ............................................................................................................................................... 5 2. Plant-derived medicines ........................................................................................................................... 9 3. Stimulants ................................................................................................................................................. 23 4. Chemicals in popular plant based foods and drinks ........................................................................... 31 5. Summary ......................................................................... ........................................................................... 41 References .................................................................................................................................................42

INTRODUCTION

eople depend on plants in every aspect of their existence. Plants produce the oxygen we breathe, are consumed as food and used as raw materials for buildings and clothes. From foraging to farming our civilisation developed by taking advantage of the nutritional and medicinal properties of the Plantae Kingdom. The world as we know today, our dietary habits, economy and culture, has been shaped by passing on the ancestral knowledge of plants, cultivating and trading crops and manufacturing plant-based products. Our botanical knowledge has developed through many years of careful observation of our natural environment and through trial and error.

mental effects of different foods on our health.

As scientific research progressed throughout the centuries we unwrapped and revealed the secrets behind some “magical” effects of many plant species. Yet the more we discover about phytochemistry and about the human body, the more complex this relationship appears. Many studies are conducted to prove or deny the beneficial properties of plants on human health and fighting disease. A lot of inconclusive results are produced and heated discussions are carried on nutrition, food supplements and the common use of certain drugs and herbal remedies in preventing so-called “civilisation diseases” like cancer, diabetes, cardiovascular and heart disease. Despite the advances in technology and knowledge we are still bombarded with contradictory information about the beneficial and detri-

The chemistry of many food crops, herbs and stimulants commonly used for centuries have been nowadays thoroughly researched, busting some myths and explaining their effects on human body.

In the age of highly processed food products, chemically-derived supplements and highly engineered medicines many people perceive the use of herbs as a more natural and healthier way to remediate common mild infections and ailments. Yet a lot modern medicines originate from traditional medicine. Around 11% of drugs considered basic and essential by the World Health Organisation come directly from plants. Nearly 50% of all the medicines approved between 1982 and 2012 occur in nature or are derived from natural components 2.

In this book there are examples of plants, the chemical properties of which have had an impact on people and the world we know today. Some of these, like the Yew (Taxus spp.), and the chemical Paclitaxel, are used in curing some forms of breast cancer. Some are popular stimulants grown commercially on a very large scale and which have an effect not only on the health of individuals but also on global economy. Some are known as common weeds but hide a few interesting historical and chemical facts.

PLANT-DERIVED MEDICINES

According to the WHO, over 60% of overall deaths are caused by noncommunicable diseases like cancer, cardiovascular and heart disease and diabetes. While genetic factors play an important role, the risk of many these can be reduced by adopting an active lifestyle and changing our dietary habits1.

English yew Taxus baccata

OH O

O O

Paclitaxel

Yew trees grow very slowly and often live between 400 and 600 years. The oldest yew tree in Europe is believed to be between 2000 and 5000 years old.

n 2008, cancer caused 13% of deaths globally. Lung and breast cancers were the main contributors to mortality rates1. A number of plants are known to have cancer-curing properties and have been researched towards developing new drugs

disassembling which leads cells getting clogged and dying2,3.

Yew trees grow very slowly and often live between 400 and 600 years2. The oldest yew tree in Europe is believed to be between 2000 and 5000 years old. The amount of bark In 1964 the US National Cancer needed to treat one patient would Institute (NCI) discovered cytotoxic require harvesting an amount of bark properties of the extract from the bark large enough to kill a tree, making of Pacific yew Taxus brevifolia. The the extraction highly unsustainable. active compound, taxol, was reported In 1989, a semisynthetic method was to kill cancer cells by mitotic inhibideveloped using a compound called tion. During mitosis, microtubules 10-DAB occurring in other, more are formed as a polymer of tubule in commonly occurring species of yews. cell cytoplasm. They play key role in A fully synthetic method of obtaining transporting chromosomes in dividtaxol was discovered in 1995; however, ing cell. Taxol stimulates formation of this comprised of 46 steps and wasnâ&#x20AC;&#x2122;t the microtubules and stops them from cost effective. Currrently taxol is pro11

duced in vitro by growing endophytic fungus Penicillium raistrickii on fermented Taxus cells. The name Taxol was trademarked by the pharmaceutical company BMS and the compound is now referred to as Pacliaxel. Paclitaxel is used to treat the two most lethal cancers: breast and lung cancer. It is also used to treat ovarian cancer and AIDS related Kaposiâ&#x20AC;&#x2122;s sarcoma. Taxol became an approved drug in 1993 and it is listed as one of the 252 essentials and basic medicines by the WHO. Its history is a great example of the use of modern technology in harnessing the power of compounds naturally occurring in plants.

