Chemical investigation of metabolites produced by an endophytic fungi Phialemonium curvatum from the leaves of Passiflora edulis

One new furanone analogue from the deep-sea fungus Purpureocillium sp. SCSIO 06693

A new furanone analog, (E)-2-(8,9-dihydroxy-6,8-dimethyldec-4-en-2-yl)-met-hylfuran-3(2H)-one (1), together with six known compounds, including two diterpenoids (2 and 3), one butyrolactone (4) and three isocoumarins (5-7), were isolated from a deep-sea fungus, Purpureocillium sp. SCSIO 06693. Among them, compound 1 existed as two tautomeric forms (1a and 1b) differing in configuration of the furan ring. The chemical structures were elucidated by the basis of spectroscopic evidences, including HRESIMS, NMR and optical rotation. Isolated compounds were evaluated for their cytotoxic, antiviral, antibacterial, antioxidant, acetyl cholinesterase (AChE) and pancreatic lipase (PL) enzyme inhibitory activities. Biological evaluation results revealed that compound 4 showed modest antioxidant activity against DPPH with IC50 value of 72.03 μM. In addition, compounds 1-4 exhibited PL enzyme inhibitory activities.

Biotechnology of Passiflora edulis: role of Agrobacterium and endophytic microbes

Two forms of the genus Passiflora, belonging to the Passifloraceae family, are commonly called yellow and purple passion. These perennial woody climbers are found in the cooler regions at higher altitudes and in lowlands of tropical areas. The presence of alkaloids, terpenes, stilbenes, flavonoids, glycosides, carotenoids, etc. in different parts of the plant provides several pharmacological properties. Because of the various uses in foods and pharmaceuticals, in vitro propagation of this genus has been performed hugely and is of great interest to researchers. From different explants via direct organogenesis under controlled aseptic conditions, callus, root, shoot, and somatic embryos are induced successfully. Different PGRs are augmented in the media for the rapid multiplication or organogenesis, especially, the high ratio of cytokinin and auxin in the basal media efficiently regenerates the shoot and root respectively. The in vitro regenerated plantlets are then acclimatized and hardened properly before transferring to the field conditions. Thus, the present first of its kind review on P. edulis exclusively encompasses the wide applications of biotechnology for this species alongside its organogenesis, embryogenesis, cytology, and endophytic microbes with special emphasis on the role of genetic transformation studies mediated by Agrobacterium sp. KEY POINTS: • Critical assessment on in vitro biotechnology in P. edulis. • Agrobacterium-mediated transformation in P. edulis. • Role of endophytic microbes in P. edulis.

A Beneficial Plant-Associated Fungus Shifts the Balance toward Plant Growth over Resistance, Increasing Cucumber Tolerance to Root Herbivory

Plants allocate their limited resources toward different physiological processes, dynamically adjusting their resource allocation in response to environmental changes. How beneficial plant-associated microbes influence this allocation is a topic that continues to interest plant biologists. In this study, we examined the effect of a beneficial fungus, Phialemonium inflatum, on investment in growth and anti-herbivore resistance traits in cucumber plants (Cucumis sativus). We inoculated cucumber seeds with P. inflatum spores and measured several growth parameters, including germination rate, above and belowground biomass, and number of flowers. We also examined plant resistance to adult and larval striped cucumber beetles (Acalymma vitattum), and quantified levels of defense hormones in leaves and roots. Our results indicate that P. inflatum strongly enhances cucumber plant growth and reproductive potential. Although fungus treatment did not improve plant resistance to cucumber beetles, inoculated plants were more tolerant to root herbivory, experiencing less biomass reduction. Together, these findings document how a beneficial plant-associated fungus shifts plant investment in growth over herbivore resistance, highlighting the importance of microbes in mediating plant-herbivore interactions. These findings also have important implications for agricultural systems, where beneficial microbes are often introduced or managed to promote plant growth or enhance resistance.

