Ascorbigen: chemistry, occurrence, and biologic properties

Clinics in Dermatology (2009) 27, 217–224 

Ascorbigen: chemistry, occurrence, and biologic properties 

Anika E. Wagner, PhD, Gerald Rimbach, PhD ⁎ 

Institute of Human Nutrition and Food Science, Christian-Albrechts-University, D-24118 Kiel, Germany 

Abstract Ascorbigen (ABG) belongs to the glucosinolate family and occurs mainly in Brassica 

vegetables. It is formed by its precursor glucobrassicin. Glucobrassicin is enzymatically hydrolyzed to 

indole-3-carbinol, which in turn reacts with L-ascorbic acid to ABG. The degradation of glucobrassicin 

is induced by plant tissue disruption. The ABG formation depends on pH and temperature. The 

degradation of ABG in acidic medium causes a release of L-ascorbic acid and a formation of 

methylideneindolenine; in more alkaline medium, the degradation of ABG causes the formation of 1- 

deoxy-1-(3-indolyl)-α-L-sorbopyranose and 1-deoxy-1-(3-indolyl)-α-L-tagatopyranose. ABG may 

partly mediate the known anticarcinogenic effect of diets rich in Brassicacae. Furthermore, ABG is 

able to induce phase I and II enzymes that are centrally involved in the detoxification of xenobiotics. 

Cosmeceuticals containing ABG as an active principle are becoming increasingly popular, although the 

underlying cellular and molecular mechanisms regarding its potential antiaging and ultravioletprotective 

properties have not been fully established. 

© 2009 Elsevier Inc. All rights reserved. 

Introduction 

Epidemiologic studies revealed an inverse relationship 

between Brassica vegetable intake and the development of 

cancer. 1-4 All kinds of cabbages, brussels sprout, broccoli, 

cauliflower, kohlrabi, turnip, and suede belong to the family 

of Cruciferae and are botanically known as Brassicaceae. 

Their anticarcinogenic effect is probably due to their high 

amounts of glucosinolates. 5 One of the most commonly 

studied glucosinolate is glucobrassicin (GB). 6 This compound 

is a precursor of indole-3-carbinol (I3C) and 

ascorbigen (ABG), which are both considered to be potent 

anticarcinogens of the glucosinolate family. The present 

⁎ Corresponding author. Institute of Human Nutrition and Food Science, 

Christian Albrechts University, Olshausenstrasse 40, D-24118 Kiel, 

Germany. 

E-mail address: rimbach@foodsci.uni-kiel.de (G. Rimbach). 

review summarizes the current literature regarding the 

chemistry, occurrence, and biologic activity of ABG. 

Chemistry 

Structure 

Glucosinolates consist of a β-thioglucopyranoside group 

and a side chain that is attached to the carbon atom number 0 

in the (Z)-N-hydroximine-O-sulfonate group. 7 In all identified 

glucosinolates, this structure has been found and 

validated by chemical, x-ray, crystallographic, and nuclear 

magnetic resonance measurements. 7 Structural variations are 

caused by differences in the R group and by acylsubstituents 

on the thioglucose group. 7 Shortly after the discovery of the 

chemical structure of vitamin C by Svirbely and Szent- 

Györgyi 8 in 1932, different research groups found a 

0738-081X/$ – see front matter © 2009 Elsevier Inc. All rights reserved. 

doi:10.1016/j.clindermatol.2008.01.012

218 A.E. Wagner, G. Rimbach 

AA in a molar ratio of 1:1. The pH values of Brassica 

vegetables ranged between 5.0 and 6.5; lower pH conditions 

were tested because of ABG formation during culinary and 

industrial processing of vegetables. Obviously, ABG formation 

was strongly dependent on the pH in the medium: In a 

medium with a pH of 3, 54% of the theoretic amount of ABG 

Fig. 1 

Chemical properties of ABG and AA. 

compound called “bound L-ascorbic acid (AA)” in cabbage 

leaves that liberates L-AA after heating. 9-12 In 1957 

Prochazka and coworkers 13 isolated ABG, the “bound 

AA,” whose structure was elucidated by Kiss and Neukom 14 

in 1966. Initially it was supposed that ABG possessed 

properties similar to those of vitamin C, as a precursor. 

