Elenolic acid

Olive oil Elenolic acid derivatives bonded to tyrosol are main components (400 ppm provides protection, in low concentration prooxidative) Cooked tuna in brine Less protection of cooked tuna in oil Medina et al., 1999... 

Secoiridoids are complex phenols produced from the secondary metabolism of terpenes as precursors of several indole alkaloids (Soler-Rivas and others 2000). They are characterized by the presence of elenolic acid, in its glucosidic or aglyconic form, in their molecular structure. Oleuropein, the best-known secoiridoid, is a heterosidic ester of elenolic acid and 3,4- dihydroxyphenylethanol containing a molecule of glucose, the hydrolysis of which yields elenolic acid and hydroxytyrosol (Soler-Rivas and others 2000). 

Dialdehydic form of decarboxymethyl elenolic acid linked to p-HPEA (p-HPEA-EDA) 1 y CHO ... 

Veer, W. L. C. Preparing elenolide and elenolic acid from Oleaceae. Patent-Dutch-90,043 1959. 

Fig. (2). Structure of the dialdehydic forms of elenolic acid linked to (3,4-dihydroxyphenyl)-ethanol (compound 1) and to (p-hydroxyphenyl)-ethanol (compound 2). Compound 3 is an isomer of oleuropein aglycone.

A good correlation (r = 0.97) was foimd with the dialdehydic form of hydroxytyrosol-elenolic acid and the isomer of oleuropein aglycone (compounds 1 and 3). a -Tocopherol acted synergically with hydrox5dyrosol and the secoiridoid derivatives [45,46]. Sunlight exposure... 

In continuation of his biomimetic syntheses of heteroyohimbine alkaloids Brown" has succeeded in converting secologanin tetra-acetate (117) into elenolic acid (118), and in completing the synthesis of ajmalicine (80) essentially by the route published" earlier (Scheme 14). Contrary to the previous workers, who apparently isolated only ajmalicine. Brown eta/." obtained ajmalicine (80), 19-epiajmalicine (119) and tetrahydroalstonine (120). Since one of the lactams (121) afforded only 19-epiajmalicine (119) and in the general reaction sequence the proportion of (80), (119), and (120) in the final product depended on the length of time allowed for Schiff base formation rather than on the ratio of isomers present in the methyl elenolate [ester of (118)], it is apparent that interconversion of the imines (122) via the equilibria shown in Scheme 14 is responsible for the non-stereospecificity of the synthesis. 

Two other non-glycosidic secoiridoids (see Figure 11) have been isolated from O. europaea. Compound 27 is the elenolic acid, described by Panizzi et al. [2], whereas compound 28 is its methyl ester whose total synthesis was accomplished by MacKellar et al [29], so demonstrating the absolute configuration of these two compounds. 

Oleuropein (81), which may be isolated from several species of Oleaceae, has a role in the increase of a 50% of the coronary blood flew, and shows spasmolitic and antiarritmic effects [110]. On the other hand, it is known that elenolic acid, obtained by hydrolysis of the extracts of olive-tree leaves, has hypertensive properties. All this suggests that the glucoside ring and the 3,4-dihydroxyphenylethanol moieties, both talcing part of the oleuropein structure, but absent in the elenolic acid, are not responsible for the hypotensive activity. 

Allylic alcohol 846 has been employed in the synthesis of several natural products, as illustrated in Scheme 114 for the preparation of ( —)-elenolic acid (856), a secoiridoid monoterpene isolated from the olive Olea europea. The initial reaction is an orthoester Claisen rearrangement of 846 using triethyl orthoacetate, followed by lactonization with pyridinium / -toluenesulfonate. The resulting lactone is obtained as a 3 1 mixture of cw-850 and its trans isomer. After stereospecific alkylation of 850 with allyl bromide, the conversion of 851 to 852, which is essentially an expansion of the lactone by insertion of a methylene unit, requires five steps to accomplish. The remainder of the synthesis is uneventful, and furnishes pure 856 [234]. 

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