Lecture 2: PharmacoGnosy I PHCG 111 PDF

For First year Pharmacy Students By  CHAPTER V Factors affecting plant growth and production of drugs A.Environmental factors e.g. water, light, temperature, altitude---etc. B. Soil and its contents. C. Growth regulators: Hormones. D. Genetics and plant tissue culture A- EN...

For First year Pharmacy Students By  CHAPTER V Factors affecting plant growth and production of drugs A.Environmental factors e.g. water, light, temperature, altitude---etc. B. Soil and its contents. C. Growth regulators: Hormones. D. Genetics and plant tissue culture A- ENVIRONMENTAL FACTORS 1- WATER ❑Rain is the only source of sweet water. ❑Water is an important component of the cell, it constitutes about 90% of the cytoplasm. ❑Water is a vital factor in photosynthesis, all biological reactions and transformations as a medium, a catalyst or as end products. ❑It helps absorption of minerals and nutrients from soil and translocate them from roots and leaves to other organs. ❑Regulates plant temperature through transpiration 2- TEMPERATURE: As the temperature increases the rate of growth increases until the optimum temperature is reached, a further increase leads to a decrease in growth rate. Every plant has three temperatures: the minimum, optimum and maximum temperatures. The minimum temperature is the temperature below which the plant growth rate is very low or zero. The optimum temperature is the temperature at which the plant growth rate is the highest. The maximum temperature is the temperature above which the plant growth rate is very low or zero. Growth rate Optimum temp. Minimum Maximum temp. temp. temperature ❑In most climates, the day temperature is higher than the night temperature so that there is a regular diurnal temperature cycle. ❑Plant growth is greater in a fluctuating temperature than in constant one this fact is called “Thermoperiodicity”. The plants of temperate regions show typical thermoperiodic response. 3- ALTITUDE: ❑Temperature falls about 1oC for every 343 feet of elevation. ❑Coconut palm needs a maritime climate. ❑Sugar cane is a low land plant ❑Tea and coffee require elevation (300-500 ft) ❑Rhubarb and cinchona require elevation ❑In the case of Cinchona succirubra the plants grow well at low levels but produce practically no alkaloids. 4. LIGHT ❑Plants vary much in both the amount and intensity of the light which they require. ❑Light can affect formation of active ingredients. ❑Light is essential for photosynthesis and formation of chlorophyll. ❑Lack of light may cause morphological abnormalities. ❑The response of plants to length of day is known as photoperiodism (the relative length of day and night) ❑During the summer season, the duration of daily period of solar illumination is greater than 12 hours, whereas during the winter, it is shorter than 12 hours. ❑We recognize three broad photoperiodic classes of plants with respect to their flowering behavior: Short day plants (winter plants) which flower in short daily period of illumination. Long day plants (summer plants) which flower in long daily period of illumination. Day neutral plants which flower in short and long photo-days. (Unaffected by the length of the day)  B. SOIL AND SOIL CONTENTS [PLANT NUTRIENTS (MANURES)] ❑Soil is a mosaic of rock particles, plant roots, microorganisms, decaying organic mater (humus), water and air. ❑Absolute water capacity (A.W.C) : It is the amount of water remains in the soil after any excess water has drained away. ❑Air capacity of a soil is inversely proportional with the absolute water capacity. Sandy soils are very permeable (low AWC). On the other hand, clay soils possess a high power of absorbing water by capillary conduction, as do fine soils rich in humus. ❑ According to humus content, the soil is described as poor (if containing less than 0.5% humus) intermediate (if containing 0.5 to 1.5 % humus) rich (if containing 1.5 to 5 % humus). ❑ Humus increases the moisture absorbing power of the soil. ❑ Soil containing much humus and little lime is acidic, while those with much lime are alkaline. (Organic Manures) Humus (Plant nutrient) ❑ Manure is a mixture of organic matter (plant remains put under animals in the stable, and ultimately mixed with animal urine and excretions and some of the stable soil). ❑Humus (Organic Manures) USES: 1. Manures are used as fertilizers 2. It blocks the soil particles together and improves conditions of growth. 3. Reduces the loss of water capacity of root zone. 4. Manure is of value as a source of nutrient elements, especially nitrogen. ❑ The essential elements commonly supplied by the soil are divided into 4 groups: 1. Main nutrients or Macro-elements: involving nitrogen (N) phosphorus (P) and potassium (K). Commercial fertilizer containing one of these elements is called a simple fertilizer and if containing all of them, a complete fertilizer Nitrogen (N): ▪ Important for chlorophyll and amino acids formation. ▪ N deficiency leads to “Chlorosis” deficiency of chlorophyll (yellow colored plant). Phosphorus (P): ▪ for anabolism and catabolism and formation of ATP (the store of energy). Its deficiency leads to reduction of plant size and deep green colour. Potassium (K): ▪ for plant growth and carbohydrate formation: its deficiency leads to reduction of carbohydrate synthesis. 2. Micro-elements: Involving iron, boron, copper, manganese, zinc, cobalt, lead and molybdenum. These are needed within very minute amounts for plant growth. Any rise in this amount has poisonous effect on plants. 