The strain SCSIO 01127, isolated from the South China Sea sediment, was identified as a member of Streptomyces by the 16S rDNA sequence analysis. Two new spirotetronate antibiotics lobophorins E (1) and F (2), along with two known analogs lobophorins A (3) and B (4), were isolated from Streptomyces sp. SCSIO 01127. Their structures were elucidated on the basis of detailed IR, NMR and MS spectroscopic analyses. The new compound lobophorin F (2) showed antibacterial activities against Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212 with MIC values of 8 μg ml⁻¹ for both the strains, better than that of lobophorin B (4). Lobophorin F (2) also displayed better cytotoxic activities than lobophorin B (4), with IC₅₀ of 6.82, 2.93 and 3.16 μM against SF-268, MCF-7 and NCI-H460, respectively.

Pseudonocardians A–C (2–4), three new diazaanthraquinone derivatives, along with a previously synthesized compound deoxynyboquinone (1), were produced by the strain SCSIO 01299, a marine actinomycete member of the genus Pseudonocardia, isolated from deep-sea sediment of the South China Sea. The structures of compounds 1–4 were determined by mass spectrometry and NMR experiments (¹H, ¹³C, HSQC, and HMBC). The structure of compound 1, which was obtained for the first time from a natural source, was confirmed by X-ray analysis. Compounds 1–3 exhibited potent cytotoxic activities against three tumor cell lines of SF-268, MCF-7 and NCI-H460 with IC₅₀ values between 0.01 and 0.21 μm, and also showed antibacterial activities on Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212 and Bacillus thuringensis SCSIO BT01, with MIC values of 1–4 μg mL⁻¹.