Medicinal Plants Lecture 3 PDF

MEDICINAL PLANTS Lecture 3 Dr. Yasmin A. Mahgoub Lecturer of pharmacognosy  Chapter 2 Preparation of medicinal plants for commercial market 2 Several steps and factors are involved in the preparation and quality of medicinal plants for...

MEDICINAL PLANTS Lecture 3 Dr. Yasmin A. Mahgoub Lecturer of pharmacognosy  Chapter 2 Preparation of medicinal plants for commercial market 2 Several steps and factors are involved in the preparation and quality of medicinal plants for commercial market Collection & Cultivation Drying Grinding Harvesting Storage Extraction Adulteration 3  IV. Grinding of the dried plants It is sometimes necessary to grind the plant material after drying and before storage. When grinding plant materials, it is important to produce a powder of suitable and uniform particle size. Large particles and excessive dust (very small particles) should be avoided. 4  IV. Grinding of the dried plants Several machines are available for grinding plant materials such as: 1. Hammer mill: a common type for grinding plant materials. 2. Knife mill: useful for production of low-dust powders of leaves, barks and roots. 3. Tooth mill: used for production of very fine powders. 4. Blender 5. Mortar and pestle 5 IV. Grinding of the dried plants Following grinding, the material must be sifted to ensure proper particle size. Sifting can be performed either by sieving or blast sifting. In sieving, the material is passed through a sieve of suitable mesh size giving two fractions. The fraction passing the sieve consists of particles with a size smaller than or corresponding to the mesh size. The remaining fraction consists of coarser particles which are returned to the mill for continued grinding. 6 IV. Grinding of the dried plants Sifting can be performed either by sieving or blast sifting. In blast sifting, the material to be classified is blown with compressed air into an apparatus which allows the particles to sediment according to their weight. Coarse, heavy particles settle fast whereas small, light particles stay for a long time in the air stream. 7 Several steps and factors are involved in the preparation and quality of medicinal plants for commercial market Collection & Cultivation Drying Grinding Harvesting Storage Extraction Adulteration 8 V. Storage of medicinal plants Storage and preservation of plant crude drugs need sound knowledge of their physical and chemical properties. A good quality of the drugs can be maintained, if they are preserved properly. There are several factors that must be taken in consideration during storage. These factors are: Drug Moisture Temperature Radiations form/shape Atmospheric Fungi /mold Shelf-life Packaging oxygen /insect pests 9 V. Storage of medicinal plants There are several factors that must be taken in consideration during storage. These factors are: 1. Moisture ▪ The moisture, not only increases the bulk of the drug, but also causes impairment to the quality of crude drug. ▪ The excessive moisture facilitates enzymatic reactions resulting in decomposition of active constituents e.g. digitalis leaves. ▪ Excessive moisture causes fungi, molds and pests to develop such as mold infestation of gentian. ▪ Moisture must be eliminated from the herbs & the atmosphere. 10 V. Storage of medicinal plants There are several factors that must be taken in consideration during storage. These factors are: 1. Moisture ▪ Medicinal herbs must be dried thoroughly, until they contain only 10-12% moisture, which is considered to be the safe percentage. ▪ 15% moisture content is permissible in the case of roots or sugar-containing herbs. ▪ Quicklime (CaO), silica gel or roasted rice are used as desiccants. 11 V. Storage of medicinal plants There are several factors that must be taken in consideration during storage. These factors are: 2. Temperature ▪ The optimum temperature for medicinal herb storage is 2-8 °C, some can also be stored at room temperature 25 °C. ▪ High temperature evaporates the essential oils contained in herbs and also decomposes lipid-containing herbs, giving them a sharp bitter taste. ▪ Storage places must be well-ventilated. When stored, herbs must be periodically moved, sorted and graded. 12 V. Storage of medicinal plants These factors are: 3. Radiation due to direct sun-light also causes destruction of some active chemical constituents, e.g. ergot and digitalis. 4. Form or shape of the drug Examples: ▪ Colophony in the entire form (big masses) is preserved nicely, but if stored in powdered form, it gets oxidized. ▪ Squill, when stored in powdered form becomes hygroscopic and forms rubbery mass on prolonged exposure to air. ▪ The fixed oil in the powdered ergot becomes rancid on storage. In order to maintain a good quality of ergot, it is required that the drug should be defatted with lipid solvent prior to storage. 13 V. Storage of medicinal plants These factors are: 5. Atmospheric oxygen is also destructive to several drugs hence, they are filled completely in well closed containers, or the air in the container is replaced by an inert gas like nitrogen. 6. Fungi, mold and insect pests ▪ Different types of insects, nematodes, worms, molds and mites can infest the crude drugs during storage. ▪ Together with moisture controls, checking must be regularly carried out to detect mold development. ▪ Prompt isolation & treatment of the infected herbs must be done. 14 V. Storage of medicinal plants These factors are: 6. Fungi, mold and insect pests ▪ Pests can be controlled by sun-drying, heat-drying or the use of chemical methods such as fumigation or sterilization with aluminium phosphide. If chemicals are used, safety precautions must be taken to prevent poisoning. ▪ At times, drugs are given special treatment, such as liming of the ginger and coating of nutmeg. 