Microbial Transformation of the Trichoderma Metabolite 6-n-Pentyl-2H-pyran-2-one

Abstract

Biotransformation of the antifungal Trichoderma metabolite 6-n-pentyl-2H-pyran-2-one (6PAP) (1) by Botrytis cinerea generated the previously reported 3-(2-pyron-6-yl)propionic acid (2) and 5-(2-pyron-6-yl)pentanoic acid (3) and allowed the isolation and characterization of a previously tentatively assigned product as 5-(2-pyron-6-yl)pentan-2-ol (5), plus allowed isolation of a new transformation product identified as 5-(2-pyron-6-yl)pentanoic acid (4). The full NMR spectral assignments of these four compounds are presented here for the first time, including some corrections to assignments previously published for 6PAP. Information is also presented on the relative toxicity of 6PAP and its four biotransformation products to B. cinerea, which shows that the metabolism products have reduced toxicity to the pathogenic organism.

Hemisynthesis and absolute configuration of novel 6-pentyl-2H-pyran-2-one derivatives from Trichoderma spp.

“…Spectroscopic data for structures 2, 3, and 4 coincided with those described in the literature for compounds 6-(5-hydroxypentyl)-2H-pyran-2-one (2), 16,18 6-(4-hydroxypentyl)-2H-pyran-2-one (3), 18 and 6-(4-oxopentyl)-2H-pyran-2-one (viridepyronone) (4). 21 Products 2 and 3 have previously been described as products resulting from the biotransformation of 6-pentyl-2H-pyran-2-one (1) by several fungal isolates, 16,18 but not as secondary metabolites From the fermentations of T. viride UCA 06 carried out with the secondary metabolites elicitor (see Experimental section), in addition to 2-4, compounds 1 and 7-9 were also isolated. Spectroscopic data for product 8 coincided with those previously reported for a characteristic metabolite of this species, trichoviridine 22 (8).…”

“…From fermentation with nicotinic acid as the elicitor chromatography of the extract obtained from the broth yielded 6-pentyl-2H-pyran-2-one (1) (1.3 g), 6-(5-hydroxypentyl)-a-pyrone (2) (7.6 mg), 6-(4-hydroxypentyl)-2H-pyran-2-one (3) (1.6 mg), 16,18 viridepyronone (4) 21 (16 mg), and 6-((1 0 S,2 0 R)-2 0 -propyloxiran-1-yl)-2H-pyran-2-one (7a) (6 mg).…”

“…17 Several of these fungi are able to metabolize 1 into products of reduced toxicity to themselves, as a part of the fungal detoxification mechanism. 16,18,19 Following up on our project oriented toward the study of the secondary metabolism of Trichoderma spp. and the growth inhibition mechanism exerted by these species on phytopathogen fungi, Rubio and co-workers 20 have isolated, characterized, and functionally analyzed, by gene disruption, the first Thctf1 transcription factor gene related to 6-pentyl-2H-pyran-2-one production in Trichoderma harzianum.…”

“…As mentioned above, compounds 2-4 and several 6PP hydroxylated derivatives in position C-1 0 -C-5 0 were isolated as a result of microbial transformation of 1 by selected fungal isolates, 16,18,19 including B. cinerea. These authors concluded that different phytopathogenic fungi have the ability to transform a potentially toxic secondary metabolite, from a competitive fungus, into products of reduced toxicity to itself, indicating the existence of a detoxification mechanism in a number of fungal genera.…”

“…These authors concluded that different phytopathogenic fungi have the ability to transform a potentially toxic secondary metabolite, from a competitive fungus, into products of reduced toxicity to itself, indicating the existence of a detoxification mechanism in a number of fungal genera. 18 With this in mind, we have undertaken the study of a possible self-detoxification mechanism of 1 by Trichoderma spp. Hence, compounds 1-7 were evaluated for their in vitro antifungal activity against the phytopathogen fungus B. cinerea, following the poisoned food bioassay.…”