Medicinal Plants PDF

THE CELL AND CELL DIFFERENTIATION The Cell: Cell is the fundamental unite of a living organism (plants and animals). The Cell consists of Cell wall and nucleus appears to be suspended within cell by cytoplasm in which there may be large vacuoles with their own characteristic con...

THE CELL AND CELL DIFFERENTIATION The Cell: Cell is the fundamental unite of a living organism (plants and animals). The Cell consists of Cell wall and nucleus appears to be suspended within cell by cytoplasm in which there may be large vacuoles with their own characteristic contents (crystals and aleurone grains). Other cytoplasmic inclusions are mitochondira, Golgi bodies, lysosomes, and plastids. A group of cells with identical form and function is known as a tissue. The Cell Wall: The wall of mature Cell consists of:  The middle lamella is the intercellular substance, an amorphous, colloidal layer composed of pectic substance.  Primary wall or the original cambial wall is composed of cellulose and pectic substance.  Secondary wall is formed after the enlargement of the cell has been ceased. It consists mainly of cellulose associated with polysaccharides. It undergoes to some modifications as desposition of various chemical substance as lignin, suberin and cutin.  Tertiary wall: It is the innermost layer of the cell wall and is usually thin, highly refractive and formed of cellulose. Properties of different cell walls: A. Cellulosic Walls: Formed mainly of cellulose which may be accompanied with hemicellulose and pectin. Cellulose is polysaccharide, composed of linear chain of glucose residue. Chemical Properties:  Give blue color with iodine and sulphuric acid.  Give blue color with chloro- Zinc- iodine.  Give no color with aniline or phloroglucin and HCL.  They dissolve in ammonical solution of copper oxide (Cuoxam) and precipitated with dilute sulphuric acid. 2/ 98 B. Mucilaginous Walls: Certain cellulosic cell walls may be converted into gums and mucilages. Mucilage is polysaccharides, consisting of sugar and uronic acid combined with metals. Chemical Properties:  They are variably stained with ruthenium red, iodine sulphuric acid or corallin soda. C. Lignified Walls: Lignin is a strengthening material. Chemically it is a complex phenylpropaniod polymer. Chemical Properties:  Stain magenta red with phloroglucin and hydrochloric acid. D. Suberised and cutinized walls: Suberin and cutin are mixture of polymerized fatty acids and suberic acid Chemical Properties:  Stain red with alkanna tincture and sudan III E. Chitinous walls: Chitin is a polysaccharide derivative containing acetyl and amino group. It constitutes the organic skeletal substance of insects and many fungi. When heated with 50 % potash at 160 – 170 o C for 1 hour, it is converted into chitosan C14H26O16N2, ammonia and acids such as acetic and oxalic. Chitosan gives a deep violet coloration when treated with iodine solution followed by dilute sulphuric acid. 3/ 98  Cell Differentiation Plant tissue may be:  Paranchymatous Tissues: Is the fundamental or ground tissues of the plant. They are cellulosic, isodiametric orslightly axially elongated cells with narrow or wide intercellular spaces. The cells show different contents e.g. starch granules, calcium oxalate crystals. They constitute most of the pith and cortex of the plant.  Collenchymatous Tissues: It is a living mechanical tissue, composed of rounded or elongated cells, with unevenly thickened, nonlignified walls. The thickening is of cellulose and located commonly in the angles (angular collenchyma) or chiefly on the tangential walls (lamellar collenchyma). Collenchyma constitutes the typical mechanical tissue of the herbaceous stems, and of the petioles and midribs of leaves. 5/ 98 6/ 98  Sclerenchymatous Tissues: They are thick walled; dead, lignified celled mainly for mechanical functions, consist of sclereids and fibres. o Sclereids: They are thick, lignified cells with narrow to wide lumen and isodiametrical in shape or elongated but the length is never many times as the breadth. o Fibres: They are dead, very much elongated, thick, lignified, pitted, polygonal cells usually with tapering pointed ends. They may have a tortuous irregular outline. 7/ 98 Secretory Tissues: They may be: External: e.g. glandular hair. Internal: include secretory cells, secretory cavities or glands secretory ducts or canals and latex tissues. Secretory Cells: They occur either isolated or rarely in rows having suberised walls. They differ from the other cells; by their contents and size. The cells are named after the secretion they contain. The secretion may be volatile oil (oil cell), resin (resin cell), gum resin, mucilage, enzyme or tannin. Secretory Cavities (Glands): These are internal structures, embedded in a mass of tissue and having cavities within them in which secretions e.g. volatile oil and oleoresin, etc are secreted. According to method of formation they may be:  Schizogenous: Developed by splitting a part of cells thus enclosing a cavity which then become enlarged and lined by epithelial cells formed by the division of the surrounding cells e.g. savin.  Schizolysigenous: Developed at first schizogenously but, later on, increase in size by breaking down the bounding cells e.g. clove, Buchu.  Lysigenous: Developed by breaking down of the cells forming a cavity. It originates from single cell by the division in different direction forming a solid mass and then by the gradual disintigration of the resulting cells starting from the center e.g. Dictamnus. Secretory Ducts: They are tube like structures which may extend through the whole length of the organ e.g. leaf pinus, or even through the whole of the plant. They are developed either schizogenously as vitta of Umbelliferse, lysigenously or schizolysigenously as in Capaifera. Laticiferous Structures: These include tube-like cells and vessels with a colorless, milky white, yellowish or reddish viscous emulsion called latex. 