PHA 010: Pharmacognoy and Plant Chemistry Module 7 PDF

# PHA 010: PHARMACOGNOSY AND PLANT CHEMISTRY ## Module #7 Student Activity Sheet **Name:** **Section:** **Schedule:** **Class Number:** **Date:** ## **Lesson Title: TANNINS** **Learning Targets:** At the end of the module, students will be able to: 1. Describe tannins 2. Identify the dif...

# PHA 010: PHARMACOGNOSY AND PLANT CHEMISTRY ## Module #7 Student Activity Sheet **Name:** **Section:** **Schedule:** **Class Number:** **Date:** ## **Lesson Title: TANNINS** **Learning Targets:** At the end of the module, students will be able to: 1. Describe tannins 2. Identify the different properties of tannins 3. Recognize the different classifications of tannins; their specific sources, tests and pharmaceutical/medicinal importance ## **A. LESSON PREVIEW/REVIEW** **Materials:** SAS, Book, pen and notebook, laptop **References:** Tyler, V.E., Brady L.R., Robbers, J.E. *Pharmacognosy*, Philadelphia: Lea & Febiger, latest ed Evans, William Charles. *Trease and Evans' Pharmacognosy,* 15th ed..Edinburgh: W. B. Saunders, latest ed. Review the previous lesson being discussed last meeting. Ask the students if they have some verification or clarification about the previous topic. If no more questions, then start introducing the new topic which is "Tannins". **Properties of Tannins** **Test for Tannins** **Classes of Tannins** ## **B. MAIN LESSON** The instructor should discuss the following topics or ask the students to read, review and understand the outline of this topic. Then, tell the students to answer the check for understanding activity after the discussion or after reading the main lesson. ## **TANNINS** * **TANNINS OR TANNIN EXTRACT** * They are complex substances usually occurs as mixtures of polyphenols that are difficult to separate or isolate because they do not crystallize * Upon hydrolysis yield 3 simple polyhydric phenols ### **PROPERTIES OF TANNINS:** * Noncrystallizable, with water form colloidal solution possessing an acid reaction and sharp puckering taste * They cause precipitation of gelatin and alkaloids * They form dark blue or greenish black soluble compounds with FeCl3 and deep red with potassium ferricyanide and ammonia * They are precipitated by salts of Cu, Pb, Sn and strong aqueous potassium dichromate (or 1% chromic acid) solution * Their ability to precipitate protein makes them an antiseptic and astringent, also utilized in the process of vegetable tannin thus converts animal hides to leather ### **NOTE:** * **UTILITY AND SAFETY OF THE LONG TERM INGESTION OF PLANT RICH IN CONDENSED TANNINS ARE CONTRADICTORY BASED ON PRESENT STUDIES.** * Habitual chewing of betel nut (Areca catechu) has been linked to a high rates of oral esophageal cancer * Drinking ordinary tea (Camellia sinensis) British who add milk to tea has lower esophaged obstruction than Dutch who drank large quantities of tea without milk * Experiment shows that injection of tannin extract in rats causes a production of significant number of malignant mesenchymal tumor ## **CLASSIFICATION OF TANNINS:** 1. **HYDROLYZABLE TANNIN** * Also known as Pyrogallol tannin * These esters are easily hydrolyzed to yield phenolic acid and sugar * Gallic acid and hexahydroxydiphenic * When boiled with HCl will yield ellagic or protocatechuic acid * Produces blue black/blue color with FeCl3 * Do not precipitate with bromine T.S. * Leather type - Bloom leather 2. **NONHYDROLYZABLE OR CONDENSED TANNINS** * Also known as catechol, phlobatannins or pro anthocyanidin * When boiled with HCl, will form insoluble red phlobaphenes * Produces dark green/green color with FeCl3 * Form precipitate with Bromine T.S.. * Leather type - Tanner's red ### **PSEUDOTANNINS** * **FALSE TANNIN** * **THEY DO NOT FORM LEATHER BUT YIELD COLOR WITH Fe SALTS** ### **THEORY ABOUT TANNIN:** * They are sources of fruit acids. * They serve as a protective for the plant in certain stages of growth. * By their antiseptic action, insects and fungi are unable to attack the plants. * Finally, they are deposited as products of metabolism in the dead tissues of mature plants. Eg. Cork, heartwood and gals ### **ACTION OF TANNINS:** * Precipitate proteins in solutions and