3. Active elements: involving calcium (Ca), magnesium (Mg) and Sulphur (S). The little amount of which increases plant growth, but more than the adequate amount has no influence on plant growth. Calcium: ▪ For growth of apical meristems and formation of flowers. ▪ Deficiency of calcium leads to fail of development of terminal buds or partial development with irregular leaf margin. Magnesium: ▪ formation of chlorophyll (Essential for photosynthesis) and activation of some enzymes. ▪ Its deficiency causes Chlorosis [deficiency of chlorophyll (yellow plant)]. Sulphur: essential for cell division (Garlic, some oils) 4. Inactive elements: Involving sodium, aluminum, silicon, and iodine. They have negligible effect on plant growth although some of these elements have special effect on certain plants.  C. PLANT GROWTH REGULATORS Five groups of plant hormones: ▪ Growth stimulators: 1. Auxins 2. Gibberellins 3. Cytokinines. ▪ Growth inhibitors: 4. Abscisic acid 5. Ethylene oxide They are active in very low concentrations and regulate: ✓Cell division- Cell differentiation- Cell growth- Dormancy. I. Growth stimulators Auxins: Natural: β-indole acetic acid (IAA) Synthetic: Indole-3-butyric acid (IBA) Naphthalene-1-acetic acid (NAA) 2,4-dichlorophenoxy acetic acid (2,4-D) The main practical use of auxins: ▪ In low concentration to accelerate rooting ▪ In higher concentration to act as selective herbicides The main effects of auxins on plant growth are: 1. Stimulate the growth (Cell elongation) 2. Ovary growth 3. Cambial activity 4. Apical dominance 5. Affect formation of secondary metabolites: ❑Gibberillins: ▪ There are about 40 known Gibberillins like GA1, GA2, GA3…etc. ▪ Gibberillins are synthesized in leaves and stored in seeds and fruits. Typical effects of Gibberillins are: 1. They induce flowering at earlier stages 2.They increase the length of dwarf varieties. 3.Initiate synthesis of hydrolytic and proteolytic enzymes. 4.Stimulate the formation of secondary metabolites e.g.: volatile oils, glycosides, alkaloids ❑Cytokinines: ▪ Mainly they are cell division hormones. Typical effects of Cytokinines are: 1. Cell division. 2. Cell Differentiation and morphogenesis. 3. Also regulate production and shape of organs. II. Growth inhibitor hormones Abscisic acid ▪ It acts by antagonising GA ▪ Blocking synthesis of DNA and RNA ▪ Induces seed dormancy ▪ Inhibit shoot growth ▪ Helps to withstand drought conditions, by regulating opening of stomata. Ethylene ▪ Discovered in stored apples and help in Inhibition of potato shoots growth.  CHAPTER VI PREPARATION OF DRUGS FROM PLANTS TO PHARMACEUTICALS A- COLLECTION OF CRUDE DRUGS ❑Drugs may be collected from wild or cultivated medicinal plants. ❑The qualitative and quantitative composition may change during growing season ❑To ensure maximum quality plant should be collected in appropriate season and at the proper phase (proper time and proper part and proper stage of development) FACTORS AFFECTING COLLECTION: 1.Time of the year: ❑The plant in winter may contain substances which are not present in the same plant in summer; Examples: ❑Rhubarb contains no anthraquinones in winter, but contains anthranoles so collected in summer. ❑Colchicum corm is almost free its active constituent colchicine in autumn and is full of starch. So, used as food instead of potatoes. But it is bitter and more active in spring and early summer ❑Hyoscyamus contains less alkaloids in winter than in summer. 2-Time of the day: Time of the day is an important factor in determining the concentration of active principles in drug plants. Examples: 1. The concentration of the desired glycosides is higher in digitalis leaves collected in the afternoon than collected in the morning. The active glycosides undergo hydrolysis to physiologically less active aglycones during the night and recombine with sugars during day time. 2. Roots and rhizomes rich in mucilage and starch are usually collected in the morning. 3. The alkaloidal content of the Solanaceous leaves are higher in the morning than in the afternoon. 3. Stage of maturity and age: Examples: 1.Conium fruits contain the alkaloid coniine, when the fruits are mature but unripe. 2.Santonica flowers are most rich in santonin when they are unexpanded and when they start to open, the santonin content starts to decrease. 3.Clove is collected in the bud stage, as the volatile oil decreases greatly when the flowers open. 4.All Solanaceous leaves contain the maximum amount of alkaloids when the plant is in the flowering stage. 5.Lobelia herb must be collected towards the end of the flowering stage and beginning of the fruiting stage. GENERAL RULES FOR COLLECTING DRUGS: ▪ Leaves: the usual time for collection is when the flowers are just beginning to expand. Except: Tea leaves are collected when still unfolded in the bud. Coca leaves are collected when nearly ready to fall from the stem. Uva Ursi leaves are collected at any time of the year. ✓NB: Leaves should not be collected when covered with dew or rain. ✓Any leaves which are discolored or attacked by insects should be rejected. ▪ Flowers: must be collected in fine, dry weather. They are collected before the full expansion Clove, Red Rose and Worm Seed are collected in bud. Chamomile and insect flower (pyrethrum) are collected when just fully expanded. ▪ Storage tissues organs such as roots, rhizomes, bulbs, etc. should be collected in autumn or winter ▪ Stem barks are collected in spring when the bark can be stripped more easily ▪ Fruits: fully mature but unripe. ▪ Seeds: being storage organs are collected when mature. ▪ Unorganized drugs must be collected in dry weather and taken care to exclude vegetable parts.