- Clove is a spice of antiquity. It has been found in ceramic vessels in Syria, dated around 1721 BC. In 3rd century BC, chewing cloves was required to freshen the breath before addressing Chinese leaders in the Han Dynasty. (4)
Clove is a medium-sized evergreen tree growing to a height of 8 to 12 meters. Leaves are large. Flowers are crimson, grouped in terminal clusters. Flower buds are initially pale, gradually turning to green, then to bright red before harvest. The flower consist of a long calyx that terminates into four spreading sepals, and four unopened petals that form a central small ball. Cloves are harvested t 1.5-2.0 centimeters long.
Production of the flower buds, the commercialized part of the tree, starts after 4 years of plantation. Flower buds are collected in the maturation phase before flowering. (3)
- Native to the Philippines and Indonesia.
- Commercially cultivated in Bangladesh, Indonesia, India, Malaysia, Sri Lanka, Madagascar and Tanzania. (3)
- Cloves are a major vegetal source of phenolic compounds such as flavonoids, hydroxybenzoic acids, hydroxycinamic acids and hydroxyphenyl propens. (3)
- Eugenol is the main bioactive compound, in concentrations raging from 9,381.70 to 14,650.00 mg/100 g of fresh plant material. About 89% of clove essential oil is eugenol, 5% to 15% is eugenol acetate and ß-cariofilenol, and 2.1% is a-humulen. (3)
- Besides eugenol, other important essential oil components include acetyl eugenol, ß-caryophyllene and vanillin, crategolic acid, tannins such as bicornin, gallotannic acid, methyl salicylate, flavonoids eugenin, kaempferol, rhamnetic, and eugenitin, triterpenoids oleanolic acid, stigmasterol, and campesterol, and several sesquiterpenes. (4)
- Of the phenolic compounds, gallic acid is found in highest concentration (783.50 mg/100 g fresh weight). Other phenolic acids are caffeic, ferulic, elagic and salicylic acids. Flavonoids like kaempferol, quercetin and derivatives are found in lower concentration. (3)
- Nutrient value per 100g of edible portion yielded: (Proximates) water 9.87 g, energy 274 kcal, protein 5.97 g, total lipid (fat) 13.00 g, carbohydrate by difference 65.53 g, total dietary fiber 33.9 g, total sugars 2.36 g; (Minerals) calcium 632 mg, iron 11.83 mg, magnesium 259 mg, phosphosrus 104 mg, potassium 1020 mg, sodium 277 mg, zinc 2.32 mg; (Vitamins) vitamin C 0.2 mg, thiamin 0.158 mg, riboflavin 0.220 mg, niacin 1.560 mg, vitamin B6
0.391 mg, vitamin B12 0, folate 25 µg, vitamin A 160 IU, vitamin E (alpha-tocopherol) 8.82 mg, vitamin D 0, vitamin K 141.8 µg; (Lipids) total saturated fatty acids 3.952 g, total monosaturated FD 1.393 g, total polyunsaturated FA 3.606 g, total trans FA 0.254 g, cholesterol 0. (6)
- Study of dried clove buds volatile oil yielded major constituents of 3-allyl-6-methoxyphenol i.e. m-Eugenol (69.44%), eugenol acetate (10.79%), 4-hydroxy-4-mehtylpentan-2-one i.e. tyranton (7.78%), caryophyllene (6.80%), 1,4,7-cycloundecatriene, 1,5,9,9-tetramethyl-,Z,Z,Z-and trace amounts (<1%) of other constituents. (10)
- GC-MS analysis of extracted clove oil yielded three higher peaks and three lowest peak phytochemicals viz. eugenol, α-cubebene, iso-eugenitol and α-copaene, ß-caryophyllene oxide and ß-bipinene, respectively. (see study below) (17)
- Ethanol extract of buds yielded the presence of alkaloids, carbohydrates, proteins, amino acids, fixed oils, flavonoids, and phenolic compounds. GC-MS analysis yielded 19 compounds with eugenol as the major compound
- German Commission E lists cloves as antiseptic, antibacterial, antifungal and antiviral.