able to combine with them rendering them resistant to proteolytic enzymes, when applied to human tissues, this action is termed as "astringent action of tannins" ## **THERAPEUTIC APPLICATIONS OR USES OF TANNINS:** * Treatment of diarrhea and skin ulceration * Treatment of alkaloidal poisoning * Treatment of bum (the protein of the exposed tissues are precipitated forming a mildly antiseptic protective coat in which regeneration of new cells occur) ### **TANNIN-CONTAINING PLANT MATERIALS:** 1. **Hamamelis leaf or witch hazel leaves** * SN: Hamamelis virginiana (Fam. Hamamelidaceae) * AC: Hamamelitannin * USES: * Astringent * Hemostatic 2. **NUTGALL** * SN: Quercus infectoria * AC: Tannic acid - is a mixture of esters of gallic acid with glucose * USES: * Astringent * Used in tanning and dyeing industry and formerly in the manufacture of ink * Treatment of bedsores * For minor ulceration ### **Components of Universal Antidotes:** 1. MgO-neutralize acid 2. Tannic acid - precipitate alkaloids 3. Activated Charcoal - adsorp poisons ### **ALLIED PRODUCTS:** **JAPANESE AND CHINESE GALLS** * SN: Rhus chinensis (Fam. Anacardiaceae) * As a result of the stings of certain plant lice (Aphis). These galls are rich in tannin and, as they contain less coloring matter than the oak galls, are used in the manufacture of gallic acid. * AC: GALLIC ACID * Is 3,4,5-trihydroxybenzoic acid that crystallizes with 1 molecule of water. * It occurs in nutgall and can be prepared from tannic acid by hydrolysis with dilute acids * Bismuth subgallate - is used by ostomates to help control odors. ### **Apple** * tannin-rich plant * SN: Pyrus mallus * USE: Astringent ## **CHECK FOR UNDERSTANDING:** Answer the following questions accordingly. Write the letter of the correct answer on the space provided. 1. The excrescence obtained from the young twigs of Quercus infectoria which yields hydrolyzable tannins * A. Nutgall * B. Ergot * C. Both * D. None 2. The type of tannins which gives a greenish black color with ferric chloride and results to precipitation with bromine solution * A. Catechols * B. Condensed tannins * C. Pyrogallols * D. Both A and B 3. This is used as an antidote for alkaloidal poisoning: * A. lactic acid * B. tannic acid * C. tartaric acid * D. picric acid 4. The red-colored product formed when tannins are treated with hydrolytic agents is known as: * A. amolonin * B. diosgenin * C. phlobaphenes * D. leucocyanidin 5. Tannins have the ability to precipitate _______, which is utilized in vegetable tanning which converts animal hides to leather: * A. fats * B. carbohydrates * C. alkaloids * D. proteins 6. Blue-black color may indicate the presence of: * A. condensed tannins * B. hydrolysable tannins * C. saponin * D. all of these 7. Generally accepted medicinal use of tannins. * A. tanning of leather * B. astringent * C. laboratory precipitant * D. as ingredient in the preparation of ink 8. The following are differences of hydrolyzable from non- hydrolyzable tannins EXCEPT: * A. Hydrolysable tannins form blue- black precipitates with ferric chloride * B. Hydrolysable tannins when boiled with HCl will yield ellagic or protocatechuic acid * C. Hydrolysable tannins show no visible result with bromine water * D. none of the above choices 9. It is 3,4,5-trihydroxybenzoic acid that crystallizes with 1 molecule of water present in Japanese and Chinese galls * A. Gallic acid * B. caffeine * C. Methoxsalen * D. None of the choices 10. Scientific name of witch hazel leaves * A. Quercus infectoria * B. Rhus chinensis * C. Hamamelis virginiana * D. Pyrus mallus ## **C. LESSON WRAP-UP** Teacher directs the student to mark (encircle) their place in the work tracker which is simply a visual to help students track how much work they have accomplished and how much work there is left to do. This tracker will be part of the student activity sheet. You are done with the session! Let's track your progress. | Period 1 | Period 2 | Period 3 | |:---:|:---:|:---:| | 1 2 3 4 5 6 7 8 9 | 10 11 12 13 14 15 16 17 18 | 19 20 21 22 23 | ## **Thinking about Learning: Whip Around** Students quickly and verbally share one thing they learned in the class today. The instructor can ask 3 - 5 volunteers.