Bioconversion of Kaempferol and Quercetin Glucosides from Plant Sources Using Rhizopus spp

Unlocking the potential of fermented beetroot ketchup: Enhancing polyphenol recovery and gut microbiota interactions

The study aimed to evaluate the effect of digestion and gut microbiota interactions on beetroot ketchup formulations, focusing on the release of polyphenols, bioaccessibility, and microbial interactions on gut microbiota with polyphenols. Tested ketchup samples were evaluated using the TNO Gastro-Intestinal Model 1 (TIM-1) simulated upper part of the gastrointestinal tract and the TNO Gastro-Intestinal Model 2 (TIM-2) simulated colon system. The results showed that fermentation of ketchup with Lactobacillus johnsonii K4, increased the release of bioactive compounds during digestion, with higher polyphenol recoveries observed in fermented samples. In particular, a fermented sample has higher recovery percentages for most of the phenolic acids, flavonoids, and betalains. However, some polyphenolic compounds were degraded during fermentation, suggesting a dynamic process of polyphenol metabolism in the gut environment. The study highlights the potential of fermented foods, such as beetroot ketchup, enriched with polyphenols and beneficial bacteria, to promote gut health and overall well-being.

Synthesis of quercetin derivatives as cytotoxic against breast cancer MCF-7 cell line in vitro and in silico studies

Background: Quercetin being antioxidant and antiproliferative agent acts by inhibiting CDK2, with an increase in cancer prevalence there is a need to profile quercetin derivatives as CDK2 inhibitors.Materials & method: Schiff bases of quercetin were synthesized as cytotoxic agents against the MCF7 cell line. FTIR, 1H-NMR and 13C-NMR, CHNS/O analysis were employed along with in vivo and in silico activities.Results & conclusion: 2q, 4q, 8q and 9q derivatives have maximum cytotoxic effect with IC50 values 39.7 ± 0.7, 36.65 ± 0.25, 35.49 ± 0.21 and 36.99 ± 0.45, respectively. Molecular docking also confirmed these results 8q has the highest binding potential of -9.165 KJ/mole making it a potent inhibitor of CDK2. These derivatives can be used as lead compounds as potent CDK2 inhibitors.

Optimising the recovery of phenolic compounds and antioxidant activity from orange peels through solid-state fermentation

It is widely recognised that orange peels contain a considerable quantity of phenolics, primarily in the form of glycosides. The process of fermentation holds potential as a viable method for extracting phenolic compounds and facilitating their biotransformation into novel metabolites. The aim of this study was to assess the enhanced release of phenolic compounds through the process of solid-state fermentation of orange peels using microorganisms. Following a 6-day incubation period, the methanol extract obtained from the sample fermented with starter Banh men exhibited the highest concentration of total phenolic compounds (17.57 ± 0.34 mg GAE/g DW) and demonstrated the most significant DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity (55.03%). The Reverse Phase High Performance Liquid Chromatography (RP-HPLC) analysis revealed that the predominant phenolic compounds in all fermented samples were flavonoid aglycones, specifically naringenin, hesperetin, and nobiletin. Conversely, in the unfermented orange peels, the major compound observed was the glycoside derivative hesperidin.

Inhibitory and Stimulatory Effects of Fruit Bioactive Compounds on Edible Filamentous Fungi: Potential for Innovative Food Applications

The fermentation of fruit processing residuals (FPRs) with filamentous fungi can provide protein-rich food products. However, FPRs that contain bioactive compounds with antimicrobial properties present a major challenge. In this work, the resistance of two edible filamentous fungi, Rhizopus oligosporus and Neurospora intermedia, to 10 typically inhibiting bioactive compounds available in FPRs (epicatechin, quercetin, ellagic acid, betanin, octanol, hexanal, D-limonene, myrcene, car-3-ene, and ascorbic acid) was examined. These compounds’ inhibitory and stimulatory effects on fungal growth were examined individually. Three different concentrations (2.4, 24, and 240 mg/L) within the natural concentration range of these compounds in FPRs were tested. These bioactive compounds stimulated the growth yield and glucose consumption rate of R. oligosporus, while there was no increase in the biomass yield of N. intermedia. Ellagic acid caused an up to four-fold increase in the biomass yield of R. oligosporus. In addition, octanol and D-limonene showed antifungal effects against N. intermedia. These results may be helpful in the development of fungus-based novel fermented foods.

