An investigation on changes in composition and antioxidant potential of mature and immature summer truffle (Tuber aestivum)

Impact of ultrasonication on the contents, profiles and biofunctional properties of free and bound phenolics from white desert truffle (Tirmania nivea) and its protein fractions

The molecular and biofunctional properties of protein and phenolic fractions in edible truffles remain largely unknown. This study examined the effect of ultrasonication on the contents, profiles, and bioactive properties of free and bound phenolics (FP and BP) from desert truffle (Tirmania nivea) and its protein fractions. Protein fractions from the Osborne extraction scheme were biochemically and structurally characterized. The albumin fraction showed the highest abundance (16.8%) and yield (35.8%). Total phenolic contents were the highest in non-sonicated samples (3.5-34.1 mg/g), particularly in the albumin fraction and in whole truffle. FP extracted at 30 °C (FP-30 °C) accounted for the largest proportion of total phenolics in all protein fractions, whereas BP-30 °C and FP-60 °C were predominant in non-sonicated and sonicated truffle, respectively. The highest antioxidant activity was obtained with FP-30 °C extracts from non-sonicated albumins, globulins and truffle (91.9, 72.7 and 30.0%), followed by BP-30 °C from non-sonicated albumins (25.4%) and FP-60 °C from sonicated glutelins-1 (24.2%). High inhibition of α-amylase was evidenced in several extracts, including FP-30 °C from non-sonicated glutelins-1 (99.2%) and FP-30 °C from sonicated globulins (72.4%). Several extracts also displayed high inhibition of angiotensin I-converting enzyme (ACE), including FP-60 °C from non-sonicated glutelins-1 (65.1%) and sonicated glutelins-1 (71.1%) and globulins (64.7%). Most extracts were rich in epicatechin, gallic acid, chlorogenic acid and catechin. Correlations between phenolic content, antioxidant activity, anti-α-amylase and anti-ACE activities were influenced by sonication. Sonication reduced the particle size of the proteins and modified their structural characteristics. These findings demonstrate that white desert truffle proteins co-occur with bioactive phenolics whose functionalities can be tailored by protein fractionation and sonication.

Aromatic profile of black truffle grown in Argentina: Characterization of commercial categories and alterations associated to maturation, harvesting date and orchard management practices

Black truffle (Tuber melanosporum) is one of the most appreciated fungi in the world mainly due to its aromatic properties. In the emerging markets such as Argentina, the aroma of locally produced truffles has not been described yet. The volatile organic compounds (VOCs) from 102 black truffles from Argentina were analyzed using solid phase microextraction gas chromatography coupled with mass spectrometer detector (SPME-GC-MS). Several factors such as commercial category, maturity stage, host tree, geographical origin, and aromatic defects detected during classification were also registered and considered. As a result, 79 VOCs were detected, among which 2-methyl-propanal, 2-butanone, 2-methyl-1-propanol, butanal-3-methyl, 3-methyl-1-butanol, 2-methyl-1-butanol were present in high percentage in fresh mature truffles, whereas immature truffles were associated with 3,5-dimethoxytoluene, 2-phenyl-2-butenal, 2,3-dimethoxytoluene. The Argentine black truffles showed significant similarities in their aromatic profile when compared with their Australian and European counterparts, but with some distinctive notes.

Extraction and trapping of truffle flavoring compounds into food matrices using supercritical CO2

A supercritical fluid extraction methodology was used to extract flavoring and bioactive compounds from truffles. Some parameters such as CO₂ flow rate (1-3 mg/mL), extraction time (15-90 min) and different trapping food matrices (grape seed oil, gelatin, agar agar and water) were optimized using response surface methodology to enhance extraction and trapping yields. The optimal conditions (2.27 mg/mL CO₂ flow rate, 82.5 min when using 40 °C and 30 MPa, with 1 mL grape seed oil as trapping matrix) obtained with Tuber melanosporum were applied to three different truffle species: Terfezia claveryi, Tuber aestivum and Tuber indicum. A total of 32 metabolites were profiled in the extracts using ultra-high-performance supercritical fluid chromatography coupled to quadrupole time-of-flight mass spectrometry. Compounds such as brassicasterol ergosta-7,22-dienol, oleic and linoleic acid were found at similar amounts in all the extracts but other molecules (e.g. fungal sterols) showed a particular distribution depending on the specie studied and whether a trapping matrix was used at the SFE outlet.

