Stigmasterol, structure

Tenerife and La Palma, revealed the existence of luteolin and an array of simple phenolic derivatives as well as three known phytosterols, B-amyrin, sitosterol, and stigmasterol. The phenols identified comprised a set of phenylpropanoids myristicin [566] (see Fig. 6.16 for structures 566-573), methyleugenol [567], todadiol [568], todatriol [569], crocatone [570], elemicin [571], apiole [572], and the coumarin scopoletin [573]. The occurrence of these compounds is recorded in Table 6.5. The differences between the two profiles were taken by Gonzalez and his co-workers... 

The fourth isolated and identified compound from Palmer amaranth is chondri 11 asterol (5a-stigmasta-7,22-dien-30-ol), a sterol closely related structurally to the major plant sterols, stigmasterol and sitosterol. This compound, isolated as the free sterol, is not soluble in water or 0.1% DMS0, and germination bioassays required pretreatment of the test seed with a 0.1 mM solution of the sterol in DCM. 

Most steroids are alcohols, and accordingly are named as sterols. Important examples include cholesterol, ergosterol, estradiol, stigmasterol, and other representative sterols given in Table 30-2. As you can see from their structures, most possess the same ring skeleton but vary considerably in their peripheral structural features, stereochemistry, and in the degree of ring unsaturation. 

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. 

Figure 9.15 Chemical structures of some of the important sterols used as biomarkers in estuaries (e.g., /3-sistosterol, stigmasterol, campesterol, brassicasterol, and cholesterol).

Given are the structure and H, l3C/DEPT, COSY, HMQC, and HMBC, spectra for stigmasterol. Confirm the structure, assign all protons and carbons, and show as many correlations as possible. 

Phytosterols are structurally very similar to cholesterol and the major phytosterols (campesterol, sitosterol and stigmasterol) have the same kind of membrane viscosity modulating function in plants that cholesterol (C27 3-OH-C6 C6 G61 C5—C8) has in animals. Campesterol (24-methylcholesterol), sitosterol (24-ethylcholesterol) and stigmasterol (A22, 24-ethylcholesterol) are widespread phytosterols. The animal sterols lanosterol and cholesterol are present in particular plants. Phytosterol esters reduce cholesterol absorption and lower LDL-cholesterol. 

Phytosterols are partially absorbed in the small intestine. Human absorption efficiency is estimated to be approximately 10% for campesterol and campestanol, 4 to 5% for sitosterol and stigmasterol, and negligible for sitostanol. The absorption of cholesterol ranges from 33 to 60%. Structural features, including the length and configuration of the aliphatic side chain of phytosterols, are thought to contribute to the differences in the absorption efficiency between phytosterols and cholesterol. " Phytosterols apparently displace cholesterol by mass action and... 

While many diets call for reduced intake levels of cholesterol, the plant sterols such as stigmasterol, which are very similar in structure to cholesterol, are not restricted. One of the reasons for the lack of strictures on plant sterols is ... 

Progesterone is a hormone, secreted by the corpus luteum, that is involved in the control of pregnancy. Its structure was established, in part, by the following synthesis from the steroid stigmasterol, obtained from soybean oil. 

Kraft-mill effluent) contain various plant sterols, primarily P-sitosterol (e.85%) and stigmasterol (c.3%) (see Fig. 2.22 for structures), which have oestrogenic activity (they are known to cause masculinization in fish),... 

FIGURE 18-6 Chemical structures of major sterols and cholesterol derivatives. The major sterols in animals (cholesterol), fungi (ergosterol), and plants (stigmasterol) differ slightly in structure, but all serve as key components of cellular membranes. Cholesterol is stored as cholesteryl esters in which a fatty acyl chain (R = hydrocarbon portion of fatty acid) is esterified to the hydroxyl group. Excess cholesterol is converted by liver cells into bile acids (e.g., deoxycholic acid), which are secreted into the bile. Specialized endocrine cells synthesize steroid hormones (e.g., testosterone) from cholesterol, and photochemical and enzymatic reactions in the skin and kidneys produce vitamin D. 

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