Mariannamides A and B, new cyclic octapeptides isolated from Mariannaea elegans NBRC102301

Two new cyclic octapeptides, mariannamides A (1) and B (2), have been isolated from Mariannaea elegans NBRC102301, a Pinus densiflora-derived filamentous fungus. Their structures were elucidated to be cyclo-(l-Leu¹-l-Pro¹-l-Pro²-l-Leu²-l-Ile¹-l-Pro³-l-Val¹-l-Ile²) and cyclo-(l-Leu¹-l-Pro¹-l-Pro²-l-Leu²-l-Ile¹-l-Pro³-l-Val¹-l-Val²) based on spectroscopic data and Marfey's method. Mariannamide A (1) promoted mRNA expression of sirtuin 1 (SIRT1) in C2C12 cells, a mouse skeletal muscle myoblast cell line, and showed the antimicrobial activity against Escherichia coli and Cryptococcus neoformans.