SUMMARY OF DATA FOR CHEMICAL SELECTION

Milk Thistle Extract / Silymarin / Silybin

84604-20-6 / 65666-07-1 / 22888-70-6
August 1998

TABLE OF CONTENTS
Basis for Nomination

Chemical Identification

Production Information

Use Pattern

Human Exposure

Regulatory Status

Evidence for Possible Carcinogenic Activity

Human Data

Animal Data

Metabolism

Other Biological Effects

Structure-Activity Relationships

References

BASIS OF NOMINATION TO THE CSWG

Milk thistle extract is presented to the CSWG as part of a review of botanicals being used as dietary
supplements in the United States. Alternative herbal medicines are projected to be a $5 billion market by
the turn of the century. Milk thistle extract is consistently one of the more widely used alternative
medicines.
A review of the available literature suggests that milk thistle extract has beneficial effects on the liver,
helping reverse the damage caused by organic solvent exposure or alcoholism. The active flavolignan
isomers in milk thistle extract, termed silymarin, also appear to possess anticarcinogenic activity. In
contrast, no reports of severe side effects from the use of milk thistle extract or silymarin were reported
in the available literature. However, many reports of beneficial effects may be from intravenous
administration of a dosage form not available in the US The lack of reports on side effects for dietary
supplements in use in the US may simply indicate a lack of bioavailability of the active ingredients.

INPUT FROM GOVERNMENT AGENCIES/INDUSTRY

The American Botanical Council provided a report on milk thistle from their Botanical Series
publications.

SELECTION STATUS

ACTION BY CSWG: 9/16/98

Studies requested:

- Toxicological characterization (90-day) including reproductive testing

- Metabolism studies

- Genotoxicity

Priority: Moderate

Rationale/Remarks

- Significant human exposure

-Popular dietary supplement thought to have beneficial effects on the liver

-Metabolism studies needed to resolve questions regarding bioavailability of orally

administered milk thistle extract

- Examined as a hepatoprotectant, but limited information on safety

- NCI will conduct mouse lymphoma assay

- Consideration for further testing pending evaluation of results of 90-day toxicity study

CHEMICAL IDENTIFICATION

Milk Thistle Extract

CAS Registry Number: 84604-20-6

 Chemical Abstracts Silybum marianum
Service Name: extract

Synonyms and Trade

Names: Lady's thistle extract
Botanical mixture;
Structural Class: phytopharmaceutical

Silymarin

CAS Registry Number: 65666-07-1

Chemical Abstracts
Service Name: Silymarin
Apihepar; Laragon;
Synonyms and Trade Legalon; Pluropon;
Names: Silarine; Silepar;
Silirex; Silliver; Silmar
Mixture of
Structural Class: flavonolignans
including silidianin,
silicristin, and the major
compound, silybin

Silybin

'

CAS
Registry
Number: 22888-70-6
4H-1-Benzopyran-4-one, 2-[2,3-
Chemical dihydro-3-(4- hydroxy-
Abstracts 3-methoxyphenyl)-2-(hydroxymethyl)
Service -1,4-benzodioxin-6-yl]-2,3-dihydro-
Name: 3,5,7-trihydroxy-, [2R[2α -3β, 6(2R*,
3R*)]]- (9 CI)
4-Chromanone, 3,5,7-trihydroxy-
Synonyms 2-[3-(4-hydroxy-
and Trade 3-methoxyphenyl)-2-
Names: hydroxymethyl)-1,4-benzodioxan-
6-yl]-;
 silibinin; silibinine; silybum
substance E; silymarin I

Structural
Class: Flavonolignan

Structure, Molecular Formula and Molecular Weight:

Silybin

C25H22O10 Mol. wt.: 482.4

Chemical and Physical Properties (Silybin):

158o C (anhydrous substance); 167o C

Melting Point: (monohydrate) (Budavari, 1996)

Practically insoluble in water; soluble

Solubility: in acetone, ethyl acetate, methanol,
ethanol; sparingly soluble in chloroform
(Budavari, 1996)

Milk thistle (Silybum marianum), a member of the Aster family, is a tall herb
with large prickly white-veined green leaves and a reddish-purple flower that
ends in sharp spines. Milk thistle fruits (often erroneously referred to as seeds)
contain up to 6 percent silymarin, the active flavonoid constituent. Silymarin's
principal components are silybin, silycristin, and silydianin. The primary
investigational focus has been on silybin, which is the most biologically active.
A number of other flavonolignans have also been found in the seeds including
dehydrosilybin, desoxysilycristin, desoxysilydianin, silandrin, silybinome,
silyhermin, and neosilyhermin. In addition apigenin, silybonol, and myristic,
 palmitic, stearic, and oleic acids have been reported (Foster, 1991; Awang,
1993; Brown, 1996; Grauds, 1996).

