Natural Antioxidants and Hypertension: Promise and Challenges

Abstract

Hypertension reigns as a leading cause of cardiovascular morbidity and mortality worldwide. Excessive reactive oxygen species (ROS) have emerged as a central common pathway by which disparate influences may induce and exacerbate hypertension. Potential sources of excessive ROS in hypertension include nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, mitochondria, xanthine oxidase, endothelium-derived NO synthase, cyclooxygenase 1 and 2, cytochrome P450 epoxygenase, and transition metals. While a significant body of epidemiological and clinical data suggests that antioxidantrich diets reduce blood pressure and cardiovascular risk, randomized trials and population studies using natural antioxidants have yielded disappointing results. The reasons behind this lack of efficacy are not completely clear, but likely include a combination of (1) ineffective dosing regimens, (2) the potential pro-oxidant capacity of some of these agents, (3) selection of subjects less likely to benefit from antioxidant therapy (too healthy or too sick), and (4) inefficiency of nonspecific quenching of prevalent ROS versus prevention of excessive ROS production. Commonly used antioxidants include Vitamins A, C and E, L-arginine, flavanoids, and mitochondria-targeted agents (Coenzyme Q10, acetyl-L-carnitine, and alpha-lipoic acid). Various reasons, including incomplete knowledge of the mechanisms of action of these agents, lack of target specificity, and potential interindividual differences in therapeutic efficacy preclude us from recommending any specific natural antioxidant for antihypertensive therapy at this time. This review focuses on recent literature evaluating naturally occurring antioxidants with respect to their impact on hypertension.

Kandungan Total Polifenol dan Aktivitas Antioksidan dari Ekstrak Metanol Akar Imperata cylindrica (L) Beauv. (Alang-alang)

“…[3][4][5] Superoksida itu merupakan suatu molekul yang berumur pendek, kemudian dapat mengalami dismutasi secara enzimatik menjadi hidrogen peroksida. Superoksida itu dapat mengoksidasi protein dan lipid, atau dapat bereaksi dengan NO dari endotel menghasilkan spesies nitrogen reaktif peroksi nitrit.…”

“…Hidrogen peroksida yang dihasilkan dismutasi enzimatik O 2 , selanjutnya akan dapat dikonversi ke radikal hidroksil yang sangat reaktif (via kimia Fenton) yang dapat merusak asam deoksiribo nukleat (DNA). [3][4] Beberapa senyawa dari polifenol mempunyai aktivitas antihipertensi. Beberapa penelitian juga memperlihatkan bahwa flavonoid dan tanin yang umumnya terdapat dalam buah-buahan, sayursayuran, serta minuman mampu menghambat nicotinamida adenine dinucleotida phosphat (NADPH) oksidase melalui penghambatan ACE, peningkatan eNOS-spesifik, dan juga mengubah ekspresi siklooksigenase-2 (COX-2).…”

Aspectos oxidativos da síndrome metabólica e aterosclerose

“…Esses pacientes também têm redução nos níveis plasmáticos de ácido ascórbico e na capacidade de redução férrica do plasma que estão relacionados com a pressão sistólica e diastólica. Os radicais livres danificam diretamente o endotélio vascular e degradam o óxido nítrico [3,[43][44][45][46][47].…”

Coronary Artery Disease and Oxidative Stress

“…With regard to vitamin E, small studies show either no effect or a pressor effect from supplementation. It is important to take care with the use of higher doses of supplements, since there is the risk of an antioxidant becoming pro-oxidant when used at high doses, for example, the ascorbate increase the risk of forming oxalate renal calculi (Kizhakekuttu & Widlansky, 2010). The addition of vitamins, the L-arginine, flavonoids and mitochondria-targeted agents are part of a target group of studies.…”