New Frontiers of essential oils research: biotransformation of the phytocomplex and its pure compounds by endophytic fungi.

摘要

Terpenes are the main constituents of essential oils in plants. They play a considerable role in prevention and therapy of several diseases and constitute building blocks for the synthesis of many useful compounds. In recent years a significant preference towards biotransformation processes has been carried out by using microbial cells as biocatalysts and gathering particular interest for the high production yield of high purity compounds and for their eco-friendly technological approach. The purpose of this study was to investigate the biotransformation of the essential oil of Piper aduncum L., a plant used in traditional Ecuadorian medicine for its antiseptic and antibiotic properties, by endophytic fungi isolated from aerial parts of the plant. Biotransformations applied to terpene phytocomplexes and to their isolated pure chemicals by endophytic micro-organisms isolated from the same plant represent a new approach to the production of new molecules by in vitro strategies. Piper aduncum essential oil has been obtained by steam distillation of wild aerial parts of adult plants collected in Wasakentsa (Ecuador), in January 2006 and supplied by Fundacion Chankuap (Macas, Ecuador). The startup of the research has then been carried out at University of Ferrara Lab performing chemical composition of the essential oil by GC-MS, while the endophytic fungi isolation and subculturing of pure strains on PDA has been processed at CiVaBi (Universidad Politecnica Salesiana, Ecuador). Taxonomic identification of the strains evidencing biotransformation capacity is still in progress. The endophytic fungal strains to be tested for biotransformation activity have been inoculated in 250 ml sterile flasks with PDB liquid medium; after seven days of growing aliquots of whole essential oil or of pure terpene compounds have been added. At different times, samples of biotransforming broth have been collected and monitored for oxidation-reduction reactions. The main components of P. aduncum essential oil, i.e. dillapiol, trans-ocimene, piperitone and terpinen-4-ol, were tested for biotransformation. The biotransformation activity was recorded on two compounds: piperitone and trans-ocimene. Piperitone was transformed into 6-hydroxy-piperitone by EC19 strain evidencing the highest biotransformation yield. The trans-ocimene biotransformation showed good results with all strains tested, especially with EC19 strain giving the compounds dimethyl-octatetraene, dimethyl-octatrienol, dimethyl-octadiendiol.