Quinonemethide triterpenoids

The root extracts of Maytenus senegalensis have been shown to inhibit protein kinase C, as well as having lethality against brine shrimp. The dihydroagarofuran sesquiterpene alkaloids mayteine, putterine A and putterine B have been isolated from the root extracts. Quinonemethide triterpenoids, which have revealed potential anti-tumour and antimicrobial activities, are another diverse group of secondary metabolites from the related species Maytenus ilicifolia. ... 

A number of celastroloids with extended conjugation has been described [35]. But compounds lacking an insaturation on ring B had not been reported. A compound of this type (74) was also isolated from the roots of M. amazonica by Ch vez et al. [81] as an amorphous white solid, unlike the yellow to red colors exhibited by the rest of the quinonemethide triterpenoids. 

Fig. (45). Examples of quinonemethide triterpenoids with different grade of conjugation...

Gunatilaka, A. A. L. Triterpenoid quinonemethide and related compound (celastroloids). In Progress in the Chemistry of Organic Natural Products Hertz, W. Kirby, G. W. Moore, R. E. Steglich, W. Tamm, C., Eds. Springer-Verlag New York, 1996 Vol. 67, 1-123. 

Dirsch, V. M. Kiemer, A. K. Wagner, H. Vollmar, A. M. The triterpenoid quinonemethide pristimerin inhibits induction of inducible nitric oxide synthase in murine macrophages. Eur. J. Pharm. 1997, 336, 211-217. 

Friedelanes are the most frequently triterpenes isolated from Celastraceae. The co-occurrence of friedelanes and quinonemethides in several species, both in whole plants and cell cultures, has led to propose a biogenetic relationship between these two types of triterpenoids [17,21], Fig. (1). 

In the course of these research programmes, many characteristic bioactive compounds have been reported. Polyester sesquiterpenes and pyridine-sesquiterpene alkaloids with insect antifeedant or insecticidal properties have been isolated from some species and recently sesquiterpene pyridine alkaloids with immunosuppressive or antitumoral activities have also been described. Diterpene triepoxides with potent antileukemic and immunosupressive activities and triterpenoid quinonemethides, named as celastroloids , with antibiotic and cytostatic activities, have been isolated from species of the Celastraceae family. 

The triterpenoid quinonemethides constitute a group of unsaturated and oxygenated D A-friedo- or-oleananes, and in nature these pigments are found restricted to the Celastraceae. They are considered to be indicators of the family and Bruning and Wagner [6] coined the general name celastroloids for this class of compounds. 

The most common and basic class of celastroloids are those with a quinonemethide chromophore extended over the A and B rings of the triterpenoid skeleton. In all of them, the C-29 methyl group has undergone partial oxidation to -CH2OH (eg. excelsine, 178) [242] or complete oxidation to -CO2H (e.g. celastrol, 172) sometimes followed by methylation to produce -C02Me (e.g. pristimerin, 173). Several examples... 

CjsHseOj, Mr 420.59, yellow powder, mp. 78-80°C, [a] 5 -130° (CHCI3). An orange-yellow pigment from the lipophilic outer layer of the agaric Russula flavida in which it is accompanied by a dihydro derivative. The pigments have the same quinonemethide system (p-quinonemethane chromophore) as pentacyclic triterpenoids of the pristimerin type (celastroids). 

A. AX. Gunatilaka Triterpenoid Quinonemethides and Eelated Compounds (Celastroloids)... 

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