- Considered aphrodisiac, antimutagenic, anti-inflammatory, antioxidant, antiviral, anti-parasitic, antipyretic, anthelmintic, mosquito repellent.
- Studies have shown antitumor, antimicrobial, anti-inflammatory, analgesic, antioxidant, fertility, antidepressant, antiobesity, aphrodisiac, spermatogenesis, neuropharmacological, insecticidal, biopreservative, dental antimicrobial, larvicidal, insecticidal, antimutagenic, glucose lowering, anthelmintic, chemopreventive effects.
- Primarily used as a spice in the cuisine of Asian, African and Middle East countries, providing flavor to meats, curries, and marinades. Also used on hot beverages and as constituent of spice blends.
- For centuries of ancient medicine, used to counter tooth decay and halitosis. Used for diarrhea, bowel and liver ailments, and as nerve stimulant.
- Generally used as topical analgesic in dentistry.
- Used for asthma and other allergic conditions.
Topical applied to the stomach to warm the digestive tract. Applied to relieve toothache due to dental caries. (4)
- In Chinese medicine, considered warm, acrid, and aromatic; used to warm the middle, direct stomach qi downward, to treat hiccups, and to fortify the kidney yang. (4)
- Scenting: As spice, used for scenting, chewing tobacco, and as ingredient in betel chew. (12)
Cigarette flavor: Use as spice to flavor kretek, an Indonesian cigarette. (4) In some Western coffee bars, mixed with marijuana to create marijuana spliffs. (11)
- Repellent: Biochemical constituents allow for use as ant repellent. (4)
Combined with orange, used to make a fragrance pomander. (4)
Used in aromatherapy.
- Oil and Dental products: Clove oil used for toothache and other types of pain. Oil used in preparation of some Clovacaine solution and anesthetic toothpastes used for oral ulceration and inflammation. A mixture of eugenol and zinc oxide is used as temporary tooth cavity filling. (10)
poison: Clove oil has be used to anesthetize fish. At dose of 300 mg/l it is considered a humane means of euthanasia. (10) (also see study below:50)
- Other industrial uses: Used in manufacture of perfumes and soaps.
• Anti-Tumor / Antioxidant / Antimicrobial / Flower Buds and Roots: Study of methanolic extract of cloves flower buds yielded 11 phenolic compounds. Methanolic extract of roots was tested for anticancer activity against breast, colon, and liver cancer. IC50s were 31 µg/ml for colon cancer, 29.7 µg/ml for breast cancer and 18.7 µg/ml for hepatic cancer. The extract showed strong antioxidant activity against DPPH compared to vitamin C. Antimicrobial activity of ME of roots at concentration of 0.1 and 0.3 ml (10 mg/1 ml) showed strong inhibitory effect against most of the three bacterial and four fungal strains tested. (5)
• Minor Drug Interactions: Minor interactions with medications that slow blood clotting (anticoagulants, and antiplatelet drugs). Taking cloves with these medications may increase the chances of bruising and bleeding. (7)
• Treatment of Plaque-Induced
Periodontal Disease: Study evaluated it potential for application in the treatment of plaque-induced periodontal disease. In vitro studies have shown bateriostatic and bactericidal properties. Study suggests clove and its derivatives have potential use as specific anti-plaque and anti-inflammatory agent for the treatment of periodontal disease and suggests new formulations in the form of delivery system or topical agents. (8)
• Antifungal / Essential Oil: Study evaluated the composition and antifungal activity of clove essential oil of S. aromaticum. The EO showed high eugenol content of 85.3% and exhibited inhibitory activity against all tested fungal strains i.e., Candida, Aspergillus and collection of dermatophyte strains, including fluconazole-resistant strains. (9)
• Antioxidant / Fruits and Stems: Study evaluated the antioxidant capacity of S. aromaticum from different parts of the clove including fruits and stems using TPC, TFC, FRAP, and DPPH assays. When all measured parameters were taken into account, antioxidants were remarkable in clove fruits, followed by clove stems. (12)
