Diketopiperazines and 2H-pyran-2-ones with antioxidant activity from the rice fermented with Aspergillus luchuensis

Probiotic Potential, Antibacterial, and Antioxidant Capacity of Aspergillus luchuensis YZ-1 Isolated From Liubao Tea

Aspergillus fungi are widely used in the traditional fermentation of food products, so their safety risks and functions are worthy of investigation. In this study, one Aspergillus luchuensis YZ-1 isolated from Liubao tea was identified based on phylogenetic analyses of sequences of three genes coding for internal transcribed spacer 1 (ITS1), β-tubulin (benA), and calmodulin (CaM). The results of hemolytic activity, DNase activity, cytotoxicity assay, and antibiotic resistance assay indicated that the strain is potentially safe. The excellent gastrointestinal fluid tolerance, acid tolerance, bile tolerance, auto-aggregation, co-aggregation, cell surface hydrophobicity, and adhesion to human colon adenocarcinoma (HT29) cell line were observed on analysis of the probiotic properties. Furthermore, the results of the antibacterial activity of A. luchuensis YZ-1 indicated that the strain had strong antagonistic effects against Gram-negative and Gram-positive bacteria as well as fungi. Simultaneously, the water extracts and 80% ethanolic extracts of A. luchuensis YZ-1 cells also showed strong ABTS, DPPH, and OH- scavenging ability. Taken together, our results suggest that A. luchuensis YZ-1 has desirable functional probiotic properties and can be proposed as a biocontrol agent in the food industry.

Mycoproteins and their health-promoting properties: Fusarium species and beyond

Filamentous fungal mycoproteins have gained increasing attention as sustainable alternatives to animal and plant-based proteins. This comprehensive review summarizes the nutritional characteristics, toxicological aspects, and health-promoting effects of mycoproteins, focusing on those derived from filamentous fungi, notably Fusarium venenatum. Mycoproteins are characterized by their high protein content, and they have a superior essential amino acid profile compared to soybeans indicating excellent protein quality and benefits for human nutrition. Additionally, mycoproteins offer enhanced digestibility, further highlighting their suitability as a protein source. Furthermore, mycoproteins are rich in dietary fibers, which have been associated with health benefits, including protection against metabolic diseases. Moreover, their fatty acids profile, with significant proportions of polyunsaturated fatty acids and absence of cholesterol, distinguishes them from animal-derived proteins. In conclusion, the future of mycoproteins as a health-promoting protein alternative and the development of functional foods relies on several key aspects. These include improving the acceptance of mycoproteins, conducting further research into their mechanisms of action, addressing consumer preferences and perceptions, and ensuring safety and regulatory compliance. To fully unlock the potential of mycoproteins and meet the evolving needs of a health-conscious society, continuous interdisciplinary research, collaboration among stakeholders, and proactive engagement with consumers will be vital.

Molecular Dynamics Simulations Guide Chimeragenesis and Engineered Control of Chemoselectivity in Diketopiperazine Dimerases

In the biosynthesis of the tryptophan-linked dimeric diketopiperazines (DKPs), cytochromes P450 selectively couple DKP monomers to generate a variety of intricate and isomeric frameworks. To determine the molecular basis for selectivity of these biocatalysts we obtained a high-resolution crystal structure of selective Csp2 -N bond forming dimerase, AspB. Overlay of the AspB structure onto C-C and C-N bond forming homolog NzeB revealed no significant structural variance to explain their divergent chemoselectivities. Molecular dynamics (MD) simulations identified a region of NzeB with increased conformational flexibility relative to AspB, and interchange of this region along with a single active site mutation led to a variant that catalyzes exclusive C-N bond formation. MD simulations also suggest that intermolecular C-C or C-N bond formation results from a change in mechanism, supported experimentally through use of a substrate mimic.

Asperpyrone, a rare α-pyrone metabolite produced by an endophytic fungus Aspergillus sp. isolated from Garicinia smeathmannii (Planch. & Triana) Oliv

A new α-pyrone, asperpyrone (1) and two known compounds, stigmasterol (2) and 7-hydroxy-3-(2,3-dihydroxybutyl)-1(3H)-Isobenzofuranone (3) were isolated from the solid rice culture of the endophytic fungus Aspergillus sp., an endophytic fungus isolated from the fresh inner tissue of the barks of Garicinia smeathmannii. Their structures were determined by extensive spectral analysis including 1 D and 2 D NMR, HRESIMS and single-crystal X-ray crystallographic analysis. Asperpyrone (1) was tested against an axenic culture of Entamoeba moshkovskii, but did not exhibit any significant amoebicidal activity.

Novel indole diketopiperazine stereoisomers from a marine-derived fungus Aspergillus sp

Four dimeric diketopiperazine stereoisomers (1-4) including two new ones (1-2) had been isolated from the culture broth of one marine-derived fungus Aspergillus sp. Z3, which was found in the gut of a marine isopod Ligia exotica. The planner structures and absolute configurations of the new compounds were determined by combination of NMR, HRESIMS, electronic circular dichroism calculation, Marfey's method as well as single-crystal X-ray diffraction. Their cytotoxicity against the prostate cancer PC3 cell line was assayed by the MTT method.