Diversity and characteristics of culturable endophytic bacteria from Passiflora edulis seeds

Defense compounds generally inhibit microbial colonization of plants. In this study, we examined the presence of endophytes in Passiflora edulis seeds that accumulate resveratrol and piceatannol at extremely high levels as defense compounds. Interestingly, although no microbial colonies appeared on an agar growth medium from the cut or homogenized seeds, colonies were generated from cut seedlings derived from the seeds. A total of 19 bacterial strains were isolated, of which 15 were classified as Gram-positive. As we hypothesized that extremely high levels of piceatannol in the seeds would inhibit the growth of endophytes cultured directly from the seeds, we examined the antimicrobial activity of this compound against the isolated bacteria. Piceatannol exerted bacteriostatic rather than bactericidal effects on most of the bacteria tested. These results suggest that the bacteria remain static in the seeds due to the presence of piceatannol and are transmitted to the seedlings during the germination process, enabling colonies to be established from the seedlings on the agar medium. We also investigated the biocatalytic activity of the isolated bacteria toward resveratrol and piceatannol. One bacterium, Brevibacterium sp. PE28-2, converted resveratrol and piceatannol to their respective derivatives. This strain is the first endophyte shown to exhibit such activity.

Comparative metabolomics of Phialemonium curvatum as an omnipotent fungus cultivated on crude palm oil versus glucose

BACKGROUND

Sugars and triglycerides are common carbon sources for microorganisms. Nonetheless, a systematic comparative interpretation of metabolic changes upon vegetable oil or glucose as sole carbon source is still lacking. Selected fungi that can grow in acidic mineral salt media (MSM) with vegetable oil had been identified recently. Hence, this study aimed to investigate the overall metabolite changes of an omnipotent fungus and to reveal changes at central carbon metabolism corresponding to both carbon sources.

RESULTS

Targeted and non-targeted metabolomics for both polar and semi-polar metabolites of Phialemonium curvatum AWO2 (DSM 23903) cultivated in MSM with palm oil (MSM-P) or glucose (MSM-G) as carbon sources were obtained. Targeted metabolomics on central carbon metabolism of tricarboxylic acid (TCA) cycle and glyoxylate cycle were analysed using LC-MS/MS-TripleQ and GC-MS, while untargeted metabolite profiling was performed using LC-MS/MS-QTOF followed by multivariate analysis. Targeted metabolomics analysis showed that glyoxylate pathway and TCA cycle were recruited at central carbon metabolism for triglyceride and glucose catabolism, respectively. Significant differences in organic acids concentration of about 4- to 8-fold were observed for citric acid, succinic acid, malic acid, and oxaloacetic acid. Correlation of organic acids concentration and key enzymes involved in the central carbon metabolism was further determined by enzymatic assays. On the other hand, the untargeted profiling revealed seven metabolites undergoing significant changes between MSM-P and MSM-G cultures.

CONCLUSIONS

Overall, this study has provided insights on the understanding on the effect of triglycerides and sugar as carbon source in fungi global metabolic pathway, which might become important for future optimization of carbon flux engineering in fungi to improve organic acids production when vegetable oil is applied as the sole carbon source.

NMR-Based Metabolic Profiling of Edible Olives-Determination of Quality Parameters

Edible olive drupes (from Olea europaea L.) are a high-value food commodity with an increasing production trend over the past two decades. In an attempt to prevent fraud issues and ensure quality, the International Olive Council (IOC) issued guidelines for their sensory evaluation. However, certain varieties, geographical origins and processing parameters are omitted. The aim of the present study was the development of a method for the quality assessment of edible olives from the Konservolia, Kalamon and Chalkidikis cultivars from different areas of Greece processed with the Spanish or Greek method. A rapid NMR-based untargeted metabolic profiling method was developed along with multivariate analysis (MVA) and applied for the first time in edible olives' analysis complemented by the aid of statistical total correlation spectroscopy (STOCSY). Specific biomarkers, related to the classification of olives based on different treatments, cultivars and geographical origin, were identified. STOCSY proved to be a valuable aid towards the assignment of biomarkers, a bottleneck in untargeted metabolomic approaches.