OH O O

Aspirin

The bark of the willow (Salix spp.) is a source of salicylates, ions of salicylic acid. These are very abundant in white willow, Salix alba, and less abundant in weeping willow, Salix babylonica. Around 1890, a German pharmaceutical company, Bayer developed acetyl salicylic acid; they named the product aspirin.

White willow Salix alba.

nother drug derived from a tree bark is one many are very familiar with. The bark of the willow Salix spp. is a source of salicylates, ions of salicylic acid. These are very abundant in white willow, Salix alba, and less abundant in weeping willow, Salix babylonica. The medicinal effects of salicylic acid were discovered in the 1750s, when chewing on willow bark helped to relieve fever in Reverend Edward Stone. The drug sodium salicylate was first developed and used as a pain killer against rheumatism. It had side effects, causing stomach discomfort. Around 1890, a German pharmaceutical company , Bayer developed acetyl salicylic acid, a more gentle derivative; they named the product aspirin. Aspirin inhibits the enzyme cyclooxygenase (COX) which reduces the production of prostaglandins at inflammation sites. Prostaglandins are responsible for increase in blood flow, causing swelling, and sensitizing nerve endings, creating the feeling of discomfort and pain. Due to this effect on the human body, aspirin is used as a non-steroidal anti-inflammatory drug (NSAID). Its use in relief on symptoms of common cold and as a pain killer have now been superseded by the use of paracetamol and ibuprofen, which are considered to have fewer side effects than aspirin.

Aspirin is now mostly prescribed as a preventative drug for cardiovascular disease and cancer. COX plays important role in carcinogenesis and inhibits apoptosis, the natural, genetically scheduled death of a healthy cell which is suppressed in cancer cells. Other chemopreventive mechanisms of aspirin are investigated in colorectal, lung, breast and prostate cancers. This COX-inhibiting mechanism is responsible indirectly for a reduction in thrombus formation on the coronary artery wall. Aspirin also induces stimulation of nitric oxide synthase (NOS) in platelets and leucocytes, which leads to the synthesis of nitrogen oxide (NO)rom l-agrginine in platelets, inhibiting platelet aggregation. NO also induces the synthesis of interferon -alpha(IFN-alpha) in leucocytes which also inhibits platelet aggregation. Another important outcome of aspirin-induced increased NO synthesis is a reduction of hyperglycaemia, associated with coronary artery disease, by restoring pancreatic insulin levels. This makes aspirin an important medicine which can be used in the prevention of many non-communicable diseases like cancer, cardiovascular disease, stroke and diabetes.

Common milkweed (Asclepias syriaca) is a perennial shrub producing a thick milky sap resembling latex. The sap contains tri-terpens: Îą and Ă&#x;-amyrin, which have anti-hyper glycemic and hypolipidemic properties that could be used in developing treatment for diabetes. 14

iabetes is another so-called â&#x20AC;&#x153;civilisation diseaseâ&#x20AC;? that each year contributes to an increasing number of deaths. The WHO reports that in 2008 diabetes killed 1.3 million people in the world and projects that diabetes will be the 7th leading cause of death in 2030. There are two type of diabetes: type 1 is characterised by decreased or lack of insulin production by the pancreas. Its onset usually happens in early childhood and is often sudden. This type of diabetes cannot be prevented and is treated with insulin injected daily. In type 2 diabetes, the body develops resistance to insulin, usually later in life. Although some people might have a predisposition towards developing type 2 diabetes, the onset of the disease can be prevented or at least postponed by adopting a healthy diet low in sugar, maintaing low body weight through exercise and avoiding tobacco smoking. Consequences of diabetes include increased risk of heart disease and stroke, reduced blood flow and nerve damage in the feet which might lead to ulcers, infection and the need for amputation. Another outcome of unmanaged diabetes is damage to the small blood vessels in the eye, leading to blindness and kidney failure.

