, 2009). Ang 9 shows similarity to the drug resistance transporter, EmrB/QacA subfamily, possibly involved in secretion of secondary metabolites. Therefore, ang 1 and 9 could be responsible for the excretion of Selleck Screening Library angucyclinone antibiotics out of the

cell. Ang 6 shows similarity of 52% to the LuxR family transcriptional regulator that is a widespread and functionally diverse transcription factor and belongs to TetR protein superfamily. It could both activate and inhibit the expressions of many genes contingent on the contexts and thereby is involved in many crucial physiological events, such as virulence factors production, quorum sensing (QS), biosynthesis, metabolism, and ecological competition (Zeng & Xie, 2011). Ang 8 is identified as the TetR family transcriptional regulator,

which consists of two domains: a DNA-binding domain with a helix-turn-helix motif and a regulatory domain as signal recognition function via ligand binding. This protein family is mainly as repressors or regulator for the biosynthesis of antibiotics, drug-efflux pumps, and other proteins (Ramos et al., 2005). Therefore, the gene cluster analysis implies that Streptomyces sp. W007 has potential to produce angucyclinone antibiotic analogs. Based on the sequence data, novel angucyclinone antibiotics are isolated from the crude extract of Streptomyces sp. W007. Compounds 2, 3, 4, 5, and 6 (Fig. 2) were Selleckchem RO4929097 separated followed by compound 1. Based on 1H, 13C-NMR, and ESI-MS spectra, compounds 2, 3, 4,5, and 6 were proved to be X-14881E (Maehr et al., 1982), 6-deoxy-8-O-methylrabelomycin (Shigihara et al., 1988; Gilpin et al., 1989), 8-O-methylrabelomycin (Shigihara CYTH4 et al., 1988), kiamycin (Xie et al., 2012), and 7-acefylchrysophanol (Delle Monache et al., 1991), respectively. Besides, relative configuration of compound 1 has been reported

(Zhang et al., 2011). However, to further test the absolute configuration of compound 1, X-ray ORTEP was conducted (Fig. 3). In the structure of compound 1, ring A,C, and D show the same structure as found in known compounds 2, 3, and 4. However, ring B is not quinoid and shows novel reduction state at C-7 and C-12, and no keto or hydroxy groups at C-7 and C-12. Surprisingly, without using any staining reagent, partial compound 3 (brilliant yellow) changed into 2 (orange) quickly after exposing the TLC plate in air for only 5 minutes. The transformation is possibly due to H+-catalysis, and this process could be catalyzed by aromatase (ang 17) and reductase (ang 5 and 7) in the biotransformation.