Cyclo(L-Pro-L-Val)

Actinobacteria are well known for their potential in biotechnology and their production of metabolites of interest. Lichens are a promising source of new bacterial strains, especially Actinobacteria, which afford a broad chemical diversity. In this context, the culture medium of the actinobacteriumNocardia ignorata,isolated from the terrestrial lichenCollema auriforme, was studied. The strain was cultivated in a BioFlo 115 bioreactor, and the culture medium was extracted using an XAD7HP resin. Five known diketopiperazines: cyclo (l-Pro-l-OMet) (1), cyclo (l-Pro-l-Tyr) (2), cyclo (d-Pro-l-Tyr) (3), cyclo (l-Pro-l-Val) (4), cyclo (l-Pro-l-Leu) (5), and one auxin derivative: indole-carboxaldehyde (8) were isolated, along with two new brominated diketopiperazines: cyclo (d-Pro-l-Br-Tyr) (6) and cyclo (l-Pro-l-Br-Tyr) (7). Structure elucidation was performed using HRMS and 1D and 2D NMR analysis, and the synthesis of compounds6and7was carried out in order to confirm their structure.

Stewed beef and grilled dry aged beef were analyzed as part of an in-depth analytical program, with the aim of creating new flavors incorporating only compounds identified in the target foods and identifying new synthesis targets. In-house GC-MS analyses of several types of cooked beef have identified over 1000 volatile and semivolatile components; many for the 1st time. Among the semivolatiles detected were ten 2, 5-diketopiperazines (cyclic dipeptides) previously unreported in beef. These cyclic dipeptides are cis-cyclo(L-Ile-L-Pro), cis-cyclo(L-Leu-L-Pro), cis-cyclo(L-Pro-L-Pro), cis-cyclo(L-Pro-L-Val), cis-cyclo(L-Ala-L-Pro), cyclo(Gly-L-Pro), cyclo(Gly-L-Leu), cis-cyclo(L-Met-L-Pro), cis-cyclo(L-Phe-L-Pro), and cis-cyclo(L-Phe-L-Val). All 10 cyclic dipeptides were synthesized and evaluated organoleptically. Among them cis-cyclo(L-Leu-L-Pro), cis-cyclo(L-Met-L-Pro), and cis-cyclo(L-Phe-L-Pro) were found to be of particular organoleptic interest.

A fungal strain of Aspergillus niger was recovered from sediments collected in the Northeast coast of Brazil (Pecém's offshore port terminal). Cultivation in different growth media yielded a new ester furan derivative, 1, along with malformin A1, malformin C, cyclo (trans-4-hydroxy-L-Pro-L-Leu), cyclo (trans-4-hydroxy-L-Pro-L-Phe), cyclo (L-Pro-L-Leu), cyclo (L-Pro-L-Phe), pseurotin D, pseurotin A, chlovalicin, cyclo (L-Pro-L-Tyr) and cyclo (L-Pro-L-Val). Compound 1 was cytotoxic against HCT-116 cell line, showing IC50= 2.9 μg/mL (CI 95% from 1.8 to 4.7 μg/mL).