8,14-Epoxyergosta-4,22-diene-3,6-dione

Chemical Constituents of Papulaspora immersa, an Endophyte from Smallanthus sonchifolius (Asteraceae), and Their Cytotoxic Activity.[Reference: WebLink]

Chemistry & Biodiversity, 2010, 7(12):2941-2950.

Papulaspora immersa H. H. Hotson was isolated from roots and leaves of Smallanthus sonchifolius (Poepp. and Endl.) H. Rob. (Asteraceae), traditionally known as Yacon.
METHODS AND RESULTS:
The fungus was cultured in rice, and, from the AcOEt fraction, 14 compounds were isolated. Among them, (22E,24R)-8,14-Epoxyergosta-4,22-diene-3,6-dione (4), 2,3-epoxy-1,2,3,4-tetrahydronaphthalene-c-1,c-4,8-triol (10), and the chromone papulasporin (13) were new secondary metabolites. The spectral data of the known natural products were compared with the literature data, and their structures were established as the (24R)-stigmast-4-en-3-one (1), 24-methylenecycloartan-3β-ol (2), (22E,24R)-ergosta-4,6,8(14),22-tetraen-3-one (3), (-)-(3R,4R)-4-hydroxymellein (5), (-)-(3R)-5-hydroxymellein (6), 6,8-dihydroxy-3-methylisocoumarin (7), (-)-(4S)-4,8-dihydroxy-α-tetralone (8), naphthalene-1,8-diol (9), 6,7,8-trihydroxy-3-methylisocoumarin (11), 7-hydroxy-2,5-dimethylchromone (12), and tyrosol (14).
CONCLUSIONS:
Compound 4 showed the highest cytotoxic activity against the human tumor cell lines MDA-MB435 (melanoma), HCT-8 (colon), SF295 (glioblastoma), and HL-60 (promyelocytic leukemia), with IC₅₀ values of 3.3, 14.7, 5.0 and 1.6 μM, respectively. Strong synergistic effects were also observed with compound 5 and some of the isolated steroidal compounds.

The anti-promyelocytic leukemia mode of action of two endophytic secondary metabolites unveiled by a proteomic approach.[Reference: WebLink]

Planta Medica, 2014, 80(06):473-481.

METHODS AND RESULTS:
As a result of a program to find antitumor compounds of endophytes from medicinal Asteraceae, the steroid (22E,24R)-8,14-Epoxyergosta-4,22-diene-3,6-dione (a) and the diterpene aphidicolin (b) were isolated from the filamentous fungi Papulaspora immersa and Nigrospora sphaerica, respectively, and exhibited strong cytotoxicity against HL-60 cells. A proteomic approach was used in an attempt to identify the drugs' molecular targets and their respective antiproliferative mode of action. Results suggested that the (a) growth inhibition effect occurs by G2/M cell cycle arrest via reduction of tubulin alpha and beta isomers and 14-3-3 protein gamma expression, followed by a decrease of apoptotic and inflammatory proteins, culminating in mitochondrial oxidative damage that triggered autophagy-associated cell death. Moreover, the decrease observed in the expression levels of several types of histones indicated that (a) might be disarming oncogenic pathways via direct modulation of the epigenetic machinery.
CONCLUSIONS:
Effects on cell cycle progression and induction of apoptosis caused by (b) were confirmed. In addition, protein expression profiles also revealed that aphidicolin is able to influence microtubule dynamics, modulate proteasome activator complex expression, and control the inflammatory cascade through overexpression of thymosin beta 4, RhoGDI2, and 14-3-3 proteins. Transmission electron micrographs of (b)-treated cells unveiled dose-dependent morphological characteristics of autophagy- or oncosis-like cell death.