Phytochemistry General Introduction

Phytochemistry General Introduction

• Phytochemistry is the study of plant compounds and their properties
• This includes their chemistry, biological activity, and structure-activity relationships

Course Objectives

• Describe the chemistry and biological activity of volatile oils, resins, carbohydrates, alkaloids, glycosides, and tannins.
• Describe the structure-activity relationships of biologically active components.
• Recognize and draw chemical structures of active components.
• Describe the physical and chemical properties of active and inactive components.

Course Outline

• General introduction to phytochemistry, extraction, and isolation of natural products.
• Techniques commonly used in phytochemistry
• Volatile oils (e.g., terpenes, oxygenated terpenes, phenolic compounds)
• Alkaloids (e.g., proto-alkaloids, true alkaloids, tropane alkaloids)
• Carbohydrates
• Glycosides (e.g., alcoholic glycosides, anthraquinones, flavonoids, saponins)
• Tannins
• Bitter principles
• Resin and its combinations

What is Phytochemistry?

• Phytochemistry is the study of plants and their phytochemicals
• It involves:
  • Authentication and extraction of plant material
  • Separation and isolation of components of interest
  • Characterization of isolated compounds
  • Investigation of biosynthetic pathways to compounds
  • Quantitative evaluations
  • Pharmacological assessment of components

Historical Development of Phytochemistry

• Early knowledge of plant compounds: cane sugar, starch, camphor, benzoic acid, fats, volatile oils, resins, and their aqueous extraction.
• Key developments in the 17th-19th centuries:
  • K. W. Scheel (German apothecary) isolated citric, gallic, prussic, oxalic, and tartaric acids.
  • Nicholas Lemery (French apothecary) expanded the use of alcohol and solvents in extraction.
  • Isolation of narcotine, the first alkaloid; later followed by morphine, strychnine, emetine, and more.
• Twentieth century focus: elucidation of biosynthetic pathways

The Recent Interest

• Focus on active principles (usually alkaloids or specific glycosides) with pronounced pharmacological properties.
• Emphasis on the plant as a source of new drugs and strategies for plant extract fractionation based on biological activity, rather than on particular chemical classes.
• Chemical examination follows active fraction isolation.

Techniques Used in Phytochemistry

• Methods for analyzing and isolating plant compounds.

Preliminary Phytochemical Screening Test

• Process for identifying plant constituents
• Widely used in quality control of herbal medicines, particularly Chinese herbal medicines.
• Identifies various components like alkaloids, saponins, and flavonoids.
• Often, biologically active compounds in herbal medicines remain undetermined.

Screening and Analysis of Bioactive Compounds

• Phytochemical methods used to screen and analyze bioactive compounds.
• Contributing to the discovery of new therapeutic compounds.

Test for Tannins

• To 2 mL of water extract of different plant parts, add 2 mL of 10% ferric chloride solution in a test tube.
• Blue-black precipitate indicates tannins.

Test for Alkaloids

• To 2 mL of methanolic extract of different plant parts, add 1 mL of 1% hydrochloric acid in a test tube. Heat in a water bath for 10 minutes.
• Take 1 mL from the solution and add 6 drops of Dragendorff's reagent, Wagner's reagent, or Mayor's reagent.
• Orange, brownish-red, or creamish precipitate indicates alkaloids.

Test for Cardiac Glycosides (Keller-Kiliani Test)

• To 2 mL of methanolic extract, add 1 mL of glacial acetic acid, 6 drops of 10% ferric chloride solution, and 6 drops of concentrated sulphuric acid in a test tube.
• A green-blue color indicates cardiac glycosides.

Test for Steroids and Terpenes (Liebermann-Burchard Reaction)

• To 2 mL of chloroform extract, add 2 mL of acetic anhydride and a few drops of concentrated sulphuric acid in a test tube.
• A blue-green ring between layers indicates steroids, and a pink-purple ring indicates the presence of terpenes.

Test for Cyanogenic Glycosides

• To 3 mL of ethanol extract, add 2 mL of sterile water in a conical flask.
• Place freshly prepared sodium picrate paper at the stopper. Heat the solution to boiling.
• A change in color of the sodium picrate paper from yellow to shades of red indicates cyanogenic glycosides.

Free Anthraquinones Test

• To 5 mL of ethanol extract of different plant parts, add 10 mL of water. Boil, cool and shake with 5 mL of chloroform.
• Concentrate the chloroform layer to 2 mL and add 2-3 mL of ammonia solution.
• A pink-red color in the alkaline layer indicates free anthraquinones.

Anthraquinone Glycosides Test

• To 2.5 g of powdered plant material, add 10 mL of 20% sulphuric acid and 2 mL of 2% ferric chloride solution.
• Boil in water bath (reflux) for 30 minutes, cool and filter.
• Extract the solution with 10 mL of chloroform in a separating funnel. Concentrate to 4 mL and add 2.5 mL of 10% ammonia solution.
• A pink-red color in the alkaline layer indicates anthraquinone glycosides.

Test for Flavonoids (Shinoda's Test)

• To 2 mL of ethanol extract, add 0.5 mL of concentrated hydrochloric acid and a few magnesium turning in a test tube.
• A pink-tomato red color indicates flavonoids.

Test for Volatile Oils

• To 0.5 mL of oil sample, add 2 drops of 1% aqueous FeCl3.
• Different colors indicate different volatile oils.

Explore the fundamental concepts of phytochemistry, focusing on the study of plant compounds and their properties. This quiz covers important topics such as volatile oils, alkaloids, and carbohydrates, as well as the techniques for extracting and isolating natural products. Test your understanding of chemical structures and the biological activity of various plant components.