However, in studies with humans and guinea pigs, there was 

no evidence of vitamin C activity in ABG. In guinea pigs, 

ABG did not reduce scorbutic symptoms per se, indicating 

that guinea pigs are not able to hydrolyze ABG to AA in the 

gastrointestinal tract. 15,16 ABG cannot be metabolized by the 

mentioned species and represents a “storage” form of vitamin 

C. The chemical properties of both compounds are listed 

in Figure 1. 

ABG is not present in intact plant tissues. Its formation takes 

two consecutive steps. The first reaction is the enzymatic 

hydrolysis of GB, and the second step is a spontaneous reaction 

of the emerging intermediate (I3C) with AA. The breakdown 

of GB is induced by plant tissue disruption (eg, culinary 

procedures) and catalyzed by the enzyme myrosinase. 17 This 

enzymatic degradation of GB is a fast process 18 depending on 

the myrosinase activity (Figure 2). The product formation is 

regulated by the hydrolysis conditions, including pH 19 and the 

presence of metal ions. 20 I3C is the major product at neutral 

pH, 21 whereas in acidic conditions 3-indolyl-acetonitrile is 

the main compound formed. 22 In the presence of AA, 3- 

indolyl-acetonitrile and I3C form ABG. 23,24 

Biosynthesis 

ABG and I3C are unstable compounds that can be 

transformed into different products. There are numerous 

studies focusing on the transformation of I3C in an acidic 

environment and the identification of new breakdown 

compounds. 17 The major identified compounds are 3,3′- 

diindolylmethane, 2-(3-indolylmethyl)-3,3′-diindolylmethane, 

and 5,11-dihydroindolo[3,2-b]arbazole (ICZ). 25-27 

Hrncirik et al 17 investigated the formation of ABG at 

25°C in buffers of different pH values containing I3C and 

Fig. 2 Mechanism of ABG formation through myrosinasemediated 

hydrolysis of GB. The first step of the reaction is the 

enzymatic hydrolysis by myrosinase of GB, and the second step is 

the spontaneous reaction of the emerging intermediate (I3C) with 

AA. (Modified with the permission of Hrncirik K, Valusek J, 

Velisek J. Investigation of ascorbigen as a breakdown product of 

glucobrassicin autolysis in Brassica vegetables. Eur Food Res 

Technol 2001;212:576-81.)


was reached in 5 minutes. At pH 4, 82% was achieved after 

15 minutes, and pH 5 resulted in 89% of the theoretic amount 

of ABG. The corresponding reaction scheme is presented in 

Figure 2. In solutions with a pH of 3, the main products 

found were ABG, ABG-dimer (2′-skatylascorbigen), and 

ABG-trimer ((2′-{2′′-(skatyl-3′′′)skatyl}ascorbigen), reaching 

13% and 11%, respectively. Similar results were obtained 

at conditions of pH 4, whereas at a pH of 5 only the ABG 

dimer was detected. No ABG polymers were found in 

solutions of pH 6 and 7. In contrast with the results found by 

Kiss and Neukom, 14 who detected the highest amounts of 

ABG at pH 4.0, Hrncirik and coworkers found the maximum 

levels between pH 4.5 and 5.0 after 60 minutes. 

Degradation 

During the degradation of ABG in an acidic medium, AA 

is released and methylideneindolenine is formed. The 3- 

indolylmethyl moiety binds to another molecule of ABG to 

form ABG-dimer, ABG-trimer, 28 and 5,11-dihydroindolo 

[3,2-b]carbazole. 29 Preobrazhenskaya et al 30 demonstrated a 

transformation of ABG in mild alkaline media into indolederived 

carbohydrates 1-deoxy-1-(3-indolyl)-α-L-sorbopyranose 

and 1-deoxy-1-(3-indolyl)-α-L-tagatopyranose resulting 

from the opening of the lactone ring and decarboxylation. 

