Bitter Almond

Bitter almond is an example of cyanogenetic glycosides. Cyanogenetic glycosides are also known as cyanophoric glycosides because they contain hydrocyanic acid as an aglycone moiety. These glycosides are derivatives of mandelonitrile which yield hydrocyanic acid and benzaldehyde upon hydrolysis. These glycosides are also referred to as aldehyde glycosides. About 110 families contain cyanogenetic glycosides among these rosaceae are the most prominent family which contains cyanogenetic glycosides. These glycosidal containing drugs possess flavoring properties. They do not have any specific pharmacological property.

  • Synonym: Amygdala amara.
  • Biological source: It consists of dried ripe seeds of the plant Prunus amygdalus Batsch var Amara.
  • Family: Rosaceae.
  • Geographical source: It is indigenous to Iran and Asia and cultivated in Sicily, Italy, Protugal, Morocco, and South France.
Bitter almond plant
Fig.1: Bitter almond plant

Cultivation and Collection of Bitter Almond

The almond trees require a hot and dry climate. They do not tolerate wet soils and frosts. They are sun-loving trees and flowers well in full sunlight. Although they can tolerate partial shade but could not flower or fruit. They require well-drained, deep loamy soil. They need sufficient rainfall around 500-600mm or irrigation to produce better yields and well-filled nuts. They can also survive with less water. They especially benefitted from irrigation in early spring, during summer, and sometimes during the first months of autumn. Almonds are generally not self-pollinating. Generally, cross-pollination with another variety is required for better quality fruit production. The distance should be kept around 4 to 6 meters in between two plants. Before planting, the roots should be watered. The drugged-out hole should be deep enough for the whole root system. The root should not be bent in shape. Like many nut trees, almonds are especially sensitive to tampering with their tap root, so they should never be trimmed or forced into a hole not big enough to accommodate it. The nuts should be dried well before consumption. This can be done by leaving them on the ground for a few days after shaking them or stored safely at the dried place. The average healthy and mature almond tree can produce nearly 23-30 kg of nuts per tree.

Macroscopical Characters of Bitter Almond

  • Colour: Brown.
  • Odour: None.
  • Taste: Bitter.
  • Size: 20 mm length, 120 mm width, and 10 mm thickness.
  • Shape: Flat, Oblong, Ovoid having marks on testa.

Chemical Constituents of Bitter Almond

Bitter almond contains fixed oil (40-50 percent), Protein (20 percent), enzyme emulsion, and bitter glycoside amygdalin (1-3 percent). It also contains volatile oil (0.5 percent). Amygdalin gives benzaldehyde and hydrocyanic acid upon hydrolysis. Bitter almond oil contains 80 percent benzaldehyde and 2-6 percent hydrocyanic acid.

Structure of amygdalin, benzaldehyde, and hydrocyanic acid
Fig.2: Structure of amygdalin, benzaldehyde, and hydrocyanic acid

Chemical Tests for Bitter Almond

  1. Ferriferrocyanide Test: 1 g of the powdered drug macerated with 5 ml of alcoholic KOH (5% w/v) for five minutes. Then transfer it to an aqueous solution that contains ferrous sulphate (2.5% w/v) and ferric chloride (1% w/v). Maintain the temperature at 60-70°C for 10 minutes. Now, transfer the contents to hydrochloric acid (20%), the appearance of a distinct prussian blue colour confirms the presence of HCN.
  2. Grignard Reaction Test: Dip a strip of white filter paper into a solution of picric acid (1 % w/v in water) and drain it and then dip into a solution of sodium carbonate (10% w/v in water) and again drain it. Place the crushed and moistened drug material in a small Erlenmeyer flask. Subsequently, place the strip of the prepared sodium picrate paper above the material. Maintain the flask warm for about 1 hour. The liberated HCN will turn the sodium picrate paper original yellow colour to a brick red colour (due to the formation of sodium isopurpurate).

Uses of Bitter Almond

It is used as a sedative. The oil is used in skin lotion as a demulcent. It is also used for the preparation of amygdalin, bitter almond water, in the perfume industry and liquors preparation, due to the presence of hydrocyanic acid it is not used as a flavoring agent in the food industry.

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