A molecular dynamics perspective into estrogen receptor inhibition by selective flavonoids as alternative therapeutic options

Zearalenone is an estrogenic mycotoxin which is a common food contaminant and has been implicated in increasing the incidence of carcinogenesis and other reproductive health ailments through the estrogen receptor alpha (ERα) pathway. Competitive ERα blockers such as 4-Hydroxytamoxifen (OHT), are synthetic FDA approved drugs which, albeit being an effective anticancer agent, induces life altering side effects. For this reason, there is an increased interest in the use of naturally occurring medicinal plant products such as flavonoids. This study aimed to identity flavonoid ERα inhibitors and provide insights into the mechanism of inhibition using computational techniques. The Molecular Mechanics/Generalized Born Surface Area calculations revealed that quercetrin, hesperidin, epigallocatechin 3-gallate and kaempferol 7-O-glucoside out of 14 flavonoids had higher binding affinity for ERα than OHT. The structural analysis revealed that the binding of the compounds to the receptor lead to dynamic alterations, which induced conformational shift in the structure and orientation of the receptor resulting in stabilised, compact and low energy systems. The results of this study provide imperative information that supports the use of flavonoids in the inhibition of ERα to prevent or ameliorate the consequential adverse effects associated with zearalenone exposure.Communicated by Ramaswamy H. Sarma.

Phenolic Characterization and Bioactivity of Fennel Seed (Foeniculum vulgare Mill.) Extracts Isolated by Microwave-Assisted and Conventional Extraction

The aim of this study was to evaluate the effectiveness of microwave-assisted extraction (MAE) as an environmentally friendly approach compared to conventional heat-reflux extraction (CE) for the isolation of fennel (Foeniculum vulgare Mill.) seed polyphenols and to assess the bioactivity of the obtained extracts. Water, ethanol (30%, v/v) and acetone (30%, v/v) were used as extraction solvents, and the extraction was carried out varying the temperature (40, 60 and 80 °C), irradiation time (5 and 10 min) and microwave power (300 and 600 W). According to the total phenolic content (TPC), 30% acetone at 80 °C after 5 min of irradiation at 300 W proved to be the optimal MAE conditions for obtaining the highest yield of polyphenols. The phenolic profile of both extracts comprised 21 compounds, with cinnamic acids and flavonols being the most abundant. When compared to CE, the MAE extract showed a lower amount of TPC as well as the sum of all identified individual phenols, although both extracts showed similar antioxidant capacity. The antimicrobial activity of the extract with the highest phenolic content was weak, showing inhibitory activity only against Pseudomonas fragi, Shewanella putrefaciens and Campylobacter jejuni strains, while Gram-positive bacteria and yeasts were not sensitive to the extract.

Phenolic Profile, Antioxidant Capacity and Antimicrobial Activity of Nettle Leaves Extracts Obtained by Advanced Extraction Techniques

Nettle is a widely known plant whose high biological activity and beneficial medicinal effects are attributed to various bioactive compounds, among which polyphenols play an important role. In order to isolate polyphenols and preserve their properties, advanced extraction techniques have been applied to overcome the drawbacks of conventional ones. Therefore, microwave-assisted extraction (MAE) has been optimized for the isolation of nettle leaves polyphenols and it was compared to pressurized liquid extraction (PLE) and conventional heat-reflux extraction (CE). The obtained extracts were analyzed for their individual phenolic profile by UPLC MS² and for their antioxidant capacity by ORAC assay. MAE proved to be the more specific technique for the isolation of individual phenolic compounds, while PLE produced extracts with higher amount of total phenols and higher antioxidant capacity. Both techniques were more effective compared to CE. PLE nettle extract showed antimicrobial activity against bacteria, especially against Gram-negative Pseudomonas fragi ATCC 4973 and Campylobacter jejuni NCTC 11168 strains. This suggests that PLE is suitable for obtaining a nettle extract with antioxidant and antimicrobial potential, which as such has great potential for use as a value-added ingredient in the food and pharmaceutical industry.