Technical Products and Impurities: Milk thistle is available at health food stores
and pharmacies as well as through direct-mail companies. Extracts are supplied
as capsules, tablets, liquids, powders and creams. Some of these milk thistle
preparations are sold in combination formulas with other herbs. In Europe, a
water-soluble silybin compound is available for use in intravenous infusion
treatments (Ferenci et al., 1989; Foster, 1991; Awang, 1993).

Capsules. Capsules range in strength from 100 to 250 mg and most are
standardized to contain 80 percent silymarin. Herbal Resources offers milk
thistle extract in 150 mg capsules standardized to contain 70 percent silymarin
(as silybin). Solgar's Vegicaps contain 100 mg of milk thistle extract
(standardized to 80% silymarin) in a base of milk thistle herb and seed powder
(Herbal Resources, Inc., 1995a; Global Nutrients, 1997; Smart Basics, 1997;
Ripplecreek, 1998; Solgar Herbal Supplements, 1998). Time release capsules
of milk thistle extract are also available (Dialog, 1998a).

Tablets. Source Natural's Silymarin 80 tablets are 210 mg standardized to

deliver 168 mg of the three flavonolignans silybin, silydianin and silycristin. In
addition, the tablets contain 50 mg of whole milk thistle seed (Dialog, 1998a).

Liquid. A blend of the liquid extracts of milk thistle mature seed (20%);
dandelion root, leaf and flower (20%), Oregon grape root (20%), artichoke leaf
(16%), beet leaf (16%), and fennel seed (8%) is available from Herbal
Resources (Herbal Resources, Inc. 1995b).

Powder. Each 5 ml of a tonic powder from the Women's Health Advisory

Service contains milk thistle (330 mg), psyllium husk powder (924 mg),
dandelion root powder (330 mg), globe artichoke (165 mg), taurine (165 mg),
and slippery elm bark (82.5 mg) (Women's Health Advisory Service, 1997).

Cream. A moisturizing cream, available from Abra Therapeutic Skin Care,

contains milk thistle, green tea, and white willowbark; Derma E produces a
skin lightening cream which combines milk thistle, licorice and vitamin C
(Dialog, 1998a).

Silymarin is available from Aldrich and Sigma. The Aldrich product is a

mixture of toxifolin, silicristin, silidianin, silybin A, silybin B, isosilybin A, and
isosilybin B. The Sigma product is described as a mixture of anti-hepatotoxic
flavonolignans from the fruit of Silybum marianum. Sigma also supplies silybin
(Aldrich Chemical Co., Inc., 1996; Sigma, 1998).

EXPOSURE INFORMATION

Production and Producers: Silybum marianum, commonly known as milk

thistle, is distributed throughout Southern Europe, Australia, North and South
American, and parts of Asia (Ikram et al., 1984). Although milk thistle has
been used medicinally for over 2000 years, the active hepatoprotective
constituent, silymarin, was first isolated from the seeds (fruit) in 1968 (Brown,
1996).

The total synthesis of silybin, which constitutes about 60 percent of the

silymarin complex, has been reported (Tanaka et al., 1985; Budavari, 1996;
Boigk et al., 1997). Tanaka and coworkers (1985) achieved synthesis via a key
intermediate, 3-(4-hydroxy-3-methoxyphenyl)-2-hydroxymethyl-
1,4-benzodioxan-6-carbaldehyde. This aldehyde was converted to the
methoxymethyl ether which was condensed with an acetophenone derivative to
yield the chalcone. Oxidation of the chalcone with alkaline hydrogen peroxide
followed by treatment of the resulting epoxide with hydrochloric acid in
methanol afforded racemic silybin in 63 percent yield.