9/ 98 Latex may contain resin, gum-resin, fat wax, proteins etc. suspended in an aqueous solution of alkaloidal salts, tannins minerals, sugar enzyme etc.  Latex Cell: Usually in the form of tube, branched as in Euphorbia or unbranched as in Cannabis but not anastomosing e.g. Euphorbiaceae and Apocynaceae.  Latex Vessel: They are long simple or branching tube formed by the partial or complete fusion of the transverse walls of a longitudinal series of cells. They are anastomosing with rough walls e.g. Papaveracea and Compositae. 10/ 98   Primary metabolic products. (Food storage products) e.g. carbohydrates, proteins and lipids.  Secondary metabolic products (by-products of metabolism) e.g. alkaloids, glycosides, volatile oils, resins and tannins.  Crystalline mineral products e.g. calcium oxalate and calcium carbonate. Primary metabolites: I. Carbohydrates: are organic compounds composed of carbon, hydrogen and oxygen, where the last two elements are present of the ratio 2: 1 like that of their presence in water. They include starch and sugar.  Starch: Are polysaccharides of higher molecular weight, with the general formula (C6H10O5)n. It is formed as a result of the photosynthesis process which carried out by the green parts of the plant. The plant takes carbon dioxide from the air and absorbs water from soil and in the presence of chloroplasts and sunlight energy it forms glucose. sunlight 6 CO2 + 6 H2O C6H12O6 + 6 O2 The formed glucose molecules are condensed together with the elimination of water to give starch. It occurs in granules of varying size in almost organs of the plants, either alone or accompanied with other reserve food particles, e.g. proteins. Chemical Composition of Starch: Starch granules consist of:  Amylose: It forms the inner layers of the granule and is soluble in water.  Amylopectin: It forms the outer layers of the granule and is insoluble in water. 12/ 98 Macroscopical Characters:  Starch occurs in irregular, angular masses or as a white powder.  It is insoluble in cold water but forms a colloidal solution on boiling water, the solution forms translucent jelly on cooling.  Starch granules also undergo gelatinization when treated with caustic potash, hydrochloric acid, concentrated solutions of calcium or zinc chlorides or concentrated solution of chloral hydrate.  Starch is colored deep blue with solution of iodine; the color disappears on heating but reappears on cooling.  When starches are heated with water, the granules first swell and then undergo gelatinization. Microscopical Characters: Starches can be identified by microscopical examination when mounted in water or lactophenol. The Shape: vary from polygonal, round to oval. The hilum: It is starting point of formation of the granule in the leucoplast, it may be centric or eccentric, the hilum takes the form of a round point simple, curved or multiple cleft. The Striation: are alternate layers around the hilum, either concentric rings or transverse. The aggregation: may be simple or compound. Some of the more important microscopic characters of the principal starches are set out in the following table. 13/ 98  CELL CONTENTS The cell contents are those substances inside the plant cell and can be identified by microscopical examination or by chemical and physical tests. They include: 11/ 98 Comparison between the four important commercial starches in their microscopical features: Item Potato Wheat Maize Rice polyhedral Oval, rounded, Oval, rounded, with Polyhedral with Shape lenticular from side pyramidal rounded sharp angles view angles Size Large Medium Medium small Absent, except in Present, Present, Present, centric, large, simple Hilum eccentric, centric, cleft pointed granules, centric pointed or fissured pointed Distinct, Striation faint, concentric Absent Absent concentric Simple, Mostly Mostly compound, Mostly simple, few, Aggregation simple, few compound, few semi compound compound simple compound Chemical Tests:  Starch gives blue color with iodine solution.  Molische’s Test: suspension of starch and alcoholic α-naphthol in a test tube gives violet ring at the interface upon addition of concentrated H2SO4 on the wall of the test tube.  Starch gives a positive reduction test e.g. Fehling test, after hydrolysis with acid and neutralization of the solution. Uses:  Externally as dusting powder to allay itching or demulcent.  Internally as: o Suspending agent for barium meals before x-ray. o Antidote in the treatment of iodine poisoing. 14/ 98  Pharmaceutical as a diluent, lubricant and a tablet disintegrant.  Commercially: o It is used for paper and cloth sizing. o Nutrient. o Preparation of glucose, dextrose and dextrins. 15/ 98 II - Protiens: Proteins are nitrogenous organic compounds formed from polymers of amino acid units. In plants, protein is stored in the form of amorphous mass called aleurone grains. Aleurone Grains: They are small solid protein particles, commonly present in the seeds. The typical aleurone grains consist of:  Ground Substance: is an amorphous protein, usually soluble in water.  Crystalloid is formed of albumins, usually hardly soluble in water. It is stained brown with iodine solution, yellow with picric acid and red with Millons reagent.  