Sekgranaticin, a SEK34b-Granaticin Hybrid Polyketide from <i>Streptomyces</i> sp. 166#

Abstract

Sekgranaticin (1), a novel hybrid polyketide with a complex 6/6/6/6/6/6/6 7-ring system, was isolated together with granaticins A (2) and B (3) and methyl granaticinate (4) from the culture broth of Streptomyces sp. 166#. Its structure was elucidated by spectroscopic analysis. The absolute configuration was determined on the basis of the calculated 13C NMR and electronic circular dichroism data. Compounds 1–4 exhibited potent cytotoxicity against cancer cell lines MCF-7, A549, P6C, and HCT-116 with IC50 values of 0.02–6.77 μM. The biosynthetic pathway of sekgranaticin (1) was proposed.