Pentacyclic triterpenes oleanolic acid

Triterpenic Acids. The following pentacyclic mono- and dihydroxy triterpenic acids are present in virgin olive oil (35, 43, 44) 3p-hydroxy-17-carboxy-5-12-olea-nene (oleanolic acid) 3 3,2a-dihydroxy-17-carboxy-5-12-oleanene (maslinic acid) 3p-hydroxy-17-carboxy-8-12-ursene (ursolic acid) 2a,3p-dihydroxy-17-carboxy-5-12-ursene (2a-hydroxyursolic acid) and deoxyursolic acid (structure not fully elucidated). 

In the oleanane-ursane group of triterpenes, postulated hydride shifts [as proposed by Eschenmoser and co-workers (1955)] have now been demonstrated. Incorporation of [4- C]MVA into oleanolic acid (56), ursolic acid (63), and several other metabolites was accomplished with tissue cultures of Isodon japonicus (Lamiaceae). Following introduction of [4- C]mevalonate and [l,2- C2]acetate, the pentacyclic triterpene compounds were examined by C-NMR spectroscopy. Rings D and E were formed by the routes predicted by Eschenmoser et al. (1955). The labeling pattern at carbons 4,23, and 24 of 3- p/-maslinic acid (64) indicates that this series is formed from (35)-squalene epoxide, rather than from the (3R)-epimer. 

Oleanolic acid a monounsaturated, pentacyclic THterpene (see), with a carboxylic acid group. M, 456.71, m.p. 310°C, [a], -tSO (methanol). It differs structurally from p-amyrin by the presence of a carboxyl group in place of the 28-methyl group (see Amyrin). O.a. occurs free, esterified with acetic acid, or as the aglycon of triterpene saponins (see Sapo-nins) in many plants, e.g. sugar beet, bilberry, mistletoe, cloves and cacti. 

J. M. Castellano, A. Guinda, T. Delgado, M. Rada, J. A. Cayuela, Biochemical basis of the antidiabetic activity of oleanolic acid and related pentacyclic triterpenes. Diabetes 2013.62, 1791-1799. 

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