Isolation and Quantification of Oligomeric and Polymeric Procyanidins in the Aerial Parts of St. John's Wort (Hypericum perforatum)

The In Vitro Assessment of Antibacterial and Antioxidant Efficacy in Rosa damascena and Hypericum perforatum Extracts against Pathogenic Strains in the Interplay of Dental Caries, Oral Health, and Food Microbiota

The rising demand for novel antibiotic agents prompts an investigation into natural resources, notably plant-derived compounds. In this study, various extracts (aqueous, ethanolic, aqueous-ethanolic, and enzymatic) of Rosa damascena and Hypericum perforatum were systematically evaluated against bacterial strains isolated from dental lesions (n = 6) and food sources (raw milk and broiler carcass, n = 2). Minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC), antibiofilm activity, and time-kill kinetics were assessed across a range of extract concentrations, revealing a dose-responsive effect. Notably, some extracts exhibited superior antibacterial efficacy compared to standard clinical antibiotics, and the time-kill kinetics demonstrated a rapid elimination of bacterial loads within 24 h. The susceptibility pattern proved strain-specific, contingent upon the extract type, yet all tested pathogens exhibited sensitivity. The identified extracts, rich in phenolic and polyphenolic compounds, as well as other antioxidant properties, contributed to their remarkable antibiotic effects. This comprehensive investigation not only highlights the potential of Rosa damascena and Hypericum perforatum extracts as potent antibacterial agents against diverse bacterial strains including caries pathogens, but also underscores their rapid action and dose-dependent efficacy. The findings suggest a promising avenue for harnessing plant-derived compounds in the development of novel antimicrobial strategies against dental caries and other oral inflammations, bridging the gap between natural resources and antibiotic discovery.

In Vitro Antibacterial and Phytochemical Screening of Hypericum perforatum Extract as Potential Antimicrobial Agents against Multi-Drug-Resistant (MDR) Strains of Clinical Origin

Background

The perennial plant Hypericum perforatum is widely distributed around the world. It has been used for many years in conventional medicine to treat a variety of illnesses, including stress, mild to moderate depression, and minor injuries. This study examined the antimicrobial activity of the H. perforatum total extract and its fractions (n-hexane, ethyl acetate, chloroform, and aqueous) against multi-drug-resistant (MDR) isolates that were gathered from clinical samples, including methicillin-resistant Staphylococcus aureus (MRSA), Enterococcus faecalis, Escherichia coli, and Klebsiella pneumonia.

Materials and Methods

Aerial parts of H. perforatum were collected and extracted using various solvents and were tested versus different isolated bacterial species. The inhibition zone of tested extracts was detected using an agar diffusion assay, and MICs were measured. Phytochemical analysis of promising H. perforatum extract was done using LC-ESI-MS/MS. Ultrastructure examination for the most altered bacteria used transmission electron microscopy. Antioxidant assays were done using DPPH and ABTS scavenging capacity methods. Cytotoxicity was reported versus Vero cells.

Results

Different extracts of H. perforatum showed promising antibacterial activity against the pathogens. While the subfractions of the total extract were observed to show lesser inhibition zones and higher MIC values than the total extract of H. perforatum against MDR strains, the total extract of H. perforatum demonstrated the most potent antimicrobial action with an inhibition zone range of 17.9-27.9 mm. MDR-K. pneumoniae was discovered to be the most susceptible strain, which is consistent with the antibacterial inhibitory action of H. perforatum whole extract. Additionally, after treatment at the minimum inhibitory concentration (MIC 3.9 μg/ml), the transmission electron microscope showed alterations in the ultrastructure of the K. pneumoniae cells. Methanol extract from H. perforatum has a CC₅₀ value of 976.75 μg/ml.

Conclusion

Future inhibitors that target MDR strains may be revealed by these findings. Additionally, the extracts that were put to the test demonstrated strong antioxidant effects as shown by DPPH or ABTS radical-scavenging assays.

Quality Control of Herbal Medicines: From Traditional Techniques to State-of-the-art Approaches

Herbal medicines are important options for the treatment of several illnesses. Although their therapeutic applicability has been demonstrated throughout history, several concerns about their safety and efficacy are raised regularly. Quality control of articles of botanical origin, including plant materials, plant extracts, and herbal medicines, remains a challenge. Traditionally, qualitative (e.g., identification and chromatographic profile) and quantitative (e.g., content analyses) markers are applied for this purpose. The compound-oriented approach may stand alone in some cases (e.g., atropine in Atropa belladonna). However, for most plant materials, plant extracts, and herbal medicines, it is not possible to assure quality based only on the content or presence/absence of one (sometimes randomly selected) compound. In this sense, pattern-oriented approaches have been extensively studied, introducing the use of multivariate data analysis on chromatographic/spectroscopic fingerprints. The use of genetic methods for plant material/plant extract authentication has also been proposed. In this study, traditional approaches are reviewed, although the focus is on the applicability of fingerprints for quality control, highlighting the most used approaches, as well as demonstrating their usefulness. The literature review shows that a pattern-oriented approach may be successfully applied to the quality assessment of articles of botanical origin, while also providing directions for a compound-oriented approach and a rational marker selection. These observations indicate that it may be worth considering to include fingerprints and their data analysis in the regulatory framework for herbal medicines concerning quality control since this is the foundation of the holistic view that these complex products demand.

