Beta-Carotene

β-Carotene
IUPAC name	β,β-carotene
Other names	β-Carotene, all-trans- (8CI); (all-E)-1,1'-(3,7,12,16-Tetramethyl-1,3,5,7,9,11,13,15,17-octadecanonaene-1,18-diyl)bis[2,6,6-trimethylcyclohexene]; BetaVit; Betacarotene; C.I. 40800; C.I. Food Orange 5; Carotaben; Carotene Base 80S; CoroCare; Cyclohexene, 1,1'-(3,7,12,16-tetramethyl-1,3,5,7,9,11,13,15,17-octadecanonaene-1,18-diyl)bis[2,6,6-trimethyl-, (all-E)-; Food Orange 5; KPMK; Lucaratin; Lucarotin; Lucarotin 10CWD/O; Lucarotin 30SUN; Lurotin; NSC 62794; Provatene; Provatenol; Rovimix β-carotene; Serlabo; Solatene; all-E-β-Carotene; all-trans-β-Carotene; β-Carotene[1]
Identifiers
CAS number	7235-40-7 Y
PubChem	5280489
SMILES	CC=2CCCC(C)(C)C=2/C=CC(\C)=C\C=C\C(\C)=C\C=C\C=C(/C)\C=C\C=C(/C)\C=C\C1=C(C)CCCC1(C)C
Properties
Molecular formula	C40H56
Molar mass	536.87 g mol−1
Appearance	red-purple solid
Density	0.941 ± 0.06 g/cm3
Melting point	180-182 °C
Boiling point	654.7±22.0 °C (Press: 760 Torr)[1]
Solubility in water	Insoluble in cold water or hot water. Soluble in diethyl ether, acetone, benzene, chloroform, carbon disulfide. Moderately soluble in petroleium ether, oils.Very slightly soluble in methanol. Soluble in fat solvents
Hazards
Flash point	103 °C/218 °F [2]
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

β-Carotene is an organic compound - a terpenoid, a red-orange pigment abundant in plants and fruits. As a carotene with beta-rings at both ends, it is the most common form of carotene. It is a precursor (inactive form) of vitamin A.^[3] Being highly conjugated, it is deeply colored, and as a hydrocarbon lacking functional groups, it is very lipophilic.

The structure was deduced by Karrer et al.^[4] In nature, β-carotene is a precursor to vitamin A via the action of beta-carotene 15,15'-monooxygenase. β-Carotene is also the substance in carrots that colours them orange. β-Carotene is biosynthesized from geranylgeranyl pyrophosphate.^[3] Isolation of beta-carotene from carotenoids abundant fruits is commonly done, using colume chromatography. The separation of beta-carotene from the mixture of carotenoids is based on the polarity of a compound. Beta-carotene is a non-polar compound, so it is separated with a non-polar solvent such as hexane.^[5] Being highly conjugated, it is deeply colored, and as a hydrocarbon lacking functional groups, it is very lipophilic.

Pro-vitamin A activity

Plant carotenoids are the primary dietary source of pro-vitamin A worldwide, with β-carotene as the most well-known pro-vitamin A carotenoid. Others inlcude α-carotene and β-cryptoxanthin. Carotenoids are absorbed into the small intestine by passive diffusion. One molecule of β-carotene can be cleaved by a specific intestinal enzyme into two molecules of vitamin A.

Absorption efficiency is estimated to be between 9-22%. The absorption and conversion of carotenoids may depend on the form that the β-carotene is in (cooked vs. raw vegetables, in a supplement), intake of fats and oils at the same time, and the current levels of vitamin A and β-carotene.

Researchers list the following factors that determine the pro-vitamin A activity of carotenoids: ^[6]

• Species of carotenoid
• Molecular linkage
• Amount in the meal
• Matrix properties
• Effectors
• Nutrient status
• Genetics
• Host specificity
• Interactions between factors

Symmetric/Asymmetric Cleavage

The chain between two toluene rings either symmetrically or asymmetrically cleave. Symmetric cleavage is done by an enzyme called beta-carotene-15,15'-dioxygenase in human body. The symmetric cleavage gives two equivalent retinal and each retinal further reacts to give retinol(aka, vitamin A) and retinoic acid. Beta-carotene is also asymmetrically cleaved into two asymmetric products. The products of asymmetric cleavage is beta-apocarotenal(8',10',12'). Asymmetric cleavage reduces the level of retinoic acid significantly.^[7]

Conversion factors

Until recently, vitamin A activity in foods was expressed as international units (IU). This is still the measurement generally used on food and supplement labels. However, it is difficult to calculate the total vitamin A activity in the diet in terms of IU, because both the absorption and conversion of carotenoids, as compared with retinol, are variable. The unit retinol equivalent (RE) was developed by the Food and Agriculture Organization of the United Nations/World Health Organization (FAO/WHO) in 1967^[8]. More recently in 2001, the US Institute of Medicine proposed retinol activity equivalents (RAE) for their Dietary Reference Intakes^[9].

