Sporaviridins

Sporaviridins (SVD, Figure 1) are basic water-soluble antibiotics produced by Kutzneria viridogrisea (formerly) Streptosporangium viridogriseum) and they are active against Gram-positive bacteria, acid-fast bacteria and trichophyton. As shown in Figure 2, they consist of six components each having a 34-membered lactone ring and seven monosaccharide units, one pentasaccharide (viridopentaose) and two monosaccharides.

The SDV complex is soluble only in polar solvents such as water, methanol and n-butanol, and is extracted with n-butanol from the fermentation broth. Therefore, a two-phase solvent system containing n-butanol as a major organic solvent was mainly examined. We found that the SVD sample was entirely partitioned into the upper organic phase in a n-bu-tanol/water binary two-phase solvent system (Table 2). This result indicated that the hydrophobic-ity of the n-butanol phase must be decreased to obtain a suitable partition coefficient. A nonpolar solvent such as n-hexane or diethyl ether was added to the n-butanol solvent system as a modifier. Initially, the volume of n-butanol was fixed at 10 mL while that of the diethyl ether was varied, and a two-phase system composed of diethyl ether/n-butanol/water (10:4:10) was selected. Next, the volumes of n-butanol and diethyl ether were fixed while that of water was varied from 11 to 14. At a solvent ratio of 10:4:12, almost evenly dispersed partition coefficients among the six components were obtained as shown in Table 2. Therefore, this solvent system was selected for the separation of the SVD components.

The preparative HSCCC separation of six components from the SVD complex was performed. In this experiment the retention of the stationary phase, elu-tion time, and elution volume were 75%, 3.5 h and

Figure 1 Structures of sporaviridins. (Reproduced with permission from Oka H etal. (1998).)

500 mL, respectively. The six components were eluted in an increasing order of their partition coefficients yielding high purity of components A1 (1.4 mg), A2 (0.6 mg), B1 (0.7 mg), B2 (0.5 mg), C1 (1.1 mg), and C2 (1.4 mg) from 15 mg of the SVD

Figure 2 HPLC separation of sporaviridins. Column, Cosmosil 5C18 (5 |im, 4.6x150 mm); mobile phase, methanol/lmol L~1 ammonium chloride (74:26); flow rate, 1 mLmin~1; detection, 232 nm. (Reproduced with permission from Oka H etal. (1998).)

complex. HPLC analyses of the purified components are illustrated in Figure 3.

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