Recent investigations by Reznikova et al 31 in bovine blood 

serum and mouse liver homogenates revealed that these 1- 

deoxy-1-(indol-3-yl)-ketoses are the main products of ABG 

transformation in vivo. 

The stability of ABG significantly depends on the pH 

value and temperature. Thermal treatment for vegetable 

processing increases the degradation of ABG. During the 

first 2 hours in solutions of pH 3 to 6 at 25°C, ABG is 

relatively stable with a loss of only 3% to 5%. A pH value of 

7 caused a decomposition of ABG of approximately 25%. 

The storage at 25°C for 10 hours resulted in a 12% to 20% 

degradation of ABG at pH 3 to 6 and in a degradation of 75% 

at a pH of 7. In solutions of pH 4 the highest stability of ABG 

was observed, whereas at more alkaline conditions ABG was 

dramatically decreased. Heating at 80°C for 20 minutes 

resulted in a loss of 54%, 39%, 56%, 95%, and 100% of 

ABG at pH values of pH 3, 4, 5, 6, and 7, respectively. 

219 

broccoli, whereas the lowest amounts of AA (110 mg/kg) 

were found in Chinese cabbage. The AA amounts in white 

cabbage and cauliflower ranged in between. The GB 

amounts ranged between 25 mg/kg for Chinese cabbage 

and 142 mg/kg for cauliflower. In the next step they 

analyzed the concentration of ABG in aqueous vegetable 

homogenates in 2-hour intervals. The concentrations of 

ABG in homogenized vegetables increased during the 

incubation at room temperature (RT), reached the maximum 

after 4 to 6 hours of incubation, and finally 

decreased slowly (Figure 3). Highest amounts were 

obtained in homogenized white cabbage with 16 mg/kg 

after 2 hours of incubation at RT. The lowest amounts of 

ABG were found in Chinese cabbage (5.3 mg/kg; 2 hours 

at RT), whereas the amounts in broccoli (6.8 mg/kg; 

2 hours at RT) and cauliflower (13 mg/kg; 2 hours at RT) 

were in between. The absolute value of white cabbage in 

the study of Hrncirik and coworkers 32 was lower than the 

levels found by Aleksandrova et al, 28 which ranged from 

31 to 55 mg/kg in fresh chopped cabbage. The different 

levels of ABG found by both studies could be caused by 

different initial levels of GB in the cabbage used. As 

already pointed out, the pH value of the solution is a 

critical point for the formation and stability of ABG. 17 For 

ABG formation, the initial GB levels in vegetables are an 

important factor 32 in why the amount of ABG can 

significantly vary between different species. The yield of 

ABG depends on small differences in natural pH values of 

the vegetable homogenates. Chinese cabbage homogenates 

exhibited the lowest pH value, thus transforming approximately 

50% of GB into ABG, whereas only 20% of GB in 

Content of ascorbigen in different 

Brassica vegetables 

Hrncirik and coworkers 32 established a high-performance 

liquid chromatography method to measure the ABG 

concentrations of different members of the Brassica genus. 

White Cabbage, Chinese cabbage, broccoli, and cauliflower 

were first analyzed regarding their content of AA and GB. 

The highest amounts of AA (840 mg/kg) were found in 

Fig. 3 ABG concentrations in different homogenized Brassica 

vegetables after increasing incubation times; in homogenized 

Brassica vegetables, the ABG content depends on the incubation 

period at room temperature. (Modified with the permission of 

Hrncirik K, Valusek J, Velisek J. Investigation of ascorbigen as a 

breakdown product of glucobrassicin autolysis in Brassica 

vegetables. Eur Food Res Technol 2001;212:576-81.)


cauliflower is converted. Ciska and Pathak 33 investigated 

fermented cabbage on its concentration of glucosinolates. 

With concentrations of 43 mg/kg, ABG represented the most 

prominent compound of glucosinolates in fermented cabbage. 

