Antioxidant Potential Of Polyphenols Research Articles

Antioxidant Potential of Polyphenols: In Need for Critical Assessment of In Vitro Results

Antioxidants have become OTC (Over the Counter) prophylactic dietary supplements hit of the 21st century. Polyphenols, including flavonoids and phenolic acids, are widely distributed antioxidants and are present in medicinal drugs, fruits and vegetables (food) e.g. propolis, wine, chocolate….Individuals tend to reach for polyphenols as a source of longevity which can be related to their ability to reduce oxidative stress. Oxidative stress has been postulated as a cause of many diseases e.g. rheumatoid arthritis, diabetes, skin diseases, cataract, Alzheimer and Parkinson disease… Question that we often face is how effective commercially available product as antioxidants is. Predominantly this answer is gained through in vitro testing that includes spectrophotometry and chromatography.

Antioxidant Potential of Polyphenols: In Need for Critical Assessment of In Vitro Results

Antioxidant Potential of Polyphenols: In Need for Critical Assessment of In Vitro Results

Stability of dietary polyphenols under the cell culture conditions: avoiding erroneous conclusions.

Most data of bioactivity from dietary polyphenols have been derived from in vitro cell culture experiments. In this context, little attention is paid to potential artifacts due to chemical instability of these natural antioxidants. An early degradation time ((C)T10) and half-degradation time ((C)T50) were defined to characterize the stability of 53 natural antioxidants incubated in Dulbecco's modified Eagle's medium (DMEM) at 37 °C. The degree of hydroxylation of flavones and flavonols significantly influenced the stability in order resorcinol-type > catechol-type > pyrogallol-type, with the pyrogallol-type being least stable. In contrast, any glycosylation of polyphenols obviously enhanced their stability. However, the glycosylation was less important compared to the substitution pattern of the nucleus rings. Methoxylation of flavonoids with more than three hydroxyl groups typically improved their stability as did the hydrogenation of the C2═C3 double bond of flavonoids to corresponding flavanoids. There was no significant correlation between the antioxidant potential of polyphenols and their stability. Notably, the polyphenols were clearly more stable in human plasma than in DMEM, which may be caused by polyphenol-protein interactions. It is strongly suggested to carry out stability tests in parallel with cell culture experiments for dietary antioxidants with catechol or pyrogallol structures and pyrogallol-type glycosides in order to avoid artifacts.

An innovative microwave-assisted extraction and antioxidant potential of polyphenols from different parts of Ocimum basilicum

Microwave-assisted extraction technique is widely used for the extraction of polyphenols from plant material due to high extraction efficiency, short time for extraction and less energy consumption. Due to such advantageous properties of this technique, microwave-assisted extraction was used for the extraction of polyphenols from different parts (seed, stem, and flower) of Ocimum basilicum by using three solvents of different polarities and results were compared with other conventional techniques (heat reflux extraction and soxhlet extraction). Highest polyphenols (980 mg GAE/g) were observed in stem extract of O. basilicumprepared using microwave assisted extraction technique. Methanol was found to be most effective solvent for the extraction of polyphenols from plant parts irrespective of the technique used. Antioxidant potential was evaluated by employing five different antioxidant assays. Highest antioxidant potential was found in stem extract of O. basilicum followed by flower and seed extract. Key words: Ocimum basilicum, microwave-assisted extraction technique, polyphenols, antioxidant potential.

Antioxidant Potential of Polyphenols and Tannins from Burs of Castanea mollissima Blume

Spiny burs of Castanea mollissima Blume (Chinese chestnut) are usually discarded as industrial waste during post-harvesting processing. The objective of this study was to establish an extraction and isolation procedure for tannins from chestnut burs, and to assess their potential antioxidant activity. Aqueous ethanol solution was used as extraction solvent, and HPD 100 macroporous resin column was applied for isolation. The influence of solvent concentration in the extraction and elution process on extraction yield, tannins and polyphenols content, as well as antioxidant potential, including DPPH and ABTS radical scavenging ability, reducing power ability and cellular antioxidant ability were assessed. In both the extraction and isolation process, 50% aqueous ethanol led to superior total tannins and polyphenols content as well as significantly higher antioxidant activity. In addition, the antioxidant activity and the total tannins content in extracts and fractions had a positive linear correlation, and the predominant components responsible for antioxidant activities were characterized as hydrolysable tannins. To the best of our knowledge, this is the first report on the enrichment of tannins from burs of C. mollissim using macroporous resin chromatography, and to assess the cellular antioxidant activity of them.