22.23- Dihydrobrassicasterol

The beauty of the microbiological method lies in its ability to oxidize the structurally similar C-17 side chains of other steroids which contaminate sitosterol (e.g., campesterol, dihydrobrassicasterol, and stigmasterol—all of which carry the 3 3-hydroxy-5-ene structure) at both C-17 and 9a sites to compound XXXVIII. 

Generally the sterols in Mollusca are a complex mixture of Cje-, C27-, C28- and C29-sterols [124]. In the classes of Gastropoda, Bivalvia and Cephalopoda, A -sterols including cholesterol are the most abundant sterols. In the class Amphineura, A7-sterols are predominant in all species, and 5 -cholest-7-en-3)8-ol is the major sterol. Cephalopoda contain cholesterol as about 90% of the total sterols. Gastropoda and Bivalvia also contain cholesterol as the major sterol (50-60%). In some species of Bivalvia, the sterol fraction is a mixture of C27-, C28- and Cjg-sterols, and in some species dihydrobrassicasterol is the major sterol (34-65%). The most... 

Fig. 7. Cycloartenol, rather than lanosterol, is the first cyclized precursor of sterols and plants. Sitosterol (24a-ethylcholesterol), shown here, is the most common plant sterol, but plants generally contain complex mixtures of sterols. Other prominent phytosterols differ from sitosterol as follows. Campesterol, 24a-methyl stigmasterol, C22 double bond dihydrospinasterol, move double bond from C5 to C7 spinasterol, move C5 double bond to Cl, add C22 double bond dihydrobrassicasterol, 24/5-methyl brassicasterol, 24 -methyl, add C22 double bond.

Dihexyl ketone, see T-00156 Dihomogammalinolenic acid, in 1-00037 >Dihydroambrettolide, in H-00276 Dihydrobrassicasterol, in M-OOOl 1... 

Dihydrobrassicasterol, in M-OOOl 1 24-Mcthyl-5-cholcstcn-3-ol, M-OOOl 9 4a-Mcthyl-5a-cholcst-7-cn-3/5-ol, M-00020... 

In the case of O. malhamensis it is now clear that A formation in C 8 sterols may occur at an early stage in the biosynthetic sequence, contrary to earlier views 31-norcyclolaudenol (8-G) is converted to 22-dihydrobrassicas-terol (4-K), but this is not further metabolized to brassicasterol (4-H) by desaturation at C-22 (Goad et al., 1974). Similarly in Chlorella both 5a-ergost-8,I4-dien-3 8-ol and 4a-methyl-5a-ergost-8-en-3/3-ol are converted to 22-dihydrobrassicasterol only (Dickson and Patterson, 1972). In yeast the reaction occurs at the 5a-ei go-7,24-dien-3j8-ol 5a-ei go-7,22,24-dien-3j8-ol... 

Figure 3. Another abundant plant sterol is 24-methylcholesterol, frequently referred to as campesterol in the scientific literature. However, 24-methylcholesterol is usually a mixture two epimers 24a-methylcholesterol (campesterol) and 24P-methylcholesterol (22,23-dihydrobrassicasterol). These epimers can be separated by high-performance liquid chromatography (HPLC) (Akihisa et al, 1986 Chitwood and Patterson, 1991) and by capillary gas-liquid chromatography on long, very polar capillary columns (Thompson et al., 1981). Furthermore, their ratio can be determined by H or nuclear magnetic...

Data taken from Miettinen et al. (2000). Total absorption of campesterol and 22,23-dihydrobrassicasterol. 

A > -sterol (brassicasterol) with little or no 22-dihydro derivative present. The monoenic 24-methylcholesterols, therefore, are composed almost entirely of the 24a-eplmer (campesterol). However, in the mature leaf brassicasterol has all but disappeared and the 24-methylsterols have become the usual main line mixture of campesterol with smaller amounts of 22-dihydrobrassicasterol. It appears from this that in the synthesis of Brassica seed sterols a A22-dehydrogenase is present which declines during ontogeny suggesting functionality for the sterols used and/or produced. 

In sponge sterols the configuration 2A(S) is privileged compared with the configuration 2A R)-, consequently, dihydrobrassicasterol 2%) and clionasterol (C29) are much more frequent than campesteroi and sitosterol. 

---