Clove
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Syzygium aromaticum
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A Brief History of Cloves Cloves have been used for thousands of years in food, perfume, and medicine, and are believed to have first been imported into China from the Spice Islands (1).
The Spice Islands reside in the Indonesian archipelago of the Moluccas, also known as the Maluku Islands. The islands sit north of Australia and west of New Guinea on the Equator. While only about 5 of the islands played a key role in the European spice trade, there are hundreds of islands in the archipelago. Dense rainforests consume the volcanic islands, which remained the only source for cloves, mace, and nutmeg until the 1700s. |
Cloves were introduced to the Europeans by Arab traders sometime in the fourth century. The traders were able to keep the source of their spices a secret for a number of years until Vasco da Gama of Portugal made his journey to India in 1497 (2).
A Fight for the Islands To the locals on the islands, it was a native tradition to plant a clove tree every time a baby was born, symbolically connecting the life of the child to the tree. The clove tree grew freely and in abundance.
The Portuguese would eventually lose control of the islands to the Dutch. To strengthen their reign of the territories and drive up the cost of the spices, the Dutch would come to destroy most trees and spices on the other islands, concentrating production on the island of Amboina (and a few outlying islands) and making cloves worth more than their weight in gold. The spice trade was a significant part of human history. European sailors made perilous journeys to capitalize on the spice market. To participate and expand trade, Europeans took on the risk of sailing into uncharted waters, which led to the "exploration" of the "New World" (Christopher Columbus) and the first journey around the world by ship (Magellan). In time, cloves would be cultivated in locations more convenient for trade, increasing their availability and reducing their cost (2). By 1672, the spice trade had made its way to the United States. And because of the rapid assembly and superb craftsmanship of sailing boats, Salem (Massachusetts) would become the capital of spices in the 19th century (1). |
The Mysterious Spice Islands The Spice Islands were kept secret for many years. Eventually, a series of maps would be produced to help traders navigate to the islands. These maps are a fantastic way to examine the history of the islands and to understand their importance in the spice trade.
click the map to see more!
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"A certain Elihu Yale, who was born in 1649 in Boston, made his fortune as a spice merchant in India; he gave material support from his family home in Wales to help build up the institution that was to become Yale University." - UCLA History and Special Collections (1)
Although cloves are widely popular in Indonesian cigarettes, the general use of clove in food and medicine has been in steady decline for well over one hundred years. For a long time humans fought and died for the commodity, and now it drifts out of style like the very ships that once imported it.
What Is a Clove?
Cloves come from a tree, also known as Syzgium aromaticum, or s. aromaticum. It is a midium sized tree (26 to 40 feet) originating from the Mirtaceae family and native to the before mentioned Maluku islands in Indonesia. While it is native to this area and parts of Asia, it is now cultivated around the world, largely in coastal areas around the equatorial line. Cloves are the flower buds of the tree, which typically begin to produce after the tree has reached its fourth year.
Cloves In Medicine
For centuries spices such as clove, oregano, mint, thyme, and cinnamon have been used for medicine and as food preservatives. Cloves are considered to be the most valuable of these spices and have played an important role in human health (3).
Eugenol is one of the main bioactive compounds found in a clove and makes up anywhere from 9 to 14 grams per 100 grams of plant material (3).
In other words, Eugenol makes up approximately 89% of the essential oil extracted from a clove bud with eugenol acetate and β-cariofileno accounting for 5% and 15% of the eugenol oil, respectively (4).
In recent years science has put clove to the test. The following text include the medicinal qualities that have been discovered.
Eugenol is one of the main bioactive compounds found in a clove and makes up anywhere from 9 to 14 grams per 100 grams of plant material (3).
In other words, Eugenol makes up approximately 89% of the essential oil extracted from a clove bud with eugenol acetate and β-cariofileno accounting for 5% and 15% of the eugenol oil, respectively (4).
In recent years science has put clove to the test. The following text include the medicinal qualities that have been discovered.
Medical Research
Antioxidant Activity
Universities and private research companies have been working with the United States Department of Agriculture to produce a database which includes the antioxidant activity of different kinds of foods.
