Secondary metabolites from a marine sponge-derived actinomycete <italic>Streptomyces parvulus</italic> MA1076

Abstract

In recent years, researchers have discovered a large number of secondary metabolites with novel chemical structures and diverse activities from sponge-derived actinomycetes. Sponge-derived actinomycetes have become important sources of new drug lead compounds. The actinomycete <italic>Streptomyces parvulus</italic> MA1076 is derived from the sponge( <italic>Pseudoceratina</italic> sp.) on Yongxing Island in the South China Sea. In order to obtain the structural type and potential medicinal value of the secondary metabolites, strain identification and chemical composition analysis were carried out on the sponge-associated actinomycete <italic>Streptomyces parvulus</italic> MA1076. Bacterial genomic DNA rapid extraction kit was used to extract streptomyces genomic DNA. Streptomyces universal primers 27F and 1492R were used for PCR amplification, and the amplified products was sent for sequence testing. The sequencing result was used for strain identification through 16S rDNA sequence analysis and phylogenetic tree construction. Silica gel column chromatography, Sephadex LH-20 gel column chromatography, semi-preparative high performance liquid chromatography and other techniques were applied to separate and purify the ethyl acetate extract of the sponge-derived actinomycetes <italic>Streptomyces parvulus</italic> MA1076. The structure of the compound was identified by spectral data such as proton nuclear magnetic resonance spectroscopy (¹H-NMR), carbon nuclear magnetic resonance spectroscopy (¹³C-NMR), high-resolution mass spectrometry (HR-MS),and combined with the comparison with literature data. Six compounds were isolated and identified from the actinomycetes <italic>Streptomyces parvulus</italic> MA1076, which were actinomycin D (compound 1), daucosterol (compound 2), cyclo-((<italic>S</italic>)-Pro-(<italic>R</italic>)-Leu) (compound 3), thymidine (compound 4), 3′-<italic>O</italic>-acetylthymidine (compound 5), and indole-3-carboxyli acid (compound 6). Compounds 2-6 were isolated for the first time from <italic>Streptomyces parvulus</italic> MA1076. The six compounds were tested for their cell proliferation inhibitory activity on two pancreatic cancer cell lines (pc-12 and bc-16). Results showed that compound 1 had obvious proliferation inhibitory activity on both pancreatic cancer cell lines. Compounds 2-6 showed no obvious anti-tumor cell proliferation activity. The results of the study make full use of the abundant Chinese sponge resources and their associated microbial resources, exploring the structural diversity of sponge secondary metabolites to discover new chemical substances that may be contained in natural products, and to develop new antibacterial , antitumor drugs is of great theoretical significance and potential application value.