Reproducibility challenges in the search for antibacterial compounds from nature

BACKGROUND

Reproducibility of reported antibacterial activities of plant extracts has long remained questionable. Although plant-related factors should be well considered in serious pharmacognostic research, they are often not addressed in many research papers. Here we highlight the challenges in reproducing antibacterial activities of plant extracts.

METHODS

Plants with reported antibacterial activities of interest were obtained from a literature review. Antibacterial activities against Escherichia coli and Klebsiella pneumoniae were tested using extracts' solutions in 10% DMSO and acetone. Compositions of working solutions from both solvents were established using LC-MS analysis. Moreover, the availability of details likely to affect reproducibility was evaluated in articles which reported antibacterial activities of studied plants.

RESULTS

Inhibition of bacterial growth at MIC of 256-1024 μg/mL was observed in only 15.4% of identical plant species. These values were 4-16-fold higher than those reported earlier. Further, 18.2% of related plant species had MICs of 128-256 μg/mL. Besides, 29.2% and 95.8% of the extracts were soluble to sparingly soluble in 10% DMSO and acetone, respectively. Extracts' solutions in both solvents showed similar qualitative compositions, with differing quantities of corresponding phytochemicals. Details regarding seasons and growth state at collection were missing in 65% and 95% of evaluated articles, respectively. Likewise, solvents used to dissolve the extracts were lacking in 30% of the articles, whereas 40% of them used unidentified bacterial isolates.

CONCLUSION

Reproducibility of previously reported activities from plants' extracts is a multi-factorial aspect. Thus, collective approaches are necessary in addressing the highlighted challenges.

Geographical-based variations in white truffle Tuber magnatum aroma is explained by quantitative differences in key volatile compounds

The factors that vary the aroma of Tuber magnatum fruiting bodies are poorly understood. The study determined the headspace aroma composition, sensory aroma profiles, maturity and bacterial communities from T. magnatum originating from Italy, Croatia, Hungary, and Serbia, and tested if truffle aroma is dependent on provenance and if fruiting body volatiles are explained by maturity and/or bacterial communities. Headspace volatile profiles were determined using gas chromatography-mass spectrometry-olfactometry (GC-MS-O) and aroma of fruiting body extracts were sensorially assessed. Fruiting body maturity was estimated through spore melanisation. Bacterial community was determined using 16S rRNA amplicon sequencing. Main odour active compounds were present in all truffles but varied in concentration. Aroma of truffle extracts were sensorially discriminated by sites. However, volatile profiles of individual fruiting bodies varied more within sites than across geographic area, while maturity level did not play a role. Bacterial communities varied highly and were partially explained by provenance. A few rare bacterial operational taxonomical units associated with a select few nonodour active volatile compounds. Specificities of the aroma of T. magnatum truffles are more likely to be linked to individual properties than provenance. Some constituents of bacteria may provide biomarkers of provenance and be linked to nonodour active volatiles.

Anti-Angiogenic Effect of Cantharellus cibarius Extracts, its Correlation with Lipoxygenase Inhibition, and Role of the Bioactives Therein

Angiogenesis is a complex physiological process that cannot be treated with single agent therapy. Several edible fungi have been known to encompass bioactive compounds, and are promising sources of multi-component drugs. One such widely consumed edible fungi is Cantharellus cibarius, which has been explored for its biological activities. The present study focused on assessing the anti-angiogenic activity of petroleum ether and ethanol extracts of C. cibarius using chick chorioallantoic membrane (CAM) assay. Both the extracts showed a dose-dependent response which was compared with the anti-angiogenic activity of the positive controls silibinin, and lenalidomide. The extracts were also studied for their lipoxygenase (LOX) inhibitory potential and compared to ascorbic acid as the positive control. The IC₅₀ values of the petroleum ether extract, ethanol extract, and ascorbic acid for LOX inhibition assay were 135.4, 113.1, and 41.5 µg/mL, respectively. Although both the extracts showed similar responses in CAM assay, ethanol extract proved to be more potent in LOX inhibition assay. Finally, the extracts were investigated for their chemical composition using GC-MS. A correlation between LOX inhibition and anti-angiogenic potential was established at the molecular level. A meticulous literature search was carried out to correlate the biochemical composition of the extracts to their anti-angiogenic activity.

