Recent Advances in Palm Tocotrienol Research: Bioavailability and Health Benefits Revisited Paul W. Sylvester, Ph.D. Pfizer Endowed Professor of Pharmacology, College of Pharmacy, University of Louisiana at Monroe
Anticancer Effects of Dietary Palm Oil Intake in Rats Sylvester, P.W., Russell, M., Ip, M.M., and Ip, C. Cancer Research, 43:763-769, 1986. High dietary intake of palm oil suppressed carcinogen-induced mammary tumorigenesis in female rats.
What is so special about palm oil?
Antitumor Activity of Palm Oil Naturally contains very high levels of vitamin E, particularly tocotrienols
What are Tocotrienols? Members of the Vitamin E Family of Compounds
Tocotrienols & Tocopherols HO R 2 6 R 1 4 3 8 CH 3 O 1 1' CH 3 CH 3 CH 3 4' 8' 12' CH3 R 1 4 HO 3 6 CH 3 CH 3 CH 3 R 2 8 O 4' 8' 12' CH 3 CH 1 1' 3 R 1 R 2 α-tocotrienol CH 3 CH 3 γ-tocotrienol H CH 3 β-tocotrienol CH 3 H δ-tocotreinol H H R 1 R 2 α-tocopherol CH 3 CH 3 γ-tocopherol H CH 3 β-tocopherol CH 3 H δ-tocopherol H H Tocotrienols are more potent vs tocopherols
Concentration of Vitamin E in Various Oils and Fats Total Total Total Dietary Oil Tocopherol Tocotrienol Vitamin E (mg/l) (mg/l) (mg/l) Palm 152 738 890 Coconut 11 25 36 Coco Butter 198 2 200 Corn 800 0 802 Cottonseed 776 0 776 Peanut 367 0 367 Olive 51 0 51 Safflower 801 0 807 Soybean 958 0 958 Sunflower 546 0 546 Lard 19 7 26
Tocotrienol-Rich-Fraction (TRF) of Palm Oil α-tocopherol 20.2% α-tocotrienol 16.8% γ-tocotrienol 44.9% δ-tocotrienol 14.8%
Antitumor Activity of Palm Oil Removal of tocotrienols from palm oil results in loss of antitumor/protective activity. Subsequent cell culture studies comparing Individual isoforms of vitamin E demonstrated that tocotrienols display potent anticancer activity, but tocopherols do not. Use of isolated tocotrienols in animal tumor studies have produced inconsistent results.
Intestinal Absorption of Tocotrienols In order for lipids and fat-soluble vitamins to be absorbed in the GI tract, they must first be emulsified by bile and packaged into micelles for transport into the circulation. Bile excretion is dependent on the level and type of fat consumed. Tocotrienol absorption is significantly reduced in fasted versus full-fed individuals.
Bioavailability of Tocotrienols α-tocopherol >50% α-tocotrienol 27.7% δ- tocotrienol 8.5% γ-tocotrienol 9.1% Journal pharmacy and pharmacology 2003 55:53-58
Factors Limiting Intestinal Absorption and Bioavailability Intestinal and hepatic degradation. Passive and transporter-dependent absorption.
Oral Absorption of Tocotrienols (Intestinal and Hepatic Metabolism)
Passive Intestinal Absorption
Transporter-Dependent Absorption
Transporter-Dependent Absorption Displays Saturability
Limits of Intestinal Absorption and Bioavailability Intestinal permeability and transporter activity, as well as intestinal and hepatic metabolism are major contributors to the low bioavailability of tocotrienols following oral administration.
Bioavailability of Tocotrienols α-tocopherol >50% α-tocotrienol 27.7% δ- tocotrienol 8.5% γ-tocotrienol 9.1% Journal pharmacy and pharmacology 2003 55:53-58
In situ perfusion model One of the most reliable models to study the intestinal permeability and metabolism of drugs is the single pass intestinal perfusion model in rats (In situ model)
Intestinal Absorption of γ-tocotrienol
Peff x 10-5 (cm/s) Permeability of γ-t3 as a Function of Drug Concentration 40 35 30 25 20 15 10 5 0 P<0.05 * 0 25 50 75 100 125 150 P γ-t3 Concentration (µm) eff = Q C 2πrL *ln C If the permeability is a function of passive diffusion t 0 Abuasal.etal. DMD 2010 (in press)
Summary Intestinal uptake of γ-tocotrienol is inversely proportional to the concentration of γ-tocotrienol present in the intestinal lumen. This findings indicate that γ-tocotrienol absorption in the intestine is carrier-mediated and that this transporter becomes saturated and apparently undergoes down-regulation after exposure to high doses of γ-tocotrienol.
