Cytotoxic Metabolites Of Alternaria Alternata, An Endophyte Of The Medicinal Plant Bidens Bipinnata

Objective: Endophytes are widely spread in the plant kingdom and represent a very promising source of biologically active natural products. The medicinal plant Bidens bipinnata Lin. (Asteraceae) which is known for its anti-inflammatory, antifungal and antitumor effects has been chosen for the investigation of its endophyte to search for bioactive metabolites. Methods: An endophytic Alternaria alternata species was isolated from the leaves of the plant B. bipinnata Lin. To investigate the metabolic profile of this endophytic fungus it was cultivated in several culture media as static and shaken culture. The antimicrobial and cytotoxic activities of the ethyl acetate extracts of the fungus were examined. Extracts exhibiting highest antimicrobial activities in agar diffusion assay and cytotoxicity against HeLa cancer cell line were subjected to activity-guided chromatographic fractionation for the identification of bioactive metabolites. A cytotoxic assay was performed on the isolated compounds against HeLa cancer cell lines as well as cytostatic activity tests against HUVEC and K-562 cell lines. Results: Chromatographic fractionation resulted in the isolation and identification of alternariol and tentoxin from the extract of the fungus cultivated in medium M5 while sterigmatocystin was isolated in addition to alternariol and tentoxin from the extract of the fungus grown in medium M25. Both alternariol and sterigmatocystin proved to be of moderate cytotoxicity and weak cytostatic activity with alternariol showing higher cytotoxic activity than sterigmatocystin. Highest cytotoxicity against HeLa cell lines was observed for tentoxin with a CC50 of 22.5 µg/ml. Conclusion: This study presents the isolation and identification of the bioactive metabolites alternariol, sterigmatocystin and tentoxin from the endophyte A. alternata in addition to the antifungal activity of the strain extract as well as the cytotoxic and cytostatic activities of the isolated metabolites against HeLa, HUVEC and K-562 cell lines, respectively.

Mechanism of sterigmatocystin biosynthesis regulation by pH in Aspergillus nidulans

External pH constitutes one of the most important environmental factors that control growth, metabolism and differentiation in microorganisms, including fungi. We have analyzed the effect of external pH on sterigmatocystin biosynthesis in Aspergillus nidulans. It was observed in repeated experiments that alkaline pH, in opposition to acid pH, increased sterigmatocystin production and the transcript levels of aflR, the master gene that regulates expression of the sterigmatocystin cluster in A. nidulans. It is known that pH effects in fungi operate mostly through the Pal/Pac signaling pathway, originally described in Aspergillus nidulans. Accordingly, we studied the role of this signaling pathway in ST biosynthesis. It was observed that aflR transcript levels were increased in the "alkalinity mimicking" mutant pacCc14 and were minimal in the "acidity mimicking" mutant palA1. No sterigmatocystin was produced by palA1 or pacC- mutants at neither acid or alkaline pH of incubation. Finally, fluG and flbA, genes known to regulate both conidiation and sterigmatocystin synthesis upstream in the regulatory cascade, were up-regulated at alkaline pH.

Spices Mycobiota and Mycotoxins Available in Saudi Arabia and Their Abilities to Inhibit Growth of Some Toxigenic Fungi

The prevalence and population density of the mycobiota of 50 samples belonging to 10 kinds of spices (anise, black pepper, red pepper, black cumin, peppermint, cardamom, clove, cumin, ginger and marjoram) which collected from different places in Jeddah Governorate were studied. The natural occurrence of mycotoxins in those samples was also investigated. Fifteen genera and thirty - one species of fungi in addition to one species variety were isolated and identified during this study. The most common genera were Aspergillus, Penicillium and Fusarium. Aflatoxins (12~40 microg/kg) were detected in the extract of 5 samples of each of anise seeds and black pepper fruits; three samples of black cumin seeds and on sample only of each of peppermint and marjoram leaves out of 5 samples tested of each. Sterigmatocystin (15~20 microg/kg) was detected in some samples of red pepper, cumin and marjoram. The inhibitory effects of 10 kinds of powdered spices were tested against 3 toxigenic isolates of fungi (Aspergillus flavus, A. versicolor and Penicillium citrinum). Clove proved to be antimycotic compounds. It inhibited the growth of the tested toxigenic fungi. Black pepper, peppermint, cardamom, cumin and marjoram completely inhibited aflatoxins production, while black pepper and cardamom also completely inhibited sterigmatocystin production.