International Units

1 RE = 3.33 IU vitamin A activity from retinol

1 RE = 10 IU vitamin A activity from β-carotene

Retinol Equivalents (REs)

1 RE = 1 µg retinol

1 RE = 6 µg β-carotene

1 RE = 12 µg other provitamin A carotenoids

Retinol Activity Equivalents (RAEs)

1 RAE = 1 µg retinol

1 RAE = 2 µg all-trans-β-carotene as a supplement

1 RAE = 12 µg of all-trans-β-carotene in a food matrix

1 RAE = 24 µg other provitamin A carotenes in a food matrix

Sources in the diet

β-Carotene contributes to the orange color of many different fruits and vegetables. Vietnamese gac (Momordica Cochinchinensis Spreng.) and crude palm oil are particularly rich sources, as are yellow and orange fruits, such as mangoes and papayas, orange root vegetables such as carrots and yams and in green leafy vegetables such as spinach, kale, sweet potato leaves, and sweet gourd leaves. Vietnam gac and crude palm oil have by far the highest content of β-carotene of any known fruit or vegetable, 10 times higher than carrots for example. However, Gac is quite rare and unknown outside its native region of SE Asia, and crude palm oil is typically processed to remove the cartenoids before sale to improve the color and clarity.

The average daily intake of β-carotene is in the range 2-7 mg, as estimated from a pooled analysis of 500,000 women living in the USA, Canada and some European countries. ^[10]

The U.S. Department of Agriculture lists the following 10 foods to have the highest β-carotene content per serving.^[11]

Side effects

The most common side effect of excessive β-carotene consumption is carotenodermia, a harmless condition that presents as a conspicuous orange skin tint arising from deposition of the carotenoid in the outermost layer of the epidermis^[12]. Chronic, high doses of β-carotene supplements have been associated with increased rate of lung cancer among those who smoke.^[13] Additionally, supplemental beta-carotene may increase the risk of prostate cancer, intracerebral hemorrhage, and cardiovascular and total mortality in people who smoke cigarettes or have a history of high-level exposure to asbestos. Beta-carotene from foods does not seem to have this effect.^[14]

Beta-carotene and Lung cancer among those who smoke

Cigarette smoke increases the asymmetric cleavage of beta-carotene, decreasing the level of retinoic acid significantly. When retinoic acid is liganded to RAR-beta(Retinoic Acid Receptor), the complex acts as AP1(activator protein 1) binding site. AP1 is a protein which turns on cell proliferation when binds to its binding site on DNA. Therefore, the presence of retinoic acid prevents AP1 from binding to its binding site on DNA. AP1 is no longer expressed, and cell proliferation does not occur. However, no lung damage has been detected in those who are exposed to cigarette smoke and physiologic dose beta-carotene(6mg) in contrast to pharmacologic dose (30mg). Therefore, the oncology from beta-carotene is based on both cigarette smoke and daily doses of beta-carotene.^[15]

