Medicinal Plants And Antioxidants: Why They Are Not Always Beneficial?
Oxidative stress is defined as an imbalance between stress and the available protective elements suggested playing a crucial role in induction of diseases. Medicinal plants mostly combat these complications with their antioxidant activities. Several preclinical and epidemiological studies have found an inverse association between the consumption of fruits, vegetables and/or grains which generally are high in antioxidants and induction of diseases in humans. Antioxidants are substances that remove , prevent or delay oxidative damage to a target molecule. Therefore, an antioxidant may act to control the level of free radicals to counteract oxi-dative damage (1). There is a lot of evidence on protective and curative effects of medicinal plants on various complications. Some of these effects include antimicrobial (2, 3), anti-cancer (4), anti-diabetic (5, 6), anti-atherosclerosis (7, 8), immune-modulatory (9), and even renoprotection or hepa-to-protective effects (10–14). Medicinal plants are rich sources of polyphenols with antioxidant activities and these beneficial effects have been attributed to their antioxidant mechanisms. There has also been a linear correlation between oxygen radical absorbance capacity values and total phe-nolic contents in several medicinal plants. In a study the equivalent antioxidant capacity values of several forms of garlic extracts were correlated well with their total phenolic, flavonoid and fla-vonol contents (15). Although medicinal plants effects in prevention and treatment of disorders have been widely attributed to their antioxidants activities, however, there is increasing evidence pointing to their pro-oxidant hazardous effects, too. This property of medicinal plants is mostly contributed to their for-mulae preparation. Some of polyphenols have shown to be readily oxidized in preparation of beverages like green tea. The prescription formu-lae preparation in traditional medicine usually involves a long decoction process with water and medicinal plants for several hours. Polyphenols in the medicinal plants in this process or storage may be oxidized. This oxidation critically reduces the beneficial properties of herbal medicine products (16). Pro-oxidant however, is a chemical agent that induces oxidative stress, either by generating reac-tive oxygen species (ROS) or by inhibiting antiox-idant systems. The oxidative stress induced by this agent can damage cells and tissues. Polyphe-nols in medicinal plants can act as either antioxi-dants or pro-oxidants, depending on conditions. Concentration of the extract and whether oxygen or transition metals are present or not are of these conditions. Transition metals such as iron, copper and manganese are present in most cases of pro-oxidant activities of agents (1). Adulteration and contamination of medicinal plants …
It has been estimated that about 20% of men and 25% of women between the ages of 65 and 74 have some degrees of chronic kidney. This complication is attributed to oxidative stress. Oxidative stress is an important factor contributing to kidney damage by increasing production of oxidants, particularly insufficiency of endogenous antioxidant defense system. Medicinal plants antioxidants are able ...متن کامل
Antioxidants have important preventive roles, not only on undesirable changes in the flavor and nutritional quality of food, but also on tissue damage in various human diseases. Some of Iranian plants, despite wide spread use of them as medicines in Iran have been investigated for their beneficial use as an antioxidants or source of antioxidants. The present review deals with a list of such pla...متن کامل
Oxidative stress has been implicated in the progression of HIV to AIDS, since HIV usually replicates in a highly oxidized condition and CD4+ T lymphocytes can be activated via a cascade of internal oxidative pathways, which enhances the formation of proteins and enzymes. Thus, antioxidants should potentially be useful for the treatment and prevention of HIV infection as a new alterna...متن کامل
Various side effects of synthetic drugs, has necessitated the move to more natural antioxidants. The demand for highly effective antioxidants having low or no side effects for use in preventive medicine and the food industry is increasing. As plants produce significant amount of secondary methabolites, mostly antioxidant compounds, they are almost replacing the synthetic antioxidants. Plant ant...متن کامل
The use of herbal medicines dates back to the beginning of the human history. Today, herbal medicines still play a significant role in the prevention and treatment of disease in many cultures and communities. There are few reports about adverse effects of herbal medicines. This is why many people around the world believe that herbal medicines can't cause adverse effects. They believe plants ...متن کامل