Metabolites, fungal classified

Approximately 1200 secondary fungal metabolites were known in 1978,122 and the number at present has reached to more than 6000.109 Approximately 10% of the 6000 metabolites are classified as mycotoxins. The number of secondary metabolites yet to be discovered may be quite large since it is estimated that we know around 5% fungal species out of the world s total fungal species.123,109 Therefore, the number of mycotoxins will probably increase in future. 

Kojic acid (294), a y-pyrone, isolated from T. mairei is a typical microbial metabolite and fungal contamination of the plant extract might be a reason of its formation (227). The diterpenes taxamairins A (297) and B (298) possessing tropone skeleton displayed inhibitory activity [ICj 30.21 g/ml for taxamairin A and 26.78 g/ml for taxamairin B] against hepatoma cells in vitro (228). (+)-Abscissic acid (317) was extracted from the seeds of T. baccata (229-231). The needles of T. baccata contained 26 carboxylic acids, 80% of which were shikimic (335) and quinic acids (336) (232). Rhodoxanthin (300) has been found to be present in all the species of Taxaceae (87,233). Escholtzxanthone (301) was isolated from T. baccata leaves (234). Various compounds isolated from genus Taxus which are not otherwise classified in the text are listed in Table 10. 

The fungal alkaloids seem to be characteristic in utilizing amino acid itself as its component in contrast to the higher plant alkaloids which are biosynthesized mainly from the amine produced by decarboxylation of amino acid (7,2,5). In this chapter, discussion is limited to fungal alkaloidal metabolites isolated from Aspergillus species, which are classified by biogenetic category. 

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