Extractives in bark of different conifer species growing in Pakistan

Abstract

Abstract The amount and composition of lipophilic and hydrophilic extractives, including proanthocyanidins, has been analysed as a first screening in the bark of six Pakistani coniferous tree species, namely Pinus wallichiana, Pinus roxburghii, Pinus gerardiana, Abies pindrow, Taxus fuana and Cedrus deodara. The predominant lipophilic extractives were common fatty and resin acids, fatty alcohols and sterols. In all bark samples, short-chain fatty acids were more abundant than long-chain fatty acids. Generally, the amount of free fatty acids was also larger than the amount of triglycerides. Oleic acid was the most common fatty acid, except in C. deodara, where lignoceric acid dominated. The largest amounts of fatty acids and fatty alcohols were found in P. wallichiana and P. gerardiana. P. gerardiana contained an exceptionally large amount of resin acids, approximately 3% of the bark weight, compared to the other species. The amount of free sterols was approximately at the same level or larger than the amount of steryl esters in most samples. In addition to proanthocyanidins, different known lignans, stilbenes, ferulates and flavonoids were generally predominant amongst the hydrophilic extractives. Resveratrol glycoside was abundant in P. wallichiana, while C. deodara and P. gerardiana contained large amounts of lignans and lignan derivatives. All bark extracts contained large amounts of proanthocyanidin-related catechin and its derivatives. Furthermore, C. deodara and P. roxburghii contained quite large amounts of taxifolin. In particular, P. wallichiana and A. pindrow are potential rich sources of proanthocyanidins, representing approximately 16% and 5% of the bark weight, respectively.