Highly Substituted Phenol Derivatives with Nitric Oxide Inhibitory Activities from the Deep-Sea-Derived Fungus Trichobotrys effuse FS524

Chemical investigation on EtOAc extract of the deep-sea-derived fungus Trichobotrys effuse FS524 resulted in the isolation of six new highly substituted phenol derivatives trieffusols A-F (1-6), along with ten known relative analogues (7-16). Their structures with absolute configurations were extensively characterized on the basis of spectroscopic data analyses, single-crystal X-ray diffraction experiments, and electronic circular dichroism (ECD) calculations. Structurally, trieffusols A and B shared an unprecedented ploy-substituted 9-phenyl-hexahydroxanthone skeleton with an intriguing 6-6/6/6 tetracyclic fused ring system, which were often encountered as significant moieties in the pharmaceutical drugs but rarely discovered in natural products. In the screening towards their anti-inflammatory activities of 1-6, trieffusols C and D exhibited moderate inhibitory activities against nitric oxide (NO) production in LPS-induced RAW 264.7 macrophages with IC₅₀ values ranging from 51.9 to 55.9 μM.

Isolation of Unstable Isomers of Lucilactaene and Evaluation of Anti-Inflammatory Activity of Secondary Metabolites Produced by the Endophytic Fungus Fusarium sp. QF001 from the Roots of Scutellaria baicalensis

The filamentous fungal pathogen Fusarium sp. causes several crop diseases. Some Fusarium sp. are endophytes that produce diverse valuable bioactive secondary metabolites. Here, extensive chemical investigation of the endophytic fungus, Fusarium sp. QF001, isolated from the inner rotten part of old roots of Scutellariae baicalensis resulted in the isolation of two new photosensitive geometrical isomers of lucilactaene (compounds 2 and 3) along with lucilactaene (6) and six other known compounds (fusarubin (1), (+)-solaniol (4), javanicin (5), 9-desmethylherbarine (7), NG391 (8) and NG393 (9)). Newly isolated isomers and lucilactaene were unstable under light at room temperature and tended to be a mixture in equilibrium state when exposed to a polar protic solvent during reversed phase chromatography. Normal phase chromatography under dim light conditions with an aprotic mobile phase led to the successful isolation of the relatively unstable isomers 2 and 3. Their structures were elucidated as 8(Z)-lucilactaene (2) and 4(Z)-lucilactaene (3) based on spectroscopic data. The absolute configuration of 4 was speculated to be R by computer-assisted specific rotation analysis. The isolated compounds could inhibit NO production and suppress pro-inflammatory cytokines expression in LPS-stimulated macrophage cells. These properties of the isolated compounds indicate their potential use as anti-inflammatory drugs.

A New Alkaloid from the Aerial Parts of Bupleurum chinense DC

A new isoalloxazine alkaloid, named bupleurine A (1), along with five known compounds (2-6), were isolated from the aerial parts of Bupleurum chinense DC. The structure elucidation of the new alkaloid (1) was employed by combining NMR and HR-MS data with comparison of reference in the literature. Five known compounds (2-6) were isolated from Bupleurum genus for the first time. Additionally, their antiproliferative activities on HeLa cells were evaluated by MTT assay and IC₅₀ of compounds 1 and 4-6 were below 10 μm after treatment for 24 h.

Secondary Metabolites Produced by an Endophytic Fungus Pestalotiopsis microspora

An endophytic fungus Pestalotiopsis microspora isolated from the fruits of Manilkara zapota was cultured in potato dextrose broth media. Chromatographic separation of the EtOAc extract of the broth and mycelium led to the isolation of a new azaphilonoid named pitholide E (1), in addition to previously identified pitholide B (2), pitholide D (3), pestalotin (LL-P880α) (4), PC-2 (5), LL-P880β (6), tyrosol (7) and 4-oxo-4H-pyran-3-acetic acid (8). An endophytic fungus P. microspora from M. zapota and the isolation of compounds 1-5, 7 and 8 from P. microspora are reported here for the first time.