Hypericum triquetrifolium and H. neurocalycinum as Sources of Antioxidants and Multi-Target Bioactive Compounds: A Comprehensive Characterization Combining In Vitro Bioassays and Integrated NMR and LC-MS Characterization by Using a Multivariate Approach

Hypericum triquetrifolium and H. neurocalycinum were evaluated for their phytochemical content and in vitro bioactivity. NMR analyses were performed on the methanol extract of the aerial parts of H. triquetrifolium to establish the main classes of phytoconstituents. Then, LC-DAD-MSⁿ analyses were performed in order to compare the composition of aerial parts and roots extracts of both Hypericum species, obtained using either methanol or water as solvents. Results, processed using multivariate data analysis, showed a significantly higher phenolic content of methanol extracts compared to water extracts, while minor qualitative differences were observed between the two. Distinctive flavonoid and PAC patterns were observed for H. triquetrifolium and H. neurocalycinum, and specific compounds were exclusively detected in one or the other species. Specifically, the phloroglucinols 7-epiclusianone, hyperfirin and hyperforin were present only in H. neurocalycinum, while hyperforin was detected only in H. triquetrifolium. Extracts were assayed using different in vitro tests to evaluate their antioxidant properties and their inhibitory activity against several enzymes, showing significant antioxidant and metal chelating activities. Furthermore, inhibitory properties against acetylcholinesterase, butyrylcholinesterase and tyrosinase were observed. Multivariate approaches were used to correlate biological data with the phytochemical composition of the different extracts. The results, showing positive correlations between specific chemical constituents and the measured bioactivities, represent preliminary data that could guide future studies aimed at isolating bioactive constituents from H. neurocalycinum and H. triquetrifolium for further pharmacological evaluations.

Multistep Analysis of Diol-LC-ESI-HRMS Data Reveals Proanthocyanidin Composition of Complex Plant Extracts (PAComics)

Proanthocyanidins (PACs) are complex oligomeric or polymeric phenolic biopolymers composed of flavan-3-ol building blocks. PACs exert manifold functional bioactivities and are assessed as bioactive ingredients in a variety of food products, beverages, medicinal plants, and phytopharmaceuticals. Although analytical methods for PACs with low degree of polymerization (DP) are well established, a lack of methods for the detailed analysis of higher oligomers and polymers from complex plant extracts is obvious. For this, the present study investigated PAC-enriched extracts from four different plants, traditionally used for medical purpose (Lime flower, Hawthorn leaf and flower, Japanese Wisteria fruits without seeds, and Common Sorrel herb). PACs were separated on diol stationary-phase high-performance liquid chromatography according to the respective DP and detected by fluorescence and quadrupole time-of-flight mass spectrometry (qTOF-MS). The qTOF-MS contour plots [t_R → m/z] provided a sufficient overview on the respective PAC distribution. Subsequently, high-resolution mass spectrometry data were used for Kendrick mass defect (KMD) analysis, with (epi)catechin, the main flavan-3-ol unit in PACs, as the reference unit. The resulting KMD plots enabled an elucidation of the general polymer chain composition with regard to DP, building blocks, and potential secondary modifications (e.g., galloylation). Subsequently, analysis of MS² fragmentation patterns of PAC oligomers confirmed the structural features obtained from the KMD plots. While Lime flower contained oligomeric A- and B-type PACs, composed of (epi)catechin and (epi)afzelechin, Japanese Wisteria fruit contained PACs consisting of three different hydroxylated flavan-3-ols. Cinchonains, A-type PACs, and B-type PACs were detected in the Hawthorn plant material. Galloylated oligo- and polymeric PACs were detected in Common Sorrel herb. This multistep analysis reveals collective insights into the PAC composition of the extracts. The protocol offers a fast and reliable methodology to be used in a standard laboratory. On the other hand, this methodology reaches its limits for higher oligomeric PACs, and further optimization is necessary for a better detection of the polymers, as the optimal DP cluster detection depends on the resolution of diol stationary-phase chromatography and is therefore limited.

