Free Sterols and Steryl Esters in the Trunkwood of Picea abies (L.) Karst.

Abstract

Summary Free sterols and steryl esters were analyzed in discs from mature xylem in four trunks of Picea abies (L.) Karst. (77–86 years old). The wood of the individual discs was separated into a) outer sapwood, b) rest of the sapwood, c) sapwood-heartwood transition zone, d) outer heart-wood and e) innermost heartwood. After extraction of the wood with acetone, free sterols and steryl esters were separated by column chromatography and quantitated by color reaction. In all trunks analyzed the innermost heartwood contains the highest amounts of free sterols and steryl esters. Lipid-phosphorus, on the other hand, decreases from the younger to the older parts of the trunks. The heartwood of all trunks contains only trace amounts of lipid-phosphorus. The free sterols are made up of cholesterol, desmosterol, campesterol and sitosterol. Desmosterol was absent in the steryl ester fraction. Sitosterol was dominant in both free sterols and steryl esters. The percentage of cholesterol and desmosterol to the total free sterols decreased from the younger to the older trunkwood while campesterol and sitosterol showed no gradient in the trunks. In the steryl ester fraction, the percentage of cholesterol decreased, campesterol seemed to increase and sitosterol showed no gradient towards the center of the trunks. Calculated on dry weight basis, only cholesterol had the tendency to decrease from the younger to the older trunkwood zones.