Methodology optimization for the analysis of phenolic compounds in chestnut (Castanea sativa Mill.)

Abstract

Phenols are bioactive substances of great interest because of their involvement in plant physiology, their use in many industrial processes, and their impact on human health. This work aims to summarize the varied approaches to the phenolic analysis of chestnut (bark and wood of trunk and branches, leaves, catkins, burs, and fruit) and to collate the optimal conditions into an easy to follow and execute protocol. Phenolic compounds were extracted by solid–liquid extraction and separated by liquid–liquid extraction. Total phenols content was determined by Folin–Ciocalteu assay, condensed tannins by vanillin assay, and hydrolyzable tannins (gallotannins and ellagitannins) by high-performance liquid chromatography quantification of methyl gallate and ellagic acid following acid methanolysis. The lowest temperature for conservation (–80 ℃), lyophilization, and milling (liquid N2) were the most effective pretreatments for samples. For quantification of tannins, the use of water clearly reduced the sensitivity of the analysis of condensed tannins, whilst the more efficient degradation capacity of sulfuric acid improved the methanolysis of hydrolyzable tannins. These findings were validated using a range of chestnut tissues, and thus confirm the utility and effectiveness of this easy to implement, cost-effective, and efficient protocol.

Subcritical Water Extraction of Chestnut Bark and Optimization of Process Parameters

“…The bark and wood contain a much higher amount of phenols than the chestnut fruits [ 7 ]. Fuente-Maqueda et al [ 26 ] determined the content of total phenols of 101.2 mg GAE/g, condensed tannins of 0.59 mg CE/g, gallotannins of 9.0 mg MG/g and ellagitannins of 6.0 mg EA/g in outer chestnut bark.…”

In vitro antioxidant and antibacterial activities with polyphenolic profiling of wild cherry, the European larch and sweet chestnut tree bark

“…Many studies have explored the sweet chestnut tree for its phenolic content, particularly the shells, burs and leaves [25,26]; but only a few can be found on the bark [27]. Interestingly, chestnut leaves and burs showed lower phenolic contents of 115.4 ± 1.8 and 93.3 ± 2.4 mg GAE/g dw, respectively, compared to the bark [28]; while cherry fruits showed TPC of 284.48 ± 3.07 GAE mg/100 g of fresh cherries [14]. One of the earlier studies evaluated the phenolic content of the bark extracts after separating the outer bark from the inner bark [10]; although for practical reasons and from a commercialization point of view, we chose to study the whole bark of the tree trunks.…”

“…Other studies have evaluated the TPC values of bark of Quercus rubra (276.50 ± 3.23 mg GAE/g dw extract), Betula celtiberica (432.02 ± 3.00 mg GAE/g dw extract) [27], Larix laricina (34 ± 2 g GAE/100 g extract) [29], as well as Fagus sylvatica L. (65.22 ± 5.57 mg GAE/g dw) [30]. Reports on bark extraction using methods such as solid-liquid extraction with aqueous methanol [28], and subcritical water extraction [31] showed a lesser yield of phenolics.…”