Pharmacognosy and Health Benefits of Clove

Introduction

Clove, is a popular spice often used in Indian, African, Mexican and Middle Eastern cuisine, and has useful medicinal properties. Clove, historically for a certain period of time (around 17th century) were grown only on the Spice Islands or the Malaku Islands by the Dutch to gain monopoly. But the French succeeded in introducing the clove trees in Mauritius followed by many other countries. Before this in around third century BC clove was used in China and then by the fourth century by had gained popularity in Europe too. Due to its medicinal properties its use had started as an expectorant, anti-emetic and analgesic which still continues today. Eugenol is the active ingredient which is mainly responsible for the pharmacological properties of the drug. It is safely used in foods, beverages and toothpastes. Because of its analgesic (pain-killing) and antiseptic (bactericidal)  activity it has gained wide acceptance in dentistry. It’s analgesic and expectorant (cough-suppressing) activity makes it a very good herbal treatment for symptomatic relief of sore throat. It is also known as lavang in India.

Clove

Biological Source Dried flower buds of Syzygium aromaticum (Eugenia caryophyllata/Caryophyllus aromaticus)
Family Myrtaceae
Geographical Source The plant grows in warm climates such as that of the Molluca islands, Tanzania, Sumatra, Madagascar, Indonesia, Sri Lanka, India and Brazil. It is also cultivated in Zanzibar and Pemba.
Morphology/Macroscopical Characters
  • The plant is a tall evergreen plant about 20m high with leaves leathery in texture.
  • Clove can be bifurcated into the head and the stalk region.
  • The head portion containing the buds have four projecting calyx teeth or lobes or sepals. A hood which hides numerous stamens is formed by the folding of the four petals which are above the lobes (sepals).
  • The stalk portion of the clove consists of a cylindrical hypanthium above which lies a bilocular ovary consisting of numerous ovules.

Organoleptic properties: The clove flower buds are around 10-17.5 mm long and 2mm thick and are dark brown (almost black) in colour. Cloves have a strong aromatic and pungent taste followed by numbness (analgesia) and a spicy odour .

Microscopic Characters In a transverse section of the hypanthium, in the region below the ovary of the clove the following observations are made:

Going from outside (epidermis) to the inside (columella),

  • The epidermis of clove has a thick cuticle with anomocytic stomata and straight walled cells.
  • There is presence of schizolysigenous oil glands which are ellipsoidal in shape in the parenchyma.
  • Calcium oxalate crystals clusters too are present in the parenchymatous cells. They are around 5-25 μm in diameter. They are shaped as acicular needles.
  • Vascular bundles (lignified and thickened) are found in the oil glands zone and in the outer region of the columella.
  • Between the columella and the vascular bundles is the region of aerenchyma which is composed of air cells and supports the columella.
  • Collumella is also rich in calcium oxalate crystals and has a ring of vascular bundles in its outer ring.
  • Pollen grains are 15-20 μm in diameter and triangular in shape.
  • Starch grains are absent.
Chemistry
  • Clove consists of 14-21% of volatile oil which gives the characteristic odour and flavour to the compound. Volatile oil content is about 5% in stem and 2% in leaves.
  • The main component of distilled clove bud oil is eugenol (60-90%) and the others are acetyleugenol (3%), sesquiterpenes (α-caryophyllene and β-caryophyllene), gallotannic acid, vanillin, furfural etc. Flavanoids, lipids, carbohydrates and vitamins are also present.

    Eugenol

    Eugenol

  • Other constituents like tannins, gums, resins and glucoside sterols are also present in the bud.
  • Chemical Tests On treating with strong KOH solution, clove shows needle shaped crystals of potassium eugenate.
    Adulterants/Allied drugs/ Substitutes Adulterants:

  • Exhausted cloves: Cloves which have been exhausted of volatile oil do not sink in freshly boiled and cooled water compared to the ones rich in volatile oil (as they are heavier than water).
  • Blown cloves: If the cloves are left for a longer period of time on the trees, the buds open up and the petals shed away.
  • Mother cloves: Ripe fruits of cloves (brown, ovoid and one seeded), identified by starch in the seeds and less volatile oil.
  • Clove stalks: Can be detected by the presence of prismatic calcium oxalate crystals found unlike the original acicular needles. Also identified by presence of isodiametric sclereids.
  • Uses Clove is used as a spice and as a carminative. Topically when clove oil is applied it has counter-irritant action. It is also used as an analgesic (pain-killing) and antiseptic (bactericidal) in oral health and dentistry. It’s analgesic, antiseptic and expectorant (cough-suppressing) activity makes it a very good herbal treatment for symptomatic relief of sore throat and coughing. Non-medicinally it is used in perfumes, for oil painting or as mosquito repellant.

    Other proposed uses:

  • Eugenol present has antipyretic effects and also inhibits prostaglandin biosynthesis (showing antidiarrheal effect).
  • Antithrombotic activity and inhibition of platelet aggregation has also been reported.
  • Clove oil also shows anticarcinogenic properties due to the sesquiterpenes present.
  • Clove also is being used for its spasmolytic and anti histaminic properties.
  • It also has antibacterial, fungistatic, anthelminitic and larvicidal properties.
  • Other Notes (life cycle, extraction etc.) -
    Adverse reactions Clove oil can be a skin and mucous membrane irritant and sensitizer in some cases. In large doses it can irritate the gastro-intestinal tract.

    References:

    1. Trease and Evans’ Pharmacognosy, 16e (Evans, Trease and Evans Pharmacognosy) Elsevier: New York, 2009.
    2. Ara DerMarderosian, et. al. The Review of Natural Products 4th Edition.
    3. Kokate, C. K.; Gokhale, S. B.; Purohit, A. P. A textbook of Pharmacognosy, 29th ed.; Nirali Prakashan: Pune, 2009.

    About Sweety Mehta

    Studied B. Pharm. at Mumbai Educational Trust Institute of Pharmacy (Mumbai). Worked at Cipla, Mumbai as Marketing executive for 2 years and 9 months. Earned a diploma in marketing from Welingkar's Institute of Management Development and Research.