Can volatile organic metabolites be used to simultaneously assess microbial and mite contamination level in cereal grains and coffee beans?

A novel approach based on headspace solid-phase microextraction (HS-SPME) combined with comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-ToFMS) was developed for the simultaneous screening of microbial and mite contamination level in cereals and coffee beans. The proposed approach emerges as a powerful tool for the rapid assessment of the microbial contamination level (ca. 70 min versus ca. 72 to 120 h for bacteria and fungi, respectively, using conventional plate counts), and mite contamination (ca. 70 min versus ca. 24 h). A full-factorial design was performed for optimization of the SPME experimental parameters. The methodology was applied to three types of rice (rough, brown, and white rice), oat, wheat, and green and roasted coffee beans. Simultaneously, microbiological analysis of the samples (total aerobic microorganisms, moulds, and yeasts) was performed by conventional plate counts. A set of 54 volatile markers was selected among all the compounds detected by GC×GC-ToFMS. Principal Component Analysis (PCA) was applied in order to establish a relationship between potential volatile markers and the level of microbial contamination. Methylbenzene, 3-octanone, 2-nonanone, 2-methyl-3-pentanol, 1-octen-3-ol, and 2-hexanone were associated to samples with higher microbial contamination level, especially in rough rice. Moreover, oat exhibited a high GC peak area of 2-hydroxy-6-methylbenzaldehyde, a sexual and alarm pheromone for adult mites, which in the other matrices appeared as a trace component. The number of mites detected in oat grains was correlated to the GC peak area of the pheromone. The HS-SPME/GC×GC-ToFMS methodology can be regarded as the basis for the development of a rapid and versatile method that can be applied in industry to the simultaneous assessment the level of microbiological contamination and for detection of mites in cereals grains and coffee beans

Induced sclerotium formation exposes new bioactive metabolites from <i>Aspergillus sclerotiicarbonarius</i>

Sclerotia are known to be fungal survival structures, and induction of sclerotia may prompt production of otherwise undiscovered metabolites. Aspergillus sclerotiicarbonarius (IBT 28362) was investigated under sclerotium producing conditions, which revealed a highly altered metabolic profile. Four new compounds were isolated from cultivation under sclerotium formation conditions and their structures elucidated using different analytical techniques (HRMS, UV, 1D and 2D NMR). This included sclerolizine, an alkylated and oxidized pyrrolizine, the new emindole analog emindole SC and two new carbonarins; carbonarins I and J. We have identified the three latter as true sclerotial metabolites. All metabolites were tested for antifungal and antiinsectan activity, and sclerolizine and carbonarin I displayed antifungal activity against Candida albicans, while all four showed antiinsectan activity. These results demonstrate induction of sclerotia as an alternative way of triggering otherwise silent biosynthetic pathways in filamentous fungi for the discovery of novel bioactive secondary metabolites

The natural product Aristolactam AIIIa as a new ligand targeting the polo-box domain of polo-like kinase 1 potently inhibits cancer cell proliferation

AIM: To search for novel inhibitors of human polo-like kinase 1 (Plk1), which plays important roles in various aspects of mitotic progression and is believed as a promising anti-cancer drug target, and further investigate the potential inhibition mechanism of active compounds against Plk1, thus developing potent anti-tumor lead compounds. METHODS: Surface plasmon resonance (SPR) technology-based assay and enzymatic inhibition assay were used to screen Plk1 inhibitors. Sulphorhodamine B (SRB)-based assay, flow cytometry, confocal microscopy and Western blotting were used to further identify the potent Plk1 inhibitor. To investigate the inhibitory mechanism of the active compound against Plk1, enzymatic inhibition assay, SPR and yeast two-hybrid technology-based assays were used. RESULTS: Aristolactam AIIIa was identified as a new type of Plk1 inhibitors, targeting the Polo Box domain (PBD) which is another efficient tactic for exploring Plk1 inhibitors. Further studies indicated that it could block the proliferations of HeLa, A549, HGC and the HCT-8/V cells (clinical Navelbine-resistant cancer cell), induce mitotic arrest of HeLa cells at G(2)/M phase with spindle abnormalities and promote apoptosis in HeLa cells. The results from SPR and yeast two-hybrid technology-based assays suggested that it could target both the catalytic domain of Plk1 (CD) and PBD and enhance the CD/PBD interaction. CONCLUSION: Our current work is expected to shed light on the potential anti-tumor mechanism of Aristolactam AIIIa, and this natural product might be possibly used as a lead compound for further developing anti-tumor drugs