From the database, we know that spices have a polyphenol content higher than fruits, seeds, and vegetables. And among spices, cloves have a higher polyphenol and antioxidant level (3).
From the database, we know that spices have a polyphenol content higher than fruits, seeds, and vegetables. And among spices, cloves have a higher polyphenol and antioxidant level (3).
"Polyphenols are abundant micronutrients in our diet, and evidence for their role in the prevention of degenerative diseases such as cancer and cardiovascular diseases is emerging. The health effects of polyphenols depend on the amount consumed and on their bioavailability." - American Journal of Clinical Nutrition
A study conducted by the Department of Botany and the Department of Zoology at the University of Hong Kong tested for the correlation between polyphenol content and antioxidant activity. Among the 26 spices they tested, they found that cloves had a higher antioxidant rating and more polyphenol content than the other spices in the experiment (6).
In 2012, cloves, as well as caraway, were found to possess antioxidant activity comparable to that of a synthetic food preservative know as butylated hydroxytoluene (BHT) (10).
And in a similar study comparing eugenol and BHT, eugenol was found to have a higher antioxidant level in most of the tried methods (8).
Memory loss can be caused by oxidative stress. New research is suggesting that memory loss may be prevented, and even reversed, by the use of antioxidants.
In a study conducted by the Department of Pharmacology at the University of Delhi, oxidative stress was measured in rats exposed to pesticides. Their study found that treatment of clove essential oil decreased the oxidative stress acquired in the brains of the rats (9).
An experiment in food found that a controlled, and uncontrolled, release from clove bud extracts increased the shelf-life of soybean oil - a testament to clove's antioxidant properties (10).
Conclusion:
In 2012, cloves, as well as caraway, were found to possess antioxidant activity comparable to that of a synthetic food preservative know as butylated hydroxytoluene (BHT) (10).
And in a similar study comparing eugenol and BHT, eugenol was found to have a higher antioxidant level in most of the tried methods (8).
Memory loss can be caused by oxidative stress. New research is suggesting that memory loss may be prevented, and even reversed, by the use of antioxidants.
In a study conducted by the Department of Pharmacology at the University of Delhi, oxidative stress was measured in rats exposed to pesticides. Their study found that treatment of clove essential oil decreased the oxidative stress acquired in the brains of the rats (9).
An experiment in food found that a controlled, and uncontrolled, release from clove bud extracts increased the shelf-life of soybean oil - a testament to clove's antioxidant properties (10).
Conclusion:
- Through multiple studies, cloves have exhibited impressive antioxidant qualities.
Antimicrobial Activity
Antibacterial
Extracts of clove at 1% and 3% were tested against food-borne pathogens, alongside the antimicrobial potential of garlic, ginger, mustard, cinnamon, and mint. Among the Indian spices tested against Escherichia coli (E. coli), Staphylococcus aureus, and Bacillus cereus, only the extract of clove was effective against all three. Concentrations of 1% showed a satisfactory inhibition while 3% showed a complete bactericidal effect (11).
In a similar study published by Dorman and Deans, the antibacterial properties of clove were tested alongside thyme, oregano, nutmeg, geranium, and black pepper. The herbs were tested against 25 strains of bacteria. The essential oils that proved to have the widest spectrum of antimicrobial activity were clove, thyme, and oregano (12).
In a study that combined both eugenol and cinnamaldehyde (an organic compound found in cinnamon), tests on 31 bacterial strains were conducted. The bacteria strains, which would typically be treated with amoxicillin (antibiotics), were found to be more effectively inhibited by the eugenol and cinnamaldehyde formulation than by amoxicillin. Even more importantly, the bacteria strains showed no sign of developing resistance to the chemicals, antibiotic resistance being a major concern for modern antibiotics (15).
Amoxicillin:
In a similar study published by Dorman and Deans, the antibacterial properties of clove were tested alongside thyme, oregano, nutmeg, geranium, and black pepper. The herbs were tested against 25 strains of bacteria. The essential oils that proved to have the widest spectrum of antimicrobial activity were clove, thyme, and oregano (12).
