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