Milk thistle extract is available from Acta Pharmacal, American Ingredients,

Inc., Anmar International, Ltd., Ashland Chemical Co., Belmont Chemicals,
Inc., Bio-Botanica, Inc., China Tech, Inc., G.C.I. Nutrients, Marcor
Development Corp., Mini Star International, Inc., Motherland Herb-Pharm,
Inc., Pharmline, Inc., QBI (Quality Botanicals Ingredients, Inc.), RIA
International, Schweizerhall, Inc., F.H. Taussig, Inc., and P.L. Thomas & Co.,
Inc. (McCoy, 1997).

Silymarin is available from Amax Industries, Inc., CPB International, Inc.,

DNP International Co., Inc., Kaden Biochemicals GMBH, M.M.P., Inc.,
Marcor Development Corp., Maypro Industries, Inc., Mini Star International,
Inc., Motherland Herb-Pharm, Inc., Pharmline, Inc., and F.H. Taussig, Inc.
(McCoy, 1997).

For the 12-month period ending April 1998, milk thistle formulas were among
the strongest sellers in natural product stores with a growth rate of 83.2 percent
(Scimone & Scimone, 1998).

In the 6-month period from October 1997 to April 1998, the Port Import/Export
Reporting Service (PIERS) reported milk thistle seed and silymarin imports of
73,082 and 27,645 pounds, respectively (Dialog, 1998b).

Neither milk thistle nor silymarin are listed in the EPA's Toxic Substances
Control Act (TSCA) Inventory.

Use Pattern: Milk thistle has a long history of European cultivation for food.
Young leaves can be used in salads and as a substitute for spinach; stalks can be
eaten like asparagus; roots are eaten like salsify; and boiled flower heads used
like artichoke. Milk thistle fruit has also been used as a coffee substitute
(Awang, 1993).

Various preparations of milk thistle, especially the seeds, have been used
medicinally for over 2000 years. It was taken as a tonic, demulcent,
anti-depressant, and stimulant for milk production in nursing mothers. In
homeopathy, a tincture of the fruits is used to treat bronchitis, cough,
gallstones, hemorrhage, jaundice, peritonitis, uterine congestion, and varicose
veins. Its use as a liver-protecting agent dates to early Greek references. The
plant is not mentioned in most American works on medicinal plants until the
end of the nineteenth century (Foster, 1991; Awang, 1993).

Currently the most important medicinal application of milk thistle is its use as
an hepatoprotectant and as supportive treatment of chronic inflammatory liver
disorders such as cirrhosis, hepatitis, and fatty infiltration due to alcohol and
toxic chemicals. It has also been used in the treatment of liver damage by
poisonous mushrooms. Following the isolation of silymarin and the
development of standardized extracts in 1968, over 200 clinical studies
involving over 4,000 patients have been completed with milk thistle extracts.
Modern clinical research on the hepatobiliary effects of milk thistle began in
Germany under the guidance of Madaus AG over thirty years ago (Foster,
1991; Awang, 1993; Brown, 1996).

For the treatment of liver disease (hepatitis, cirrhosis, toxin damage), the
recommended dose of milk thistle extract is 420 mg (silymarin) a day taken in
three divided doses. Suggested treatment periods range from 4 weeks to 9
months. When milk thistle is used as a nutritional supplement or for preventive
purposes, 210 to 280 mg (silymarin) a day is recommended (Brown, 1996;
Takao Co., 1996).

Human Exposure: The primary exposure of humans to milk thistle occurs

through its use as an herbal supplement. Approximately one third of the US
adult population or approximately 60 million consumers, have increasingly
used alternative pharmaceutical preparations to prevent or treat illnesses
(Tanaka, 1997).

There is potential for worker exposure to milk thistle during the growing,
harvesting and processing of the plants. For the purposes of quantifying the
costs of food labeling regulations, the FDA (1997) estimated that there were
250 herbal/botanical firms; the number of firms producing milk thistle products
was not identified

No listing was found for milk thistle or silymarin in the National Occupational
Exposure Survey (NOES), which was conducted by the National Institute for
Occupational Safety and Health (NIOSH) between 1981 and 1983.

