Biological effects of essential oils - A review

Methods available for the measurement of antioxidant capacity are reviewed, presenting the general chemistry underlying the assays, the types of molecules detected, and the most important advantages and shortcomings of each method. This overview provides a basis and rationale for developing standardized antioxidant capacity methods for the food, nutraceutical, and dietary supplement industries. From evaluation of data presented at the First International Congress on Antioxidant Methods in 2004 and in the literature, as well as consideration of potential end uses of antioxidants, it is proposed that procedures and applications for three assays be considered for standardization: the oxygen radical absorbance capacity (ORAC) assay, the Folin-Ciocalteu method, and possibly the Trolox equivalent antioxidant capacity (TEAC) assay. ORAC represent a hydrogen atom transfer (HAT) reaction mechanism, which is most relevant to human biology. The Folin-Ciocalteu method is an electron transfer (ET) based assay and gives reducing capacity, which has normally been expressed as phenolic contents. The TEAC assay represents a second ET-based method. Other assays may need to be considered in the future as more is learned about some of the other radical sources and their importance to human biology.

https://faculty.missouri.edu/~glaserr/3700s14/Antioxidant-Capacity_jf0502698.pdf

Standardized Methods for the Determination of Antioxidant Capacity and Phenolics in Foods and Dietary Supplements

There is an increasing amount of experimental evidence that oxidative stress is a causal, or at least an ancillary, factor in the neuropathology of several adult neurodegenerative disorders, as well as in stroke, trauma, and seizures. At the same time, excessive or persistent activation of glutamate-gated ion channels may cause neuronal degeneration in these same conditions. Glutamate and related acidic amino acids are thought to be the major excitatory neurotransmitters in brain and may be utilized by 40 percent of the synapses. Thus, two broad mechanisms--oxidative stress and excessive activation of glutamate receptors--are converging and represent sequential as well as interacting processes that provide a final common pathway for cell vulnerability in the brain. The broad distribution in brain of the processes regulating oxidative stress and mediating glutamatergic neurotransmission may explain the wide range of disorders in which both have been implicated. Yet differential expression of components of the processes in particular neuronal systems may account for selective neurodegeneration in certain disorders.

https://science.sciencemag.org/content/sci/262/5134/689.full.pdf

Oxidative stress, glutamate, and neurodegenerative disorders

Polyphenols constitute one of the most numerous and ubiquitous groups of plant metabolites and are an integral part of both human and animal diets. Ranging from simple phenolic molecules to highly polymerized compounds with molecular weights of greater than 30,000 Da, the occurrence of this complex group of substances in plant foods is extremely variable. Polyphenols traditionally have been considered antinutrients by animal nutritionists, because of the adverse effect of tannins, one type of polyphenol, on protein digestibility. However, recent interest in food phenolics has increased greatly, owing to their antioxidant capacity (free radical scavenging and metal chelating activities) and their possible beneficial implications in human health, such as in the treatment and prevention of cancer, cardiovascular disease, and other pathologies. Much of the literature refers to a single group of plant phenolics, the flavonoids. This review offers an overview of the nutritional effects of the main groups of polyphenolic compounds, including their metabolism, effects on nutrient bioavailability, and antioxidant activity, as well as a brief description of the chemistry of polyphenols and their occurrence in plant foods.

Polyphenols: Chemistry, Dietary Sources, Metabolism, and Nutritional Significance

The antioxidant activities and total phenolics of 28 plant products, including sunflower seeds, flaxseeds, wheat germ, buckwheat, and several fruits, vegetables, and medicinal plants were determined. The total phenolic content, determined according to the Folin−Ciocalteu method, varied from 169 to 10548 mg/100 g of dry product. Antioxidant activity of methanolic extract evaluated according to the β-carotene bleaching method expressed as AOX (Δ log A470/min), AA (percent inhibition relative to control), ORR (oxidation rate ratio), and AAC (antioxidant activity coefficient) ranged from 0.05, 53.7, 0.009, and 51.7 to 0.26, 99.1, 0.46, and 969.3, respectively. The correlation coefficient between total phenolics and antioxidative activities was statistically significant. Keywords: Antioxidant activity; phenolics; medicinal plants; oilseeds; buckwheat; vegetables; fruits; wheat products

Antioxidant Activity and Total Phenolics in Selected Fruits, Vegetables, and Grain Products

Antioxidant and prooxidant behavior of flavonoids: structure-activity relationships.