A metabolomics approach to evaluate post-fermentation enhancement of daidzein and genistein in a green okara extract

BACKGROUND

Okara is a major agri-industrial by-product of the tofu and soymilk industries. Employing food-wastes as substrates for the green production of natural functional compounds is a recent trend that addresses the dual concepts of sustainable production and a zero-waste ecosystem.

RESULTS

Extracts of unfermented okara and okara fermented with Rhizopus oligosporus were obtained using ethanol as extraction solvent, coupled with ultrasound sonication for enhanced extraction. Fermented extracts yielded significantly better results for total phenolic content (TPC) and total flavonoid content (TFC) than unfermented extracts. A qualitative liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) analysis revealed a shift from glucoside forms to respective aglycone forms of the detected isoflavones, post-fermentation. Since the aglycone forms have been associated with numerous health benefits, a quantitative high-performance liquid chromatography (HPLC) analysis was performed. Fermented okara extracts had daidzein and genistein concentrations of 11.782 ± 0.325 μg mL-1 and 10.125 ± 1.028 μg mL-1 , as opposed to that of 6.7 ± 2.42 μg mL-1 and 4.55 ± 0.316 μg mL-1 in raw okara extracts, respectively. Lastly, the detected isoflavones were mapped to their metabolic pathways, to understand the biochemical reactions triggered during the fermentation process.

CONCLUSION

Fermented okara may be implemented as a sustainable solution for production of natural bioactive isoflavonoids genistein and daidzein. © 2021 Society of Chemical Industry.

Quercetin as a Precursor for the Synthesis of Novel Nanoscale Cu (II) Complex as a Catalyst for Alcohol Oxidation with High Antibacterial Activity

Quercetin (3,3′,4′,5,7-pentahydroxyflavone) is one of the dietary flavonoids, distributed in medicinal plants, vegetables, and fruits. Quercetin has the ability to bind with several metal ions to increase its biological activities. In the last two decades, quercetin has attracted considerable attention due to the biological and pharmaceutical activities such as antioxidant, antibacterial, and anticancer. In the present study, quercetin and ethanolamine were used for the synthesis Schiff base complex, which was characterized by IR, ¹H NMR, and ¹³C NMR spectroscopy. The Schiff base has been employed as a ligand for the synthesis of novel nanoscale Cu (II) complex. The product was characterized by FT-IR spectroscopy, FESEM, and XRD. Significantly, the product showed remarkable catalytic activity towards the oxidation of primary and secondary alcohols. The antibacterial activity of the final product was assessed against Staphylococcus aureus (Gram‐positive) and Escherichia coli (Gram‐negative) bacteria using an inhibition zone test. The synthesized nanoscale Cu (II) complex exhibited a strong antibacterial activity against both Gram-positive and Gram-negative bacteria.

Targeting fish spoilers Pseudomonas and Shewanella with oregano and nettle extracts

