Fermentation, Isolation, and Antitumor Activity of Sterigmatocystins

Abstract

In a screening program for antitumor substances from microbial fermentations, a compound was isolated from the mycelium of an Aspergillus species which proved to be the mycotoxin 5-methoxysterigmatocystin. This and the subsequently isolated sterigmatocystin gave significant inhibition of the transplanted mouse leukemias P-388 and L-1210. Preparation and testing of several derivatives of 5-methoxysterigmatocystin suggest that certain functions in the molecule are essential for tumor inhibition. Although slight antitumor effects have been reported for the chemically related aflatoxins, we believe this is the first report of antitumor activity of sterigmatocystins.During the course of screening fungal fermentations for antitumor effects, weak inhibition of P-388 lymphatic leukemia was noted with filtrates from an Aspergillus species. The original broth had only slight antimicrobial activity and was without effect at 1:10 dilution on either HeLa or KB cells in tissue culture. Refermentations conducted in an effort to optimize conditions gave highly variable antitumor effects. The reason for this became apparent as a result of a preliminary extraction which indicated virtually all the active principle was in the mycelium. A crudely crystalline solid with significant antitumor activity was recovered in the first such extraction. Subsequent isolation and purification established that the active substance was the well-known mycotoxin 5-methoxysterigmatocystin (5-MS), for which antitumor effects have not previously been described. The fermentation. isolation, chemical preparation, and antitumor effects of several sterigmatocystins are presented. Vegetative culture (4 ml) was transferred to a 500-ml Erlenmeyer flask with 100 ml of production medium consisting of 2% glucose, 3% Staclipse J starch, 2% washed brewers' yeast, and 0.5% CaCO,. MATERIALS AND METHODS ProductionThe production culture was incubated at 27 C on a shaking machine rotating at 270 rpm. Samples were taken after 5, 6, and 7 days of incubation, and the mycelium was extracted with acetone. The quantity of 5-MS in the extract was estimated chromatographically using a silica gel thin-layer plate and a solvent system consisting of 1% methanol in toluene. The agent was made visible with ultraviolet light. Tank fermentations were carried out with the same vegetative culture medium and production medium as used in flasks. A seed tank with 6 gallons (ca. 23 liters) of vegetative culture medium was inoculated with 100 ml of spore suspension. The culture was incubated for 48 h at 81 F (27.2 C) with 0.7-ft2/min r flow and 3-lb/in2 back pressure without agitators. The 10-gallon (ca. 38 liters) production broth was inoculated with 0.5 gallons (ca.

Preparation and antitumor activities of some derivatives of 5-methoxysterigmatocystin

“…3 The antitumor activities for some derivatives were reported at the same time and tentative conclusions were drawn as to structural features in the molecule necessary for the observed biological activity. We have subsequently prepared derivatives of 5-MS in which (a) some functional groups have been modified and (b) new functional groups have been introduced, with the goals of further defining the important functional groups and increasing the biopotency.…”

Bioactive Secondary Metabolites from the Mangrove Endophytic Fungi <i>Nigrospora oryzae</i>

“…Sterigmatocystin 1 was able to inhibit the growth of the cell line by 64% at the concentration of 10 µg/mL. The moderate cytotoxic activity of sterigmatocystin 1 and its derivatives have been earlier reported [20][21]. Pestalopyrone 2 was not tested due the limited quantity of the material.…”

The Structure of the Antibiotic Hedamycin. I. Chemical, Physical and Spectral Properties

“…-Hedamycin is a yellow, crystalline metabolite, which can be isolated from cultures of Streptomyces griseoruber [l]. It is a potent antibacterial agent and has antitumor activity [2]. Thus, the growth of a large number of bacteria is strongly inhibited, whereas the effect with yeasts and protozoa is not so pronounced.…”