Studies on the chemical constituents from the mycelia of marine fungus Aspergillus versicolor / 中国海洋药物

Objective To study the chemical constituents from mycelium of marine fungus Aspergillus versicolor.Methods The compounds were separated by column chromatography and their structures were elucidated based on chemical and spectral analysis. Results Seven compounds have been isolated from the acetone and methanol extracts from the mycelia of Aspergillus versicolor. Their structures were determined as sterigmatocystin (I), 6-methoxysterigmatocystin (II), averufin (III), tyrosine (IV), 3-methyl-pyrrolopiperazine-2, 5-dione (V), 3-isopropyl-pyrrolopiperazine-2, 5-dione (VI), carbamide (VII). Conclusion Compounds IV,V and VI were isolated for the first time from this genus of marine fungi.

Effects of sterigmatocystin on IL-4 mRNA expression and protein secretion of murine spleen cells in vitro / 中国病理生理杂志

AIM: To explore the effects of sterigmatocystin (ST) on IL-4 expression and secretion of murine spleen cells in vitro. METHODS: The secretion and expression of IL-4 in murine spleen cells were studied with ELISA and semi-quantitative RT-PCR method after ST pretreatment at five different dosages (0.125 mg/L, 0.25 mg/L, 0.5 mg/L, 1 mg/L, 2 mg/L) for 2 h and 12 h, respectively. RESULTS: Semi-quantitative RT-PCR analysis showed that the expression of IL-4 mRNA in ST 0.125, 0.25 and 0.5 mg/L treated groups were higher than that in control group, especially in ST 0.5 mg/L group ( P

Effects of sterigmatocystin on IL- 2 and IFN - ? secretion and expression in murine spleen cells in vitro / 中国病理生理杂志

AIM: To explore the effects of sterigmatocystin (ST) on IL-2 and IFN-? expression and secretion in murine spleen cells in vitro. METHODS: The secretion and expression of IL-2 and IFN-? in murine spleen cells after ST pretreatment at five different dosages (0.125 mg/L, 0.25 mg/L, 0.5mg/L, 1mg/L, 2mg/L) were studied with ELISA and semi-quantitative RT-PCR method, respectively. RESULTS: Pretreatment of murine spleen cells in vitro with ST at five different dosages affected the IL-2 and IFN-? secretion at protein level and expression at mRNA level of the treated cells. The effects varied dependently to the ST dosage. At relatively lower dosages, ST induced the expression of IL-2 and IFN-? in murine spleen cells, while at relatively higher dosages, inhibitory effects were found, with the most significant inhibitory effects seen in ST 1 mg/L group. CONCLUSION: ST affected the secretion and expression of IL-2 and IFN-? in treated murine spleen cells. At relatively lower dosage, ST induced IL-2 and IFN-? secretion and expression, while at relatively higher dosages, inhibitory effects appeared.

Effects of sterigmatocystin on interferon-? secretion of human peripheral blood mononuclear cells in vitro / 中国病理生理杂志

AIM: To explore the putative effects of sterigmatocystin (ST) on human help T lymphocyte(Th1)function. METHODS: The effects of ST on interferon-?(IFN-?)secretion of human peripheral blood mononuclear cells(HPBMc) in vitro were determined with ELISA method. RESULTS: The effects of ST on IFN-? secretion of HPBMc in vitro were closely dependent on ST concentrations. ST at relatively lower concentrations (0.03125-0.12500 mg/L) showed inhibiting effects on IFN-? secretion. While, stimulating effects could be found when ST concentration was above 0.25mg/L. The highest level was seen in ST 1 mg/L group ( P

ULTRASTRUCTURAL CHANGES OF CEREBRAL TISSUE IN THE LATERAL RECESS OF THE FOURTH VENTRICLE IN BALB/c MICE AFTER SINGLE ORAL ADMINISTRATION OF STERIGMATOCYSTIN / 解剖学报

Objective To investigate the effects of sterigmatocystin(ST) on the ependymal cells,neurons and endothelial cells of blood vessel of the lateral recess of the fourth ventricle in BALB/c mice in vivo after single oral administration. Methods BALB/c mice were treated intragastrically by gavage with ST 3000??m/kg.The mice were killed 1 hour,2 hours,4 hours,8 hours,16 hours after oral administration respectively for observing ependymal cells,neurons and endothelial cells of blood vessel of the lateral recess with transmission electron microscopy(TEM).Results After oral administration of ST pinocytosis vesicles began to increase in endothelial cells of blood vessel in 1 hour,apocrine of ependymal cells began to increase and myelin sheath degeneration appeared in 2 hours,extensive myelin sheath degeneration and mitochondrion degeneration and incisure and vacuoles in nucleus of neuron were found in 4 and 8 hours.Lipofuscin was found in cytoplasm of neuron 16 hour.Conclusion Oral ST exposure in mice could cause myelin sheath degeneration and damaged changes of neurons.