15 V. Storage of medicinal plants These factors are: 7. Shelf-life ▪ Prolonged shelf storage is labour-consuming and may lead to deterioration in quality. ▪ It is recommended that stored herbs be distributed every year as the new crops become available. 8. Packaging ▪ All the drugs should be stored in well closed and, possibly in filled containers. They should be stored in water-proof, fire proof and rodent proof place. ▪ Appropriate packing materials, dust-free and water-proof. ▪ Small quantities of crude drugs stored in airtight, moisture proof & light proof containers such as tin, cans, or amber glass containers. ▪ Wooden boxes & paper bags should not be used for storage. ▪ Precious items are stored with desiccants in sealed tin boxes. 16 Several steps and factors are involved in the preparation and quality of medicinal plants for commercial market Collection & Cultivation Drying Grinding Harvesting Storage Extraction Adulteration 17 VI.Extraction of medicinal plants For commercial market, medicinal plants can be used as a whole, parts of the plant or the plant extract. A plant extract is obtained from a solid-liquid extraction which is an operation to separate elements contained in a solid body (the plant material) by solubilization with a solvent. There are different types of extracts which are: 1. Dry extracts: all solvent has been removed so have solid consistency. 18 VI.Extraction of medicinal plants There are different types of extracts which are: 2. Soft extracts: have consistency between dry and fluid extracts (semi- solid) and are obtained by partial evaporation of the solvent. 3. Fluid extracts: are concentrated liquid extracts prepared with mixtures of water and ethanol as solvent. 4. Tinctures: are prepared by extraction of the plant with 5 to 10 parts of ethanol, without concentration of the final product. 19 Several steps and factors are involved in the preparation and quality of medicinal plants for commercial market Collection & Cultivation Drying Grinding Harvesting Storage Extraction Adulteration 20 VII. Adulteration of medicinal plants Herbal adulteration is one of the common malpractices in herbal raw- material trade. Adulteration is substituting original crude drug partially or wholly with other similar-looking substances. The substance, which is mixed, is free from or inferior in chemical and therapeutic property. In general, adulteration is considered as an intentional practice. However, unintentional adulteration can also happen. 21 VII. Adulteration of medicinal plants Unintentional Adulteration May be due to the following reasons: 1. Confusion in plant names between indigenous systems of medicine and local dialects. 2. Lack of knowledge about the authentic plant. 3. Non-availability of the authentic plant. 4. Similarity in morphology and/or aroma. 5. Careless collection. 22 VII. Adulteration of medicinal plants Intentional Adulteration May be due to the following reasons: 1. Adulteration using manufactured substances ▪ The original substances are adulterated by materials that are artificially manufactured. ▪ The materials are prepared in a way that their general form and appearance resemble the original drug. 23 VII. Adulteration of medicinal plants Intentional Adulteration May be due to the following reasons: 2. Substitution using inferior commercial varieties ▪ The original drugs are substituted using inferior quality drugs that may be similar in morphological characters, chemical constituents or therapeutic activity. ▪ For example, Japanese ginger (Zingiber mioga) has been used to adulterate medicinal ginger (Zingiber officinale). 24 VII. Adulteration of medicinal plants Intentional Adulteration May be due to the following reasons: 3. Substitution using exhausted drugs ▪ The active constituents of the main plant are extracted out & the medicinal plants are used again. ▪ This could be done for the commodities that would retain its shape and appearance even after extraction, or the appearance and taste could artificially mimic the original by adding colouring or flavouring agents. 25 VII. Adulteration of medicinal plants Intentional Adulteration May be due to the following reasons: 3. Substitution using exhausted drugs ▪ This technique is frequently adopted for the drugs containing volatile oils, such as: clove, fennel, etc. ▪ E.g, using whole clove from which part of the volatile oil has been removed by distillation (spent cloves). ▪ Another example is that saffron and red rose petals are recoloured by artificial dyes after extraction. 26 VII. Adulteration of medicinal plants Intentional Adulteration May be due to the following reasons: 4. Substitution with superficially similar inferior natural substances ▪ The substituents used may be morphologically similar but do not have any relation to the genuine crude drug in their constituents or therapeutic activity. ▪ For example, addition of yellow coloured starch powder to medicinal ginger powder. 27 VII. Adulteration of medicinal plants Intentional Adulteration May be due to the following reasons: 5. Adulteration using the vegetative parts of the same plant ▪ The presence of vegetative parts of the same plant with the drug in excessive amount is also an adulteration. ▪ For example, presence of stems of the same plant mixed with the medicinally used roots. 28 VII. Adulteration of medicinal plants Intentional Adulteration May be due to the following reasons: 6. Addition of toxic materials ▪ Materials used for adulteration would be toxic in nature. 7. Adulteration of powders ▪ Powdered drugs are found to be adulterated very frequently. Adulterants used are generally powdered waste products of a suitable colour and density. 29 VII. Adulteration of medicinal plants Intentional Adulteration May be due to the following reasons: 8. Addition of synthetic drugs ▪ Synthetic pharmaceutical drugs are used for their therapeutic value. ▪ For example, the herbal products labelled to improve sexual performance in men, when analysed, contained sildenafil (Viagra®). 30 T H E E N D