Introduction to Volatile Oils and Resins – PST05210 Basic Pharmacognosy
NTA Level 5 • Semester 2 • PST05210 Introduction to Volatile Oils and Resins Basic Pharmacognosy • Source Session/Topic 30 Full source-text version: all educational wording from the extracted learning source is retained; only presenter/tutor metadata and web-layout noise are removed, while formatting is improved for readability. Session 30: Introduction to Volatile Oils and Resins Total Session Time: 120 minutes Prerequisites None Learning Tasks By the end of this session students are expected to be able to: • List characteristics of volatile oils • Describe the composition of volatile oils • Classify volatile oils • Describe extraction of volatile oils • List therapeutic uses of volatile oils Resources Needed: • Flip charts, marker pens, and masking tape • Black/white board and chalk/whiteboard markers • LCD Projector and Laptop SESSION OVERVIEW |Step |Time |Activity/ |Content | | | |Method | | |1 |05 minutes |Presentation |Introduction, Learning Tasks | |2 |25 minutes |Presentation |Characteristics of Volatile Oils | | | | |and Resins | |3 |20 minutes |Presentation |Composition of Volatile Oils | | | |Brainstorm | | |4 |15 minutes |Presentation |Classification of Volatile Oils | |5 |30 minutes |Presentation |Extraction of Volatile Oils | |6 |15 minutes |Presentation |Therapeutic Uses of Volatile Oils | | | |Small group | | |7 |05 minutes |Presentation |Key Points | | 8|05 minutes |Presentation |Evaluation | SESSION CONTENTS STEP 1: Presentation of Session Title and Learning Tasks (5 minutes) READ or ASK students to read the learning tasks and clarify ASK students if they have any questions before continuing. STEP 2: Characteristics of Volatile Oils (25 minutes) • Volatile oils, also known as essential oils, are concentrated, odoriferous liquids that entirely or almost entirely volatile in steam • Volatile oils are referred to as "essential" in the sense that they carry a distinctive scent, or essence of the plant • Essential oils do not as a group need to have any specific chemical properties in common, beyond conveying characteristic fragrances (Essential oils should not be confused with essential fatty acids) • Volatile oil originates from plants, possess a unique odour or flavour, mainly used in perfumes and flavourings • Essential oils have the following general characteristics o They evaporate under atmospheric pressure at room temperature o They are soluble in alcohol and other organic solvents o They are insoluble in water o They have high refractive index o They are optically active o Most of them are colourless or pale yellow o They are odoriferous o They are sensitive to air (resinify on exposure to air) o Most of them are terpenoid in nature • Resins o Resins are hydrocarbon secretions of many plants, more or less solid amorphous products of complex chemical nature o Resin produced by most plants is a viscous liquid o Resins may be associated with volatile oils or gum or may be found in irregular masses which are insoluble in water but soluble in alcohol o Resins, oleoresins (resins associated with oils) and gum resins (resins associated with gums) are usually secreted into secretory cavities or ducts STEP 3: Composition of Volatile Oils (20 minutes) |Activity: Brainstorming (10 minutes) | | | |DIVIDE students into small manageable groups | | | |ASK students to discuss on the following question | | | |What is composition of volatile oils? | | | |ALLOW students to discuss for 15 minutes | | | |ALLOW few groups to present and the rest to add points not | |mentioned | | | |CLARIFY and SUMMARIZE by using the contents below | • Volatile oils are chemically derived from terpenes (mainly from mono and sesqui terpenes) o Terpenoids are hydroxycarbons of plant origin with general formula (C5H8) n i.e. isoprene units o Terpenoids are naturally occurring and give plants and flowers their fragrance • Many oils are terpenoid in origin, some oils such as cinnamon and clove contain principally aromatic (benzene) derivatives mixed with terpenes • With the exception of oils derived from glycosides (e.g. bitter almond oil and mustard oil), volatile oils are mixtures of hydrocarbons and oxygenated compounds derived from these hydrocarbons • Some oils are acyclic, aromatic or contain sulphur or nitrogen • In some oils (e.g. Oil of turpentine) the hydrocarbons predominate and only limited amount of oxygenated constituents are present, other volatile oils (e.g. Oil of cloves) the bulk of the oil consists of oxygenated compounds STEP 4: Classification of Volatile Oils (15 minutes) • Volatile oils can be classified based on extraction method into; o Concretes ▪ Uses solvent e.g. hexane and waxes or resins to contact the plant materials and then the solvent removed by gent heating e.g. jasmine oil o Pomades ▪ Obtained by enfleurage (hot or cold) e.g. oils from flowers o Resinoids ▪ Extraction with resinous materials i.e. to prolong effect of fragrance o Absolutes ▪ Remains after alcoholic extraction from pomades or concretes • Volatile can be classified on the basis of their functional groups into; o Hydrocarbon volatile oils e.g. turpentine o Alcoholic volatile oils e.g. peppermint, cardamom and coriander oils o Aldehydic volatile oils e.g. lemon oil, orange oil, cinnamon o Ketonic volatile oils e.g. camphor, spearmint oils o Phenolic volatile oils e.g. clove, anise, nutmeg oils o Phenolic ether volatile oils e.g. fennel oil o Oxide volatile oils e.g. rosemary oil STEP 5: Extraction of Volatile Oils (30 minutes) • The following methods are used as general extractions for volatile oils; o Distillation ▪ Water (Simple) distillation (for dry plant materials, materials not destroyed by boiling e.g. turpentine oil) ▪ Water and steam distillation (for dry plant materials not destroyed by direct heating e.g. clove and cinnamon oils) ▪ Steam distillation (for fresh plant materials e.g. peppermint and spearmint oils) • Simple steam distillation • Saturated steam distillation • Hydrodifusion o Scarification ▪ Sponge extraction ▪ Ecuelle method ▪ Enzymatic hydrolysis o Soxhlet extraction o Solvent extraction ▪ Extraction by non-volatile solvents • Enfleurage (hot or cold) • Maceration • Spraying or pneumatic method o Extraction by