Invited Review ArticleEffects of Selected Bioactive Natural Products on the Vascular EndotheliumAhmad, Ajaz PhD*; Khan, Rao M. A. PhD*; Alkharfy, Khalid M. PharmD, PhD*,† Author Information *Department of Clinical Pharmacy, College of Pharmacy; and †Biomarkers Research Program, King Saud University, Riyadh, Saudi Arabia. Reprints: Khalid M. Alkharfy, PharmD, PhD, Department of Clinical Pharmacy, College of Pharmacy, King Saud University, PO Box 2457, Riyadh 11451, Saudi Arabia (e-mail: [email protected]). The authors report no conflicts of interest. Supported by a grant from Distinguished Professor Fellowship Program, King Saud University, Riyadh, Saudi Arabia. Received November 16, 2012 Accepted March 13, 2013 Journal of Cardiovascular Pharmacology: August 2013 - Volume 62 - Issue 2 - p 111-121 doi: 10.1097/FJC.0b013e3182927e47 Buy Metrics Abstract The endothelium, a highly active structure, regulates vascular homeostasis through the release of numerous vasoactive factors that control vascular tone and vascular smooth cell proliferation. A larger number of medicinal plants and their isolated chemical constituents have been shown to beneficially affect the endothelium. For example, flavonoids in black tea, green tea, and concord grape cause a vasodilation possibly through their antioxidant properties. Allicin, a by-product of the enzyme alliinase, has been proposed to be the main active metabolite and responsible for most of the biological activities of garlic, including a dose-dependent dilation on the isolated coronaries. Thymoquinone, the principal phytochemical compound found in the volatile oil of the black seed, and the hawthorn extract have also been shown to improve aging-related impairment of endothelium-dependent relaxations in animal models. In this review, the effect of some of the natural products, including Camellia sinensis (black tea and green tea), Vitis labrusca (concord grape), Allium sativum (garlic), and Nigella sativa (black seed) and Crataegus ssp (hawthorn extract), is explored. The molecular mechanisms behind these potential therapeutic effects are also discussed. © 2013 by Lippincott Williams & Wilkins.