Modified citrus pectin refers to citrus pectin which has been hydrolyzed to yield smaller molecular weight molecules which appears to render it more absorbable. Unmodified citrus pectin is not absorbable. Pectin (see Pectin) is a soluble fiber that is found in citrus fruits (oranges, lemons, grapefruits) and apples. Pectin obtained from orange or lemon rinds, both rich sources of pectin, is referred to as citrus pectin. Citrus pectin is a linear polysaccharide containing from about 300 to 1,000 monosaccharide units. D-galacturonic acid, an acid form of the sugar D-galactose, is the principal monosaccharide unit of citrus pectin. The D-galacturonic acid residues are bonded together by alpha-1,4 glycosidic linkages in linear chains. Neutral sugars, present in side chains on the pectin molecule, include D-galactose, L-arabinose, D-xylose and L-frucose. L-Rhamnose is also found in pectin. Some of the galacturonic acid residues in pectin are in the form of methyl esters. The molecular weight of citrus pectin ranges from 20,000 to 400,000 daltons, with the majority of the molecules having molecular weights ranging from 50,000 to 150,000 daltons.
Modified citrus pectin is formed from citrus pectin via a depolymerization process in which citrus pectin is first treated with sodium hydroxide at a pH of 10 for a short time, and then hydrochloric acid at a pH of 3 for a much longer period of time. The pectin fragments that are formed are principally comprised of D-polygalacturonates, absent the methoxyl groups. The molecular weight of modified citrus pectin ranges from 1,000 to 15,000 daltons, with an average weight of about 10,000 daltons. Modified citrus pectin is comprised of linear polygalacturonate chains containing from 5 to 90 galacturonic acid residues, with an average of approximately 55 residues. Also present, are D-galactose residues in side chains. Modified citrus pectin is also known as modified pectin, depolymerized pectin and pH-modified pectin. It is abbreviated as MCP. It is water soluble.
Actions & Pharmacology
Modified citrus pectin has putative anticarcinogenic activity.
Mechanism of Action
Modified citrus pectin, when administered orally to rats, was found to inhibit spontaneous prostate carcinoma metastasis. It had no effect on the growth of the primary tumor. Injected modified citrus pectin was found to inhibit metastasis of melanoma cells in mice. The mechanism of these anticarcinogenic effects is not clear.
Galectins comprise a family of galactoside-binding mammalian lectins. Lectins themselves comprise a group of hemagglutinating proteins found in plant seeds, which bind the branching carbohydrate molecules of glycoproteins and glycolipids on cell surfaces, resulting in agglutination or proliferation, among other things. Galectins are proteins that can bind to carbohydrates via carbohydrate recognition domains (CRDs). At present, the galactin family includes 10 members. Apparently, galectins are secreted from cells via nonclassical secretory pathways. Galectin-3, one of the members of the family, is thought to be involved in mitosis and proliferation. On the cell surface, galectin-3 mediates cell-cell adhesion and cell-matrix interaction via binding to its complementary glycoconjugates, such as laminin and fibronectin, and thereby is thought to play an important role in the pathogenesis of cancer metastasis.
Some metastic events may involve cellular interactions that are mediated by cell surface components, including galectins. The galactose-containing carbohydrate side chains of modified citrus pectin may interfere with these cellular interactions by competing with the natural ligands of the galectins and by doing so, inhibit the metastatic process. It is thought that galectins may play a role in human prostate cancer, and in particular, human prostate cancer metastasis.
There is little on the pharmacokinetics of modified citrus pectin in humans. Based on rat studies, modified citrus pectin is probably absorbed to some degree following ingestion. However, research is necessary to determine its absorption efficiency, as well as its distribution, metabolism and excretion.
Indications & Usage
Modified citrus pectin has shown some ability to inhibit metastasis of prostate cancer in a rat study. It has also shown some activity against melanoma cells in culture and in mice. More research is needed before there can be any indication for the use of modified citrus pectin in cancer.
Modified citrus pectin is available as a dietary supplement both as a powder and in capsule form. Dosage is variable. See precautions regarding its use.
LiteratureGopalkrishnan RV, Roberts T, Tuli S, et al. Molecular characterization of prostate carcinoma tumor antigen-1, PCTA-1, a human galectin-8 related gene. Oncogene. 2000; 19:4405-4416.Hsieh TC, Wu JM. Changes in cell growth, cyclin/kinase, endogenous phosphoproteins and nm23 gene expression in human prostatic JCA-1 cells treated with modified citrus pectin. Biochem Mol Biol Int. 1995; 37:833-841.Inohara H, Raz A. Effects of natural complex carbohydrate (citrus pectin) on murine melanoma cell properties related to galectin-3 functions. Glycoconj J. 1994; 11:527-532.Pienta KJ, Naik H, Akhtar A, et al. Inhibition of spontaneous metastasis in a rat prostate cancer model by oral administration of modified citrus pectin. J Natl Cancer Inst. 1995; 87:348-353.Platt D, Raz A. Modulation of the lung colonization of B16-F1 melanoma cells by citrus pectin. J Natl Cancer Inst. 1992; 84:438-442.Rabinovich GA, Riera CM, Landa CA, Sotomayor CE. Galectins: a key intersection between glycobiology and immunology. Braz J Med Biol Res. 1999; 32:383-393.Raz A, Pienta KJ. Method for treatment of cancer by oral administration of modified citrus pectin. United States Patent Number 5,895,784. Date of Patent: Apr. 20, 1999.
Research & Summary
There was the suggestion in one in vitro study of modified citrus pectin that it might have some ability to inhibit melanoma metastasis. Stronger, but still preliminary evidence emerged from a rat study that modified citrus pectin might similarly inhibit the spread of prostate cancer. The lungs of rats treated with this substance had significantly fewer metastatic colonies than controls. There was no effect on the primary tumor. Follow-up is needed.
Contraindications, Precautions & Adverse Reactions
Modified citrus pectin is contraindicated in those hypersensitive to any component of a modified citrus pectin-containing product.
The use of modified citrus pectin for the management of prostate cancer or any type of cancer is considered experimental. Those who wish to use modified citrus pectin for the management of prostate cancer or any type of cancer must be under medical supervision.
Modified citrus pectin should be avoided by pregnant women and nursing mothers.