Abstract
Fractionation and purification of the ethyl acetate extract of the culture of a sponge-derived actinomycete, Streptomyces species Call-36, resulted in the isolation and identification of a new diketopiperazine, actinozine A (1), cyclo(2-OH-d-Pro-l-Leu) (2), two new nucleosides, thymidine-3-mercaptocarbamic acid (3) and thymidine-3-thioamine (4), together with cyclo(d-Pro-l-Phe) (5) and cyclo(l-Pro-l-Phe) (6). The structure assignments of the compounds were carried out by interpretation of 1D and 2D NMR data and mass spectral determinations. The absolute configurations of 1 and 2 were determined by Marfey’s method and by comparison of the experimental and TDDFT-calculated ECD spectra. Actinozine A possesses an unprecedented hydroperoxy moiety at C-2 of the proline moiety, while 3 and 4 possess unusual mercaptocarbamic acid and thiohydroxylamine functionalities at N-3 of the thymine moiety. The isolated compounds displayed variable cytotoxic and antimicrobial activities.
Highlights
Secondary metabolites played a vital role in discovery and development of drugs and saved the lives of millions of people over the past decades [1,2]
Optical rotations were measured on a JASCO DIP-370 digital polarimeter at 25 ◦ C at the sodium
UV spectra were recorded on a Hitachi 300 spectrometer
Summary
Secondary metabolites played a vital role in discovery and development of drugs and saved the lives of millions of people over the past decades [1,2]. There is a continuous need for novel chemical entities with new mechanisms of action to overcome drug resistance and to fulfill the medical needs for new drugs [3]. This need forced the chemists to search for understudied microbial. Marine actinobateria, including actinomycetes, have proven to be producers of novel chemical entities with diverse bioactivities such as antitumor, antimicrobial, anti-inflammatory, antiparasitic, antimalarial, antiviral, antioxidant, anti-angiogenesis and many others [5,6]. DKPs are represented in structurally diverse groups of secondary metabolites, with different examples showing significant bioactivities including antimicrobial, antitumor, analgesic, and many other biomedical indications [7].
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