Chemical composition and evaluation of antioxidant, antimicrobial and antiproliferative activities of Tuber and Terfezia truffles

Ten truffle species of Tuber and Terfezia genera were chemical characterized, assessing their proximate composition, individual nutrient compounds and some bioactive molecules. The bioactive properties of these species were also evaluated, namely their antioxidant, antimicrobial and cytotoxic potential. Carbohydrates were the main macronutrients present in truffles, followed by proteins. Furthermore, the levels of polyunsaturated fatty acids (PUFA), subsequently presented as a percentage, were higher in truffles (38.2-79.3%) except in Tuber magnatum and Terfezia arenaria, which have a more saturated fatty acids (SFA) profile (70.7% and 53.7%, respectively). Comparing the species, T. magnatum revealed the highest levels of total phenolic compounds (TPC) (290 mg GAE/100 g truffle), as also the best results in the four methods used to evaluate the antioxidant activity. On the other hand, only five extracts obtained from some studied truffle species (Terfezia magnusii, Tuber aestivum, Tuber gennadii, and Tuber melanosporum) showed a slight inhibition of microbial growth, tested against different bacteria. Terfezia and T. gennadii extracts, showed potential to inhibit the cellular growth of NCI-H460, HeLa, HepG2, and MCF-7 cell lines (GI₅₀ concentrations range: 19-78, 33-301, 83-321 and 102-321 µg/mL, respectively), indicating anti-proliferative activity. Nevertheless, T. arenaria revealed some potential hepatotoxicity, inhibiting the growth of PLP2 cells (GI₅₀ concentration of 220 µg/mL), a primary cell culture obtained from porcine liver.

A study on the fatty acid composition of lipids in truffles selected from Europe and Africa

The gas chromatography of hexane extracts from ascocarps of Tuber maculatum (mostly the first report), T. aestivum/unicantum, T. borchii, T. melanosporum and Tirmania nivea dominantly showed palmitic, stearic, oleic and linoleic acids followed by traces of polyunsaturated fatty acids. The fatty acid content varied from ca. 8-61 mg g^- 1, dry-weight-basis with species with highest for T. maculatum. Polyunsaturated fatty acids contributions varied from ca. 42-59%. The dominant fatty acid varied with the species. A comparison with existing reports on same species cultivated in different regions showed differences in contributions by saturated, monounsaturated and polyunsaturated fatty acids as well as dominant fatty acids detected. Lesser explored species such as T. borchii, T. maculatum call for further research. This is a preliminary study that indicates fatty acid composition as a potential tool for distinction like aroma between truffle species and geographies of cultivation. This forms the basis for further studies in different species and regions.

Anti-angiogenic and anti-inflammatory activity of the summer truffle (Tuber aestivum Vittad.) extracts and a correlation with the chemical constituents identified therein

Fungi are a huge source of unexplored bioactive compounds. Owing to their biological activities, several fungi have shown commercial application in the health industry. Tuber aestivum Vittad. is one such edible fungi with an immense scope for practical biological applications. In the present study, the anti-angiogenic activity of petroleum ether and ethanol extracts of T. aestivum was investigated using the chick chorioallantoic membrane assay and compared to the positive controls silibinin and lenalidomide. Both the extracts showed a dose-dependent anti-angiogenic response. The extracts were also assessed for their anti-inflammatory potential by lipoxygenase-inhibition assay. The IC₅₀ values for LOX inhibition assay, computed by the Boltzmann plot, were 368.5, 147.3 and 40.2 µg/mL, for the petroleum ether extract, ethanol extract, and the positive control ascorbic acid, respectively. The ethanol extract of T. aestivum showed superior anti-angiogenic and anti-inflammatory activity than the petroleum ether extract. Compositional investigation of the extracts by GC-MS revealed the presence of various bioactive compounds. The compounds were correlated to their anti-angiogenic and anti-inflammatory activity based on a meticulous literature search.