Environmental Occurrence: Milk thistle (Silybum marianum), a member of the

Aster family, is a widespread wayside herb of uncultivated ground and
wasteplaces throughout much of Europe. The plant is naturalized in the Eastern
United States, California, and South America (Foster, 1991).

Regulatory Status: Since 1994, dietary supplements have been regulated under
the Dietary Supplement Health and Education Act (DSHEA). For dietary
supplements on the market prior to October 15, 1994, the DSHEA requires no
proof of safety in order for them to remain on the market. The labeling
requirements for supplements allow warnings and dosage recommendations as
well as substantiated "structure or function" claims. All claims must
prominently note that they have not been evaluated by the FDA, and they must
bear the statement "This product is not intended to diagnose, treat, cure, or
prevent any disease" (Croom & Walker, 1995).
EVIDENCE FOR POSSIBLE CARCINOGENIC ACTIVITY

Human Data: No epidemiological studies or case reports investigating the association of

exposure to milk thistle extract and cancer risks in humans were identified in the available
literature.

Adverse effects are rarely found in human studies with milk thistle extracts. A mild laxative
effect has been observed in isolated cases and mild allergic reactions have been reported
(Foster, 1991, Awang, 1993; Brown, 1996).

Numerous studies, mostly German, have examined the effectiveness of silymarin as a

treatment for liver disorders and as an hepatoprotectant.

Ferenci and coworkers (1989) conducted a prospective, double blind, randomized study to
determine whether silymarin improved the prognosis of patients with cirrhosis of the liver.
Eighty-seven patients (46 alcoholic, 41 non-alcoholic) received 140 mg of silymarin orally
three times a day; 83 patients (45 alcoholic, 38 non-alcoholic) received a placebo. The mean
duration of treatment was 41 months. Long-term treatment with silymarin reduced the
mortality of patients with cirrhosis (4-year survival, 58& vs. 39%, P = 0.036). The
beneficial effect of silymarin was more pronounced in alcoholic cirrhosis although the
researchers estimated that 60 percent of the patients with alcoholic cirrhosis continued to
consume appreciable quantities of alcohol during the study. No side effects of drug
treatment were observed.

The hepatoprotective effects of silymarin in workers exposed to organic solvents were

evaluated by Szilard and coworkers (1988). Forty-nine workers who had been exposed to
toluene and/or xylene for 5 to 20 years were selected for the study based on abnormal liver
function tests (increased Aspartate and Alanine-aminotransferase, AST and ALT) and/or
abnormal hematological values (low platelet count, leukocytosis, relative lymphocytosis).
Thirty of these workers were treated with 140 mg of Legalon® (silymarin) orally 3 times a
day for one month. The remaining 19 workers received no treatment. The liver function
tests and platelet counts improved significantly with silymarin treatment. The leukocytosis
and relative lymphocytosis showed a nonsignificant tendency of improvement.

Additional clinical studies reviewed by Foster (1991), Awang (1993), and Brown (1996)
indicate that silymarin and silybin are effective in the treatment of viral hepatitis and
Amanita mushroom poisoning.

Animal Data: The LD50 of orally administered silymarin in mice is > 1600 mg/kg (NLM,
1998).

Animal experiments have been reported to demonstrate the safety of milk thistle seed
extracts with even large doses being virtually free of adverse or embryotoxic effects (Foster,
1991; Awang, 1993).

No 2-year carcinogenicity studies of milk thistle extract were identified in the available
literature. Several protocols have been used to examine the tumor inhibiting-potential of
silymarin.
Mammary gland. Silymarin was tested for prevention of 7, 12-dimethylbenz(a)anthracene
(DMBA)-induced lesions in a Balb mouse mammary gland organ culture assay. Mammary
glands were exposed to 2 mg of DMBA/ml for 24 hours followed by a 5-day exposure to 25
ng/ml of 7,12-tetradecanoylphorbol-13-acetate (TPA); 1 μ M silymarin was added to the
medium for 4 days beginning prior to carcinogen treatment (anti-initiator) or for 15 days
beginning 5 days after carcinogen treatment (antipromoter). Silymarin was an effective
inhibitor when administered during the promotional phase with a lesion incidence of 33
percent vs 80 percent in controls. It was ineffective as an anti-initiating agent (Mehta &
Moon, 1991).

