Pharmacognosy of Clove

Pharmacognosy of Clove consists of dried flower buds of Eugenia caryophyllus (Sprengel) Bullock & Harrison (Syzygium aromaticum Linn).

Synonyms: Clove bud, Laung, Lavang, Caryophyllum.

Biological source: It consists of dried flower buds of Eugenia caryophyllus (Sprengel) Bullock & Harrison (Syzygium aromaticum Linn).

Family: Myrtaceae.

Geographical source: It is native to the Mollucca Island and traditionally cultivated in Tanzania (Zinziber), Madagascar, Indonesia, Srilanka and India (mainly in Nilgiri hills, Kanyakumari, Kottayam and Quilon hills of Kerala).

Cultivation and Collection:

The deep rich loamy soil is good for clove cultivation but it can also grow in sandy loam and laterite soil. It favours a warm humid climate with annual rainfall in the range of 150 to 250 cm. It grows well at an altitude of 900 meters from sea level. The seeds are sown from august to October for cultivation purposes. The seeds are sown in the nursery bed at a distance of 10 cm. the seeds germinate in four or five weeks and these seedlings are transplanted to pots after six months. These seedlings are kept in pots for nearly about 12 months. Then they are transferred into the open field. The shade is provided in the initial stage because the plants cannot bear the full sunshine. It can also be cultivated along with other plants like areca nut, coconut or nutmeg. Suitable fertilizers like ammonium sulphate, superphosphate, potash etc are provided to the plants in two doses. The first dose should be given in May or June and the second dose is in October. The plants started bearing after 7 to 8 years and gives abundant yield per hectare after 15 to 20 years of growth. Generally, the clove plant produces about 3 to 4 kg of drug per year.

The clove buds are handpicked or by beating with bamboo. Sometimes platform ladders are also used in the case of tall trees. The collection starts when clove buds is change their colour from green to light pink. The cloves are sun-dried and kept free from foreign matter. After drying the colour of the cloves changes and becomes crimson or brownish-black.

Clove plant and Clove buds
Figure 1.1: Clove plant and Clove buds

Macroscopic Characters:

Colour: Crimson red to brown.

Odour: Characteristic or aromatic.

Taste: Aromatic and pungent.

Size: Length (10 to 18 mm), width (3 to 4 mm) and thickness (2 mm).

Shape: Flower bud is nail-shaped, Hypanthium – Quadrangular (length 10 to 12 mm × diameter 2 to 3 mm), Head – Globulous.

Hypanthium corresponds to the inferior ovary, and a globulous head, surrounded by four divergent sepal lobes consisting of four imbricated petals wrapped in numerous incurved stamens. The pulverized drugs show the presence of large secretory cavities, calcium oxalate crystals, pollen grains, and fibres with thick, lignified punctate walls.

Chemical Constituents:

It mainly contains volatile oil (15-20 per cent), gallotannins (10 to 15 per cent), resin, chromone and eugenin. Eugenol (70 to 90 per cent), eugenol acetate, caryophyllenes, traces of esters, ketones and alcohols are the constituents of volatile oil which is present in oil ducts of clove.

Chemical structure of clove constituents
Figure 1.2: Chemical structure of clove constituents

Properties of Clove Oil:

Colour: Clove oil is colourless to pale yellow.

Specific gravity: 1.038 to 1.06

Refractive index: 1.527 to 1.535

Boiling point: 250°C

It should be stored in proper conditions because it becomes dark and thick in storage.

Chemical Test:

Needle-shaped crystals are seen when the section of clove is treated with a strong potassium hydroxide solution.

Uses of Clove Oil

Clove-based phytomedicines are used locally to treat minor wounds after cleansing, as an analgesic (headache, toothache), as an analgesic in disease of the mouth, pharynx, or both (in the form of lozenges), in mouthwashes for oral hygiene. Internally it is used to treat symptoms of gastrointestinal disturbances like epigastric bloating, improper digestion and flatulence.

In Germany, clove-based products are used in mouthwashes for swelling of the mouth and throat. In Indonesia, it is consumed as ‘Kretek’ cigarettes.

Adulterants of Cloves

Table 1.1: Adulterants of Cloves

Sr. No.AdulterantCharacters
1.  Exhausted clovesOil-free or contain very less amount of oil, darker in colour, shrinked, floats on water.
 2. Clove stalksGenerally used for adulteration of powdered cloves, ash value is high, fibre content is high, calcium oxalate prism is present, and contains 5 per cent of oil.
 3. Blown clovesExpanded flowers of the clove tree, stamens-free, contain less volatile oil.
 4.Mother cloveDark brown in colour, oval in shape, slightly aromatic, starchy, and contains less volatile oil.
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