Botany - Phytochemistry PDF

BOT TERM 1 CLASS 3A: PHYTOCHEMISTRY DR. FIONA SMULDERS ND LEARNING OBJECTIVES By the end of this lesson, students will be able to: 1. Name primary and secondary plant metabolites and understand the difference between them 2. Classify herbal constituents and understand their solubility 3. Defi...

BOT TERM 1 CLASS 3A: PHYTOCHEMISTRY DR. FIONA SMULDERS ND LEARNING OBJECTIVES By the end of this lesson, students will be able to: 1. Name primary and secondary plant metabolites and understand the difference between them 2. Classify herbal constituents and understand their solubility 3. Define and give herbal examples of herbal actions 4. List herbs with selected tissue affinities 5. Describe the herbal monograph as a learning resource and know how/where to access reliable herbal information in order to apply information to case presentations HERBAL CONSTITUENTS THE CHEMICAL PARTS WITHIN A PLANT PRIMARY & SECONDARY PLANT METABOLITES • Plants can contain hundreds to thousands of unique chemicals which include: • Primary metabolites - fundamental to the life of the plant (e.g. proteins, lipids, carbs, chlorophyll). • Secondary metabolites do not appear to be fundamental to sustain life but serve diverse functions within plants. • ~200,000 secondary plant metabolites have been discovered. • estimated that science has yet to uncovered 80-90% of them • in herbalism are referred to as plant constituents. Chalker-Scott, L. How Plants Work: The science behind the amazing things plant do. Portland, OR; Timber Press; 2015. SECONDARY METABOLITES AKA CONSTITUENTS Plant constituent are made by the plant for their own purpose, which we can also benefit from • Ex: flavonoids help protect the plant from UV radiation The constituents within a plant are responsible for diverse functions such as protection, interaction with other species, color, fragrance and the structure of a plant CONSTITUENT CLASSIFICATION MAJOR CLASS EXAMPLES Carbohydrates inulin, arabinogalactans, beta-glucans, gum, mucilage Lipids alkamides, fatty acids Phenolics salicylic acid, coumarins, flavonoids, isoflavones, lignans, quinones, tannins Terpenoids volatile oils, resins, saponins, phytosterols, carotenoids, cardiac glycosides, iridoids Alkaloids isoquinoline, pyrrolizidine Phenolic ring Isoprene unit *Read Constituent & Actions document for definitions & examples A NOTE ABOUT GLYCOSIDES… Glycosides are compounds that have two different molecules attached via a glycosidic bond 1. Glycone – sugar unit 2. Aglycone – any other compound Phenolic glycosides have a sugar unit (glycone) attached to a phenolic compound (aglycone) – many are tannins, flavonoids, salicylate, etc *typically the aglycone unit is the biologically active component and often requires our gut flora to cleave and activate it Having the added sugar unit helps make them more water soluble CONSTITUENT SOLUBILITY Every solvent (extraction medium or “menstruum”) has varying affinities for different groups of phytochemicals • Water-based solutions will extract water soluble constituents like mucilage, polysaccharides and tannins • “Fat”-based solutions (alcohol, vinegar, glycerin, oil) will extract fat-soluble constituents like alkaloids, resins and volatile oils INFLUENCES ON CONSTITUENT SOLUBILITY 1. Structure & size of the phytochemical molecule 2. Polarity of its molecular skeleton and attached functional groups 3. Synergistic and companion compound content 4. Temperature of extraction solvents 5. Plant matrix 6. Type of solvent & solution pH (ionization) Constituent Solvent Required Notes Alkaloids 45-60% alcohol There is no absolute guide to their solubility. Are generally not very soluble in water and more so in alcohol Flavonoids Water or 25-50% alcohol Vary in solubility depending on their glycoside Mucilage Water A polysaccharide that absorbs water and may form a sludge in alcohol Salicylates Water or 25% alcohol Readily soluble in water or alcohol Saponins Water + 40% alcohol Partially soluble in both water & alcohol Resins 90% alcohol or oil Insoluble in water Tannins Water or 25% alcohol Readily soluble in water or alcohol Volatile Oils Volatize in hot water, 40% alcohol, or oil Soluble in alcohol and fixed oils, slightly soluble in water (steam distillation & heat) SUMMARY • Plants have both primary and secondary metabolites • Herbal constituents are considered secondary metabolites that provide a diverse array of functions for the plant that we can also benefit from • Constituent classification depends on their chemical structure and are responsible for an herb’s herbal actions • Different constituents will be extracted in different solutions, it is important to have a good understanding of constituent solubility in order to choose the right herbal preparation *Read the Constituents & Actions PDF on ecampus