See also

• Vitamin A
• Lycopene
• Lutein
• Zeaxanthin

References

1. ^ ^{a b} {{cite webpage | title = SciFinder - CAS Registry Number 7235-40-7 | author = Unknown | accessed year = 2009 | accessed month/day = 10/21 | url = https://scifinder-cas-org.proxy.library.nd.edu:9443/scifinder/view/substance/substanceDetail.jsf?nav=rO0ABXQAAWF0ACRDQkI3ODNFOS04NkYzLTUwQjAtNzhCOS1BMkVFMjY2ODQ4QzF0AAFic3IAEWphdmEubGFuZy5JbnRlZ2VyEuKgpPeBhzgCAAFJAAV2YWx1ZXhyABBqYXZhLmxhbmcuTnVtYmVyhqyVHQuU4IsCAAB4cAAAAAN0AAFvc3EAfgADAAAAAXQAAnJ2c3IAEWphdmEubGFuZy5Cb29sZWFuzSBygNWc-u4CAAFaAAV2YWx1ZXhwAHQAAnNzc3IAK29yZy5jYXMub3NjYXIuc2VydmVyLmRvbWFpbi5jb21tb24uU29ydFNwZWM8kKugHZfgygIAAkwADG15T3JkaW5hbEtleXQAKExvcmcvY2FzL29zY2FyL3NlcnZlci9kb21haW4vY29tbW9uL0tleTtMAAdteVNvcnRzdAAZTGphdmEvdXRpbC9MaW5rZWRIYXNoU2V0O3hwcHNyABdqYXZhLnV0aWwuTGlua2VkSGFzaFNldNhs11qV3SoeAgAAeHIAEWphdmEudXRpbC5IYXNoU2V0ukSFlZa4tzQDAAB4cHcMAAAAED9AAAAAAAAAeA
2. ^ {{cite webpage | title = 22040 β-Carotene BioChemika, purum, ≥97.0% (UV) | author = Unknown | accessed year = 2009 | accessed month/day = 10/21 | url = http://www.sigmaaldrich.com/catalog/ProductDetail.do?lang=en&N4=22040|FLUKA&N5=SEARCH_CONCAT_PNO|BRAND_KEY&F=SPEC
3. ^ ^{a b} Susan D. Van Arnum (1998). Vitamin A in Kirk-Othmer Encyclopedia of Chemical Technology. New York: John Wiley. pp. 99–107. doi:10.1002/0471238961.2209200101181421.a01. 
4. ^ P. Karrer, A. Helfenstein, H. Wehrli, A. Wettstein (1930). "Pflanzenfarbstoffe XXV. Über die Konstitution des Lycopins und Carotins". Helvetica Chimica Acta 13: 1084–1099. doi:10.1002/hlca.19300130532. 
5. ^ Mercadante, A.Z., Steck, A., Pfander, H. (1999). "Carotenoids from Guava (Psidium guajava L.): Isolation and Structure Elucidation". J. Agric. Food Chem. 47: 145-151. 
6. ^ Tanumihardjo, SA (2002). "Factors influencing the conversion of carotenoids to retinol: bioavailability to bioconversion to bioefficacy". Int J Vit Nutr Res 72 (1): 40-5. PMID 11887751. 
7. ^ Kiefer, C.,Hessel, S.,Lampert, S.M.,Vogt, K.,Lederer, M.O.,Breithaupt, D.E.,von Lintig, J. (2001). "Identification and Characterization of a Mammalian Enzyme Catalyzing the Asymmetric Oxidative Cleavage of Provitamin A". The Journal Of Biological Chemistry 276 (17): 14110–14116. 
8. ^ Food and Agriculture Organization/World Health Organization (1967). Requirement of Vitamin A, Thiamine, Riboflavin and Niacin.. FAO Food and Nutrition Series B. Rome. 
9. ^ Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. Washington, DC: National Academy Press. 2001. 
10. ^ Koushik, A.; Hunter DJ, Spiegelman D, Anderson KE, Buring JE, Freudenheim JL, Goldbohm RA, Hankinson SE, Larsson SC, Leitzmann M, Marshall JR, McCullough ML, Miller AB, Rodriguez C, Rohan TE, Ross JA, Schatzkin A, Schouten LJ, Willett WC, Wolk A, Zhang SM, Smith-Warner SA. (2006). "Intake of the major carotenoids and the risk of epithelial ovarian cancer in a pooled analysis of 10 cohort studies.". Int J Cancer 119 (9): 2148-54. PMID 16823847. 
11. ^ "USDA National Nutrient Database for Standard Reference, Release 21". http://www.ars.usda.gov/Services/docs.htm?docid=17477. Retrieved 2009-07-24. 
12. ^ Stahl W, Heinrich U, Jungmann H, et al. (1998). "Increased Dermal Carotenoid Levels Assessed by Noninvasive Reflection Spectrophotometry Correlate with Serum Levels in Women Ingesting Betatene". Journal of Nutrition 128 (5): 903-7. PMID 9567001. 
13. ^ Tanvetyanon T, Bepler G (July 2008). "Beta-carotene in multivitamins and the possible risk of lung cancer among smokers versus former smokers: a meta-analysis and evaluation of national brands". Cancer 113 (1): 150–7. doi:10.1002/cncr.23527. PMID 18429004. 
14. ^ http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-betacarotene.html#Safety
15. ^ Russel, R.M. (2002). "Beta-carotene and lung cancer". Pure Appl. Chem. 74 (8): 1461–1467. 

External links

• A11CA02
• USDA Webpage on β-carotene Content of Gac - Fatty Acids and Carotenoids in Gac (Momordica Cochinchinensis Spreng) Fruit.