Phenolic antioxidant activity bioactivity

Extracts of V. africana are used to treat AIDS. Phytochemical screening revealed the presence of important antioxidant bioactive molecules such as tannins, flavonoids and phenols in bark extracts (S). They concluded that the antioxidant activity in this medicinal plant may be a contributing factor to its therapeuctic applications. Additional medicinal applications of Voacanga have been reviewed in relation to other African medicinal plants 3, 70). 

The occurrence in the olive pomace of unique oleuropein oligomers (14) with a degree of polymerization of up to five oleuropein monomers was reported by Cardoso et al. [27]. Their bioactivities have, however, not yet been studied. In fact, besides the evidence that olive phenolic compounds can have antioxidant, cardioprotective, antimicrobial, antihypertensive, anti-inflammatory, and chemo-preventive properties [26], the majority of the studies have focused on hydroxytyrosol (15). This compound has revealed remarkable pharmacological and antioxidant activities and thus has been further studied for its bioavaUability and metabolism in humans in order to establish its health-beneficial effects [29-31]. 

Plant foods contain a number of bioactive substances, including phenoUcs. Phenolics such as flavonoids, phenolic acids, lignans and tannins have antioxidant properties, whilst the fermentation process has been d onstrated to modify the amount of these contents. l,l-Diphenyl-2-picryldrazyl (DPPH) and 2,2 -azinobis-(3-ethylbenzothi-azoline-6-sutfonic acid) (ABTS) are tests commonly used to detennine the free radical-scavenging effectiveness of componnds in evaluating the antioxidant activity of food systems. 

Polyphenols are considered secondary metabolites of plants involved in the chemical defense of plants against predators and in plant-plant interactions. Polyphenols are found in virtually all families of plants, and comprise up to 50% of the dry weight of leaves. The main activity related to phenolic compounds is antioxidant activity. In addition to their strong antioxidant activities, plant polyphenols are known to possess other activities including antibacterial, chemopreventive, UV-protective, anticancer, and anti-inflammatory effects, act as detoxifying agents against heavy metals, and have myriad other bioactivities that could potentially be exploited for application in functional foods. ... 

The presented characteristics of various berry fruit species point to vast differences in the type of their bioactive compounds. Such differences are observed with regard to both the content and the qualitative composition of those compounds. The most significant health benefits are ascribed to phenolic compounds and vitamin C. Owing to the rich and diversified compositions of bioactive compounds and their health-promoting properties which result mostly from their antioxidant activity, berry fruits are widely recognized as natural functional products (Szajdek and Borowska 2008). 

The most important seaweed derived phenolic phytochemicals are phlorotannin polyphenols, which are uniquely found only in brown seaweeds [96], Phlorotannins are polymers which contain phloroglucinol as their monomeric component, and they are termed phlorotaimins since phloroglucinol is a common monomer unit [96]. As most tannins, similarly phlorotannins have the potential for cardiovascular disease management through an increase of HDL cholesterol and prevention of atherosclerosis [136-140], However, many recent reports have indicated more unique potential health benefits of phlorotaimins for a wide variety of diseases. A study by Li et al. [141] revealed that E. cava contains plenty of phlorotannin derivatives with interesting bioactivities. Chemical composition and antioxidant activity studies on E. cava showed that the major phlorotannins present are phloroglucinol, eckol. 

Rapeseed phenolics isolated by Vuorela et al. (2004) were tested for radical scavenging and for liposome and low-density lipoprotein (LDL) model systems. The inhibition of hexanal and conjugated diene hydroperoxides formation was reported (>90% and >80%, respectively). All isolates also exhibited inhibition of LDL particles oxidation by >90%. The antioxidant activity of methanol and acetone extracts of canola hulls in a P-carotene-linoleate model system was comparable to that displayed by butylated hydroxyanisole (Naczk et al., 2005). These extracts showed more than 95% scavenging effects (at 40 p/assay on DPPH radical). Vuorela et al. (2005a,b) indicated that rapeseed phenolics were excellent antioxidants towards oxidation of phosphatidylcholine membrane (liposomes) and rapeseed oil (crude) phenolics were effective radical scavengers (DPPH test). The authors suggested that these phenolic isolates from rapeseed are safe and bioactive for possible food applications including functional foods intended for health benefit. 

Balasundram, N., Sundram, K., Samman, S., 2006. Phenolic compounds in plants and agri-industrial by-products antioxidant activity, occurrence, and potential uses. Food Chem. 99, 191-203. Brigelius-Flohe, R., 2006. Bioactivity of vitamin E. Nutr. Res. Rev. 19,174-186. 

Phenolics are one of the major groups of non-essential dietary components that have been associated with the inhibition of atherosclerosis and cancer. The bioactivity of phenolics may be related to their antioxidant behavior, which is attributed to their ability to chelate metals, inhibit lipoxygenase, and scavenge free radicals. However, phenolics can also function as prooxidants by chelating metals in a manner that maintains or increases their catalytic activity (Fig. 6). Also, poly-phenolics reduce metals, thereby increasing their ability to form free radicals from peroxide. 

Rosemary is composed of various phenolics such as rosmarinic acid, the flavonoid hesperidin, and the terpenoids camosic acid, camasol, and rosmanol (Al-Sereiti et al. 1999). Rosemary is well known for antioxidant and antimicrobial activity (Naghibi et al. 2005). Multiple extracts and bioactive constituents of rosemary were evaluated for in vitro effect on human cancer cells (Yesil-Celiktas etal. 2010). These included human small cell lung, prostate, liver, breast, and myeloid leukemia, all rosemary extracts and finctionated compounds were toxic to the cell lines at low doses but camosic acid was most effective (Yesil-Celiktas et al. 2010). Bakirel etal. reported in 2007 that ethanol extracts of rosemary reduced blood glucose, and increased insulin levels of rabbits with induced diabetes. They also noted increased levels of the antioxidants SOD and CAT in these animals. 

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