In a study that combined both eugenol and cinnamaldehyde (an organic compound found in cinnamon), tests on 31 bacterial strains were conducted. The bacteria strains, which would typically be treated with amoxicillin (antibiotics), were found to be more effectively inhibited by the eugenol and cinnamaldehyde formulation than by amoxicillin. Even more importantly, the bacteria strains showed no sign of developing resistance to the chemicals, antibiotic resistance being a major concern for modern antibiotics (15).
Amoxicillin:
Amoxicillin is used to treat bacterial infections in many different parts of the body. It is also used with other medicines (e.g., clarithromycin, lansoprazole) to treat H. pylori infection and duodenal ulcers. Amoxicillin belongs to the group of medicines known as penicillin antibiotics. - APUA
Antifungal
The Research and Development Center in Kilpest India created a "scale of sensibility" to present a chromatographic analysis of the antifungal activity of clove oil and its main component, eugenol. Rana IS, Rana AS, and Rajak RC found that eugenol caused lysis of spores and micelle (13).
Lysis:
Lysis:
1. Immunology, Biochemistry: the dissolution or destruction of cells by lysins.
2.Medicine/Medical: the gradual recession of a disease. - Dictionary.com
The anticandidal activity of eugenol was tested in an experiment on vaginal candida by the Faculty of Sciences in the Laboratory of Biotechnology in Fes, Morocco. Their results showed eugenol to be an effective antifungal agent for the treatment and prevention of vaginal candidiasis (14).
Conclusion:
- Studies have shown eugenol to contain impressive antimicrobial properties with the potential to be more effective than modern antibiotics in some applications.
Antinociceptive
Medical Definition of antinociception:
The action or process of blocking the detection of a painful or injurious stimulus by sensory neurons Compared with systemic narcotic analgesia, intraspinal narcotic antinociception has a longer duration.
- Merriam-Webster
There are multiple chemical-related effects happening when clove oil is used as an analgesic (painkiller). The main compound responsible for the effect is eugenol.
The feeling of pain occurs by sensory receptors:
The feeling of pain occurs by sensory receptors:
When we feel pain, such as when we touch a hot stove, sensory receptors in our skin send a message via nerve fibres (A-delta fibres and C fibres) to the spinal cord and brainstem and then onto the brain where the sensation of pain is registered, the information is processed and the pain is perceived. - mydr.com.au
Antiviral
In the following two studies, eugenol was tested against different strains of the herpes virus.
In the first study, conducted by the Medical and Pharmaceutical University of Sugitani in Toyama, Japan, a specific chemical, eugeniin, was isolated from the herbal extraction of cloves. The isolated extraction was found to be effective at concentrations of 5 micrograms in multiple capacities. The extract inhibited the growth of multiple strains of the herpes simplex virus (HSV) by disrupting protein synthesis in the infected Vero cells, without prohibiting cellular protein synthesis (18).
The second study was based on ancient Chinese remedies for the treatment of various human diseases. Targeting HSV-1 in mice, a selection of 10 herbal extracts were picked for the experiment. Extract of Syzygium aromaticum (cloves) showed stronger anti-HSV-1 activity than the majority of the 10 extracts selected for the study. The extracts were used safely on the mice and caused no negative reactions or signs of toxicity (19).
Conclusion:
In the first study, conducted by the Medical and Pharmaceutical University of Sugitani in Toyama, Japan, a specific chemical, eugeniin, was isolated from the herbal extraction of cloves. The isolated extraction was found to be effective at concentrations of 5 micrograms in multiple capacities. The extract inhibited the growth of multiple strains of the herpes simplex virus (HSV) by disrupting protein synthesis in the infected Vero cells, without prohibiting cellular protein synthesis (18).
The second study was based on ancient Chinese remedies for the treatment of various human diseases. Targeting HSV-1 in mice, a selection of 10 herbal extracts were picked for the experiment. Extract of Syzygium aromaticum (cloves) showed stronger anti-HSV-1 activity than the majority of the 10 extracts selected for the study. The extracts were used safely on the mice and caused no negative reactions or signs of toxicity (19).
