Abstract
PurposeThe purpose of this study is to use a molecular docking approach to identify potential estrogen mimics or anti-estrogens in phytochemicals found in popular dietary herbal supplements.MethodsIn this study, 568 phytochemicals found in 17 of the most popular herbal supplements sold in the United States were built and docked with two isoforms of the estrogen receptor, ERα and ERβ (a total of 27 different protein crystal structures).ResultsThe docking results revealed six strongly docking compounds in Echinacea, three from milk thistle (Silybum marianum), three from Gingko biloba, one from Sambucus nigra, none from maca (Lepidium meyenii), five from chaste tree (Vitex agnus-castus), two from fenugreek (Trigonella foenum-graecum), and two from Rhodiola rosea. Notably, of the most popular herbal supplements for women, there were numerous compounds that docked strongly with the estrogen receptor: Licorice (Glycyrrhiza glabra) had a total of 26 compounds strongly docking to the estrogen receptor, 15 with wild yam (Dioscorea villosa), 11 from black cohosh (Actaea racemosa), eight from muira puama (Ptychopetalum olacoides or P. uncinatum), eight from red clover (Trifolium pratense), three from damiana (Turnera aphrodisiaca or T. diffusa), and three from dong quai (Angelica sinensis). Of possible concern were the compounds from men’s herbal supplements that exhibited strong docking to the estrogen receptor: Gingko biloba had three compounds, gotu kola (Centella asiatica) had two, muira puama (Ptychopetalum olacoides or P. uncinatum) had eight, and Tribulus terrestris had six compounds.ConclusionsThis molecular docking study has revealed that almost all popular herbal supplements contain phytochemical components that may bind to the human estrogen receptor and exhibit selective estrogen receptor modulation. As such, these herbal supplements may cause unwanted side effects related to estrogenic activity.
Highlights
The use of alternative medicines in the United States, herbal supplements, has dramatically increased since the beginning of the 21st century (Figure 1)
The United States does not classify herbal supplements as drugs, and supplements are not required to undergo the extensive testing that pharmaceutical drugs do before put on the market
Molecular docking Protein-ligand docking studies were carried out based on the crystal structures of human estrogen receptor α [Estrogen receptor α (ERα): Protein data bank (PDB) 1X7E (Manas et al 2004a), PDB 1X7R (Manas et al 2004b), and PDB 3ERD (Shiau et al 1998)] and human estrogen receptor β [Estrogen receptor β (ERβ): PDB 1U3Q, 1U3R, 1U3S (Malamas et al 2004), 1U9E, 1X7B, 1X76, 1X78 (Manas et al 2004a), and 1X7J (Manas et al 2004b)]
Summary
The use of alternative medicines in the United States, herbal supplements, has dramatically increased since the beginning of the 21st century (Figure 1). The United States does not classify herbal supplements as drugs, and supplements are not required to undergo the extensive testing that pharmaceutical drugs do before put on the market. Courtesy of the “Dietary Supplement Health and Education Act of 1994”, herbal supplements are not evaluated by the Food and Drug Administration (Calixto 2000) making it easy for supplement companies to rapidly introduce new supplements to consumers, with or without the knowledge of possible harmful side effects. Unspecified drugs, contaminations, toxins, and/or heavy metals (Au et al 2000) can be included in an herbal supplement, and since companies are not Powers and Setzer In Silico Pharmacology (2015) 3:4
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