Intestinal Absorption of γ-tocotrienol
Conclusions The efficiency of intestinal absorption of γ-t3 is concentration dependent. Absorption at low concentrations is predominantly carrier mediated. However, at higher concentrations the carrier displays saturation and down regulation and passive diffusion, which is minimal, is the predominant mechanism of absorption. γ-t3 intestinal metabolism is minimal and is not a primary reason for low bioavailability.
Tocotrienol Bioavailability It is clearly evident that oral administration of tocotrienol displays limited bioavailability. Tocotrienol filled capsules that are presently commercially available as oral supplements do not circumvent the limits in intestinal absorption and hence, relatively low levels of tocotrienol reach the blood using this type of oral delivery system.
How do we bypass the natural limits of γ-tocotrienol intestinal absorption in order to increase bioavailability?
Novel Delivery Systems to Increase Tocotrienol Bioavailability Microemulsions (oral delivery) Nanoparticles (injectable delivery)
Effects of TRF Filled Microemulsions vs Free TRF on Mammary Tumor Cell Viability Percent Viability 100 Free TRF CET COMP 80 60 40 20 0 1 2 3 4 5 6 7 TRF Concentration in Media (µm) Ali, Shirode, Sylvester and Nazzal. Colloids and Surfaces 353:43-51, 2009
Tumor Growth Following Treatment with Tocotrienol Filled Vesicles Administered i.v. Relative tumor growth 30 20 10 Controls Vesicles Free TRF Nontargeted TRF Vesicles Targeted TRF Vesicles 0 0 5 10 15 20 25 30 3 Days End of treatment Fu, Baltchford, Tetley, Dufes. J Control Release 140:95-99, 2009
Conclusion Microemulsion formulations greatly display greatly enhanced intestinal absorption following oral administration and a greater therapeutic response and suggest reduce dose requirement for tocotrienol therapy. Injectable nanoparticles completely bypass intestinal limitations on bioavailability and targeting allows large concentrations of tocotrienol to be
Prodrug Derivatives of Tocotrienols α-tocopherol exhibits greater bioavailability than tocotrienols because of transfer proteins and transports mechanism that display selective preference for α-tocopherol. Prodrug and polar forms of tocotrienols can be synthesized that are water soluble, and are absorbed passively and bypass transporter mechanism
Redox-Silent Semisynthetic Tocotrienol Derivatives R 2 O R 3 5 R 1 4 O 2 8 1' 5' 9' HO O 3'' 5'' O OH HO O 2'' 1'' 3'' 6'' O OH 1'' 2'' O a O b 1'' O 6'' O O O O 3'' 1'' 3'' 5'' 1'' OH 3'' 4'' OH 7'' c d e O 1'' 3'' OAc O 1'' 3'' 8'' 7'' AcO f OAc 5'' OAc g OAc
Relative Antiproliferative Potency of Tocotrienol Derivatives Against Malignant Mammary Tumor Cells Cells per Well (1X10-5 ) 3 2 1 +SA Cells 4 5 6 7 8 0 0.0 1.0 2.0 Treatment Concentration (µm)
Relative Antiproliferative Potency of Tocotrienol Derivatives Against Normal Mammary Epithelial Cells Cells per Well (1X10-5 ) 6 4 2 CL-S1 Cells 4 5 6 7 8 0 0.0 1.0 2.0 Treatment Concentration (µm)
Passive Intestinal Absorption
Results and Conclusions Novel Prodrug tocotrienol derivatives are highly soluble in aqueous solutions and bypass the natural limits of tocotrienol absorption, transport and metabolic breakdown. These redox-silent tocotrienol analogues also display significantly greater bioavailability, as well as, more potent anticancer activity.
In Summary Although cell culture studies clearly demonstrate the anticancer potency of tocotrienol, these results have been difficult to repeat in animal studies. However, greater understanding to tocotrienol kinetics has lead to the development of prodrug derivatives and novel delivery systems that optimize bioavailability and therapeutic response.
Acknowledgements Collaborators Karen P. Briski Barry S. McIntyre Abdul Gapor Sumit Shah Ganesh Samant Vikram Wali Sunitha Bachawal Amit Shirode Nehad Ayoub Support Mohamed Akl National Cancer Institute at NIH Malaysian Palm Oil Board Carotech Malaysian Palm Oil Council First Tech International Ltd.
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