Phyletic and Phylogenetic Relationships

Sterols are found in the tall oil that results from the kraft (sulfate) process of making wood pulp. Tall soap (-3% sterol by dry weight, or 50% of the non-saponifiable fraction) yields tall oil (90 kg per ton of cellulose) by acidification with dilute sulfuric acid and then tall pitch (-20% of the tall soap) as a residue after distillation. Sterols tend to be retained and concentrated to -10% in the tall pitch. However, losses are encountered between tall soap and tall pitch. Sterols are obtained from these fractions by extraction with organic solvents. A simple example depends on an extraction with warm alcohol from which the crude product 

While sapwood contains very little sterol in the ester form (traces to 0.15 moles/g, dry weight basis), the amount rises strongly to about 1.1 moles/g in the inner heartwood (37, 38). Holl and Pieczonka (38) found the acid component of the esters in both cases was comprised of a number of fatty acids. In terms of the usual nomenclature (chain length number of double bonds), the fatty acid composition of the steryl esters in spruce heartwood was found to be 12 0 (10%), 14 0(12%), 16 0(20%), 16 1 (12%), 18 0(14%), 18 1 (16%), 18 2(5%), and unidentified (11%). The composition varied only slightly from this in sapwood. In both sapwood and heartwood of the spruce, the ester was a minor form of the total sterol. The ester to free sterol ratio was about 1 2 in the inner heartwood (37). Sitosterol and other sterols have also been found to exist partly in the ester form in the heartwood of angiosperms - e.g., the slippery elm (Ulmus rubra) (24). Similarly, the sterols in the bark of the western white pine (Pinus monticola) are partly (60%) esterified (13). In both heartwood and bark the steryl composition of the ester fraction approximately reflected the composition of the free sterol fraction in that sitosterol was the major component followed by its 24-methyl analogs (13, 37). A similar situation has been observed with non-woody angiosperms - e.g., Zea mays (71). 

The heartwoods of the American trees, Betula alleghaniensis and B. lenta (Betulaceae), are reported to contain sitosterol yS-D-glucoside (78) (98). Similarly, from the heartwood of Melia birmanica (Meliaceae) this glucoside was isolated (0.016% of shavings) and very well characterized (88). There is also a report of its presence in heartwood of the legume Piptadenia macrocarpa (57). 

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