Isolation and Identification of DAQH (1) and DAQJ (2).
Screening of our actinomycete secondary metabolite library
against M. tuberculosis in the microplate Alamar Blue assay
(MABA) and low-oxygen-recovery assay (LORA) led to the
selection of Lake Michigan-derived strain B026 for further
chemical investigation. A 28 L fermentation of B026 was
performed, and following the extraction of secondary
metabolites from the fermentation broth and several chromatographic
steps using bioassay-guided fractionation, 0.3 mg each
of 1 and 2 was purified using RP-C18 semipreparative HPLC
(2.4 mL min−1, gradient of 50% aqueous ACN to 100% ACN
for 25 min, followed by an isocratic flow of 100% ACN for 15
min; tR 18.6 and 22.0 min, respectively).