Investigation of the cytotoxic fractions of the ethyl acetate extract of the fermentation broth of the tunicate-derived
Aspergillus sp. DY001 afforded two new dipeptides, asperopiperazines A and B (
1 and
2), along with the previously reported compounds (+)-citreoisocoumarin (
3)
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Investigation of the cytotoxic fractions of the ethyl acetate extract of the fermentation broth of the tunicate-derived
Aspergillus sp. DY001 afforded two new dipeptides, asperopiperazines A and B (
1 and
2), along with the previously reported compounds (+)-citreoisocoumarin (
3) and (−)-6,8-di-
O-methylcitreoisocoumarin (
4). Analyses of the 1D and 2D NMR spectroscopic data of the compounds supported their structural assignments. Asperopiperazine A (
1) is a cyclic dipeptide of leucine and phenylalanine moieties, which are substituted with an
N-methyl and an
N-acetyl group, respectively. On the other hand, asperopiperazine B (
2) is a cyclic dipeptide of proline and phenylalanine moieties with a hydroxyl group at C-2 of the proline part. The absolute configuration of the amino acid moieties in
1 and
2 were determined by Marfey’s analyses and DFT NMR chemical shift calculations, leading to their assignment as cyclo(
l-
NMe-Leu-
l-
NAc-Phe) and cyclo(
d-6-OH-Pro-
l-Phe), respectively. Asperopiperazines A and B displayed higher antimicrobial effects against
Escherichia coli and
Staphylococcus aureus than
Candida albicans. Furthermore, compounds
1–
4 displayed variable growth inhibitory effects towards HCT 116 and MDA-MB-231 cells, with asperopiperazine A as the most active one towards HCT 116.
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