In screening for newantifungal agents from fungi, a new lipopeptide antifungal agent, L-671,329, similar to echinocandin B, has been isolated from Zalerion arboricola. Studies indicate that L-671 ,329 is produced under both solid and liquid fermentation conditions. Echinocandins/aculeacins are lipopeptide antifungal agents. The polar, cyclic hexapeptide portion of these compoundsis structurally unusual in that all the amino acids contain one or more hydroxyl groups. In sharp contrast to the peptide portion is the extremely non-polar, fatty side chain, which is amide-linked to the amino group of an ornithine-derived amino acid residue^. Variation has been observed in both the cyclic peptide (hydroxylation and amino acid substitution patterns)2'^and in the lipophilic side chain (length, branching, and degrees of unsaturation)3>4).The antibiotic activity of echinocandins appears to be limited to yeasts, especially Candida sp.5). While both natural2~4) and chemical6) variation of the echinocandin structure have shown that the biological activity can be manipulated via structural modification, enzymatic removal of the fatty side chain has shown that the cyclic peptide is inactive alone7), as is the fatty acid. LY121019, a semisynthetic derivative of echinocandin B which showed good in vitro and in vivo anti-Candida activity, was reported to be at least 20-fold less toxic than amphotericin B and, therefore, promises to be important in treating these types of infections in the clinic8).In this paper the fermentation and isolation of L-671,329, a new echinocandin, will be discussed; in the following papers the structural elucidation9) and biological activities10) of this compound will be described.
Materials and MethodsThe methods of detection utilized in the following studies and isolations were antifungal activity as measuredvia zones of inhibition in a disc diffusion assay on agar plates seeded with Candidaalbicans (MY 1028), Merck Culture Collection, HPLCon C18 reversed-phase, or both.Antifungal Assays Seeded agar plates were prepared as follows. Potato dextrose broth (50 ml, Difco) was inoculated with a lyophilized pellet of C. albicans, and the culture was incubated for 24 hours at 28°C, with agitation at 220 rpm. This culture was used as a 1 %inoculum to seed potato dextrose agar (PDA, Difco). Assay samples (20^1) were applied to 6.2 mm-filter discs and air dried at room temperature before being placed on the seeded assay plates. After incubation at 28°C for 24 hours, zones of inhibition were measured via image analysis from the extreme edges of clearing against the background lawn, A standard curve was generated using compoundL-671,329. The critical variation of standard concentrations ranged from 3~8 %.