Common milkweed Asclepias syriaca. 15

The antidepressant properties of St. John’s wort have been scientifically proven and are associated with a chemical called hyperforin.

n recent times the awareness of mental disorders has risen. One of the most common mental illness, affecting approximately 350 million people worldwide, is depression, and the number of cases reported is growing. Depression is a common cause of disability in developed countries and it tends to affect women more than men. Symptoms of depression are: low mood, low self-esteem, loss of interest and enjoyment, low energy and poor concentration, low activity levels. Disturbed sleep and change of appetite, feelings of guilt, are all common signs of anxiety, which also accompanies depression. Although depression is not considered lethal, in extreme cases it may lead to suicide. Treating depression is complex and often combines antidepressant drugs with psychotherapy.

Although most commonly prescribed antidepressants are synthetically derived selective serotonin re-uptake inhibitors (SSRIs), a lot of people choose to use natural herbal remedy for mild depression - St.John’s wort Hypercium perforatum. The antidepressant properties of St. John’s wort have been scientifically proven and are associated with a chemical called hyperforin. Hyperforin acts as a reuptake inhibitor of mono amino oxidase (MAO). Monamines include serotonin, norepinephrine and dopamine. St. John’s wort has an impact on the bioavailability of other drugs and therefore the use of it should be discussed with a doctor. Neither amyrin nor St. John’s wort are registered drugs - but their effect on human health has been researched and recognised.

O O

Hyperforin

St. Johnâ&#x20AC;&#x2122;s Wort Hypercium perforatum.

Deadly nightshade Atropa belladonna.

Atropine

O O

ome plant chemicals can reverse the effects of stimulants, by preventing acetylcholinestrase from breaking down acetylcholine and decreasing the dopamine levels. Atropine, alkaloid, isolated from deadly nightshade Atropa belladonna, has such properties. The name Atropa refers to the toxic nature of the plant and comes from the name of the Greek goddess Atropos, one of the three Moirai, goddesses of fate and destiny. Atropos was the one who cut the thread of life in mortals. Belladonna means “beautiful lady” in Italian – and indeed, atropine was used by women in ancient Rome to dilate their pupils to enhance their beauty. Today atropine is widely used in ophthalmology to examine the inside of the eye. Atropine is listed on the WHO’s list of Essential Medicines1,3.

The sweet wormwood Artemisia annua, also known as qinghao, is a Chinese herb containing the active ingredient artemisinin. The herb has been used to treat malaria in China since 200 BC.

O O

O O Artemisinin

lant-derived chemicals can also cure infectious diseases. It is estimated that in 2012 malaria killed approximately 627 000 people globally, 90% of deaths occurred in Africa. Malaria is caused by a protozoan parasite of the genus Plasmodium and it is spread in humans by Anopheles mosquitoes. Plasmodium falciparum is known to cause the majority of deaths by malaria with over 500 million infections a year. Other Plasmodium species causing malaria are Plasmodium vivax, Plasmodium malaria and Plasmodium ovale. Parasite’s sporozoites are transferred in human blood by a mosquito and end up in the liver where they turn into schizonts. After 5 to 7 days schizonts release merozoites which enter the blood cells. Merozoites develop into trophozoites which reproduce either

asexually, producing more schizonts, or sexually, turning into gametocytes which are ingested by mosquitoes to develop into sporozoites. The Sweet wormwood Artemisia annua, also known as Qinghao, is a Chinese herb containing the active ingredient artemisinin. The herb has been used to treat malaria in China since 200 BC, but the research and development of artemisinin into an anti-malaria drug didn’t happen until 1972. Prior to artemisinin, quinine was commonly used to treat malaria. Artemisinin is a sesquiterpene lactone with a peroxide bridge. The peroxide bond is responsible for killing the parasite by binding iron present in the haem, which interferes with the parasites’ calcium pump. Artemisinin is poorly soluble and needs to be extracted by soaking in