Globoid consists of globulin combined with calcium and magnesium salts of hexaphosporic acid. It is insoluble in water. Examination of aleurone Grain:  The material, either in section or in powder form, is defatted first by maceration in alcohol-ether mixture or then stained. The defatted material is placed in picric acid solution for few minutes, washed with alcohol to remove the excess of stain. Then add alcoholic solution of eosin and finally wash well with alcohol. The stained aleurone grain show yellow crystalloid, colorless globoid and red ground substance.  Proteins give red color with Millons reagent. III - Lipids: They include fixed oils, fats and waxes. These substances are widely distributed in the plant, commonly in the seeds and fruits. Fixed oils are esters of unsaturated, higher molecular weight fatty acids with glycerols. (Liquids) Fats are esters of saturated, higher molecular weight fatty acids with glycerols. (Solids) Waxes are esters derived from higher monohydric alcohol combined with fatty acids. Fixed oils and fats are hydrolyzed by aqueous caustic alkalis to give soap and glycerol. (Specification). 16/ 98 Microscopical Identification of Oils:  The oil globules are colored black with 1 % solution of osmic acid.  The oil globules are colored red with sudan III. Secondary Metabolites I - Alkaloids: Alkaloids are naturally occurring organic compounds containing one or more nitrogen atoms in a heterocyclic ring, usually basic and have marked physiological action on man or animals. The term alkaloid means originally alkali-like. Alkaloids are present in plants either as free bases or as salts of some acids. Characters:  Free bases are sparingly soluble in water but soluble in organic solvents while the alkaloidal salts are soluble in water and sparingly soluble in organic solvents.  Most alkaloids are precipitated from neutral or slightly acidic solution by Mayers reagent giving yellowish precipitate, by Wagners reagent giving reddish brown precipitate, by Dragendorffs reagent giving reddish brown precipitate. Caffeine and other purine bases do not give these precipitates. II - Glycosides: Naturally occurring organic compound of plant organ consisting of sugar part (glycone) and non sugar part (aglycone). Classification: There are four different systems for classification of glycosides:  According to the linkage between glycone and aglycone e.g. O- glycosides, S-glycosides and C-glycosides.  According to pharmacologic action e.g. cardiac glycosides, laxative glycosides etc.  According to sugar moiety e.g. glucoside, rhamnoside, glucorhamnoside etc.  According to aglycones e.g. phenolic, anthracene, flavone etc. 17/ 98 Properties of glycosides:  Glycosides are polar compounds soluble in polar solvents.  Glycosides can be hydrolyzed by acids or enzymes. III - Volatile Oils: Volatile or essential oils are volatile in steam. They are secreted in oil cells, in secretion canals or cavities or in glandular hairs. They are generally mixtures of hydrocarbons and oxygenated compounds derived from these hydrocarbons. Volatile oils are used for flavoring, in perfumery, as spices, and for their therapeutic action as antiseptic, antispasmodic and carminative. Volatile oils are not saponified by alkalies and are detected by sudan III. IV - Tannins: They are water soluble polyphenol compounds present in plant extracts which are able to combine with proteins of animal hides to prevent their putrefaction and convert them into leather. Most true tannins have high molecular weights. Uses of drugs containing tannins:  Astringents in the gastrointestinal tract and on skin abrasions (hemostatic).  In the treatment of burns, where proteins of the exposed tissues are precipitated and form a mildly antiseptic, protective coat under which regeneration of new tissues may take place.  Tanning of leather.  Antidotal treatment of alkaloidal and heavy metals poisoning.  Preparation of ink. Tannins are classified into two main groups: o Hydrolysable Tannins: These may be hydrolyzed by acids or enzymes such as tannase. They are formed from several molecules of phenolic acids such as gallic. On dry distillation, gallic acid and similar components are converted into pyrogallol 18/ 98  so they termed pyrogallol tannins. The hydrolysable tannins give blue black color with ferric chloride. o Condensed Tannins: these are not hydrolyzed to simpler molecules and they do not contain a sugar moiety. Condensed tannins when treated with acids or enzymes are converted into red insoluble compounds known as phlobaphenes. Condensed tannins on dry distillation they yield catechol and these tannins are therefore called catechol tannins. They give green color with Ferric chloride. Pseudotannins: Are compounds of lower molecular weight than true tannins, they also do not respond to the gold to the gold beater s skin test. Test of Tannins:  Gold beater’s Skin test: o Soak a piece of goldbeater skin (membrane of ox-intestine) in 2% HCL then rinse with water. o Place the soaked piece in the solution to be tested for 5 minutes. o Wash with distilled water and transfer to 1 % solution of ferrous sulph1ate. A brown or black color on the skin denotes the presence of tannins.  Ferric Chloride Test: o Tannins are extracted from vegetable powdered plant with hot water; add few drops of ferric chloride solution a blue color is produced with hydrolysable tannins and green color with condensed tannins. Calcium Oxalate It is a common plant cell content, formed as an end product of metabolism. It is found in more or less crystalline form. They are usually useful for the microscopical examination of the drugs as well as detection of adulteration. Characters:  Calcium oxalate crystals are insoluble in water. 19/ 98