During the storage of up to 17 weeks, the amount of 

ABG remained stable. Therefore, fermented cabbage seems 

to be a good source of ABG, especially during the winter 

period when the availability of fresh vegetables is lower. 

Another benefit of fermented cabbage is the stability of ABG 

for a long period of time. 

Cellular effects of ascorbigen 

Anticarcinogenic effects of ascorbigen 

There are a few studies focusing on the anticarcinogenic 

effect of ABG (Table 1). Studies by Sepkovic et 

al 34 on catechol estrogen production in rat microsomes 

revealed an anticarcinogenic effect of ABG, I3C, and the 

cytochrome P450 1A1 inducer β-naphthaflavone. 16-αhydroxyestrone 

(16α-OHE 1 ) is a genotoxic compound that 

can be formed from estrogen. The protective effect of I3C, 

ABG, and β-naphthaflavone is probably due to a decrease 

of the estrogen pool, thereby reducing the possibility to 

generate 16α-OHE 1 (Figure 4). The study by Sepkovic and 

coworkers showed an increase of 2-hydroxylation of 

estradiol in the microsomes of Sprague-Dawley rats after 

dietary I3C intake. A pretreatment of microsomal incubates 

from rats with ABG and β-naphthoflavone demonstrated an 

increase of estradiol 2-hydroxylation. The ability of ABG 

and I3C to induce the C-2 hydroxylation of estradiol and 

therefore to decrease the circulating levels of 16α-OHE 1 

may be the potential mechanism by which compounds 

reduce the risk of developing mammary tumors. 34 

These results indicate that I3C itself is not able to induce 

phase 1 enzymes that are responsible for the increasing 

estradiol 2-hydroxylation. Bradfield and Bjeldanes 21 

observed that I3C must be first activated by a low pH 

environment, as in the stomach, to form 3,3′-diindolylmethane, 

ICZ, and various other compounds that are able to 

activate the cytochrome P450 monooxygenase, mediating 

the activation of phase 1 enzymes. 

Stephenson et al 35 investigated the mechanism of the in 

vitro modulation of CYP1A1 activity by ABG. CYP1A1 is 

an enzyme involved in xenobiotic metabolism. In a mouse 

hepatoma cell line, Hepa 1c1c7, the authors observed an 

induction of CYP1A1 activity by ABG in a concentrationdependent 

manner. In addition, the authors found an 

increased activity of 7-ethoxyresorufin O-deethylase that is 

caused by an ABG-arranged induction of CYP1A1 protein. 

By conducting chloramphenicol acetyl transferase (CAT)- 

reporter gene experiments, it became apparent that ABG 

induced aryl hydrocarbon (Ah) receptor-driven CAT activity. 

The activation of the Ah receptor is a well-known 

mechanism for the induction of CYP1A1 protein and 

enzyme activity. Although Gillner et al 36 detected a 

decreased binding affinity of ABG to the Ah receptor, 

Stephenson and coworkers noticed that ABG is transformed 

into a more potent ligand and CYP1A1 inducer, such as ICZ. 

Another study, conducted by Kravchenko et al, 37 focused 

on the effects of indoles on the activity of xenobiotic 

metabolizing enzymes. The authors fed two groups of rats, 

one with the basal control diet and one with an indoleenriched 

diet, containing I3C, ABG, and sulforaphane (SUL) 

from broccoli. Eight days before the study was terminated, 

half of the animals of each group received 0.8 mg/kg T-2 

Table 1 

Studies regarding the anticarcinogenic activity of ascorbigen in rat microsomes, cultured cells, and laboratory rats 

Organism Ascorbigen (concentration) Finding Reference 

Rat microsomes 7 mmol/L Increases C2-hydroxylation of estradiol 34 

to 2-hydroxyestrone, thereby decreasing 

the circulating levels of 16á-hydroxyestrone 

Hepa1c1c7 (mouse hepatoma cell line) 1–1000 μmol/L CYP1A1 activity increased dose-dependently; 48 