cold – rather than hot – water. This makes it expensive to produce and demand currently exceeds the supply. In its pure form artemisinin has short lifetime in human body. In addition to poor bioavailability, Plasmodium parasites can develop resistance to artemisinin, which is exaggerated by the distribution of substandard drugs, which do not contain enough active substance. The World Health Organisation (WHO) recommends using artemisinin in combination with other drugs for the effective treatment of malaria. Research is being conducted to develop cheaper ways to synthesise artemisinin and it’s more bioavailable derivatives to make drug production and distribution affordable for poorer countries where malaria thrives. Nevertheless, artemisinin is still considered as a first-line treatment for the disease and its discovery still contributes to saving many lives.

Sweet wormwood Artemisia annua

STIMULANTS

ome active components in plants have stimulating effects on the central nervous system in people. The recreational drug cocaine is derived from the coca plant Erythroxylum coca, native to South America. Stimulants can sometimes be used for therapeutic purposes, for example in treating Attention Deficit Hyperactivity Disorder (ADHD). The main use of stimulants, however, is to aid alertness and attention in healthy people. Two major commercially grown crops, coffee and tobacco, are commonly used as stimulants. Caffeine in coffee and nicotine in tobacco are the psychoactive substances that increase dopamine

and, used regularly, can develop/prompt various levels of dependency. Whilst there are mixed opinions on the effects of caffeine consumption, it is considered safe in moderate doses or even positive according to some studies. In contrast, tobacco smoking has a very negative impact on human health. The use of both coffee and tobacco has a big impact on the global economy. Another commercially and culturally important stimulant is cacao, the main ingredient of chocolate, and derived from the cocoa plant Theobroma cacao. The stimulating effect of the active ingredient of cocoa â&#x20AC;&#x201C; theobromine â&#x20AC;&#x201C; is a lot milder than that of caffeine and nicotine.

Two major commercially grown crops, coffee and tobacco, are commonly used as stimulants.

This page: Nicotiana tabacco flowers, next page: Nicoatiana tobacco plant.

The tobacco plant is a source of nicotine, a strongly addictive stimulant. N

T N

Nicotine

here are over 70 species of Nicotiana, the majority of which originate in South America. Aztec tobacco Nicotiana rustica was used by the Mayans during ceremonies and rituals. Tobacco leaves were chewed, eaten or smoked. Tobacco grown commercially nowadays is a hybrid of woodland tobacco, Nicotiana sylvestris, and Nicotiana tomentsiformis2. The globalisation of tobacco trade begun shortly after discovery of America by Christopher Columbus in 14927. Tobacco smoke contains large amount of carcinogenic substances including benzene and arsenic. It is estimated that cigarette smoking causes 100,000 deaths in the United Kingdom alone. The World Health

Organisation reported that in 2004 12% of population over 30 years old died directly from the results of tobacco use, which equaled to one person dying every six seconds. Smoking-related deaths include mainly lung cancer, cardiovascular disease and diseases of the respiratory system. Other adverse effects of smoking are premature ageing and poor circulation, among others1,2. The tobacco plant is a source of nicotine, a strongly addictive stimulant. Nicotiana tobacco contains between 0.6 and 3% of dry weight of nicotine while Nicotiana rustica contains almost 9% of the substance6. Nicotine is produced by the plant to deter insects and it can be used as a pesticide on cultivated crops. Neonicotinoid pesticides are derived from nicotine and are associated with the Colony Collapse Disorder in honey bees7.

Nicotine has various effects on the human body. It releases adrenaline and glucose while decreasing insulin levels. It speeds up the metabolism and suppresses appetite. The addictive properties of nicotine are due to activating the acetylcholine receptors, releasing dopamine â&#x20AC;&#x201C; the neurotransmitter responsible for the feeling of reward. The ability to increase dopamine levels is higher in nicotine than in cocaine or heroin, which makes it one of the most addictive substances to man. Withdrawal symptoms include sleeplessness, increased appetite and low mood which may lead to depression2. There are some positive effects of nicotine on human health: it can be used in treating and preventing Parkinsons and Alzheimerâ&#x20AC;&#x2122;s disease, epilepsy, as well as some mental disorders2.