Colon/Small Intestine. Silymarin significantly (P<0.05) inhibited the number of 1,2-

dimethylhydrazine (DMH)-induced colon tumors in male Sprague-Dawley rats. Tumors of
the small intestine were not significantly different. Silymarin was administered at 0.1
percent in the diet for 32 weeks beginning 2 weeks prior to the administration of 20 mg/kg
of DMH by gavage once a week for 15 weeks. The number of animals with colon tumors
was 11/16 in silymarin-treated rats vs. 19/22 in controls. The total numbers of colon
adenocarcinomas were 60 and 132 in the silymarin and controls groups, respectively
(Gershbein, 1994).

Skin. The protective effect of silymarin against photocarcinogenesis was assessed in the
SKH-1 hairless mouse model. Female mice were subjected to the following: UVB-induced
tumor initiation followed by TPA-mediated promotion; DMBA tumor initiation followed by
UVB-mediated tumor promotion; or UVB-induced complete carcinogenesis. Forty mice
were used in each protocol and were divided into control and treatment groups. Silymarin
was applied topically at 9 mg before UVB exposure. In the protocol with UVB-initiation,
silymarin treatment reduced tumor incidence by 20 percent and tumor multiplicity by 67
percent; tumor volume showed a 66 percent reduction. These differences were not
significant. In the protocol with UVB-promotion, silymarin reduced tumor incidence 40
percent (P<0.003) and tumor multiplicity 78 percent (P<0.0001); tumor volume reduction
was 90 percent (P<0.003). The strongest inhibition was seen in the protocol with
UVB-induced complete carcinogenesis. Silymarin reduced tumor incidence 75 percent
(P<0.0001) and tumor multiplicity 92 percent (P<0.0001); tumor volume reduction was 97
percent (P<0.0001). No signs of toxicity, body weight loss, or mortality were observed
following silymarin treatment in all three protocols (Katiyar et al., 1997).

Silymarin was also an effective inhibitor of DMBA-initiated and TPA- or okadaic acid
(OA)-promoted skin tumors in female Sencar mice. Topical application of 6 mg of
silymarin 30 minutes prior to each TPA treatment of DMBA-initiated mouse skin resulted in
almost complete protection in terms of tumor incidence (85%, P<0.0001) as well as
multiplicity (94%, P<0.0001). In the OA-promotion study, application of 6 mg of silymarin
30 minutes prior to OA treatment in DMBA-initiated mouse skin resulted in complete
protection against tumorigenicity (Zi et al., 1997).

Agarwal and coworkers (1996) examined the stage specificity of silymarin against phorbol
ester-type tumor promoters as well as its effect against benzoyl peroxide (BPO), a
nonphorbol ester-type promoter. Application of silymarin prior to that of TPA in stage I or
mezerein in stage II in DMBA-initiated Sencar mouse skin, resulted in highly significant
protection in stage I where silymarin showed 74 percent and 92 percent reductions in tumor
incidence and multiplicity, respectively; the protective effect of silymarin was 26 percent in
the stage II protocol. Application of silymarin prior to BPO in DMBA-initiated mouse skin,
also showed significant protection in terms of both tumor incidence (70%) and multiplicity
(67%).

Short-Term Tests: The effect of silymarin on DNA damage in human cells has been
investigated in the comet assay. When tested at doses up to 1000 &M, silymarin induced
DNA strand breakage in epithelial cells (HeLa). It was negative in colon cells (Caco-2) and
liver cells (HepG2). At doses up to 100 μM silymarin was also negative in human
lymphocytes however, genotoxicity became evident at 1000 &M. Silymarin inhibited cell
growth in HeLa cells at 250 μM; no cytotoxicity was indicated even at the highest doses
tested. Silymarin did not increase the level of damaged pyrimidine bases above the
endogenous level in Hela cells, indicating that it did not induce oxidative damage to DNA
(Duthie et al., 1997).

The comet assay has also been used to assess silymarin-induced DNA damage in human
sperm. At doses of 100-500 μM, silymarin produced a positive response based on a
reduction in percentage sperm head DNA. In combination with the food mutagens 3-amino-
1-methyl-5H-pyrido (4,3-b)indole (Trp) and 2-amino-3-methylimidazo-(4,5-f) quinoline
(IQ), 100-500 μ M silymarin produced a protective response (Anderson et al., 1997).

