Pachybasin

Anthraquinone-derivatives, chrysophanol and pachybasin, were purified by a silica column chromatography with two different solvent systems from Trichoderma harzianum ETS 323. The fungus was incubated in sugarcane bagasse solid medium at room temperature without rotation. Structure of chrysophanol was solved by X-ray diffraction and pachybasin by NMR spectra. About 233+/-13 mg of pure chrysophanol and 773+/-40 mg of pure pachybasin were recovered per kg of solid cultural medium, with yields 1.7+/-0.2% and 5.6+/-0.5%, respectively.

To document the safety of pachybasin, a secondary metabolite of Trichoderma harzianum, for use as a bioagricultural agent, it was subjected to general toxicological testing in mice and developmental toxicity in zebrafish. With either 5 or 20 mg kg-1pachybasin i.p. injection, mice behavioral responses such as motor coordination, spontaneous locomotor activity, or nociceptive pain were not influenced. In long-term effect (daily injection for 14 days), the physiological, hematological, liver, and kidney functions were not altered either. Evidence for the developmental toxicity of pachybasin (10-100 μM) in 72-h exposure period was shown in zebrafish larvae, based on developmental retardation, impairment of chorion, and increase of mortality. In summary, there are no significant general toxicities presented in the pachybasin-treated adult male mice. However, the embryo-toxicity in aquatic biota should be taken into consideration during bioagricultural agent application.

Our aim was to determine the effects of two secondary metabolites secreted by Trichoderma harzianum, pachybasin and emodin, on the mycoparasitic coiling behavior and cAMP content of T. harzianum. The number of T. harzianum coils around Nylon 66 fiber was increased in the presence of R. solani. The number of T. harzianum coils around R. solani hyphae and Nylon 66 fiber were significantly increased in the presence of pachybasin and emodin. The cAMP level in T. harzianum was significantly increased by close contact with R. solani and much higer cAMP level in the presence of exogenous pachybasin and emodin. A cAMP inhibitor diminished the effect of pachybasin and emodin on T. harzianum coiling around Nylon 66 fiber. The results suggest that pachybasin and emodin mediate the increase in the number of Trichoderma mycoparasitic coils via cAMP signaling. This is the first report to suggest that pachybasin and emodin play roles in the biocontrol mechanism of Trichoderma.