Arabica coffee Coffea arabica, left: plant with beans, top: roasted beans, bottom: ground , roasted beans. 26

O N

N O

Caffeine

offee is one of the most popular drinks in the modern world. It is estimated that over 400 billion cups are consumed every year which makes coffee an important commercial commodity. It is believed that the stimulating properties of coffee were discovered in Abyssinia â&#x20AC;&#x201C; today Northern Ethiopia â&#x20AC;&#x201C; around 850 AD. The legend has it that a goat herder named Kaldi noticed his goats behaving unusually lively when eating the red berries of a coffee tree. Coffee then started to be grown in the gardens of monasteries across the Arab world to help keep monks awake during religious ceremonies. Coffee beans are rich in purine alkaloid caffeine, which has stimulating effects on the nervous system. Arabica coffee beans (Coffea arabica) contain caffeine at a concentration of approximately 1% of dry weight. Caffeine is rapidly absorbed in the upper gastrointestinal tract, reaching peak concentration

in the bloodstream 20 to 30 minutes after consumption. It raises levels of adrenaline and noradrenaline, which leads to increased alertness and may improve mental performance. Caffeine is an adenosine antagonist which elevates the levels of dopamine in the brain. Dopamine, in turn, enhances the effects of serotonin - the hormone of pleasure, which results in an improvement in mood. This is a common addictive mechanism that caffeine shares with other psychoactive drugs. Another property of caffeine is the promotion of glucose synthesis in cells by inhibiting the enzyme cyclic AMP-phosphodiesterase and accumulation of AMP. Increased glucose production combined with the relaxing of smooth brachial muscles, increase in cardiac output and blood flow, and release of fatty acids contribute to an enhancement of physical performance during exercise in athletes.

Caffeine is metabolised in the liver into theobromine, theophyline and paraxanthine. The half-life of caffeine varies between 2.5 and 4.5 hours. Half-time is extended in pregnant women to about 10 hours. Caffeine metabolism is significantly slower in young children and people with liver disease. Consumed in excess, caffeine can have adverse effects on health resulting in sleeplessness and anxiety. Caffeine withdrawal symptoms include low mood, headaches, fatigue and impaired cognitive function. Coffee beans are seeds of coffee cherries. The pulp of the fruit is removed by either soaking it in water or drying it in the sun. The beans are then roasted and become dark brown in colour. Roasting is responsible for the rich aroma and flavour of coffee. The drink is made by pouring hot water over ground, roasted coffee beans.

Coffee beans are seeds of coffee cherries. The pulp of the fruit is removed by either soaking it in water or drying it in the sun. The beans are then roasted and become dark brown in colour. Roasting is responsible for the rich aroma and flavour of coffee. The drink is made by pouring hot water over ground, roasted coffee beans. 27

Cocoa fruits are called pods and contain between 30 and 40 seeds. The seeds are what we refer to as cocoa beans. During processing the fruit pulp is first fermented for approximately 6 days. Then the beans are dried and as such are traded to the producers. In the next step, cocoa beans are roasted and the outer shells, called hull is removed. Beans with hull removed are called the nibs. At this stage the nibs contain approximately 55% fat. The nibs are pressed to separate the fat to produce cocoa butter. What is left after removing of the fat is used to produce cocoa powder.

