Hello everyone,
I have a query regarding ''the possible reasons behind the higher phenolic content but lower antioxidant activity''. I used the raw bamboo shoots and it showed good amount of phenolic/flavonoid content and antioxidant activity but when I prepare candies from it without adding any other antioxidant rich ingredient, processing decline the phenolic content but antioxidant activity increase significant higher. Kindly suggest what could be the reason behind it.
The major antioxidant components of these common foods are the phenolic compounds. Their antioxidant activity seems to be related to their molecular structure, more precisely to the presence and number of hydroxyl groups, and to double bond conjugation and resonance effects (Rice-Evans et al., 1996).
Article Antioxidant and structure–activity relationships (SARs) of s...
Dear Vikas,
Individual phenolic compounds may exhibit low to high antioxidant activity. This depends on aspects involving its structure and chemical function. In order for you to make sure that the antioxidant activity is low analyze several antioxidant methods FRAP, DPPH, CUPRAC and ABTS (for example). These methods have different principles and evaluate different forms of antioxidant activity.
Regards,
Alessandro
Dear Israel, its ug GAE/mg (Gallic acid) for phenolics and ug RU/mg (Rutin) for flavonoids.
Thank you all for your valuable suggestion to understand the basic chemical behavior of antioxidants.
Dear Vikas,
During food processing, complex chemical reactions take place which affect the individual phenolic compounds as well as the antioxidant activity. sometimes phenolic compounds are destroyed and at the same time some new compounds with potent antioxidant activity are formed.
The FC and aluminum chloride methods for phenols and flavonoids respectively and most of the antioxidant activity tests like DPPH, FRAP are no longer effective or reliable and cannot be used to truly know the concentration and bioactivity of phytochemicals in foods.
I would approach this study by first identifying and quantifying individual phenols and flavonoids using HPLC and either use in vivo tests for antioxidant activity or correlate each of the individual antioxidant compounds against the in vitro antioxidant activity tests.
Dear Vikas,
Sometimes the treatment destroyed the structure of phenolic compound. so, the OH groups Will react with differents reagents in the medium which gives a high antioxiant quantity but since their structure is modified this may gives a low antioxiant activity. But, sometimes treatment(thermal treatment) of raw material may enhances the antioxiant activity for the sime phenolic compound quantity.
Thabi you
Dear Vikas,
The contribution of phenolic compounds to antioxidative activity is complicated, involving many factors. For eamples, the inherent antioxidative ability of phenolic compounds (which mainly depends on their structures), the concentration of which presenting in your samples, and the antioxidative assays that you choose. We have two articles about the contribution of the phenolics (the main groups and some individual compounds) to in-vitro antioxidant activity of berry and leaf extract, I hope they can give you some help ( Sephadex LH-20 fractionation and bioactivities of phenolic compounds from extracts of Finnish berry plants , 2018; Antioxidative and antibacterial activities of aqueous ethanol extracts of berries, leaves, and branches of berry plants, 2017).
Also, some phenolics can be distroyed or generate during food processing. My suggestion is to identify and quantify the phenolics in both baboom shoot extracts and candy products, then compare the results.
Best regards,
Ye
...because phenolic compounds differ in molecular configuration which often determines their molecular weight, as well as steric hindrance and steric synergy effects. Note: Higher molecular weight, stronger steric hindrance and/or synergy effects all increase antioxidant acivity and vice versa.
Dear Vikas,
It depends on structure of phenolic compouds (number and position of functional groups)
Dear Vikas,
The total antioxidant capacity or content or power and the concentration of specific antioxidants in samples are not always positively linear. This evidents shows the weakness of TAC method. For example, FRAP method implies a balance between samples ferrous and ferric ions or for example ABTS method implies sample balance between hydrophobic and hydrophlic compounds.
In my opinion, the best way is to determine more than 2-3 TAC methods and some oxidative stress biomarkers.
read the following paper to understand deeply the relation between diferent methods:
Does high antioxidant capacity indicate low oxidative stress?
David Costantini Simon Verhulst
Dear Vikas,
antioxidant power is often higher in larger molecules. I.e., when you process your samples the polyphenolic fraction will partially polymerize and lead to more powerful antioxidative structures, which will give you higher values in the test system you're using.
Dear Vikas
Broadly, phenol compounds have antioxidant activity. however, it is not always positively correlated. If a single phenol compound has been oxidized to complex phenol compounds (such as tannins), the antioxidant activity will be weak. Maybe that's one of the causes.
may phenolic compound breakdown or binding to oxidized component, as inhibit the activity as antioxidant.
Dear Vikas,
Having higher phenolic content does not necessarily mean a high antioxidant power because the antioxidant power depends primarily on the chemical nature of the phenolic compound (position and number of OH, presence of a carbohydrate moiety. .etc) and the chemical matrix in which it is located. Moreover, the measurement of the antioxidant power has always been a problem. Indeed and in view of the complexity of the oxidation process and the diversified nature of the antioxidants, with both hydrophilic and hydrophobic components, there is not one universal method by which the antioxidant activity can be quantitatively measured in a very precise way. Most often, the answers of different and complementary tests must be combined to obtain an indication of the antioxidant capacity of the sample to be tested.
Best
Dr Benkhaled A
it may be due to nature of the phenolic compounds, their orientation and symmetry they attain.
