Phenolic Metabolites from Humicola grisea var. thermoidea

Antibiotics have been useful in our battles against infectious bacteria and fungi for over 50 years. However, many antibiotics are used commercially, or are potentially useful, in medicine for activities other than their antibiotic action. They are used as antitumor agents, immunosuppressive agents, hypocholesterolemic agents, enzyme inhibitors, antimigraine agents, and antiparasitic agents. A number of these products were first discovered as antibiotics which failed in their development as such, or as mycotoxins. In addition to the above alternative applications, new powerful antibiotics have been discovered and commercialized in recent years and others are in clinical testing. A few successful secondary metabolites appear to have no antibiotic activity [1]. The aim of this work was to evaluate the antimicrobial activity and applications of secondary metabolites produced by Humicola grisea var thermoidea. The production of secondary metabolites was carried out by cultivating 10⁶ spores/g in solid medium (rice) at 40°C for 60 days. The culture was filtered and submitted to the process of liquid-liquid partition with organic solvents. Then, the dicloromethane extract was concentrated under vacuum, and submitted to vacuum liquid chromatography technique, followed by preparative TLC for the isolation of dimethyl terefthalate (DMT), which was elucidated by spectroscopy means (NMR). This compound was submitted to antibacterial assay to determine the minimum inhibitory concentration (MIC) against Escherichia coli, Kocuria rhizophila, Pseudomonas aeruginosa and Staphylococcus aureus. The interval of concentrations evaluated was from 50 µg/mL to 400 µg/mL. The obtained MIC values against K. rhizophila and E. coli were 350 µg/mL. The dimethyl tereftalate is used for production by biopolymer polytrimethylterefthalate (PTT), when polymerized with 1,3-propanediol. Nowadays DMT is obtained from petroleum. Therefore, the production of this compound from fermentative means, using microorganisms would be a promising strategy. Acknowledgment: Financial Support: FAPESP (Grant 01/07935-6) and FCFRP/USP. References: [1] Demain A, Adrio JL (2003) International Microbiology 6: 191–199.