• Anti-Obesity Potential: Study investigated the anti-obesity potential of S. aromaticum extract and its effect on adipocyte differentiation in 3T3-L1 cells in mice. In vitro study on 3T3-L1 cells showed efficient inhibition of the conversion of cells into adipocytes in a dose dependent manner. In vivo study showed SAE supplementation significantly decreased HFD-induced increased in body weight, liver weight, WAT mass, and serum TG, TC, lipid, glucose, insulin and leptin levels. Inhibition of fat accumulation in HFD-mice was attributed to suppression of transcription factors integral to adipogenesis and lipogenesis, suggesting its potential in obesity prevention. (13)
• Aphrodisiac / Effect on Sexual Behavior: Study evaluated the aphrodisiac activity of 50% ethanolic extracts of Myristica fragrans (nutmeg) and Syzygium aromaticum (clove) in male mice. Both extracts enhanced sexual behavior of male mice as evidenced by stimulation of mounting behavior and significant increase in their mating performance. The extracts were devoid of any conspicuous general short term toxicity. (14) Study evaluated the effect of 50% ethanol extract of clove on general mating behavior, libido, potency, along with gastric ulcerative effects and adverse effects on sexual behavior of normal male albino rats. Results showed significant and sustained increase in sexual activity of normal male rats, without gastric ulcerative effects. The aphrodisiac effects supports claims for traditional usage in sexual disorders. (20)
• Cytotoxicity to Human Skin Cells: Although clove oil and its components are generally considered "safe", this in-vitro study demonstrates cytotoxic properties of both oil and eugenol towards human fibroblasts and endothelial cells. Clove oil was highly cytotoxic at concentrations as low as 0.03% (v/v) with up to 73% attributable to eugenol. (15)
• Toxicity on Male Reproductive System / Decreased Spermatogenesis: Study evaluated the effects of S. aromaticum extract on male reproductive system in a mice model. High dose-treated animals showed a significant decline in sperm count, motility, and testosterone but a significant increase in estradiol concentration. (16)
• Clove Oil as Food Bio-Preservative: Study evaluated the antimicrobial activity of clove oil against a range of food borne pathogens i.e., bacteria and fungal autochthonous microorganisms.
GC-MS analysis yielded various secondary bioactive compounds. The oil was found very effective at lowest MIC of 2.5% (v/v) against Staphylococcus epidermis and Staphyl. sp and Aspergillus niger and Rhizopus sp. among the fungi. Clove oil was found more effective than both clove extract and Sorbic acid. (17)
• Neuropharmacological / Essential Oil: Study evaluated the anticonvulsant, anxiolytic, and hynoptic activities of clove essential oil. The CEO significantly increased the onset of convulsion and reduced duration in a dose dependent manner in mice using strychnine and picrotoxin-induced convulsion model. The CEO showed significant increase in latency time, ambulation and significant decrease in grooming. There was a marked hypnotic effect with significant dose dependent decrease in time of onset of sleep in thiopental sodium induced sleep test. (18)
• Effect on Ethanol Consumption and Abstinence: Study evaluated the effect of clove on biochemical parameters of rats subjected to ethanol consumption and abstinence. Administration of clove tea alone or ethanol alone did not change serum parameters of glucose, triglycerides, TC, TP and albumin, with no alteration in weight gain. Administration of clove tea before or after ethanol administration led to significant changes in several parameters. Results suggest prolonged alcohol intake should be avoided when clove tea is consumed daily. (19)
• Insecticidal / Stored Grain Pests / Oil: GC-MS study of essential oil yielded evaluated the essential oil from S. aromaticum yielded 2-methoxy-4-(2-propenyl)-phenol (83%), and transcaryophyllene (12%) as most common main compounds. The the pure compounds and clove oil were tested for toxicity and repellency against Rhyzopertha dominica, Sitophilus oryzae, and Tribolium castaneum. There were no differences in mortality activity, suggesting that the activity of clove oil was sole due to the 2-methoxy phenol compound. Repellency testing showed 2-methoxy-4-(2-propenyl)-phenol was more repellent than clove oil. (21)
• Dental Antimicrobial / Strep mutans: Study evaluated various antimicrobial herbal extracts i.e. Neem, Liquorice, Cinnamon, Clove and Babool for the prevention of dental caries and root canal failures. Babool and Liquorice extracts were effective in inhibiting growth of cariogenic pathogens like Strep mutans while Babool and Clove extracts showed effective antimicrobial effect against Enterococcus faecalis and can be used to reduce root canal microflora and root canal failures. (22)