The regional distributions of iron, copper, zinc, magnesium, and calcium in parkinsonian brains were compared with those of matched controls. In mild Parkinson's disease (PD), there were no significant differences in the content of total iron between the two groups, whereas there was a significant increase in total iron and iron (III) in substantia nigra of severely affected patients. Although marked regional distributions of iron, magnesium, and calcium were present, there were no changes in magnesium, calcium, and copper in various brain areas of PD. The most notable finding was a shift in the iron (II)/iron (III) ratio in favor of iron (III) in substantia nigra and a significant increase in the iron (III)-binding, protein, ferritin. A significantly lower glutathione content was present in pooled samples of putamen, globus pallidus, substantia nigra, nucleus basalis of Meynert, amygdaloid nucleus, and frontal cortex of PD brains with severe damage to substantia nigra, whereas no significant changes were observed in clinicopathologically mild forms of PD. In all these regions, except the amygdaloid nucleus, ascorbic acid was not decreased. Reduced glutathione and the shift of the iron (II)/iron (III) ratio in favor of iron (III) suggest that these changes might contribute to pathophysiological processes underlying PD.

Transition metals, ferritin, glutathione, and ascorbic acid in parkinsonian brains.

Different cultivars of four Vaccinium species [Vaccinium corymbosum L (Highbush), Vaccinium ashei Reade (Rabbiteye), Vaccinium angustifolium (Lowbush), and Vaccinium myrtillus L (Bilberry)] were analyzed for total phenolics, total anthocyanins, and antioxidant capacity (oxygen radical absorbance capacity, ORAC). The total antioxidant capacity of different berries studied ranged from a low of 13.9 to 45.9 μmol Trolox equivalents (TE)/g of fresh berry (63.2−282.3 μmol TE/g of dry matter) in different species and cultivars of Vaccinium. Brightwell and Tifblue cultivars of rabbiteye blueberries were harvested at 2 times, 49 days apart. Increased maturity at harvest increased the ORAC, the anthocyanin, and the total phenolic content. The growing location (Oregon vs Michigan vs New Jersey) did not affect ORAC, anthocyanin or total phenolic content of the cv. Jersey of highbush blueberries. A linear relationship existed between ORAC and anthocyanin (rxy = 0.77) or total phenolic (rxy = 0.92) content. In general,...

Antioxidant capacity as influenced by total phenolic and anthocyanin content, maturity, and variety of Vaccinium species

Previously, some fruits were shown to contain high antioxidant activities. In this paper, we report the antioxidant activities of 22 common vegetables, one green tea, and one black tea measured using the automated oxygen radical absorbance capacity assay with three different reactive species:  a peroxyl radical generator, a hydroxyl radical generator, and Cu2+, a transition metal. Based on the fresh weight of the vegetable, garlic had the highest antioxidant activity (μmol of Trolox equiv/g) against peroxyl radicals (19.4) followed by kale (17.7), spinach (12.6), Brussels sprouts, alfalfa sprouts, broccoli flowers, beets, red bell pepper, onion, corn, eggplant (9.8−3.9), cauliflower, potato, sweet potato, cabbage, leaf lettuce, string bean, carrot, yellow squash, iceberg lettuce, celery, and cucumber (3.8−0.5); kale had the highest antioxidant activity against hydroxyl radicals followed by Brussels sprouts, alfalfa sprouts, beets, spinach, broccoli flowers, and the others. The green and black teas had muc...

Antioxidant Capacity of Tea and Common Vegetables

Significant differences in the content of iron (III) and total iron were found in post mortem substantia nigra of Parkinson's disease There was an increase of 176% in the levels of total iron and 255% of iron (III) in the substantia nigra of the parkinsonian patients compared to age matched controls In the cortex (Brodmann area 21), hippocampus, putamen, and globus pallidus there was no significant difference in the levels of iron (III) and total iron Thus the changes in total iron, iron (III) and the iron (II)/iron (III) ratio in the parkinsonian substantia nigra are likely to be involved in the pathophysiology and treatment of this disorder

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Papers

Antioxidant and prooxidant behavior of flavonoids: structure-activity relationships.

Transition metals, ferritin, glutathione, and ascorbic acid in parkinsonian brains.

Antioxidant capacity as influenced by total phenolic and anthocyanin content, maturity, and variety of Vaccinium species

Antioxidant Capacity of Tea and Common Vegetables

Increased iron (III) and total iron content in post mortem substantia nigra of parkinsonian brain.