3-sitosterol, phytosterol quantity

Lipophilic extracts of sabal fruit (Serenoa repens syn. Sabal seruulata) are used in the treatment of benign prostatic hyperplasia (BPH) (see Chapter 55). The hexane extract of the pulp and seed contains a complex mixture of free fatty acids and their esters, small quantities of phytosterols (such as [3-sitosterol), aliphatic alcohols, and polyprenic compounds. The efficacy of this extract was recently compared with that of the 5a-reductase inhibitor finasteride for 6 months, in a randomized, double-blind trial involving almost 1100 men with moderate BPH. Dwarf palm and finasteride reduced the International Prostate Symptom Score by 37 and 39% and increased urinary peak flow by 2.7 and 3.2 ml/sec, respectively. In contrast to finasteride, dwarf palm had little effect on prostate volume. 

Presence of phytosterols in oat oil was first reported by Idler et al. in 1953 (128). Oat grain contains 35-60 mg phytosterols/100 g grain (127). Phytosterol content of oat oil varies between 0.19% to 0.32% (125). p-Sitosterol (40-70% of total sterols) is the major phytosterol in oats. A - and A -Avenasterol are the two other phytosterols that present in significant quantities in oats. Campesterol, stigmasterol, A -stigmasten-3p-ol, A -cholesten-3p-ol, and cholesterol were also present in oat grain. 

Coleoptera. The confused flour beetle, Tribollum confusum, was the first phytophagous insect we found that produces an appreciable amount of a sterol other than cholesterol from radiolabeled dietary C28 and C29 phytosterols. We found this insect produced large quantities of 7-dehydrocholesterol, equivalent to as much as 70% of the total tissue sterols isolated (12). It was further determined that cholesterol and 7-dehydrocTfolesterol were in equilibrium in this flour beetle. Another new intermediate, 5,7,24-cholestatrien-3B-ol was identified as an intermediate between desmosterol and 7-dehydrocholesterol (Figure 3). We found very similar pathways of sterol metabolism to exist in the closely related flour beetle, Tribolium castaneum (13). However, another flour beetle, Tenebrio moHtor, nad only about one-third or less of the levels of 7-dehydrocholesterol as the two Tribolium species, but still much higher levels of this sterol than has been found in most species. Fucosterol 24,28-epoxide was also implicated as an intermediate in the synthesis of cholesterol from sitosterol in T. mol i tor (14). 

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