Cyclic Dipeptides: The Biological and Structural Landscape with Special Focus on the Anti-Cancer Proline-Based Scaffold

Cyclic dipeptides, also know as diketopiperazines (DKP), the simplest cyclic forms of peptides widespread in nature, are unsurpassed in their structural and bio-functional diversity. DKPs, especially those containing proline, due to their unique features such as, inter alia, extra-rigid conformation, high resistance to enzyme degradation, increased cell permeability, and expandable ability to bind a diverse of targets with better affinity, have emerged in the last years as biologically pre-validated platforms for the drug discovery. Recent advances have revealed their enormous potential in the development of next-generation theranostics, smart delivery systems, and biomaterials. Here, we present an updated review on the biological and structural profile of these appealing biomolecules, with a particular emphasis on those with anticancer properties, since cancers are the main cause of death all over the world. Additionally, we provide a consideration on supramolecular structuring and synthons, based on the proline-based DKP privileged scaffold, for inspiration in the design of compound libraries in search of ideal ligands, innovative self-assembled nanomaterials, and bio-functional architectures.

Unambiguous Stereochemical Assignment of Cyclo(Phe-Pro), Cyclo(Leu-Pro), and Cyclo(Val-Pro) by Electronic Circular Dichroic Spectroscopy

2,5-diketopiperazines (DKPs) are cyclic dipeptides ubiquitously found in nature. In particular, cyclo(Phe-Pro), cyclo(Leu-Pro), and cyclo(Val-Pro) are frequently detected in many microbial cultures. Each of these DKPs has four possible stereoisomers due to the presence of two chirality centers. However, absolute configurations of natural DKPs are often ambiguous due to the lack of a simple, sensitive, and reproducible method for stereochemical assignment. This is an important problem because stereochemistry is a key determinant of biological activity. Here, we report a synthetic DKP library containing all stereoisomers of cyclo(Phe-Pro), cyclo(Leu-Pro), and cyclo(Val-Pro). The library was subjected to spectroscopic characterization using mass spectrometry, NMR, and electronic circular dichroism (ECD). It turned out that ECD can clearly differentiate DKP stereoisomers. Thus, our ECD dataset can serve as a reference for unambiguous stereochemical assignment of cyclo(Phe-Pro), cyclo(Leu-Pro), and cyclo(Val-Pro) samples from natural sources. The DKP library was also subjected to a biological screening using assays for E. coli growth and biofilm formation, which revealed distinct biological effects of cyclo(D-Phe-L-Pro).

Isolation, Structural Characterization and Antidiabetic Activity of New Diketopiperazine Alkaloids from Mangrove Endophytic Fungus Aspergillus sp. 16-5c

Six new DIKETOPIPERAZINE alkaloids aspergiamides A-F (1-6), together with ten known alkaloids (7-16), were isolated from the mangrove endophytic fungus Aspergillus sp. 16-5c. The structures of the new compounds were elucidated based on 1D/2D NMR spectroscopic and HR-ESIMS data analyses. The absolute configurations of aspergiamides A-F were established based on the experimental and calculated ECD data. All the compounds were evaluated for the antidiabetic activity against α-glucosidase and PTP1B enzyme. The bioassay results disclosed compounds 1 and 9 exhibited significant α-glucosidase inhibitory with IC₅₀ values of 18.2 and 7.6 μM, respectively; compounds 3, 10, 11, and 15 exhibited moderate α-glucosidase inhibition with IC₅₀ values ranging from 40.7 to 83.9 μM; while no compounds showed obvious PTP1B enzyme inhibition activity.

Protective effects of culture extracts (CB08035-SCA and CB08035-SYP) from Marinobacter hydrocarbonoclasticus (strain CB08035) against oxidant-induced stress in human colon carcinoma Caco-2 cells

The present study investigated the effect of culture extracts (CB08035-SCA and CB08035-SYP) from Marinobacter hydrocarbonoclasticus (strain CB08035) on cell viability and the potential protective effects attributed to molecular mechanisms underlying antioxidant response to survive oxidative stress injuries. Caco-2 cells were submitted to oxidative stress by treatment with tert-butyl hydroperoxide (t-BOOH). Both extracts prevented cell damage and enhanced activity of antioxidant defenses (NQO1 and GST activities and GSH levels) reduced by treatment with t-BOOH. Increased ROS and caspase 3/7 activity induced by t-BOOH were dose-dependently prevented when cells were treated with the extracts. CB08035-SCA caused up-regulation of Nrf2, AKT1 and Bcl-2 gene expressions. Moreover, CB08035-SCA and CB08035-SYP treatments reduced significantly Bax, BNIP3, APAF1, ERK1, JNK1, MAPK1, NFκB1, TNFα, IL-6, IL-1β and HO-1 gene expressions of apoptosis, proinflammation and oxidative stress induced by t-BOOH. CB08035-SCA and CB08035-SYP CPE extracts confer a significant protection against oxidative insults to cells. Our results show that culture extracts CB08035-SCA and CB08035-SYP from M. hydrocarbonoclasticus (strain CB08035) appeared to have antioxidant potential, based on their ability to protect antioxidant enzymes and mRNA gene expressions linked to apoptosis/oxidative pathways. These results suggest that culture extracts CB08035-SCA and CB08035-SYP can be a potential ingredient in the pharmaceutical and cosmeceutical industries.