pharmacognosy

• glycosides/ether sugar - any molecule in which a sugar group is bonded through its anomeric carbon to another functionalgroup via glycosidic bond.
• glycosides - compounds that yield one or more sugars among theproducts of hydrolysis
• Two Portions:

  glycone

  aglycone
• Glycone

  • insoluble in organic solvents
  • sugar component
  • consist of a single sugar group or several sugar groups

  Ex. Glucose, rhamnose, deoxysugars (cymarose)
• Aglycone (Genin)

  • non-sugar component
  • soluble in organic solvents (benzene, ether)
• Characteristics of glycosides;

  1. Crystalline or amorphous substances
  2. Water & alcohol soluble
  3. Insoluble in organic solvents

  (Glycone: insoluble in OS; Aglycone: soluble in OS)

  4. Hydrolyzed by the presence of water, enzymes and

  mineral acids

  5. Optically active

  Isomeric Forms:

  a. α-form

  b. β-form

  • most common form of all the natural glycosides
  • occur in all the natural glycosides
• Important role in plants of glycosides:

  1. Regulatory
  2. Protective
  3. Sanitary Functions
• glycosides can be classified by:

  • basis of glycone
  • basis of glycosidic linkage
  • basis of aglycone
• 1. Basis of Glycone - naming glycosides based on the glycone group present
• • Glucoside: glycone group of glycoside is glucose
  • Fructoside: glycone group of glycoside is fructose
  • Glucuronide: glycone group of glycoside is glucuronic acid
• Basis of Glycosidic Linkage

  • o-glycosides
  • n-glycosides
  • s-glycosides
  • c-glycosides
• o-glycosides - Sugar molecule is combined with phenol or –OHgroup of aglycon; Oxygen-glycoside.

  Ex. Amygd-aline, Indesine, Arbutin, Salicin, cardiac glycosides, few anthraxquinone glycosides
• • N-glycoside: Sugar molecule is combined with N of the –NH(amino group) of aglycon; Nitrogen-glycoside

  Ex. nucleosides
• • S-glycoside: Sugar molecule is combined with the S or SH (thiol group/sulfur group) of aglycon; Sulfur-glycoside

  Ex. Sinigrin
• • C-glycoside: Sugar molecule is directly attached with C—atom ofaglycon; Carbon-glycoside

  Ex. Anthraquinone glycosides (Aloin, Barbaloin, Cascaroside) &Flavan glycosides
• Basis of Aglycone

  • most commonly followed and organized way in classifying glycosides
  • based on aglycone moiety
• Anthraquinone Glycosides

  • Borntragers test
  • modified Borntragers test
• • Borntragers Test: Pink or Red Color; test O type anthraquinone glycosides
• • Modified Borntragers Test: Pink or Red Color; test C type anthraquinone glycosides
• Saponin Glycosides

  • hemolysis
  • foam test / froth test
• • Hemolysis Test: Rupturing of RBCs
  • Foam Test (Froth Test): Foam/Froth; Persist for 60-120seconds
• Steroid Glycosides

  • Libermann Burchard Test: Violet/Blue Color; Most Sensitive
  • Salkowaski Test: Yellow turns Red after 2 mins
  • Antimony Trichloride Test: Pink color
  • Trichloro Acetic Acid Test: Colored precipitate (usually brown or yellow)
  • Tetranitro Methane Test: Yellow color
  • Zimmermann Test: Violet color in the presence Ketosteroid
• Cardiac Glycosides

  • Keller-Killiani Test: Test for Deoxysugar present inglycosides; Reddish Brown layer which turns Bluish Green after standing due to presence of Digitoxose
  • Legal Test: Pink color
  • Baljet Test: Yellow to Orange color
  • 3,5-Dinitro Benzoic Acid Test: Pink color
• coumarin glycosides

  1. FeCl3 (Ferric Chloride) Test: Deep Green color turns Yellow by addition of conc. Nitric acid
  2. Fluorescence test: Blue-Green
• Cyanophoric Glycosides

  • Sodium Picrate Test: Brick Red color
• Flavonoid Glycosides

  • Ammonia Test: Yellow Spot
  • Shinoda Test: Deep Red to Magenta Color
  • Vanillin HCl Test: Pink Color
• Anthracene (Anthraquinone) Glycosides

  consists of glycosides formed from aglycone moieties like

  anthraquinones, anthranols, anthrone, and their derivatives

  first termed as anthracene glycoside because of its struc
• Yellow or light-grey to grey-green solid crystalline powder Melts at 286°C and boils at 379.8°C Reduced derivatives are more active than oxidized aglycones Insoluble in water and alcohol but soluble in nitrobenzene and aniline
• Senna Leaf (Alexandria Senna) (Tinevelly Senna) consists of the dried leaflets of Cassia acutifolia and Cassia angustifolia (Leguminosae)
• Alexandria senna: Cassia acutifolia; uses broken leaflet Tinevelly Senna: Cassia angustifolia; uses full leaflet
• Best Grade: Blue-green leaves Poorest Grade: Yellow leaves cultivation resembles rice paddies (wet land)
• Sennoside A & B major constituent Sennoside C & D minor constituent
• Aloe (Aloes) is the dried latex (juice) collected by incision of the leaves of Aloe barbadensis (Curacao: Curacao aloe) or Aloe vera, Aloe ferox (hybrid), Aloe spicata (African) (Liliaceae) Chemical Constituents: a. Aloin o-glycoside b. Barbaloin c-glycoside
• Rhubarb (Rheum) (Chinese Rhubarb) consists of the dried rhizomes and roots of Rheum officinale or of Rheum palmatum (Polygonaceae) Chemical Constituents: a. Rhein principal constituent C-glycoside b. Chrysophanol c. Aloe-emodin d. Emodin
• Cascara Sagrada (Cascara Bark) (Sacred Bark) (Rhamnus Purshianus) is the dried bark of Rhamnus purshiana (Rhamnaceae) which is collected at least one year before use macerated in magnesium oxide to produce the reduced form Reduced form: less irritating; milder cathartic activity similar to the classification of emodin from Aloe
• O-glycosides based on emodin constitutes 10-20% of the cascara sagrada

  C-glycosides ased on aloin constitutes 80-90% of cascara sagrada