Metabolism: The biliary excretion of silybin, the main active component of silymarin, was
evaluated in nine cholecystectomy patients with T-tube drainage following single oral doses
of silymarin (120 mg, expressed as silybin equivalents). The bile collected after silymarin
intake contained silybin as well as isosilybin and very low levels of silydianin and
silycristin. The amount of silybin recovered in bile in free and conjugated form within 48
hours accounted for 3 percent of the dose. Recovery of silycristin and silydianin accounted
for 1 percent of the administered dose. Samples for the determination of silybin and other
flavonolignans in plasma were obtained from 3 patients at 0, 1, 3, 5, and 9 hours following
the administration of silymarin. Silybin was detected in 2 of the 1-hour samples at levels of
5 and 20 ng/ml, respectively. The authors noted that with T-tube drainage only a fraction of
the bile is collected and they calculated that the actual biliary excretion of silybin could be
as high as 12 percent of the silymarin dose. This study also examined the pharmacokinetics
of Silipide, a silybin-phosphatidylcholine complex, which was developed to improve the
oral bioavailability of silybin. There is no indication that this product is available in the US
(Schandalik et al., 1992).

Morazzoni and coworkers (1992) compared the bioavailability of silybin and Silipide in
rats. After the administration of 200 mg/kg of silybin by gavage to Sprague-Dawley rats,
the biliary and urinary excretion accounted for 0.001 percent and 0.032 percent of the dose,
respectively. The plasma levels of both the unconjugated and total compound were below
the detection limit. Silipide was shown to have higher bioavailability which was attributed
to increased gastrointestinal absorption.

Other Biological Effects: A number of studies have examined the biochemical mechanisms
of action of silymarin and silybin. Valenzuela and Garrido (1994) have reviewed findings
from different in vivo and in vitro experimental models, such as whole animals, perfused
organs, cell tissue homogenates and isolated nuclei. They note that three levels of action
have been proposed for silymarin in experimental animals: 1) as an antioxidant, by
scavenging prooxidant free radicals and by increasing the intracellular concentration of the
 tripeptide glutathione; 2) regulatory action of the cellular membrane permeability and
increase of its stability against xenobiotic injury; 3) at the nuclear level, by increasing the
synthesis of ribosomal RNA by stimulating DNA polymerase I and by exerting a
steroid-like regulatory action on DNA transcription.

Kim and coworkers (1994) demonstrated that silymarin and silybin are inhibitors of
β-glucuronidases of intestinal bacteria, human feces, and rat microsomal fraction. The
enzyme catalyzes the hydrolysis of β-glucuronides produced in the body, such as
benzo(a)pyrene glucuronides, and of natural plant glucuronides such as glycyrrhizin. The
authors speculated that silymarin and its components reduce the risk factor of colon cancer
and protect the liver by inhibiting the hydrolysis to glucuronides of proximate metabolites.

Letteron and coworkers (1990) conducted a series of in vivo and in vitro studies in order to
determine the mechanisms involved in the protective effects of silymarin against carbon
tetrachloride (CCl4)-induced hepatotoxicity. They concluded that silymarin prevents CCl

4
-induced lipid peroxidation and hepatotoxicity in mice, firstly, by decreasing the metabolic
activation of CCl4 and secondly, by acting as a chain-breaking antioxidant.

In studies of the inhibition of mouse skin tumor promoters, silymarin was shown to
significantly inhibit TPA-caused induction of ornithine decarboxylase (ODC) activity and
mRNA expression in mouse epidermis. Topical application of silymarin on mouse skin prior
to that of TPA or OA also resulted in highly significant to complete inhibition against both
TPA- and OA-caused induction of tumor necrosis factor α (TNFα) mRNA expression.
TNFα one of the inflammatory cytokines, has been shown to act as an endogenous tumor
promoter and a central mediator of tumor promotion (Agarwal et al., 1994; Zi et al., 1997).

Structure Activity Relationships: Milk thistle consists of a complex mixture of natural

products which does not lend itself to traditional structure activity analysis.

