Monday, November 11, 2013

Polyphenols and biochar

     Polyphenols include several classes of compounds, such as phenols, phenolic acids, flavonoids, anthocyanins, and others, with more complex structures, tannins and lignins. Polyphenols are secondary metabolites produced by plants in response to stress conditions (Bennet and Wallsgrove, 1994), such as infections, large amounts of UV rays or other factors (Popa et al., 2007). 

     Oxidized polyphenols also inhibit growth and development of certain microbial strains. The toxicity mechanism of polyphenols may be explained by the inhibition of hydrolytic enzymes, or by other interactions, such as blocking protein transport, non-specific interactions with carbohydrates, etc. (Popa et al., 2007). Stimulus or inhibition capacity on plant growth and development is closely correlated with the concentration of Polyphenolic compounds used (Anghel, 2001). Polyphenols, a large class of chemicals which  are found in plants, have attracted much attention in the last decades due to their properties and the hope that they will show beneficial health effects, when taken as a dietary input or as complement (Hu, 2007). 

     Phenolic compounds constitute one of the most extensive groups of chemicals in the plant kingdom. It is estimated that more than 8000 compounds have been isolated and described (Ramos, 2007).  

Ingredients are standardized for total polyphenols (1-10%)

Total phenolic content and extraction yield from extracts of jambul peels (Syzygiumcumini) obtained through various methods of extraction. Source:

     In order to test the content of polyphenols in biochar derived from agriculture wastes research has been done, some investigations had found that the combination of charcoal and polyphenols addition have potential to improve the growth and yield of radish. The mixed combination of biochar and polyphenols applied at 1.5 % w/w to compost led to highest root yields (Jordan et al., 2011), in a similar research Niggli and Schmidt (2010) tested biochar applications of biochar in Vineyards and found that grapes from biochar-treated plots had a 10% higher polyphenol content. Together with the much higher amino acid content, this was an indication of a greater aromatic quality of the grapes, which is then passed into the wine.

Comparison between radish treated with and without biochar 
     The formation of root nodules in leguminous plants is initiated by their release of flavonoids, which are polyphenolic signaling compounds (Jain and Nainawatee, 2002). Biochar is highly effective in the sorption of phenolic compounds, including flavonoids (Gundale and DeLuca, 2006). Therefore, high biochar applications may interfere with signal reception and initiation of the legume root infection process.

    Various papers published in the 1960’s point out that polyphenols could inhibit the activity of digestive enzymes and might accelerate nutritional proteins (Bernays, et al., 1989).

Source: 1st International Conference on Food Digestion, Cesena, 19th March 2012.

     Polyphenols have also been acknowledged as regulators of soil processes and mechanisms. It has been proposed that they might inhibit nitrification (Baldwin et al., 1983), decomposition and nutrient recycling (Horner et al., 1988; Kuiters, 1990) as an outcome of the anti-herbivore function that they have.


     Between species, the variation in polyphenol production by plants has been understood as a defense against herbivores (Haslam, 1981; Bernays et al., 1989). Recent evidence proposes that the pools and variations of inorganic and organic soil nutrients can be influenced by polyphenols (Northup et al., 1998; Schimel et al., 1998). In terms of nutrient competition between plants and microbes, these effects may possibly have wide-ranging consequences, also for retention and nutrient cycling in ecosystems. (Hättenschwiler and Vitousek, 2000).

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