Pharmacognosy: Bark Structure and Types

Bark

• Bark is the outermost layers of stems and roots of woody plants.
• A regular stem consists of epidermis, cortex, endodermis, pericycle, phloem, cambium, and xylem.
• Bark consists of cork, phellogen, phelloderm, cortex, and phloem.

Cinchona Bark

• Origin: Dried stem and root bark of Cinchona succirubra (Red Cinchona), Cinchona ledgeriana (Yellow Cinchona), and Cinchona officinalis (Pale Cinchona) from the family Rubiaceae.
• Composition: Lignified fusiform phloem fibers, cork cells, parenchyma containing starch grains, and parenchyma containing microcrystals of calcium oxalate.
• Active Constituents: Quinoline alkaloids (quinine, quinidine, cinchonine, and cinchonidine), glycosides, tannins (cinchotannic acid), and bitter principles.
• Uses: Quinine is used as an antimalarial agent, quinidine is used as an anti-arrhythmic agent, cinchonine and cinchonidine have anti-rheumatic properties, and cinchona powder is used as a tonic and bitter stomachic.
• Chemical tests for identification: Mayer's test for alkaloids and dry heat test.

Cinnamon Bark and Cassia Bark

• Origin: Dried decorticated bark of Cinnamomum zeylanicum (Family Lauraceae) for Cinnamon bark and dried stem bark of Cinnamomum cassia (Family Lauraceae) for Cassia bark.
• Composition: Cinnamon powder contains oil cells, sclereids, lignified fusiform phloem fibers, parenchyma containing small starch grains, and parenchyma containing acicular crystals of calcium oxalate.

Learn about the structure of bark, its layers, and types of bark including Cinchona Bark. This quiz is based on the lecture notes of Dr. Eman Sanad from the Department of Pharmacognosy, Suez Canal University.