Gwanakosides A and B, 6-Deoxy-α-l-talopyranose-Bearing Aromatic Metabolites from a Streptomyces sp. and Coculture with Pandoraea sp.

Single-strain cultivation of a mountain soil-derived Streptomyces sp. GA02 and its coculture with Pandoraea sp. GA02N produced two aromatic products, gwanakosides A and B (1 and 2, respectively). Their spectroscopic analysis revealed that 1 is a new dichlorinated naphthalene glycoside and 2 is a pentacyclic aromatic glycoside. The assignment of the two chlorine atoms in 1 was confirmed by the analysis of its band-selective CLIP-HSQMBC spectrum. The sugars in the gwanakosides were identified as 6-deoxy-α-l-talopyranose based on ¹H–¹H coupling constants, Rotating frame Overhauser enhancement spectroscopy (ROESY) NMR correlations, and chemical derivatization followed by spectroscopic and chromatographic analyses. The absolute configuration of 2, whose production was enhanced approximately 100-fold in coculture, was proposed based on a quantum mechanics-based chemical shift analysis method, DP4 calculations, and the chemically determined configuration of 6-deoxy-α-l-talopyranose. Gwanakoside A displayed inhibitory activity against pathogenic bacteria, including Staphylococcus aureus (MIC = 8 μg/mL) and Mycobacterium tuberculosis (MIC₅₀ = 15 μg/mL), and antiproliferative activity against several human cancer cell lines (IC₅₀ = 5.6–19.4 μM).