Page 205 - PG 101-Course notes مذكرة النظري 24-25 with spec

Medicinal plants (PG 101) Level 1 Clinical Pharmacy-PharmD

Crude Drugs occurring naturally in powdered form

Commercial Starches (amylum)

➢ Starch constituents the main form of carbohydrate reserve of plants and is to be

found in the form of granules especially in seeds and subterranean organs.

Famous commercial starches are obtained from the endosperm of the grains of Zea

mays L., known as maize starch, of Triticum vulgare Vill., known as wheat

starch, or of Oryza sativa L., known as rice starch (Graminae), or from the

tubers of Solanum tuberosum L. (Solanaceae), known as potato starch.

1-Macroscopical Characters

• Starch occurs in irregular, angular or as a white powder. It is odorless and almost

tasteless. It is insoluble in most of organic solvents such as ether and ethanol. It is

insoluble in cold water but forms a colloidal solution on boiling with about 15

times its weight of water, the solution forming a translucent jelly on cooling.

Starch mucilage is colored deep blue with iodine, the color disappearing on

heating but reappearing on cooling. When starches are heated with water, the

granules first swell and then undergo gelatinization. Starch granules also undergo

gelatinization when treated with caustic alkali, Conc. HCL, Conc. Zinc or

calcium chloride, or Conc. Chloral hydrate solution. According to the method of

preparation, the pH of starches differs. Maize starch is neutral, but other

commercial starches frequently show an acid (wheat and potato) or alkaline (rice)

reaction.

2-Microscopical Characters

• Starches can be identified by microscopical examination. They should be mounted

in water or smith` s starch reagent (equal part of waters, glycerol and 50% acetic
acid). The size, shape, and structure of starch granules (hilum, striation, and

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