EROD activity is inhibited 

LS-174 cells 700 μmol/L The detoxification enzymes CYP1A1, 5 

Caco-2 cells 

Human colon epithelial cells 

SV40-transformed Indian muntjac cells 688 μmol/L 

AKR1C1, and NQO1 were induced 

ABG did not cause any chromosome 38 

aberrations or sister chromatid exchanges 

Male Wistar rats 

Indole-enriched diet containing 

indole-3-carbinol, ABG, and SUL 

(final concentration 0.1% indoles) 

Increase of xenobiotic enzymes 

(cytochrome P450, benz(o)apyrene 

hydroxylase, epoxide hydrolase, 

carboxylesterase, pNP-UDP-glucuronosyl 

transferase, HBP-UDP-glucuronosyl 

transferase, and glutathione-S-transferase) 

37 

ABG, ascorbigen; AKR1C1, aldo-keto-reductase 1C1; EROD, 7-ethoxyresorufin-O-deethylase; HBP-UDP, 4-hydroxy-biphenyl-uridindiphosphate; pNP- 

UDP, p-nitrophenyl-uridindiphosphate; SUL, sulforaphane.


221 

Fig. 4 ABG increases the C2-hydroxylation of estradiol to 2-hydroxyestrone, thereby decreasing the circulating levels of 

16á-hydroxyestrone. 

toxin, a trichothecene mycotoxin, whereas the control 

animals received an equal volume of solvent (0.1% aqueous 

solution of ethanol). The 3-week indole-enriched diet 

application did not have a significant influence on animal 

growth, relative weight of internal organs, enzyme activity in 

liver lysosomes, and morphology of internal organs and 

tissues. The activity of the xenobiotic metabolizing enzymes 

increased during the consumption of an indole-enriched diet. 

T-2 treatment of rats fed the basal diet without ABG or SUL 

caused signs of toxicity: The body weight decreased, the liver 

weight increased significantly, and the xenobiotic metabolizing 

enzymes showed a decreased activity. Morphologic 

changes were also apparent in response to the T-2 treatment. 

However, the symptoms of T-2 toxicity decreased when the 

animals were treated with T-2 and fed an indole-enriched diet. 

No changes in body weight of the animals were then 

detectable. Only 11% of the rats exhibited an increased liver 

weight, and macroscopic changes were obvious in only 50% 

of the animals. Compared with T-2–treated rats receiving the 

basal diet, the xenobiotic metabolizing enzyme activities 

were 1.5 to 2.0-fold higher in ABG-treated animals. 

Recent studies by Bonnesen et al 5 focus on the 

mechanism by which glucosinolate hydrolysis products 

prevent colon cancer. The authors investigated different 

adenocarcinoma cell lines, including LS-174, Caco-2, and 

the human colon epithelial cell on the toxicity of indoles 

and isothiocyanates. There was no hint of toxicity of ABG 

and I3C on LS-174, Caco-2, and human colon epithelial cell 

lines; the IC 50 values were more than 500 μmol/L. 3,3′′- 

diindolylmethane and indole [3,2-b] carbazole (ICZ) were 

more toxic in human colon cells compared with ABG or 

I3C. All three cell lines tolerated the aliphatic isothiocyanate 

SUL better than the aromatic isothiocyanates benzyl 

isothiocyanate and phenethyl isothiocyanate. All phytochemicals 

examined induced apoptosis in transformed LS- 

174 and Caco-2 cell lines, but none of the test components 

stimulated apoptosis in untransformed hman colon epithelial 

cells. Furthermore, Bonnesen and coworkers 5 demonstrated 

that the detoxication enzyme activity of the analyzed cell 

lines could be enhanced by 3,3′-diindolylmethane, ABG, 

I3C, ICZ, SUL, benzyl isothiocyanate, and phenethyl 

isothiocyanate. In another experiment, the authors studied 

the drug-metabolizing enzyme CYP1A1 in colon cells; 

