Identification of melatonin in Trichoderma spp. and detection of melatonin content under controlled-stress growth conditions from T. asperellum

T. koningii, T. harzianum, T. asperellum, T. longibrachiatum, and T. viride were analyzed using liquid chromatography‐tandem mass spectrometry to determine whether melatonin is present. Results showed that there were abundant amounts of endogenous melatonin in five Trichoderma species, but no melatonin was found in any of the culture filtrates. T. asperellum had the highest amount of melatonin (27.588 ± 0.326 μg g−1 dry mass), followed by T. koningii, T. harzianum, T. longibrachiatum, and T. viride. The endogenous melatonin content of T. asperellum in controlled‐stress growth conditions was also detected. The data showed that chemical stressors (CdCl2, CuSO4, and H2O2) provoked an increase in endogenous melatonin levels. CdCl2 had the highest stimulatory effect on melatonin production, as the product reached reaching up to three times the melatonin content of the control. NaCl stimulated a decrease of melatonin. Acidic conditions (pH 3 and pH 5) as well as slightly alkaline conditions (pH 9) resulted in an increase in the melatonin content, whereas pH11 resulted in a significant decrease in the melatonin content, only 12.276 ± 0.205 μg g−1 dry mass. The current study is first to report melatonin content and the change of melatonin content under different stress situations in Trichoderma spp.