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Prostate Cancer, Nutrition, and Dietary Supplements (PDQ®)

  • Last Modified: 10/10/2014

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Other Prostate Health Supplements

Overview
African Cherry/P. africanum
Beta-Sitosterol



Overview

Many widely available dietary supplements are marketed to support prostate health. African cherry (Pygeum africanum) and beta-sitosterol are two related supplements that have been studied as potential prostate cancer treatments.

African Cherry/P. africanum

P. africanum is a tree from the Rosaceae family that grows in tropical zones. It is found in a number of African countries including Kenya, Madagascar, Uganda, and Nigeria. Bark from the P. africanum tree was used by African tribes to treat urinary symptoms and gastric pain.[1] In the 18th century, European travelers learned from South African tribes that P. africanum was used to treat bladder discomfort and “old man’s disease” (enlarged prostate).

Since 1969, bark extracts from P. africanum have been available as prescription drugs in Europe and have been widely used to treat benign prostatic hyperplasia.[2,3] The bark contains a number of compounds including saturated and unsaturated fatty acids, phytosterols (e.g., beta-sitosterol), pentacyclic triterpenoids (e.g., oleanolic acid), alcohols, and carbohydrates. The extract is obtained by macerating and solubilizing the bark in an organic solvent. The extract is then purified from the solvent.[1]

Two components of P. africanum bark extracts, atraric acid and N-butylbenzene-sulfonamide, are androgen receptor inhibitors, as indicated by both in vitro [4-6] and animal in vivo [7] studies. This activity is produced by each of these components at concentrations that are significantly lower than the clinically achieved concentration of the antiandrogen flutamide.[8]

Beta-Sitosterol

Beta-sitosterol is a phytochemical found at various concentrations in plants such as P. africanum, saw palmetto, and some legumes. Specifically, it is a type of phytosterol (or plant sterol) and has a similar structure to cholesterol. Phytosterols, including beta-sitosterol, reduce absorption of dietary cholesterol and their potential to protect against cardiovascular disease is under investigation. Mean plasma beta-sitosterol concentration in a small group of healthy male volunteers in Vienna, Austria, was 2.83 μg /mL (approximately 7 μM).[9] Interestingly, however, a rare condition caused by mutations in the adenosine triphosphate -binding cassette (ABC) transporter ABCG5 or ABCG8 genes results in an inherited sterol storage disease with markedly increased serum concentrations of plant sterols such as sitosterol and leads to premature atherosclerosis and large xanthomas.[10]

Research has also suggested that phytosterols may have anticarcinogenic properties, but the exact mechanisms are unknown.[11] Phytosterols may exert antitumor effects by acting on immune and hormonal systems, or by directly targeting cell cycles and inducing apoptosis in tumor cells.[12]

Beta-sitosterol at concentrations around 16 mM has been shown to significantly inhibit growth of PC-3 prostate cancer cells and induce apoptosis.[13,14] Associated with these effects are decreasing levels of cell cycle regulators p21 and p27 in the cancer cells and an increased production of reactive oxygen species.

References
  1. Brackman FG, Edgar A, Coates PM: Pygeum. In: Coates PM, Betz JM, Blackman MR, et al., eds.: Encyclopedia of Dietary Supplements. 2nd ed. New York, NY: Informa Healthcare, 2010, pp 650-5. 

  2. Ishani A, MacDonald R, Nelson D, et al.: Pygeum africanum for the treatment of patients with benign prostatic hyperplasia: a systematic review and quantitative meta-analysis. Am J Med 109 (8): 654-64, 2000.  [PUBMED Abstract]

  3. Levin RM, Das AK: A scientific basis for the therapeutic effects of Pygeum africanum and Serenoa repens. Urol Res 28 (3): 201-9, 2000.  [PUBMED Abstract]

  4. Papaioannou M, Schleich S, Prade I, et al.: The natural compound atraric acid is an antagonist of the human androgen receptor inhibiting cellular invasiveness and prostate cancer cell growth. J Cell Mol Med 13 (8B): 2210-23, 2009.  [PUBMED Abstract]

  5. Papaioannou M, Schleich S, Roell D, et al.: NBBS isolated from Pygeum africanum bark exhibits androgen antagonistic activity, inhibits AR nuclear translocation and prostate cancer cell growth. Invest New Drugs 28 (6): 729-43, 2010.  [PUBMED Abstract]

  6. Schleich S, Papaioannou M, Baniahmad A, et al.: Extracts from Pygeum africanum and other ethnobotanical species with antiandrogenic activity. Planta Med 72 (9): 807-13, 2006.  [PUBMED Abstract]

  7. Shenouda NS, Sakla MS, Newton LG, et al.: Phytosterol Pygeum africanum regulates prostate cancer in vitro and in vivo. Endocrine 31 (1): 72-81, 2007.  [PUBMED Abstract]

  8. Handratta VD, Vasaitis TS, Njar VC, et al.: Novel C-17-heteroaryl steroidal CYP17 inhibitors/antiandrogens: synthesis, in vitro biological activity, pharmacokinetics, and antitumor activity in the LAPC4 human prostate cancer xenograft model. J Med Chem 48 (8): 2972-84, 2005.  [PUBMED Abstract]

  9. Duchateau G, Cochrane B, Windebank S, et al.: Absolute oral bioavailability and metabolic turnover of β-sitosterol in healthy subjects. Drug Metab Dispos 40 (10): 2026-30, 2012.  [PUBMED Abstract]

  10. Tsubakio-Yamamoto K, Nishida M, Nakagawa-Toyama Y, et al.: Current therapy for patients with sitosterolemia--effect of ezetimibe on plant sterol metabolism. J Atheroscler Thromb 17 (9): 891-900, 2010.  [PUBMED Abstract]

  11. Awad AB, Fink CS: Phytosterols as anticancer dietary components: evidence and mechanism of action. J Nutr 130 (9): 2127-30, 2000.  [PUBMED Abstract]

  12. Bradford PG, Awad AB: Phytosterols as anticancer compounds. Mol Nutr Food Res 51 (2): 161-70, 2007.  [PUBMED Abstract]

  13. Awad AB, Burr AT, Fink CS: Effect of resveratrol and beta-sitosterol in combination on reactive oxygen species and prostaglandin release by PC-3 cells. Prostaglandins Leukot Essent Fatty Acids 72 (3): 219-26, 2005.  [PUBMED Abstract]

  14. Scholtysek C, Krukiewicz AA, Alonso JL, et al.: Characterizing components of the Saw Palmetto Berry Extract (SPBE) on prostate cancer cell growth and traction. Biochem Biophys Res Commun 379 (3): 795-8, 2009.  [PUBMED Abstract]