The Brazilian higher plant Baccharis coridifolia has been shown to synthesize de novo a series of highly toxic macrocyclic trichothecene antibiotics heretofore found to be produced only by fungi. These compounds are produced only by female plants that have undergone pollination. Neither the male nor female plant is sensitive to the toxic effects of trichothecenes, whereas North American Baccharis species are. The macrocyclic trichothecenes found in B. coridifolia are the same as those produced by Myrothecium fungi, and it is suggested that the plant has acquired the toxin-producing genes from this fungus.

In Sri Lanka, rice is the main staple which is mostly processed into parboiled rice. The levels of aflatoxin B1 (AFB1) and aflatoxin G1 (AFG1) in parboiled and raw milled rice collected from major rice producing areas and rice consuming townships were estimated. In almost all the samples of parboiled rice examined, the AFB1 and AFG1 contents were significantly higher than in raw milled rice. The highest AFB1 content was 185 micrograms/kg and AFG1 content 963 micrograms/kg. These samples were collected from a major rice producing/milling district where the mean relative humidity is 78% and mean annual temperature 27 degrees C which is the highest amongst the rice growing areas in Sri Lanka. Raw rice was either free of aflatoxins or when toxins were detected, they occurred in less than 10% of the samples. The frequency of occurrence of surface fungal flora (Aspergillus/Penicillium) and aflatoxin content in market samples was closely related. Brownish or greenish moldly rice samples with fermented odour contained over 1000 micrograms/kg of AFB1.

No abstract

The comparative biological activity of 21 ntuWrally occurring or synthetically derived steroids, 7 tetracyclh: and pentacylic triterpenoids, and antheridiol incubated with cultures of Phytophthora cactor.mm has been examined. There was greater dependence on precise steric features of the sterol side chain than on the extent of nuclear unsaturation in .nducing oospore formation. There was no significant effect on oospore foimation by changing nuclear unsaturation in ring B from A5 to A7 or ';o A5. Converting the unsaturated, sterol to its corresponding stanol resuited in a significant reduction in the number of oospores produced. The effectiveness of sterols bearing different; side chains in inducing oospores was found to be in the following relative order 24a-ethyl = trans-A22-24a-ethyl > trams- A22-24,8-ethyl = requirement for the induction of oospore formation in Phytophthora cactorum. The latter conclusion was inferred from the fact that cholesterol will induce formation of oospores while cholestanol will not. Elliott has also shown that there are other structural requirements. Of the eight sterols used to supplement P. cactorum, C-24 ethyl sterols produced maximal numbers of oospores while minimal numbers were produced with cholesterol and the C-24 methyl sterol ergosterol (2). The latter indicates a structural preference for alkylation to the C-2 stage at C-24 of the sterol side chain. Elliott and coworkers (4,6) have also shown that neither cycloartenol nor lanosterol induced oospore formation. The purpose of this paper is to extend the findings of Elliott by expanding the results to a number of other steroids and triterpenoids. The 21 steroids used in our study were chosen for their ability to reveal the extent to which steric and nuclear changes in the molecule affect sexual reproduction in P. cactorum. The triterpenoids were chosen because some pentacyclic compounds e.g., an oxidation product of fl-amyrin, have hormonal activity in higher plants (8).Therefore, it was of interest to know whether they would exert similar activity in Phytophthora. Antheridiol and 29 hydroxyporiferasterol were incubated with the fungus because it was possible they might act as hormones in the Pythiaceae. MATERIALS AND METHODSChemicals. Twenty one steroids were used in the present work. Cholesterol, 6-ketocholestanol, and stigmasterol were recrystallized commercial samples. H. Kircher supplied A5-ergostenol, A5, ergostanol, campestanol, campesterol, and cholestanol. M. Thompson supplied sitostanol,isocholesterol (in which the conformer is skew and probably preferred) are the gifts from W. R. Nes. Spinasterol, chondrillasterol, fucosterol, saringosterol, and ergosterol were previously isolated and spectroscopically identified (18,20,21). All compounds except 26-homocholesterol and saringosterol have been shown to be configurationally pure samples by nuclear magnetic resonance spectroscopy (12,15,16,21). Prior to incubation, each steroid was recrystallized and its GLC behavior relative to cholesterol (RRT4) was dete...

The fungal flora of 6 Asian medicinal plants, Aerva lanata (Linn.) Juss. Alyssicarpus vaginalis D.C., Tribulus terrestris Linn. Adhatoda vasica Nees., Centella asciatica (L.) Urb., Cardiospermum halicacabum Linn. was determined. After surface disinfection Aspergillus spp. were most frequently observed. Aspergillus flavus, isolated from Alyssicarpus vaginalis and Aerva lanata produced aflatoxins in culture. Aflatoxin B1 was also detected in a sample of Aerra lanata at a level of 0.5 micrograms/g. Plant material destined for medicinal use should be stored carefully prior to its use to prevent growth of naturally occurring toxigenic mold fungi.