Reduction of 5-hydroxymethylfurfural formation by flavan-3-ols in Maillard reaction models and fried potato chips

BACKGROUND

5-Hydroxymethylfurfural (HMF) is regarded as a thermal process contaminant in foods. Six flavan-3-ol fractions were isolated or semisynthesized from sorghum, cranberry and grape seed. Their unit compositions, interflavan linkages and degree of polymerization were characterized. The aim of this study was to investigate the effect of flavan-3-ols on the formation of HMF in chemical reaction models and fried potato chips.

RESULTS

Results showed that all flavan-3-ols significantly mitigated the HMF formation at concentrations of 50, 100 and 200 µg mL^-1 in the chemical model system, and the inhibition was positively related to dose. Using the food model, HMF content was reduced by about 50% when potato chips were soaked in an optimal concentration of 0.1 mg mL^-1 flavan-3-ol solutions before frying. Based on the same mass concentration, B-type flavan-3-ols mitigated more HMF than A-type, and oligomeric proanthocyanidins had stronger inhibitory activity than polymers. At suitable addition levels (0.01-0.1 mg mL^-1 ), the browning of auto-oxidized flavan-3-ols under high temperature compensated the anti-browning effect along with the supression of the Maillard reaction; therefore, the color of fried potato chips was not affected.

CONCLUSION

This study demonstrates that flavan-3-ols could be effective additives for reducing HMF levels in fried potato chips without changing sensory properties. © 2018 Society of Chemical Industry.

Investigation of the flavan-3-ol patterns in willow species during one growing-season

Flavonoids, proanthocyanidins (PAs) and salicylic alcohol derivatives are the main groups of ingredients in Salix needed as defensive tools and signal molecules, but have also pharmaceutical importance. The present study investigated total PA content, complete PA pattern, the oligomeric/total PAs quotient and the contents of catechin and epicatechin during one growing-season for the leaves and this year's sprouts in ten willows (Salix pentandra L. ♂, S. alba L. ♂, S. fragilis L. ♀, S. caprea L. ♂ & ♀, S. cinerea L. ♂, S. caprea x cinerea ♂, S. daphnoidesVill. ♂ & ♀ and S. purpurea L. ♀; all Salicaceae). Comparison of the different species revealed distinct seasonal fluctuations of the oligomeric and polymeric PA fractions, but the contents of both groups always developed in the same direction. All willows prefer the synthesis of PAs with DP-2 - DP-4 within the oligomeric fraction (DP-2 - DP-10) and species with rather low PA contents like S. purpurea (0.1-2.6 mg/g) as well as species with rather high PA contents like S. alba (3.8-14.7 mg/g) were found. Only slight gender specific differences could be observed for both sexes of S. daphnoides and S. caprea. The PA pattern of the hybrid S. caprea x cinerea seems to be influenced by both parents. Thus, the accumulation of the oligomeric PAs accorded to S. caprea and the polymeric PAs matched S. cinerea resulting in an overall depression of PAs in the sprouts and a varying seasonal trend in the leaves. In contrast, the content of catechin remained high and seemed to be not influenced in the hybrid. Although only one individual of each Salix species could be considered in this screening study, the present results demonstrate the variability of the flavan-3-ol pattern within the genus Salix but also some preliminary correlations could be observed. Future studies with more Salix species will provide more insights into chemotaxonomic correlations.

Bioassay-Guided Fractionation of a Leaf Extract from Combretum mucronatum with Anthelmintic Activity: Oligomeric Procyanidins as the Active Principle

Combretum mucronatum Schumach. & Thonn. is a medicinal plant widely used in West African traditional medicine for wound healing and the treatment of helminth infections. The present study aimed at a phytochemical characterization of a hydroalcoholic leaf extract of this plant and the identification of the anthelmintic compounds by bioassay-guided fractionation. An EtOH-H₂O (1:1) extract from defatted leaves was partitioned between EtOAc and H₂O. Further fractionation was performed by fast centrifugal partition chromatography, RP18-MPLC and HPLC. Epicatechin (1), oligomeric proanthocyanidins (OPC) 2 to 10 (mainly procyanidins) and flavonoids 11 to 13 were identified as main components of the extract. The hydroalcoholic extract, fractions and purified compounds were tested in vitro for their anthelmintic activity using the model nematode Caenorhabditis elegans. The bioassay-guided fractionation led to the identification of OPCs as the active compounds with a dose-dependent anthelmintic activity ranging from 1 to 1000 μM. Using OPC-clusters with a defined degree of polymerization (DP) revealed that a DP ≥ 3 is necessary for an anthelmintic activity, whereas a DP > 4 does not lead to a further increased inhibitory effect against the helminths. In summary, the findings rationalize the traditional use of C. mucronatum and provide further insight into the anthelmintic activity of condensed tannins.