Polyester sesquiterpenes

In the course of these research programmes, cytotoxic quinones, polyester sesquiterpenes and pyridine-sesquiterpene alkaloids with antifeedant and/or insecticidal properties have been isolated from Latin American species, in particular those of the Maytenus genus which is extensively used by rural communities and tribes in the Andes and the Amazon basin. Recently some sesquiterpene alkaloids with immunosuppressive activity and sesquiterpenes with antitumoral activity have also been described [3]. 

The salient feature of the family has been its wealth of sesquiterpenes with almost a hundred of these compounds being isolated and characterized chemically. This group of metabolites very common in Latin American species have the eudesmane basic skeleton, and originate the well-known (3-dihydro-agarofuran skeleton polyester sesquiterpenes which are esterified by a series of common organic acids - acetic, benzoic, 3-furoic, trans-cinnamic acid, etc. (Table I). 

The interest generated by polyester sesquiterpenes from the Celastraceae has increased in line with die complexity of the substances isolated and the possibility of their being applied to combat insect plagues instead of synthetic insecticides. The complexity and increasing numbers of these sesquiterpenes makes it difficult to arrange them systematically. They can however, be treated as derivatives of a basic polyhydroxy skeleton and thereafter organized in simpler series. 

Sesquiterpene alkaloids have similar structures to polyester sesquiterpenes except that the hydroxy groups of the eudesmane basic skeleton are esterified by nicotinic acid and/or its derivatives. Little has been published about sesquiterpene alkaloids from American species which tend to be found in the roots of the plants (Table II). 

Celastraceae also elaborate other, more complex, alkaloids, also polyester sesquiterpenes, incorporating a macrocycle derived from an evonic, wilfordic, cassinic or other type pyridine dicarboxylic acid with an additional alkyl chain of the basic eudesmane cycle at C-3 and C-7 (Table III). Celastraceae alkaloids are well-documented for the European and Asian genera, particularly Catha, Celastrus, Euonymus and Trypterigium but are relatively rare among the Latin... 

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. 

This type of polyester sesquiterpenes, is a family of macrolactones that contain a pyridine dicarboxylic acid, such as, evoninic, isoevoninic, wilfordic, isowilfordic, hydrox ilfordic, cassinic, edulinic or cathaic Fig. (11), which bridge the positions C3-C13 of the highly functionalized sesquiterpenoid cores evoninol, euonyminol and isoeounyminol. Fig. (12). 

Shellac is a complex mixture made of mono- and polyesters of hydroxy-aliphatic and sesquiterpene acids, which can be separated into two fractions the soft resin, soluble in ether, mainly consisting of monoesters [134], constituting about 30% of the total resin and the hard resin, ether insoluble, which has quite a complex polyester composition, and... 

These sesquiterpene polyesters are found in a variety of oxygenated forms, being esterified by either aliphatic (acetic, 2-methylbutyric, hydroxyisobutyric, etc.) or aromatic (benzoic, furoic, cinnamic, epoxycinnamic, etc.) acids. Despite their sesquiterpene core, when the ester function is due to nicotinic acid or its derivatives, they are termed sesquiterpene pyridine alkaloids [119]. 

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