Conclusion:
- Eugenol is capable of inhibiting virus development, especially when combined with other chemicals and isolates, justifying the use of cloves in ancient Chinese medicine.
Cytotoxicity of Eugenol
When we read the word cytotoxicity, we should think "cell-toxicity".
1. the degree to which an agent has specific destructive action on certain cells.
2. the possession of such destructive action, particularly in reference to lysis of cells by immune phenomena and to antineoplastic agents that selectively kill dividing cells.
- the Medical Dictionary
Being cytotoxic means that the said "agent", in this case eugenol, is capable of destroying a cell that is performing irregularly. Another term for cell irregularity is cell mutation, which can also be defined as cancer.
Ths Cytokine Research Lab at the University of Texas spent several years of intense research identifying molecular targets for the purpose of preventing and treating cancer (20).
While the study primarily focused on fruits and vegetables as the "molecular targets", some herbs, including cloves, were also sampled. They concluded that the molecular ingredients of the targets were cytotoxic, reaffirming that the consumption of antioxidant rich foods can help prevent and treat cancer on a molecular level (20).
Ths Cytokine Research Lab at the University of Texas spent several years of intense research identifying molecular targets for the purpose of preventing and treating cancer (20).
While the study primarily focused on fruits and vegetables as the "molecular targets", some herbs, including cloves, were also sampled. They concluded that the molecular ingredients of the targets were cytotoxic, reaffirming that the consumption of antioxidant rich foods can help prevent and treat cancer on a molecular level (20).
This work reaffirms what Hippocrates said 25 centuries ago, "let food be thy medicine and medicine be thy food." - PubMed.gov 16563357
Conclusion:
- The research shows us that cloves can be added to the list of foods that should be consumed to help fight and prevent cancer.
Toxicity and Pharmacokinetics
Cloves and eugenol oil are considered relatively safe to eat. While you should never ingest pure essential oil, the World Health Organization has established that concentrations of "2.5 mg per kg of weight in humans", per day, is safe for consumption (21).
A study by the University of Montreal in Canada tested the half-life of eugenol in the body (how long the chemical stays in a system). Their research found that eugenol is readily absorbed into the body when ingested (eaten, taken orally) and has an average half-life of up to 18.3 hours in the blood and up to 14 hours in plasma. They conclude that ingesting cloves, or eugenol oil, as a daily supplement can help relieve neuropathic pain because of the build-up of eugenol in the blood and plasma (22).
A study by the University of Montreal in Canada tested the half-life of eugenol in the body (how long the chemical stays in a system). Their research found that eugenol is readily absorbed into the body when ingested (eaten, taken orally) and has an average half-life of up to 18.3 hours in the blood and up to 14 hours in plasma. They conclude that ingesting cloves, or eugenol oil, as a daily supplement can help relieve neuropathic pain because of the build-up of eugenol in the blood and plasma (22).
Works Cited:
1) Clove. https://unitproj.library.ucla.edu/biomed/spice/index.cfm?displayID=7
2) Spice Islands (Moluccas): 250 Years of Maps (1521-1760). https://libweb5.princeton.edu/visual_materials/maps/websites/pacific/spice-islands/spice-islands-maps.html
3) Clove (Syzygium aromaticum): a precious spice. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3819475/
4) Chemical composition and antioxidant properties of clove leaf essential oil. https://www.ncbi.nlm.nih.gov/pubmed/16910723
5) Polyphenols: food sources and bioavailability. http://ajcn.nutrition.org/content/79/5/727.full
6) Antioxidant capacity of 26 spice extracts and characterization of their phenolic constituents. https://www.ncbi.nlm.nih.gov/pubmed/16190627
7) Gülçin I, Elmastaş M, Aboul-Enein HY. Antioxidant activity of clove oil-A powerful antioxidant source. Arab J Chem. 2012;5(4):489–499.