ocoa tree is native to South America and it grows in equatorial latitudes. Evidence of ancient pictograms and artefacts show that cacao was consumed since ancient times by Olmecs, Mayans and Aztecs consecutively as a beverage/ brew. Cocoa beans were an important trading commodity in Aztec culture. The word “chocolate” derived from the mispronunciation of the Native American word for their coca beverage/brew, “cacahuatl”6. Theobromine is one of the metabolites of caffeine as well as a dominant purine alkaloid occurring in cocoa beans. Theobromine is named after the scientific name of the cocoa plant

procyanidins. The reduction of risk of cardiovascular disease associated with cocoa consumption is linked to the flavan-3-ols. A study undertaken on the population of Kuna Native Americans occupying San Blas Island off the Caribbean coast of Panama shows that high cocoa beverage consumption results in significant reduction of deaths due to cardiovascular disease, cancer and type 2 diabetes in comparison to their mainland counterparts. Kuna people consume up to 5 cups of cocoa brews a day which equals to an approximate daily intake of 900 mg of Apart from theobromine, cocoa flavan-3-ols. However, the commerseeds are source of flavan-3-ols in cial way of processing cocoa removes form of monomers catechin (-) - epia large amount of the beneficial catechin and (+) - catechin and dimers flavan-3-ols6. Theobroma cacao. The name theobroma is of Greek origin and means “food of the gods”, (theo meaning god and broma meaning food). Mature cocoa beans contain 2.2 - 2.7% of theobromine and small amounts of caffeine. Theobromine is known to have mild stimulating effects on the nervous system and heart. It is a vasodilator which results in lowering blood pressure and, like caffeine, is a diuretic. Theobromine is very slowly metabolised by dogs and cats and therefore toxic to them2,6.

Theobromine

O N

HN O

Catechins

OH 29

CHEMICALS IN POPULAR PLANT BASED FOODS AND DRINKS

Many plants that we consume daily owe their popularity in culinary use to their active chemical compounds. These include spices and herbs, alcoholic beverages, fruit and vegetables. Chemicals influence the smell and flavour of plants, as well as the bioavailability of macro and micro nutrients in dishes. Many of them are considered beneficial to health and are part of a balanced diet. We often have a vague idea of the effects of some of the chemicals occurring in the plants that we eat. This chapter will help the mechanisms of action of these chemicals.

ops – Humulus lupulus – were first used as a preservative in yeast around 4000 years ago. In medieval times hops were used in brewing beer and added to ale to stop it turning sour. Hops are responsible for the characteristic bitter taste of the beverage2. Hops grow on vines which grip surfaces tightly. Male and female flowers occur on different plants and only female plants are cultivated commercially. Female flowers resemble cones and are harvested and dried in kilns called oast houses. The mixture of unfermented sweet liquid malt and dried hops is boiled and added to the beer at the end of brewing process2. Hops contain α-acid humulone, which during the boiling process is converted to isohumulone. Isohumulone has anti-bacterial properties against gram-positive bacteria. It is the main ingredient responsible for stopping the ale from turning sour. This property was exploited throughout the centuries, when available water was often contaminated: weak ale was used as a main source of hydration by many communities. Sailors were known to drink about a gallon per day of Indian Pale Ale and perhaps that is how they gained their constantly drunk reputation. In the human body, isohumulone, like aspirin, acts as a COX inhibitor. It also has anti-viral and anti-bacterial properties. Hops have sedative effects on the central nervous system. It was confirmed that bitter acids, especially ß-acids (colupulone, lupulone and adlupulone) are mainly responsible for this3. Hence dried hops flowers are often used along with lavender in aromatherapy to aid sleep2.

Hops Humulus lupulus.

Isohumulone has antibacterial properties against gram positive bacteria. It is the main ingredient responsible for stopping the ale from turning sour.

HO O

Isohumulone

HO O

Capsaicin

H N O

hilli peppers are native to South and North America and were introduced in Asia and Europe in the 16th century2. They are used to spice food worldwide and are especially popular in Asia. Chillies are famous for causing a burning sensation when eaten or applied to skin. The chemical responsible for this is capsaicin, which activates the heat receptor TRVP1, sometimes referred to as the capsaicin receptor. It causes burning pain, increases sweating and also releases endorphins. Mucous membranes are particularly sensitive to capsaicin. The activation of the heat receptor does not however raise thve body temperature. Casein in milk neutralises the burning sensation caused by capsaicin, therefore spicy dishes are often accompanied by yoghurtbased sides.

