Triterpenes alkenes

The structure-activity relation of triterpene QMs on the anti-inflammatory effect has been investigated with a series of analogues by comparing inhibition of the IL-1 (3 production in the LPS-induced monocytes.93-94 Clearly, the conjugated QM structure with alkenes is essential for the observed inhibition, and similar inhibitory effect was found with derivatives that are capable to form the conjugated QM through hydrolysis and/or oxidation.93-94 Also, the presence of the E ring in the triterpene QM structure is an additional contributor. 

Ring A diosterols.3 The ring A diosterols (3 and 4) of triterpenes can be prepared from the A2-alkene (1) by osmylation to form the two possible cis-diols (2), which on Swern oxidation give the a-diketone (3). The same diketone is also obtained by Swern oxidation of the 2(3,3a-diol, the product of peracid oxidation followed by acid cleavage. The diketone 3 rearranges to the more stable diosphenol (4) in the presence of base. 

Hydrocarbons are very minor components of oils and fats but are of dietary and legislative interest. They include alkanes, alkenes such as squalene and carotenes, and polycyclicaromatic hydrocarbons. Squalene (C30H50) is a highly unsaturated open-chain triterpene. It is used in the cosmetic industry after hydrogenation to squalane (C30H62). The most abundant source of squalene is the liver oil of the deep-sea dogfish (Squalus acanthus—hence the name squalene) and some other marine species. Vegetable sources of potential interest include olive oil and amar-anthus (Section 6). 

In addition to the above mentioned hydrocarbons, oils also contain alkenes and monoterpenic and sesquiterpenic hydrocarbons. For example, the amount of alkenes in olive oils range from 0.5 to 2 mg/kg and includes a series of alk-9-enes from C22 to C27, heptadec-8-ene and 6,10-dimethyl-undec-l-ene. An important compound is the linear triterpenic (C39) hydrocarbon squalene (3-81), aIl-tra s-2,6,10,15,19,23-hexamethyltetracosa-2, 6,10,14,18,22-hexaene, which is the universal precursor of all triterpenoids and steroids. It was given this name because it was discovered in the Hver of sharks (Squalidae). Shark Hver oil contains about 30% squalene, about 7% pristane (2,6,10,14-tetramethylpentadecane) and smaller amounts of phytane (2,6,10,14-tetramethylhexadecane). Squalene occurs in small amounts in edible oils and especially in oHve oil, where its content is in the tenths of a percent (1-7 g/kg). 

Figure 9.8 Examples of sesterterpenes, triterpenes and polyunsaturated linear alkenes isolated from Rhizosolenia setigera (Sinninghe Damste...

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