References

Agarwal R., Lahiri, M., Mohan, R.R. & Mukhtar, H. (1996) Anti-tumor promoting potential of silymarin
against both phorbol and nonphorbol ester type tumor promoter-caused promotion in Sencar mouse skin.
J. Invest. Dermatol., 106(4), 856

Agarwal, R., Katiyar, S.K., Lundgren, D.W. & Mukhtar, H. (1994) Inhibitory effect of silymarin, an
anti-hepatotoxic flavonoid, on 12-O-tetradecanoylphorbol-13-acetate-induced epidermal ornithine
decarboxylase activity and mRNA in Sencar mice. Carcinogenesis, 15(6), 1099-1103

Aldrich Chemical Co., Inc. (1996) Aldrich Catalog/Handbook of Fine Chemicals 1996-1997.
Milwaukee, WI, p. 1323

Anderson, D., Basaran, N., Dobrzynska, M.M., Basaran, A.A. & Yu, T.W. (1997) Modulating effects of
flavonoids on food mutagens in human blood and sperm samples in the comet assay. Teratog. Carcinog,
Mutagen., 17, 45-58

Awang, D. (1993) Milk thistle. Can. Pharm. J., 126 (Oct.), 403-404, 422
Boigk, G., Stroedter, L. Herbst, H., Waldschmidt, J., Riecken, E.O. & Schuppan, D. (1997) Silymarin
retards collagen accumulation in early and advanced biliary fibrosis secondary to complete bile duct
obliteration in rats. Hepatology, 26(3), 643-649

Brown, D.J. (1996) Phytotherapy: Herbal medicine meets clinical science. NARD J., 118 (May), 41- 52

Budavari, S., ed. (1996) The Merck Index, 12th ed., Whitehouse Station, NJ, Merck & Co., Inc., p. 1464

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1998 [Accession Nos. 0726854, 07329185, 07561021, 06996441]

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Duthie, S.J., Johnson, W. Dobson, V.L. (1997) The effect of dietary flavonoids on DNA damage (strand
breaks of oxidised pyrimdines (sic)) and growth in human cells. Mutat. Res., 390(1-2), 141- 151

FDA (1997) Food Labeling; Statement of Identity, Nutrition Labeling and Ingredient Labeling of
Dietary Supplements; Compliance Policy Guide, Revocation. Fed. Regist., 62(184), 49825-49858

Ferenci, P., Dragosics, B., Dittrich, H., Frank, H., Benda, L., Lochs, H., Meryn, S., Base, W. &
Schneider, B. (1989) Randomized controlled trial of silymarin treatment in patients with cirrhosis of the
liver. J. Hepatol., 9(1), 105-113

Foster, S. (1991) Milk thistle, Silybum marianum. Botanical Series No. 305, Austin, TX, American
Botanical Council, pp. 3-7

Gershbein, L.L. (1994) Action of dietary trypsin, pressed coffee oil, silymarin and iron salt on
1,2-dimethylhydrazine tumorigenesis by gavage. Anticancer Res., 14(3A), 1113-1116

Global Nutrients (1997) Milk Thistle Extract (Silymarin 150 mg 80%). [http://www.nutrients.com/
new-products/025200.html]

Grauds, C. (1996) Milk thistle: A potential life-saver. Pharm. Times, 62(Mar.), 95

Herbal Resources, Inc. (1995a) Alternate Medicine Health Product: Sil-150. [http://www.
herbsinfo.com/pages/psil-150.htm]

Herbal Resources, Inc. (1995b) Dandelion-Milk Thistle Compound. [http:www.herbsinfo.com/pages/

dande.htm]

Ikram, M., Ahmad, N. & Bibi, R. (1984) Silybum marianum for Silymarin and Edible Oil. Peshawar,
Pakistan, Pakistan Council of Scientific & Industrial Research Laboratories, pp. 3-8

Katiyar, S.K., Korman, N.J., Mukhtar, H. & Agarwal, R. (1997) Protective effects of silymarin against
photocarcinogenesis in a mouse skin model. J. Natl. Cancer Inst., 89(8), 556-566

Kim, D.H., Jin, Y.H., Park, J.B. & Kobashi, K. (1994) Silymarin and its components are inhibitors of
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