Phenolic contents of different woods and their antioxidant activities

The antioxidant activity and the phenolic content were determined in six different wood types. In this study, the heart of the seedling date palm wood (SPW), old date palm wood (OPW), oak wood (OW), pine wood (PW), quibracho wood (QW), and banana (BW), showed an excellent correlation of antioxidant activity with respect to the phenolic, flavonoid, tannin, and lignin contents. The soluble and insoluble-bound phenolic compounds from wood types specified above were extracted and characterized. SPW contained the highest amount of both soluble and insoluble-bound phenolics. The phenolics were predominantly present in the soluble form in all woods tested. The highest soluble flavonoid content was found in the OPW. Tannins were determined as mg cyaniding equivalents/g sample. The highest soluble tannins were found in SPW, followed by OPW, QW, OW, PW, and BW respectively. The tannins exhibited excellent antioxidant activity, which is a unique characteristic of all condensed tannins. The hydrolysable tannins were expressed as mg of tannic acid equivalents (TAE) per g of wood and the highest content was found in SPW; while BW had the lowest contents. The extracted phenolics were subsequently evaluated for their antioxidant activities using in vitro methods including DPPH radical scavenging and metal chelating abilities. This research suggests that wood extracts can be used as a source of natural antioxidants, due to the presence of compounds such as protocatechuic acid, syringic acid, and catechin, which were identified in the selected woods. The lignin content was determined in the various wood extracts of which SPW contained the highest amount, followed by OPW, QW, OW, PW, and BW, respectively. In short, SPW exhibited had the highest antioxidant activity by virtue of its higher contents of phenolics, tannins, and lignin.