Chemical constituents from the deep sea-derived Streptomyces xiamenensis MCCC 1A01570 and their effects on RXRα transcriptional regulation

From the deep sea-derived Streptomyces xiamenensis MCCC 1A01570, eight cyclic dipeptides (1–8) and five phenolics (9–13) were obtained. Cyclo-(I-Pro-D-Leu) (4) could moderately promote the gene transcriptional function of nuclear receptor RXRα, while 2, 3, and 13 showed weak reduction in RXRα gene transcriptional activities induced by 9-cis-retinoid acid (RA). These compounds might have beneficial effects against intractable diseases with relation to RXRα, such as cancer and metabolic diseases, due to their potential activities on regulating the transcriptional activation function of RXRα. In addition, 1–6, 8, 10, and 12 (20 μM) showed mild in vitro cytotoxicity against three cancer cell lines of ECA-109, Hela-S3 and PANC-1 with the inhibition rates arranging from 50% to 65%.