indoles and isothiocyanates induced this enzyme. In CATreporter 

gene assays, it was shown that the induction of 

gene expression by dietary indoles and isothiocyanates is 

mediated through different molecular mechanisms. Indoles 

induce the xenobiotic response element-driven CAT activity, 

whereas the isothiocyanates induce the antioxidant response 

element-driven CAT activity. Bonnesen et al 5 investigated 

the protection of DNA damage by the application of 

phytochemicals (1 μmol/L ICZ or 5 μmol/L SUL): LS-174 

cells were treated with benz(a)pyrene or H 2 O 2 for the 

induction of DNA damage. The amount of DNA damage 

was measured by the Comet assay. After pretreatment with 

ICZ and SUL, the colon cells were significantly protected 

from DNA single-strand breaks compared with the nonsupplemented 

cells.


Clastogenic and mutagenic properties 

of ascorbigen 

In SV40-transformed Indian muntjac cells, ABG and 

Me-ABG were tested for potential clastogenic activities. 

The mutagenic activity was determined by the Ames test 

with Salmonella typhimurium strains TA-98 and TA-100. 

For ABG there was no induction of either chromosome 

aberrations or sister chromatid exchanges at any concentrations 

tested, or an induction of mutations in the abovementioned 

Salmonella strains. Furthermore, no effect on the 

clonal survival of SV40-transformed Indian muntjac cells at 

concentrations less than 688 μmol/L was detected. 38 

However, Me-ABG was more cytotoxic and induced sister 

chromatid exchanges and mutations in the Ames test, but 

no chromosome aberrations were observed. 38 Studies 

conducted by Musk and coworkers 39 investigated the 

breakdown products of ABG on their genotoxic properties. 

ABG-dimer and Me-ABG-dimer, the products formed in 

acidic solutions, did not show any genotoxicity, whereas 

ISPP and Me-ISP that are formed in alkaline media tested 

positive at levels greater than 0.125 μg/mL. These findings 

should be taken into consideration when using ABG as a 

dietary compound. Figure 5 summarizes the different 

properties of ABG. 

Skin protective properties of ascorbigen 

Cosmeceuticals containing ABG as an active principle are 

becoming increasingly popular, although the mode of action 

regarding its potential ultraviolet (UV)-protective and 

antiaging properties has not been established. 

It is possible that ABG mediates some of its biologic 

activity in the skin as the result of AA, its precursor GB, or 

I3C. Furthermore, ABG may affect signal transduction 

pathways similar to SUL. Similar to AA, ABG may 

promote collagen synthesis, photoprotection from UVA 

and UVB light, and an improvement of a variety of 

inflammatory dermatoses. 40 UV radiation is the main factor 

responsible for most nonmelanoma skin cancers. Dinkova- 

Kostova et al 41 supplemented HaCaT human or PE murine 

keratinocytes with SUL and observed a dose-dependent 

induction of intracellular nicotinamide adenine dinucleotide 

phosphateQO1 and glutathione levels. The topical application 

of SUL in the form of broccoli sprouts extracts elevated 

NQO1 activity in mouse skin. In another experiment, 

Dinkova-Kostova and coworkers 41 exposed SKH-1 hairless 

mice to relatively low doses of UVB radiation (30 mJ/cm 2 ) 

twice per week for 20 weeks; this resulted in “high-risk 

mice” that subsequently developed skin cancer in the 

absence of further UV treatment. 42 This animal model is 

able to represent humans who have been heavily exposed to 

the sun in their childhood but have limited their exposure as 

adults. The treatment was terminated after 11 weeks; 100% 

of the animals in the control group developed tumors, 

whereas 48% of the animals obtaining 1 μmol SUL in the 

form of sprout extract did not generate cancer. Similarly, the 

tumor multiplicity was reduced by 58% in the group treated 

with 1 μmol SUL. 