To control Pseudomonas and Shewanella as important psychrotrophic spoilage bacteria in fish meat, we used ethanolic extracts of oregano (Origanum vulgare subsp. vulgare) and nettle (Urtica dioica), with phytochemical characterisation of the extracts and their bioactive compounds. Liquid chromatography coupled with photodiode array detection and electrospray ionisation-mass spectrometry was used for qualitative compositional determination of the extracts. Four main compounds were identified in the oregano extract, with rosmarinic acid the most abundant, followed by three glycosylated phenolics, one of which is reported for the first time in O. vulgare: 4'-O-β-d-glucopyranosyl-3',4'-dihydroxybenzyl-4-hydroxybenzoate. Six main compounds were identified in the nettle extract, as caffeoylmalic acid and five flavonoid glycosides. These oregano and nettle ethanolic extracts showed in-vitro antimicrobial activities against selected Pseudomonas and Shewanella strains in broth and fish meat homogenate when evaluated at two inoculum concentrations. The antimicrobial activities were more pronounced for the nettle extract at the lower inoculum concentration, and for both the Shewanella strains. Growth inhibition in the fish meat homogenate was evaluated at 3.13 mg/mL and 1.56 mg/mL at 5 °C. Again, the nettle extract showed greater antimicrobial activity, which was seen as the lowest maximum growth rate, followed by the oregano extract, which was inhibitory only at 3.13 mg/mL. Finally, the extracts were applied to fish meat that was then stored at 5 °C for 9 days. Evaluation here was for the counts of the mesophilic, psychrotrophic, Pseudomonas and H2S producers. These confirmed the better antimicrobial effects of the nettle extract, especially against the H2S-producing bacteria, which included Shewanella. Both of the extracts were rich in glycosides of flavonoids and phenolic acids. The enzymatic activities of the Pseudomonas and Shewanella spoilage bacteria and their actions on the phenolic glycosides from natural sources will be further investigated.

Assessment of hyperspectral indicators related to the content of phenolic compounds and multispectral fluorescence records in chicory leaves exposed to various light environments

Hyperspectral analysis represents a powerful technique for diagnostics of morphological and chemical information from aboveground parts of the plants, but the real potential of the method in pre-screening of phenolics in leaves is still insufficiently explored. In this study, assessment of the sensitivity and reliability of non-invasive methods of various phenolic compounds, also analyzed by HPLC in chicory plants (Cichorium intybus L.) exposed to various color light pretreatments was done. The hyperspectral records in visible and near infrared (VNIR) spectra were recorded using a handheld spectrometer and relationships between the specific hyperspectral parameters and the contents of tested phenolic compounds in chicory leaves were analyzed. Moreover, the correlations between the hyperspectral parameters and related parameters derived from the multispectral fluorescence records were assessed to compare the sensitivity of both techniques. The results indicated a relatively high correlation of anthocyanin-related parameters (ARI, mARI, mACI indices) with the content of some of tested phenolic compounds (quercetin-3-gluconuride, isorhamnetine-3-gluconuride, etc.), as well as with fluorescence ANTH index. Similar trends were observed in flavonoid parameter based on the near infra-red spectral bands (700, 760 nm), which expressed a high correlation with chlorogenic acid. On the other hand, the most frequently used flavonoid (FLAVI) indices based on UV-to-blue band reflectance showed very weak correlations with phenolic compounds, as well as with fluorescence FLAV index. The detailed analysis of the correlation between reflectance and fluorescence flavonoid parameters has shown that the parameters based on spectral reflectance are sensitive to increase of UV-absorbing compounds from low to moderate values, but, unlike the fluorescence parameter, they are not useful to recognize a further increase from middle to high or very high contents. Thus, our results outlined the possibilities, but also the limits of the use of hyperspectral analysis for rapid screening phenolic content, providing a practical evidence towards more efficient production of bioactive compounds for pharmaceutical or nutraceutical use.

Influence of Harvest Date and Postharvest Treatment on Carotenoid and Flavonoid Composition in French Marigold Flowers

The aim of this study was to characterize carotenoids and flavonoids present in French marigold flowers (Tagetes patula "Durango Red") as well as to assess the effects of harvest dates and postharvest treatments on these compounds. Carotenoids and flavonoids were quantified using their respective standards or semiquantified using relevant related standards. Lutein and its derivatives largely dominated the flower carotenoids, while the flavonoids were diverse with patuletin leading the list. Of the different postharvest treatments, ensilage leads to the highest content of carotenoids (from 5.0 to 7.8 g kg^-1 dw) and flavonoids (from 19 to 50 g kg^-1 dw). The composition of individual flavonoids was greatly influenced by different postharvest treatments, while the influence of harvest dates was secondary. Ensilage and drying induced separate metabolic pathways leading to degradation of high-molecular glycosidic compounds, converting the compounds either to their aglycones or into the intermediate flavonoid glycosides. We conclude that according to the intended industrial application, different postharvest techniques can be employed to acquire desired flavonoids on a large scale.