Plants form an impressive diversity of natural products. The majority of biologically active compounds originate from secondary (specialized) metabolism. Elucidation of biosynthetic pathways and their regulation provides the basis for targeted metabolic modification and approaches of synthetic biology. The goal is to reconstruct plant biosynthetic pathways in engineered microbes for increased product yields. The methods used include transcriptomics, bioinformatics, metabolic engineering and synthetic biology. continuing...
Benzophenone metabolism yields complex constituents, which belong to the polyprenylated polycyclic acylphloroglucinols (PPAP). Approximately 650 PPAP were isolated and structure elucidated. They are either bridged bicyclic ring systems or tri- and tetracyclic compounds with caged skeletons. Many PPAP possess interesting pharmacological activities, such as antitumoral, antibacterial and antiviral properties. However, their concentrations in plants (primarily Hypericaceae and Clusiaceae) are low, which limits their pharmaceutical development and stimulates biotechnological approaches. continuing...
Extracts of Hypericum perforatum (St. John’s wort) are able to efficiently relieve mild to moderate depression. An important active constituent is hyperforin, the prototype of PPAP. The compound non-selectively inhibits the reuptake of neurotransmitters from the synaptic cleft into the axoplasm. The target structure is TRPC6. Hyperforin is both a structurally and a functionally novel antidepressant. In addition, it possesses further interesting pharmacological properties. continuing...
Biphenyls and dibenzofurans are the phytoalexins of the Malinae, a subtribe of the Rosaceae (formerly subfamily Maloideae). The Malinae include a number of economically important fruit trees, such as apple and pear, and the medicinally used whitethorn. The accumulation of biphenyls and dibenzofurans is an active pathogen defense strategy, which is restricted to the Malinae. The contribution of phytoalexin formation to protection against fire blight and scab and to overcoming replant disease (soil sickness) is under study. continuing...
Besides their involvement in benzophenone and biphenyl biosyntheses, benzoic acids are the precursors of a variety of natural products such as taxol, cocaine and reserpine. In addition, salicylic acid and its methyl ester are important signal molecules in systemic acquired resistance, i.e. enhanced resistance to secondary infection. Benzoic acids are biogenetically related to aromatic aldehydes and alcohols, e.g. vanillin and saligenin. Oxidative decarboxylation leads to simple phenols such as hydroquinone. continuing...
In a phylogenetic tree of type III polyketide synthases (PKS), the amino acid sequences from angiosperms diverge into two clusters. One group consists of chalcone synthases (CHS). CHS is ubiquitously distributed in higher plants. The second cluster is formed by PKSs, which functionally diverge from CHS, such as benzophenone synthase (BPS) and biphenyl synthase (BIS). continuing...
