Discovery and characterisation of catedehas A–C, a new class of antioxidant α,β-dehydroamino acid derivatives

Dehydroamino acids are a class of noncanonical unsaturated amino acids commonly found in various naturally occurring peptides and proteins. In this study, we successfully cloned and heterologously expressed the cda biosynthetic gene cluster from Streptomyces nitrosporeus ATCC 12769 in Streptomyces lividans TK24, leading to the identification of three α,β-dehydroamino acid derivatives, designated as catedehas A–C (1–3). Among these, compound 2, although previously reported, lacked any detailed characterisation data. Their structures were elucidated by high-resolution electrospray ionisation mass spectrometry, 1D and 2D nuclear magnetic resonance spectroscopy, along with other spectroscopic techniques. Compounds 1–3 exhibited remarkable antioxidant activity in DPPH· free radical scavenging assay, with IC50 values of 27.52, 12.51, and 8.32 μM, respectively.