The structure of misamycin (1) was established by various spectroscopic methods, whereas the structures of other known compounds (2–9) were confirmed by comparing their 1H and 13C-NMR data with these of compounds in the literature. In this paper, we would like to report the isolation, structure determination and biological activity of 1.

The strain YIM66403 was isolated using glycerol-asparagine medium (1% glycerol, 0.1% asparagine, 0.1% dipotassium hydrogen phosphate, 1.2% agar, pH 7.2) from a healthy stem of the traditional Chinese medicinal plant Isodon eriocalyx obtained from Xishuangbanna, Yunnan, China, and was identified as Streptomyces sp. by 16S rRNA gene sequence. The seed medium consisted of 0.4% malt extract, 0.5% yeast extract, 0.5% glucose (adjusted to pH 7.2 before sterilization). Strain YIM66403 was cultured in 500 ml erlenmeyer flasks each containing 200 ml seed culture. After 4 days of incubation at 28 °C on a rotary shaker (125 r.p.m.), 10 ml portion of the culture was inoculated into 1000 ml erlenmeyer flasks each containing 250 ml of fermentation medium consisting of 0.5% yeast extract, 2.4% soluble starch, 0.1% glucose, 0.3% beef extract, 0.3% peptone, 0.4% calcium carbonate (adjusted to pH 7.0 before sterilization). The fermentation was carried out at 28 °C on a rotary shaker (125 r.p.m.) for 8 days. A total of 100 l of fermentation broth was collected, and the broth and mycelium were separated. The broth was extracted with ethyl acetate, and the combined extracts were concentrated under reduced pressure to give the crude residue (23 g). The mycelium was extracted with acetone for 30 min. The solvent was removed under vacuum and the remaining water phase was extracted with ethyl acetate; after concentration, 500 g oily crude extract was obtained. A flow diagram for the extraction of anthracyclines is shown in Scheme 1.

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