Long exposure overwhelms the nerves and therefore reduces their ability to report pain. This results in capsaicin being used topically in a form of gel to relieve pain and inflammation. Capsaicin is used in high concentration in pepper spray. It is used mainly by police in self-defence. It causes tears, pain and temporary blindness when applied to the eyes. It can also be used as a deterrent to wild animals in certain regions2. There are many different species, each containing different amounts of capsaicin. A hotness scale was developed by Wilbur Scoville in 1912; heat was measured by an organoleptic test 2. Some of the hotter chilli kinds include Scotch bonnet â&#x20AC;&#x201C; Capsicum chinese â&#x20AC;&#x201C; and tabasco peppers â&#x20AC;&#x201C; Capsicum frutenses var. tabasco.

Menthol

Some of the most familiar chilli peppers varieties belong to the species Capsicum annum. These also vary in capsaicin content. Some well-known varieties are jalapeño, cayenne and bird’s eye chillies as well as bell peppers, very popular in western countries; these, however, contain no capsaicin at all. Mint is a herb commonly used to flavour food and drinks. The genus Mentha includes many species; of these, spearmint – Mentha spicata – and peppermint – Mentha piperita – are the most widely used in the food industry. Peppermint leaves infused in hot water make a hot beverage often drunk after a large meal to aid digestion.

The active ingredient of mint is menthol. Menthol is responsible for inducing a cooling sensation, by activating the cold receptor TRPM8. Like capsaicin, it does not change body temperature, and prolonged exposure can desensitise the nerves and numb the area, relieving pain. For this purpose menthol is applied to skin in form of ointments and creams. Menthol applied to the nasal mucous membrane slows down respiration and aids breathing. It is therefore often used to relieve symptoms of the common cold and flu2. Due to its cooling properties the menthol fragrance is considered “fresh”. It also has anti-microbial properties and for this reason is used in oral hygiene products.

Left: Pepper mint Mentha piperita, right: bananna mint Mentha arvensis. Previous page: Chilli pepper Capsicum annum.

DADS

arlic Allium sativum is used to flavour food worldwide. It is one of the main ingredients of curry dishes. Conventional wisdom says that garlic can prevent or reduce the duration of common cold and flu. It has characteristic smell that some people and animals perceive as unpleasant. Mainly the bulbs are eaten, however stems and flowers are also edible and can be used as salad ingredients2.

Garlic owes its characteristic taste to activation of the receptor TRPA1 which is a sensor for irritants, pain, cold and stench. Activation of this receptor by allicin and DADS causes vasodilation leading to reduced blood pressure, it also stops aggregation of platelets2. There is plenty of scientific evidence that DADS has chemopreventive properties against lung, breast, colon, and prostate human cancer cells3.

Garlic contains allin and the enzyme allinase, which are separated inside the cells. Allin and allinase are released from cells during the mechanical phase of digestion. Allinase converts allin into allicin â&#x20AC;&#x201C; an unstable compound producing amongst others, diallyl disulphide (DADS). This is defence mechanism used by the plant against pests. Allicin, being very unstable, provided a long-standing challenge for scientists to harness its anti-microbial and anti-cancer properties2,3.

Garlic has strong anti-bacterial properties - it can be used to disinfect wounds. Its use as a cold and flu relief might be contributed to the fact that is increases the potency of non-steroidal anti-inflammatory drugs (NSAIDs) and antibiotics2,3. Onions Allium cepa and chives Allium schoenoprasm belong the same genus as garlic and also contain sulphurous compounds.

Garlic has strong anti-bacterial properties - it can be used to disinfect wounds. Conventional wisdom says that garlic can prevent or reduce the duration of common cold and flu.