It is known that UV light induces activator protein 

(AP)-1 involved in skin carcinogenesis. Zhu et al 43 treated 

HCL14 cells (human keratinocytes) that were stably 

transfected with an AP-1-luciferase reporter gene with 

SUL or tert-butylhydroquinone. The authors found an 

increase of quinone reductase, a marker of global cellular 

Fig. 5 

Potential molecular mechanisms by which ABG mediates anticarcinogenic activities.


phase II enzymes, and cellular glutathione levels. In 

electrophoretic mobility shift assays, a direct application 

of SUL inhibited the AP-1 DNA binding, whereas tertbutylhydroquinone 

was ineffective. The elevated phase II 

enzymes and glutathione levels in human keratinocytes are 

not able to inhibit the activation of AP-1 through UVB. 

One mechanism of how SUL exhibits its inhibitory effect 

on UVB-induced AP-1 activation is the direct inhibition of 

AP-1-DNA-binding. 

The nuclear factor E2-related factor 2 (Nrf2) is a 

transcription factor involved in the regulation of many 

detoxifying antioxidant enzymes in response to oxidative 

or electrophilic stress. 44 Xu and coworkers' 45 study on 

Nrf2(+/+)- and Nrf2(-/-)-mice showed that the Nrf(-/-) 

mice were more vulnerable to skin tumorigenesis. The 

treatment of Nrf(+/+)- and Nrf (-/-) mice with SUL caused 

a significant inhibition of skin tumorigenesis in Nrf(+/+) 

mice but not in Nrf(-/-) mice. In addition, when 100 nmol 

SUL was topically applied to the Nrf2(+/+) mice once per 

day for 14 days, a robust increase of Nrf2 protein levels 

was detected. These results indicate that the chemopreventive 

effect of SUL is at least in part mediated by Nrf2. 

ABG may have effects similar to those of SUL on skin. 

This should be investigated in future studies. 

A study conducted by Srivastava and Shukla 46 showed 

that topical I3C treatment, the precursor of ABG, inhibited 

the tetradecanoylphorbol-13-acetate promotion of 7,12- 

dimethylbenz[a]anthracene–initiated mouse skin tumors. 

Cope and coworkers 47 irradiated Crl:SKH1:hr-BR hairless 

mice and fed them a control diet, a chlorophyllin (a cancer 

chemopreventative), or a I3C diet. Although the chlorophyllin 

group did not show a significant effect, the I3C group 

showed a significantly reduced overall tumor multiplicity. In 

addition, the different diets did not show any effect on the 

UV-induced dorsal skin swelling response at doses of 0.75 

and 1 kJ UVB. Doses of 1.5 kJ UVB in the chlorophyllin diet 

significantly decreased the dorsal skin swelling responses of 

the mice, whereas the I3C and control diets had no effect. 

Cope and coworkers 47 observed that dietary supplementation 

with I3C exerted significant protection from photocarcinogenesis 

related to overall tumor multiplicity but not from 

squamous cell carcinoma. 

Conclusions 

ABG is the major product of the GB degradation pathway. 

It is formed in two consecutive steps: 1) GB is hydrolyzed by 

the enzyme myrosinase, and 2) a spontaneous reaction of the 

emerging intermediate I3C with AA forms ABG. ABG 

induced phase 1 enzymes via the Ah receptor and caused 

apoptosis in transformed colon cancer cell lines. Another 

study revealed an increase of C-2-hydroxylation of estradiol, 

thereby causing a decrease of the circulating levels of 16α- 

OHE 1 ; this could be one reason for the observed anticarcinogenic 

effects of ABG. In rats fed an indole-enriched 

diet (containing I3C, ABG, and SUL), an induction of 

xenobiotic metabolizing enzymes, including cytochrome 

P450, glutathione-S-transferase, and uridindiphosphate-glucuronosyl 

transferase, was found. Systematic investigations 

regarding the potential photoprotective and antiaging properties 

of ABG in cultured cells and in vivo are warranted. 

Furthermore, human studies are necessary to obtain robust 

data regarding the bioavailability and metabolism of ABG. 

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Ascorbigen: chemistry, occurrence, and biologic properties

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