Roridin E

Macrocyclic trichothecenes are a class of mycotoxins, some of which exhibit substantial antileukemic properties. These compounds vary in their toxicity by approximately 100 fold and are suspected immunotoxins. We studied 11 of these mycotoxins: roritoxin B, myrotoxin B, roridin A, verrucarin A, 16-hydroxyverrucarin A, verrucarin J, baccharinoid B12, roridin D, roridin E, baccharinoid B4 and baccharinoid B5 for their immunotoxicity in CD-1 mice. An equitoxic dose was prepared in 1% DMSO in saline and administered i.p. at half the LD50. Organ weights, WBC, RBC, differentials of blood cell counts, blastogenesis of splenic lymphocytes in response to concanavalin A (Con A), lipopolysaccharide (LPS), phytohemagglutinin (PHA) and pokeweed mitogen (PWM), and mixed lymphocyte reaction (MLR) were studied on day 4 after administration of each mycotoxin. Organ weights showed significant differences between the controls and the baccharinoids with a decrease in spleen weight in baccharinoid B12 and an increased liver weight in B4 and B5 treated animals. Administration of myrotoxin B, roridin A, verrucarin J and roridin E had total WBC counts statistically different from controls, while mice administered myrotoxin B shoed a decrease in numbers of RBC. Differentials of WBC were unremarkable regardless of the mycotoxin. Roritoxin B and baccharinoid B5 increased Con A stimulation of splenic lymphocytes. Roridin A and baccharinoid B12 increased LPS stimulation of splenic lymphocytes while baccharinoid B5 decreased the LPS response. Stimulation of splenic lymphocytes with PHA was significantly increased by roridin A and baccharinoid B5. Stimulation of splenic lymphocytes with PWM was not altered significantly by any mycotoxin.(ABSTRACT TRUNCATED AT 250 WORDS)

A careful investigation of cultures of Myrothecium verrucaria has shown that this fungus produces all four roridin E isomers (3a-d), diastereomeric at the C-6' and C-13' centers. The stereochemistries at these centers were established by a combination of X-ray crystallographic analysis, NMR spectroscopy, and chemical transformations. NMR data from these and other macrocyclic trichothecenes allows for the assignment of configurations at the C-6' and C-13' centers for most of these compounds, the exceptions being those congeners having a C-4' ketone group in the macrolide ring.

Myrothecium verrucaria was found to be an effective pathogen against kudzu grown in the greenhouse and the field. M. verrucaria produced large amounts of macrocyclic trichothecenes when cultured on solid rice medium, including epiroridin E (16.8 mg/g crude extract), epiisororidin E (1 mg/g), roridin E (8.7 mg/g), roridin H (31.3 mg/g), trichoverrin A (0.6 mg/g), trichoverrin B (0.1 mg/g), verrucarin A (37.4 mg/g), and verrucarin J (2.2 mg/g). Most of these toxins were also isolated from M. verrucaria spores and mycelia grown on potato dextrose agar medium, including epiroridin E (32.3 mg/g), epiisororidin E (28.6 mg/g), roridin E (0 mg/g), roridin H (60 mg/g), trichoverrin A (1.3 mg/g), trichoverrin B (1.8 mg/g), verrucarin A (13.8 mg/g), and verrucarin J (131 mg/g). When M. verrucaria was cultured on liquid media, the numbers but not the amounts of toxins decreased. Only epiroridin E (28.3 mg/g), epiisororidin E (29.6 mg/g), verrucarin B (195 mg/g) and verrucarin J (52.6 mg/g) were measured when the fungus was cultured on cornsteep medium. On soyflour-cornmeal broth M. verrucaria produced several toxins, including epiroridin E (58.1 mg/g), epiisororidin E (5.8 mg/g), verrucarin B (29.9 mg/g) and verrucarin J (32 mg/g). In contrast, no macrocyclic trichothecenes were detected by HPLC analysis of plant tissues of kudzu, sicklepod, and soybean treated with aqueous suspensions of M. verrucaria spores formulated with a surfactant. Chloroform-methanol extracts of kudzu leaves and stems treated with M. verrucaria spores were less cytotoxic to four cultured mammalian cell lines than the corresponding extracts from control plants. Purified macrocyclic trichothecenes (verrucarin A and T-2 toxin) were very cytotoxic to the same cell lines (< or = 2 ng/ml). These results show that neither intact macrocyclic trichothecenes nor toxic metabolites could be detected in plant tissues after treatment with M. verrucaria spores. These results argue for both safety and efficacy for the use of M. verrucaria in biological control of kudzu and other noxious weeds, and support proceeding to animal feeding trials for further evaluation of safety.