Left: mouse garlic Allium angulosum; flower, this page garlic Allium sativum cloves and bulb. 37

ß-carotene

arrots have been cultivated from wild carrots Dacus carota for around 2000 years. Carrots are native to Europe, North Africa and Asia. Most popular in Western Europe are orange carrots, however many different colour varieties are grown worldwide. Carrots are famous for containing ß-carotene, which is a conjugated polyene, containing alternating double and single carbon bonds. This chemical structure is sensitive to sunlight and is also a strong antioxidant. ßcarotene is precursor to vitamin A - retinol. Facial creams containing retinol make skin sensitive to sunlight. Carrots are one of the most powerful antioxidant vegetables which have a protective effect on cardiovascular system. Vitamin A is essential in production of a pigment rhodopsin essential to low light level vision. It is common wisdom that eating carrots improves night vision, but this effect hasn’t been confirmed by any studies. A lot of animals that are orange in colour owe this to eating carotenoid rich food. Ma-

rine algae containing ß-carotene are a food source for shrimp and salmon. Shrimp is eaten by flamingoes in the wild which gives them characteristic pinkish red colour. Flamingoes have special glands near the feathers on their tails that secrete carotenoids mixed with wax. Pigments are spread through frequent preening - this is considered to make them more attractive to potential partners. Pigments need to be frequently reapplied due to fading on exposure to sunlight. Captive flamingoes need to be fed carotenoid rich foods to maintain their colour. Carotenoids are used as a food colouring agent with the symbol E160a. It is added in juices, fizzy drinks and many deserts. Consuming too many foods and drinks containing ß-carotene can cause orange skin colouration in people. Many other vegetables are source of ßcarotene including, butternut squash, pumpkin, spinach, and kale. The biggest source of carotenoids is sweet potatoes2.

A lot of animals that are orange in colour owe this to eating carotenoid rich food. Marine algae containing Ă&#x;-carotene are a food source for shrimp and salmon. Shrimp is eaten by flamingoes in the wild which gives them characteristic pinkish red colour.

Previous page: orange carrots Dacus spp., above: Chilean flamingo Phoenicopterus chilensis. 39

SUMMARY

ceutical companies are reluctant to invest in costly research and finding ways to extract natural plant compounds cost effective. It is also harder to own the exclusive right to sell and market a naturally accruing product3.

t is impossible to list all significant facts about plant derived chemicals and their use in improving of human health. The above examples show only few, popular and important plants and their properties, discovery of which had a big impact on our health, history and economy.

It sometimes seems that once the beneficial effects of plant is discovered a lot of effort goes into developing synthetic equivalents and then improving their bioavailability. Whilst in case of taxol there might have been genuine reasons for doing so, in many cases this can be done solely to increase the potential profits.

There is an ongoing search for new phytopharmaceutics as well as improving bioavailability and synthesis of the already known ones. There are many reasons for which the natural medicine is not as well researched as it should be considering the technology that we currently possess. A lot of properties of common herbs and plants still are considered a common wisdom and anecdotal due to lack of sufficient research or inconclusive results. More energy seems to be directed into developing synthetic drugs which are easier to patent and trademark and often cheaper to mass produce. Major pharma-

This ethical controversy and general trends to favour natural products means that the popularity of herbal medicine is growing. There is proof that at least in case of nutrition, that eating fresh and natural products is by far more beneficial than taking supplements.

References

1. World Health Organisation Fact Sheets, www.who.int/research/en/, accessed August 2014. 2. Gwenda Kyd, Mo Sibbons, Molecules, Medicines and Mischief: a Year on the Chemical Trail Around Cambridge University Botanic Garden, Vervain Publishing 2014. 3. Valdir Cechinel-Filho, Plant Bioactives and Drug Discovery, Principles, Practice, and Perspectives, Universidade do Vale do Itajai (UNIVALI) Itajai-SC, Brazil, Wiley Series in Drug Discovery and Development 2012, page 285, 196, 184, 183, 187, 360 and 499. 4. Dilan M. Demir, Aspirin, Therapeutic Uses, Adverse Effects and Pharmacokinatics, Nova Science Publishers, Inc. 2011, page 18. 5. Marta P. Ortega, Irene C. Gil, New Developments in Medicinal Chemistry, Nova Science Publishing Inc. 2009, page 143. 6. Alan Crozier, Hiroshi Ashihara, Francisco Tomas-Barberan, Teas, Cocoa and Coffee, Plant Secondary Metabolites and Health. 7. Richard M. Florio, Bees, Biology, Threats and Colonies, Animal Science, Issues and Professions, Nova Publishing Inc. 2012, page 230.