8) Antioxidant activity of eugenol: a structure-activity relationship study. https://www.ncbi.nlm.nih.gov/pubmed/21554120
9) Reversal of propoxur-induced impairment of memory and oxidative stress by 4'-chlorodiazepam in rats. https://www.ncbi.nlm.nih.gov/pubmed/20012268
10) Chatterjee D, Bhattacharjee P. Comparative evaluation of the antioxidant efficacy of encapsulated and un-encapsulated eugenol-rich clove extracts in soybean oil: shelf-life and frying stability of soybean oil. J Food Eng. 2013;117(4):545–550.
11) Sofia PK, Prasad R, Vijay VK, Srivastava AK. Evaluation of antibacterial activity of Indian spices against common foodborne pathogens. Int J Food Sci Technol. 2007;42(8):910–915.
12) Antimicrobial agents from plants: antibacterial activity of plant volatile oils. https://www.ncbi.nlm.nih.gov/pubmed/10736000
13) Evaluation of antifungal activity in essential oil of the Syzygium aromaticum (L.) by extraction, purification and analysis of its main component eugenol. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3768706/
14) Evaluation of carvacrol and eugenol as prophylaxis and treatment of vaginal candidiasis in an immunosuppressed rat model. https://www.ncbi.nlm.nih.gov/pubmed/15456732
15) Antimicrobial activities of Eugenol and Cinnamaldehyde against the human gastric pathogen Helicobacter pylori. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1373661/
16) Eugenol Inhibits ATP-induced P2X Currents in Trigeminal Ganglion Neurons. https://www.ncbi.nlm.nih.gov/pubmed/19967073
17) The selective capsaicin antagonist capsazepine abolishes the antinociceptive action of eugenol and guaiacol. https://www.ncbi.nlm.nih.gov/pubmed/9126180
18) Purification and characterization of eugeniin as an anti-herpesvirus compound from Geum japonicum and Syzygium aromaticum. https://www.ncbi.nlm.nih.gov/pubmed/9454821
19) Efficacy of traditional herbal medicines in combination with acyclovir against herpes simplex virus type 1 infection in vitro and in vivo. https://www.ncbi.nlm.nih.gov/pubmed/7486956
20) Molecular targets of dietary agents for prevention and therapy of cancer. https://www.ncbi.nlm.nih.gov/pubmed/16563357/
21) Gülçin I, Elmastaş M, Aboul-Enein HY. Antioxidant activity of clove oil-A powerful antioxidant source. Arab J Chem. 2012;5(4):489–499.
22) Pharmacokinetics of eugenol and its effects on thermal hypersensitivity in rats. https://www.ncbi.nlm.nih.gov/pubmed/17321520
23) Fumigant activity of plant essential oils and components from garlic (Allium sativum) and clove bud (Eugenia caryophyllata) oils against the Japanese termite (Reticulitermes speratus Kolbe). https://www.ncbi.nlm.nih.gov/pubmed/15913300
24) Laboratory evaluation of aromatic essential oils from thirteen plant species as candidate repellents against Leptotrombidium chiggers (Acari: Trombiculidae), the vector of scrub typhus. https://www.ncbi.nlm.nih.gov/pubmed/19009361
25) Toxicity and repellency of compounds from clove (Syzygium aromaticum) to red imported fire ants Solenopsis invicta (Hymenoptera: Formicidae). https://www.ncbi.nlm.nih.gov/pubmed/23448024
26) Essential oils and their compositions as spatial repellents for pestiferous social wasps. https://www.ncbi.nlm.nih.gov/pubmed/23081867
27) Structure-activity relationships of eugenol derivatives against Aedes aegypti (Diptera: Culicidae) larvae. https://www.ncbi.nlm.nih.gov/pubmed/22674880
2) Spice Islands (Moluccas): 250 Years of Maps (1521-1760). https://libweb5.princeton.edu/visual_materials/maps/websites/pacific/spice-islands/spice-islands-maps.html
3) Clove (Syzygium aromaticum): a precious spice. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3819475/
4) Chemical composition and antioxidant properties of clove leaf essential oil. https://www.ncbi.nlm.nih.gov/pubmed/16910723
5) Polyphenols: food sources and bioavailability. http://ajcn.nutrition.org/content/79/5/727.full
6) Antioxidant capacity of 26 spice extracts and characterization of their phenolic constituents. https://www.ncbi.nlm.nih.gov/pubmed/16190627
7) Gülçin I, Elmastaş M, Aboul-Enein HY. Antioxidant activity of clove oil-A powerful antioxidant source. Arab J Chem. 2012;5(4):489–499.
