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Garlic & Health
WP 5.2 Cholesterol biosynthesis
Frank Struck, Doris Kellert
Dr. Sebastian Zellmer, Dr. Gayane Buniatian
Organosulphur Compounds
Organosulphur compounds of Garlic:
Inhibition of cholesterol biosynthesis
Potency of Inhibition:
Aim: Characterization of the effects on cholesterol biosynthesis
0,1 1 10 100 1000 104
Concentration ( M)
0
20
40
60
80
100
120
Ch
ole
ster
ol B
iosy
nth
esis
(%
)
Allicin
DADS
AM1,3-VDT
1,2-VDT
Gebhardt and Beck, Lipids 1996;31:126-1276
Organosulphur Compounds
Organosulphur compounds of Garlic:
Inhibition of cholesterol biosynthesis
Indirect Mechanism of Inhibition:
Aim: Characterization of the mode of action
Garlic Powder: reinvestigation
UnexpectedResult !!Garlic Powder
(Low Quality Garlic):
Stimulation of cholesterol biosynthesis !
0.01 0.1 1
Concentration (mg/ml)
0
20
40
60
80
100
120
140
160
Ch
ole
ste
rol
Bio
sy
nth
es
is (
%)
Hepatoc.
HepG2
Garlic Powder: reinvestigation
Challenge for present project research:
New milestones:
- Analysis of responsible compounds
- Elucidation of mechanism of action
Garlic Powder: reinvestigation
Challenge for present project research:
New milestones:
- Analysis of responsible compounds
- Elucidation of mechanism of action
Extraction Procedure
Separation scheme for garlic compounds with different effects on hepatic cholesterol biosynthesis:
Garlic orGarlic Powder
Solvent 2 /evapuration / reuptake Solvent 1
Fraction with very strong stimulating effect
1.Pellet
Solvent 1
2.Pellet
Fraction with strong inhibiting effect
Needs to be keptunder nitrogen
Conclusions:
• Using a sequential extraction procedure a stimulating fraction and an inhibiting fraction can be separated from fresh garlic or garlic powder
• At least the inhibiting compound is very labile in solution but stable in dry powder
• Garlic contains (two) compounds with opposite effects on cholesterol biosynthesis
Questions:
• What is the chemical nature of these compounds?
• What are the effects of these compounds on other cellular functions?
Garlic & Health
WP 5.2 Garlic flavonoids
Flavonoids in Garlic:
Literature Results
Starke & Hermann, 1976 only trace amounts of quercetin andMichahelles, 1974 kaempferol in peeled garlicKaneta et al., 1980Leighton et al., 1992
Carotenuto et al., 1996 Kaempferol-glycosides in Allium ursinum(no quantitative data)
Miean & Mohamed, 2001 detailed HPLC analysis, but poorly describedplant material
Myricetin693 mg/kg dry weightQuercetin 47Luteolin not detectableApigenin 217
Structure of Favonoids used
All tested flavonoids belong to the flavonol group
They differ only in the amount and/or position of one or twohydroxyl groups
In the case of Luteolin and Kaempferol, several glycosideswere also tested
Comparison of the effects of Kaempferol, Luteolinand their glycosides in rat hepatocytes
Kaempferol: sensitive stimulation of cholesterol biosynthesis
high cytotoxicity (responsible for decline)0.01 0.1 1 10 100
Concentration ( M)
0
20
40
60
80
100
120
140
160
Inc
orp
ora
tio
n o
f [
14C
]ac
eta
te (
%)
Kaempferol
K.-3O-Glucosid
0.01 0.1 1 10 100
Concentration ( g/ml)
0
20
40
60
80
100
120
140
160
[14C
]Ac
eta
te i
nc
orp
ora
tio
n (
%)
*
*
*: P < 0.01*
LuteolinLuteolin-7O-Gluc.
Luteolin: inhibition of cholesterol biosynthesis (no significant stimulation)
low cytotoxicity
Comparison of the effects of Myricetin, Kaempferoland Luteolin in HepG2 cells
Myricetin: stimulation of cholesterol biosynthesis
0.1 1 10 100 1000
Concentration ( g/ml)
0
20
40
60
80
100
120
140
14C
-Ac
eta
te I
nc
orp
ora
tio
n (
%)
0.1 1 10 100 1000
Concentration ( g/ml)
0
20
40
60
80
100
120
14C
-Ac
eta
te I
nc
orp
ora
tio
n (
%)
*
** *
*
Luteolin
Kaempferol
Kaempferol: no significant effect
Luteolin: inhibition of cholesterol biosynthesis
Flavonoids in Garlic:
Hypothesis:
Flavonoids of garlic, particularly Kaempferol and Myricetin, may be responsible for the stimulatory effects of garlic powder on cholesterol biosynthesis.
Future tasks:
• Elucidation of the mode of action of flavonoids like Kaempferol and Myricetin
• Detection and quantitation of these flavonoids in garlic powders and otherpreparations