We were gratified by the interest expressed in publishing a large number of presentations from the NIDA organized Workshop on “Natureceuticals (Natural Products), Nutraceuticals, Herbal Botanicals, Psychoactives: Drug Discovery and Drug-Drug Interactions”. The number of manuscripts received necessitated two volumes of proceedings. In this brief summary of the second volume, we present an introduction to the roles of organizations such as National Center for Complementary and Alternate Medicine and Office of Dietary Supplements, both at the National Institutes of Health, and the Food and Drug Administration. These agencies are involved in research and regulation of dietary supplements and related products. Next, a brief summary of each of the fifteen articles is provided. The first four articles are related to regulatory and standardization aspects: issues related to botanicals (Khan); USP and dietary supplements (Srinivasan); dietary supplement reference materials (Sander et al.); and proposed cGMPs and the scientific basis behind the proposed regulations by FDA (Melethil). The next three articles relate to the methodologies employed in research: LC/MS for the pharmacokinetic analysis polyphenols from dietary supplements (Barnes et al.); proteomic analysis of grape seed extract (Kim et al.); and a nematode model, C. elegans, in Alzheimer’s and ginkgo biloba extract for mechanistic studies; another model, a hepatocyte tissue culture model for drug herbal interaction, is reviewed later and presented by Venkataramanan. The next four chapters are on specific dietary supplements: green tea and the polyphenolic catechins (Zaveri); curcumin (Maheswari et al.); tocotrienols (alpha-tocotrienol, Sen and Roy), gamma-tocotrienol (Sree Kumar et al.). This topic is followed by drug interaction studies: in vitro and in vivo assessment methodologies (Venkataramanan); flavonoid-drug interactions (Morris); MDR and CYP3A4-mediated drug-herb interaction (Pal and Mitra); and evidence-based examination of drug-herb interaction (Chavez and Chavez).
In nature, eight substances have been found to have vitamin E activity: alpha-, beta-, gamma- and delta-tocopherol; and alpha-, beta-, gamma- and delta-tocotrienol. Yet, of all papers on vitamin E listed in PubMed less than 1% relate to tocotrienols. The abundance of alpha-tocopherol in the human body and the comparable efficiency of all vitamin E molecules as antioxidants, led biologists to neglect the non-tocopherol vitamin E molecules as topics for basic and clinical research. Recent developments warrant a serious reconsideration of this conventional wisdom. Tocotrienols possess powerful neuroprotective, anti-cancer and cholesterol lowering properties that are often not exhibited by tocopherols. Current developments in vitamin E research clearly indicate that members of the vitamin E family are not redundant with respect to their biological functions. alpha-Tocotrienol, gamma-tocopherol, and delta-tocotrienol have emerged as vitamin E molecules with functions in health and disease that are clearly distinct from that of alpha-tocopherol. At nanomolar concentration, alpha-tocotrienol, not alpha-tocopherol, prevents neurodegeneration. On a concentration basis, this finding represents the most potent of all biological functions exhibited by any natural vitamin E molecule. An expanding body of evidence support that members of the vitamin E family are functionally unique. In recognition of this fact, title claims in manuscripts should be limited to the specific form of vitamin E studied. For example, evidence for toxicity of a specific form of tocopherol in excess may not be used to conclude that high-dosage “vitamin E” supplementation may increase all-cause mortality. Such conclusion incorrectly implies that tocotrienols are toxic as well under conditions where tocotrienols were not even considered. The current state of knowledge warrants strategic investment into the lesser known forms of vitamin E. This will enable prudent selection of the appropriate vitamin E molecule for studies addressing a specific need.
Gamma-tocotrienol (GT) is a member of the vitamin E family. Our preliminary studies indicated that it protected mice from lethal irradiation, so we hypothesized that GT might be a radiation sensitizing agent for tumors. To test this, we induced prostate tumors by injecting PC3 cells into nude BALB/c mice. When the tumors were about 5 mm in diameter, mice were injected subcutaneously with 400 mg/kg gamma-tocotrienol and irradiated 24 h later at the site of the tumor with a dose of 12 Gy (60)Cobalt. Tumor size was monitored for 24 days after radiation. Tumor tissues as well as normal tissues like rectum, kidney, and liver were monitored for lipid peroxidation on day 4 and day 24 after radiation. The results indicated that the size of the tumors was reduced by almost 40%, but only in GT-treated and irradiated mice. In unstimulated and Fe-stimulated lipid peroxidation groups, lipid peroxidation in the tumors from irradiated mice increased to 135% and 150%, respectively, four days after irradiation and 33% and 66% in the same groups, respectively, 24 days after irradiation. In general, lipid peroxidation in the rectum did not increase in GT-treated and irradiated mice, although there was a slight increase in Fe-stimulated lipid peroxidation (29%) four days after irradiation. Unexpectedly, the kidneys were as equally sensitized to lipid peroxidation as the tumors. Liver tissue was protected in the short-term from radiation-induced lipid peroxidation. These studies indicate that the radiotherapy efficacy of prostate cancer can be increased with GT and a pro-oxidant if the kidneys can be shielded.