8) Antioxidant activity of eugenol: a structure-activity relationship study. https://www.ncbi.nlm.nih.gov/pubmed/21554120
9) Reversal of propoxur-induced impairment of memory and oxidative stress by 4'-chlorodiazepam in rats. https://www.ncbi.nlm.nih.gov/pubmed/20012268
10) Chatterjee D, Bhattacharjee P. Comparative evaluation of the antioxidant efficacy of encapsulated and un-encapsulated eugenol-rich clove extracts in soybean oil: shelf-life and frying stability of soybean oil. J Food Eng. 2013;117(4):545–550.
11) Sofia PK, Prasad R, Vijay VK, Srivastava AK. Evaluation of antibacterial activity of Indian spices against common foodborne pathogens. Int J Food Sci Technol. 2007;42(8):910–915.
12) Antimicrobial agents from plants: antibacterial activity of plant volatile oils. https://www.ncbi.nlm.nih.gov/pubmed/10736000
13) Evaluation of antifungal activity in essential oil of the Syzygium aromaticum (L.) by extraction, purification and analysis of its main component eugenol. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3768706/
14) Evaluation of carvacrol and eugenol as prophylaxis and treatment of vaginal candidiasis in an immunosuppressed rat model. https://www.ncbi.nlm.nih.gov/pubmed/15456732
15) Antimicrobial activities of Eugenol and Cinnamaldehyde against the human gastric pathogen Helicobacter pylori. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1373661/
16) Eugenol Inhibits ATP-induced P2X Currents in Trigeminal Ganglion Neurons. https://www.ncbi.nlm.nih.gov/pubmed/19967073
17) The selective capsaicin antagonist capsazepine abolishes the antinociceptive action of eugenol and guaiacol. https://www.ncbi.nlm.nih.gov/pubmed/9126180
18) Purification and characterization of eugeniin as an anti-herpesvirus compound from Geum japonicum and Syzygium aromaticum. https://www.ncbi.nlm.nih.gov/pubmed/9454821
19) Efficacy of traditional herbal medicines in combination with acyclovir against herpes simplex virus type 1 infection in vitro and in vivo. https://www.ncbi.nlm.nih.gov/pubmed/7486956
20) Molecular targets of dietary agents for prevention and therapy of cancer. https://www.ncbi.nlm.nih.gov/pubmed/16563357/
21) Gülçin I, Elmastaş M, Aboul-Enein HY. Antioxidant activity of clove oil-A powerful antioxidant source. Arab J Chem. 2012;5(4):489–499.
22) Pharmacokinetics of eugenol and its effects on thermal hypersensitivity in rats. https://www.ncbi.nlm.nih.gov/pubmed/17321520
23) Fumigant activity of plant essential oils and components from garlic (Allium sativum) and clove bud (Eugenia caryophyllata) oils against the Japanese termite (Reticulitermes speratus Kolbe). https://www.ncbi.nlm.nih.gov/pubmed/15913300
24) Laboratory evaluation of aromatic essential oils from thirteen plant species as candidate repellents against Leptotrombidium chiggers (Acari: Trombiculidae), the vector of scrub typhus. https://www.ncbi.nlm.nih.gov/pubmed/19009361
25) Toxicity and repellency of compounds from clove (Syzygium aromaticum) to red imported fire ants Solenopsis invicta (Hymenoptera: Formicidae). https://www.ncbi.nlm.nih.gov/pubmed/23448024
26) Essential oils and their compositions as spatial repellents for pestiferous social wasps. https://www.ncbi.nlm.nih.gov/pubmed/23081867
27) Structure-activity relationships of eugenol derivatives against Aedes aegypti (Diptera: Culicidae) larvae. https://www.ncbi.nlm.nih.gov/pubmed/22674880