• Insecticidal / Larvae of Tuta absoluta: Tomato leafminer, Tuta absoluta, is a major pest of tomatoes in Morocco. Study evaluated the toxicity of EO of SA buds against larvae of T. absoluta. Results confirmed a high degree of toxicity of the buds on filter paper against the larvae of T. absoluta. (23)
• Antimutagenic / Phenylpropanoids: Antimutagenic phenylpropanoids were isolated from the buds of cloves of S. aromaticum. The isolated compounds suppressed the expression of umu gene following the induction of SOS response in S. typhimurium TA2535/pSK1002 that was treated with various mutagens. (24)
• Analgesic / Antidiarrheal / Antimicrobial: Study evaluated the antidiarrheal, analgesic and antimicrobial effects of a clove aqueous extract and clove oil. In vitro studies showed inhibition of rhythmic contractions and Ach-induced contractions of isolated rabbit intestine, in both CO showed more potent activity than CAE. CO showed potent antispasmodic and antidiarrheal effect in castor oil-induced diarrhea in mice and showed dose-dependent analgesic action in acetic acid-induced writhing in mice. In in-vitro antimicrobial studies, the CO inhibited the growth of Staphylococcus aureus, Klebsiella, E. coli and Proteus and effectively inhibited the growth of Candida albicans. (25)
• Antifungal / Eugenol / Essential Oil: Study evaluated the antifungal activity of essential oil of S. aromaticum against common fungal pathogens of plants and animals viz. Fusarium oxysporum, Aspergillus sp., Mucor sp., Trichophyton rubrum, and Microsporum gypseum. All the fungi were inhibited by the oil. Study suggests the antifungal action of clove oil is due to its high eugenol content. (26)
• Antimicrobial / Mechanism of Activity: Study evaluated the potential of clove extract for use as antimicrobial drug and food additives. Results showed the clove extract displayed significant antimicrobial effect on all tested strains. Eukaryotic translation elongation factor 1 alpha (eEF1A) protein was induced by the clove ethanolic extract. Suppression of the expression of eEF1A could be the reason for growth inhibition. Study results suggest potential scientific basis for the application of clove extract as natural antifungal drug and food preservatives. (27)
• Silver Nanoparticles / Antioxidant / Anti-Inflammatory: Study evaluated the antioxidant and anti-inflammatory activity of S. aromaticum silver nanoparticles. The AgNPs showed dose-dependent antioxidant property with 80% radical scavenging at 0.25 mg/ml. Inhibition of protein denaturation assay also showed the AgNPs as having higher activity (66%) compared with aspirin (55%) and aqueous extract (56%). Results showed the AgNPs were more active than aqueous extract and may be considered for use in inflammatory disorders. (28)
• Activity Against Aspergillus Species: Study evaluated the in vitro susceptibility S. aromaticum against Aspergillus species viz. A. niger, A fumigatus, A. flavus, A. terreus, A clavatus, A. glaucus and A. nidulans. All the species isolated from patients showed 100% sensitivity to S. aromaticum. Results suggest potential use in pharmacology. (29)
Anti-Cholinesterase Activity / Potential for Alzheimer's / Essential Oil: Study evaluated the anti-cholinesterase activity of methanol extract of clove, its oil, and eugenol. Acetylcholinesterase (AChE) and butyrylcholinesteerase (BChE) inhibition studies showed eugenol possess exhibited better inhibition of the enzymes than the extract or oil. The content of eugenol in the EO was 0.5 µg/ml. Results suggest a potential for the use of clove as anti-cholinesterase for the management of cognitive ailments like Alzheimer's. (31)
• Anti-Depressant Effects / Toxicity Testing / Essential Oil: Study in mice evaluated the safety and anti-depressant effects of essential of S. aromaticum. Single LD50 was about 4500 mg/kg on 24-hr acute toxicity study. In long term repeated toxicity study, only 400 mg/kg induced a significant decrease in body weight, with no significant changes in organ weights and histopathological analysis. EO by gavage exerted anti-depressant effects on forced swimming test and tail suspension test. On long-term EO treatment, there was increased sucrose preference and elevated protein levels of hippocampal p-ERK, p-CREB, and brain-derived neurotrophic factor in mice exposed to chronic unpredictable mild stress. Results suggest the potent anti-depressant effect might be attributed to improvement in hippocampal pERK1/2-pCREB-BDNF pathway in rats exposed to chronic unpredictable mild stress. (32)
