The key difference between hydrolysable tannins and condensed tannins is that hydrolysable tannins are hydrolyzed from weak acids or weak bases, giving carbohydrate and phenolic acids, whereas condensed tannins are formed from the condensation of flavans.
Tannins are water-soluble polyphenols that can be found in many plant foods. Some common food items that are rich in tannins include legume seeds, cider, tea, nuts, peas, cocoa, leafy green vegetables, and coffee. These are commonly known as tannic acids. These compounds are responsible for the decrease in feed intake, feed efficiency, growth rate, net metabolizable energy, and protein digestibility considering experimental animals. Therefore, tannins are considered nutritionally undesirable components due to features such as the precipitation of proteins, inhibition of digestive enzymes, and adverse effects on the use of vitamins and minerals.
Tannins are interesting compounds due to their countless properties. For example, their ability to produce functional coatings on different materials. Hydrolysable tannins and condensed tannins are two types of tannin compounds. These compounds can be found in tannosomes.
CONTENTS
1. Overview and Key Difference
2. What are Hydrolysable Tannins
3. What are Condensed Tannins
4. Hydrolysable Tannins vs Condensed Tannins in Tabular Form
5. Summary – Hydrolysable Tannins vs Condensed Tannins
What are Hydrolysable Tannins?
Hydrolysable tannins are organic compounds that can yield gallic or ellagic acid upon heating with HCl or sulfuric acid. When considering the structure of hydrolysable tannins, these molecules contain a carbohydrate molecule at the centre. Generally, this carbohydrate is a D-glucose molecule. The hydroxide groups of the sugar molecule are either partially or completely esterified with phenolic groups. Therefore, these compounds are mixtures of polygalloyl glucose.
Figure 01: Hydrolysable Tannins
The name of these tannins comes from their ability to undergo hydrolysis upon reaction with weak acids and weak bases. The hydrolysis reaction produces carbohydrates and phenolic acid. Hydrolysable tannins are naturally occurring compounds. We can extract these compounds from vegetable plants such as chestnut wood, oak wood, tara pods, etc.
What are Condensed Tannins?
Condensed tannins or CT are a class of secondary plant metabolites that can be found in several forage plants. These are organic compounds and polymer materials made via the condensation of flavan. These compounds have no sugar residues as a part of the compound. Other common names for condensed tannins include proanthocyanidins, polyflavonoid tannins, catechol-type tannins, pyrocatecollic type tannins, non-hydrolyzable tannins, or flavolans.
Figure 02: The Chemical Structure of Condensed Tannins
Most condensed tannins are water-soluble compounds, and they are sometimes soluble in organic solvents such as octanol. However, some large condensed tannins are not soluble in water. Therefore, we can observe that the biological function of these compounds depends on water solubility.
We can find condensed tannins naturally occurring in different plants, such as Prunus species. These compounds form in tannosomes, which are specified organelles in vascular plants. There are different techniques we can use to characterize condensed tannins; for example, asymmetric flow field flow fractionation, small-angle X-ray scattering[13], and MALDI-TOF mass spectrometry.
What is the Difference Between Hydrolysable Tannins and Condensed Tannins?
The key difference between hydrolysable tannins and condensed tannins is that hydrolysable tannins are hydrolyzed from weak acids or weak bases, giving carbohydrate and phenolic acids, whereas condensed tannins are formed from the condensation of flavans.
The below infographic presents the differences between hydrolysable tannins and condensed tannins in tabular form for side by side comparison.
Summary – Hydrolysable Tannins vs Condensed Tannins
Hydrolysable tannins are organic compounds that can yield gallic or ellagic acid upon heating with HCl or sulfuric acid. Condensed tannins or CT are a class of secondary plant metabolites that can be found in several forage plants. The key difference between hydrolysable tannins and condensed tannins is that hydrolysable tannins are hydrolyzed from weak acids or weak bases, giving carbohydrate and phenolic acids, whereas condensed tannins are formed from the condensation of flavans.
Reference:
1. Moccia, Federica, et al. “Hydrolyzable vs. Condensed Wood Tannins for Bio-Based Antioxidant Coatings: Superior Properties of Quebracho Tannins.” MDPI, Multidisciplinary Digital Publishing Institute, 31 Aug. 2020.
Image Courtesy:
1. “QuinineStorkSynthPart3” By V8rik (CC BY-SA 3.0) via Commons Wikimedia
2. “Schematic condensed tannins” By Nono64 – Own work (Public Domain) via Commons Wikimedia