(4) Steviol Glycosides - Saponins

Steviol glycosides

• the aglycone portion is a steviol

• found their use as natural sweeteners, as substitute for sugar (40-300 times sweeter than sucrose)

stevia

steviol glycosides source

Stevia rebaudiana

stevia SN

saponins

• steroidal/triterpenoid glycosides characterized by their ability to froth when agitated - used as detergent

• exert a powerful hemolytic action on RBCs and are highly toxic when injected into the the bloodstream - used as fish poison

• harmless when taken orally

sapotoxin

• poisonous saponin

• interesting spermicidal & molluscicidal activity

steroidal
triterpenoidal

two types of saponins

steroidal

• monocot

• dioscoreaceae

triterpenoidal

• dicot

• agavaceae

glucose
arabinose
xylose
glucuronic acid

saponin - glycone - sugar

steroids

saponin - aglycone - sapogenin - neutral saponins:

triterpenoids

saponin - aglycone - sapogenin - acid saponins:

neutral / steroidal saponins

C-27 (nature of aglycone)

acid saponins / triterpenoids

C-30 (nature of aglycone)

neutral lead acetate
basic lead acetate
hydrogen sulfide

synthesis reagent use

neutral lead acetate

use to produce acid saponin if precent are precipitated as lead salts

basic lead acetate

use to precipitate neutral saponin

hydrogen sulfide

use to decompose lead precipitate

properties of saponin glycosides

• amorphous, soluble in water and alcohol

• form persistent froth with water

• cause hemolysis of RBCs if reach the blood

• has bitter, acrid taste and drugs

froth test
agar cup hemolytic test
fehling’s test
baryta water test
lead acetate test

saponin tests

froth test

honeycomb froth greater than 2 cm persistent for 10 minutes

agar cup hemolytic test

clear zone of hemolysis (hemolytic halos)

fehling’s test

• brick red ppt

• presence of sugar, glycone portion

baryta water test

• formation of precipitate

• barium hydroxide reacts with neutral saponins

neutral saponins

___ have no acid-base groups

lead acetate test

• formation of precipitate

• basic ___ reacts with neutral saponins

gugo extract

saponins physical test

golden yellow to orange

gugo extract color

odorless

gugo extract odor

slightly bitter
acrid

gugo extract taste

licorice
yam
ginseng
gugo

saponins source

Glycyrrhiza glabra

licorice SN

Dioscorea floribuna

yam SN

Panax ginseng

ginseng SN

Entada phaseoloides

gugo SN