• Effect on Sperm Count and Testes Histology: Study evaluated the effect of methanolic extract of SA on histology of testes and sperm parameters of adule male wistar rats. Results showed that in low to moderate intake of Syzygium aromaticum can act as aphrodisiac and cause increase in sperm count with preservation of testicular tissue. However, excessive intake could be toxic with damage to testicular tissues and may cause infertility. (33)
• Antibacterial / Quinones / Flowers:Study of flower bud extract showed antibacterial activity against two bacterial isolates i.e., Bacillus and Serratia marcescens. The main constituents of the extracts were ketones and anthraquinones. Activity was attributed to the presence of quinones in the extract. (34)
• Modulation of Intestinal Glucose Handling: Previous studies have shown glucose lowering effects of Syzygium aromaticum-derived triterpenes i.e., oleanolic acid (OA) and maslinic acid (MA) Study evaluated the effect of triterpenes on intestinal glucose handling in STZ-induced diabetic rats. In vitro studies showed both OA and MA possess inhibitory effects on the activity of α-amylase, α-glucosidase and sucrase comparable with standard drug acarbose. Both significantly (p<0.05) inhibited intestinal glucose transport in everted intestinal sacs in a dose-dependent manner. Results showed antidiabetic properties attributed, in part, to modulation of intestinal glucose handling. (35)
/ Oil: Study evaluated the antiepileptic effect of essential oil of clove on pentylenetetrazole (PTZ)-induced seizures in animal models. Results showed clove oil produced significant antiepileptic effect at all test doses. Sodium valproate was used as standard. (36)
• Effect on Seminiferous Tubules and Oxidative Stress After Testicular Torsion: Study evaluated the protective effect of S. aromaticum extract on damaged tissues and oxidative stress after testicular torsion in a rat model. Results suggest the use of Syzygium aromaticum may have provided a protective support against torsion detorsion injury followed by treatment with SZ extract. (37)
/ Dried Clove Powder: In-vitro study evaluated the anthelmintic activities of A. sativum, F. asafoetida, and Syzygium aromaticum against liver fluke Fasciola gigantica. Results showed the plants may be used as anthelmintic. The ethanol extract of S. aromaticum (2h LC50 2.95 mg/ml) was more toxic against F. gigantica than A. sativum and F. sativum. The 8h LC50 of S. aromaticum was 1.02 mg/ml. (38)
• Glucose Lowering Effect: Study evaluated the glucose lowering effect of a 50% ethanol extract of S. aromaticum in STZ-induced diabetic rats. There was a marked dose-related decrease in blood glucose to near normal values. The 750 mg/kg body weight dose produced the maximum effect. (39)
• Essential Oil / Streptococcus mutans: Study evaluated the activity of essential oil of S. mutans with emphasis on antimicrobial property. The presence of eugenol as active ingredient in the oil was checked and was evaluated against planktonic cells Streptococcus mutans ATCC. Results showed greater antimicrobial activity at concentrations of 1000, 500, and 250 µg/ml. (40)
• Antibacterial / Antibiotic Promotion / Essential Oil: Study evaluated the chemical composition of essential oils of Piper nigrum and Syzygium aromaticum and their antimicrobial effect in combination with different antibiotics towards S. aureus, S. enteritidis, and S. typhi. EO of S. aromaticum yielded three main compounds representing 89% of identified compounds viz. beta-caryophyllene (43.63%), eugenol (42.67%, and alpha-humulene (3.73%). SA alone was more effective PN. In combination with selected antibiotics, S. aromaticum gave better results, the best with gentamicin. Combination of different EOs with gentamicin did not show to be acutely toxic to rats after 14 days at doses 10 times the MIC. (41)
• Antiradical Power / Effect on Lipid Profile
