Cyclo(L-Ala-L-Pro)

Cyclo(l-Ala-l-Pro) inhibits aflatoxin production in aflatoxigenic fungi without affecting fungal growth. The mode of action of cyclo(l-Ala-l-Pro) in inhibiting aflatoxin production of Aspergillus flavus was investigated. A glutathione S-transferase (GST) of the fungus, designated AfGST, was identified as a binding protein of cyclo(l-Ala-l-Pro) in an experiment performed using cyclo(l-Ala-l-Pro)-immobilized Sepharose beads. Cyclo(l-Ala-l-Pro) specifically bound to recombinant AfGST and inhibited its GST activity. Ethacrynic acid, a known GST inhibitor, inhibited the GST activity of recombinant AfGST and aflatoxin production of the fungus. Ethacrynic acid reduced the expression level of AflR, a key regulatory protein for aflatoxin production, similar to cyclo(l-Ala-l-Pro). These results suggest that cyclo(l-Ala-l-Pro) inhibits aflatoxin production by affecting GST function in A. flavus, and that AfGST inhibitors are possible candidates as selective aflatoxin production inhibitors.

Bioassay-guided fractionation of the supernatant of the biocontrol strain Bacillus amyloliquefaciens W1 led to the isolation of eight acaricidal cyclodipeptides from the active fractions by column chromatography separation and HPLC purification. The chemical structures of these compounds were identified as cyclo-(Gly-l-Phe), 2, cyclo-(l-Phe- trans-4-OH-l-Pro), 3, cyclo-(Gly-l-Tyr), 4, cyclo-(l-Ala-l-Pro), 5, cyclo-(l-Pro- trans-4-OH-l-Pro), 6, cyclo-(Gly-l-Pro), 7, cyclo-(l-Pro-l-Pro), 8, and cyclo-(l-Tyr- trans-4-OH-l-Pro), 9. Those cyclodipeptides displayed significant acaricidal activities with LC50 values of 13.85-98.24 μM. Cyclo-(l-Tyr- trans-4-OH-l-Pro) (LC50 13.85 μM) was five times more effective than the positive control abamectin (LC50 72.06 μM). The results indicated that the hydroxyl group is an important component. This is the first report on the acaricidal capabilities of cyclodipeptides against Tetranychus urticae. The results revealed that the acaricidal activity of the biocontrol strain B. amyloliquefaciens W1 was dependent on its constituent cyclodipeptides, which have the potential to be safe and environmentally friendly acaricides.

In the present study, nine compounds (1-9) were isolated from Talaromyces wortmannii LGT-4 (an endophytic fungus from Tripterygium wilfordi) which was cultured in CYM Medium. Their structures were determined as 4-hydroxyphthalide (1), Fumitremorgin C (2), Ergosterol (3), 3-(2-hydroxypropyl)-8-hydroxy-3,4- dihydroisocoumarin (4), Cis-cyclo(L-Ala-L-Pro) (5), 6-Amino-3-(4-hydroxybenzyl)- 1,4-diazonane-2,5-dione (6), Aspergillumarin B (7), Deacetylisowortmin B (8), and Entonaemin A (9) based on NMR spectral data, as well as comparing with previous literature data. This is the first report of the isolation of compounds 1-2 and 4-7 from Talaromyces genus. All compounds were tested for their monoamine oxidase and phosphoinositide 3-kinase (PI3Kα) inhibitory activities. Compound 1, 5 showed moderate anti-monoamine oxidase activity with IC50 value of 35 μg/mL, 28 μg/mL, respectively. Compound 9 showed PI3Kα inhibitory activity with IC50 value of 10.3 μg/mL.