Separation of avermectin components from Streptomyces avemitilis extraction using high-speed counter-current chromatography
Three compounds of antibiotics-avermectins from fertilizing product of Streptomyces avemitilis are achieved by high-speed counter-current chromatography (HSCCC) with a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (6:4:5:5, v/v) on a preparative scale. The separation condition was: 1.5 mL/min (0 to 200 min) and 2.0 mL/min (200 to the end), 900 rpm and 20?C based on the peak resolution. About 11.9 mg of avermectin B1a, 1.0 mg of avermectin B1b and 9.6 mg of avermectin B2a from 50 mg of crude extract were obtained by one-step separation. The purities of the three compounds determined by HPLC were 99.7%, 96.2% and 97.6%, respectively. Their chemical structures were identified by electron spray ionization mass spectroscopy (ESI-MS), 1H, 13C nuclear magnetic resonance (NMR).