/ Antimicrobial / Essential Oil: Study investigated cold pressed clove oil (CO) for its lipid profile, radical scavenging potential and antimicrobial properties. The CO showed 94.7% neutral lipids, followed by glycolipids and phospholipids. Main fatty acids were linoleic and oleic, together comprising about 80% of total FA. CO quenched to% of DPPH radicals compared to virgin olive oil at only 45%. The CO inhibited the growth of all tested microorganisms. (42)
• Antimicrobial / Virulence-Modulating Effects on C. jejuni / Clove Essential Oil: Study investigated the antimicrobial effect of clove on zoonotic pathogen Campylobacter jejuni. RT-PCR and 2D PAGE showed CO affects the expression of virulence-associated genes taking part in the synthesis of flagella, PEB1, PEB4, LPS and serine protease. Eugenol and other CO components possessed bactericidal activity against C. jejuni. Results showed clove EO has marked antibacterial and potential virulence-modulating effect on C. jejuni. (43)
• Larvicidal Against Aedes aegypti: Study evaluated the larvicidal potential S. aromaticum and C. sinensis essential oils, alone or in combination with temephos, on Ae. aegypti populations with different organophosphate resistance. The essential oils exhibited similar larvicidal activity in resistant and susceptible populations, and are suitable for use in mosquito resistance management. The combination with temephos did not decrease resistance profiles. (44)
• Potential Chemopreventive Agent for Lung Cancer / Apoptogenic / Anti-Proliferative: Study evaluated the chemopreventive potential of aqueous solution of clove during benzo[a]pyrene (BP)-induced lung carcinogenesis in strain A mice. Western Blot analysis showed the clove infusion upregulated the expression of anti-apoptoci Bcl-2 in the precancerous stages. It also downregulated the expression of some growth-promoting proteins, viz., COX-2, cMyc, Hras. Results signify the chemoprentive potential through its apoptogenic and anti-proliferative properties. (45)
• Toxicity Study / Growth Impairment and Hepatonephrotoxicity: Study evaluated the effects of various doses (50 to 800 mg/kg for two weeks) of water extract of SA buds on parameters of growth, serology, hematologic and pathologic characteristics of Wistar rats. Impairment of growth and hepato-nephrotoxicity were observed in rats of all groups. Oral administration of buds water extract is not fatal but caused damage to vital organs as evidenced by cytoplasmic vacuolation and necrosis of centrilobular hepatocytes, packing of nephons, dilatation of renal tubules, and intestinal lymphocytic infiltration and desquamation. (46)
• Ameliorative Effects on Male Fertility / Exposure to Manganese / Essential Oil: Study evaluated the effect of S. aromaticum essential oil on fertility in male rats exposed to manganese. Chronic exposure to manganese cause degeneration of the seminiferous tubules and the gremlin cell, with decrease in sperm levels and rise in morphological abnormalities. Treatment with IP administration of EO from flower buds showed an ameliorative effect as evidenced by a significant rise in sperm concentration and reduction of morphological abnormalities associated with significant regeneration of seminiferous tubules and interstitial cells. (47)
• Antitumor / Antimicrobial: Clove showed a strong antibacterial against Staphylococcus aureus, Bacillus cereus, E. coli and P. aeruginosa and antifungal activity against Candida albicans.
Clove also showed anticancer activity against MCF-7 breast cancer cell lines. (48)
• Zinc Nanoparticles / Antimicrobial: Study reported on the biosynthesis of ZnS nanoparticles using a methanol extract of S. aromaticum as antimicrobial agent.
The biosynthesized ZnS showed excellent antimicrobial activity against all test microorganisms, viz., Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Candia albicans, and Aspergillus niger. (49)
• Fish Sedating Effect / Clove Buds: Study evaluated ground clove buds (GCB) for effective sedative concentration on sexually immature zebrafish (Danio rerio). LC50 was identified at 198.23 ppm while effective and safe sedative concentration was estimated at 19.52 ppm (p<0.05). This concentration caused mild sedative for at least 48 hours with signs of irritation nor histopathological lesions and without any mortality within 96 hours of exposure to GCB. (50)
- Clove bud essential oil in the cybermarket.