Synthesis and biological activity of new 1,3-dioxolanes as potential antibacterial and antifungal compounds

In vitro antibacterial, antibiofilm activities, and phytochemical properties of Posidonia oceanica (L.) Delile: An endemic Mediterranean seagrass

In the antibiotic resistance era, utilizing understudied sources for novel antimicrobials or antivirulence agents can provide new advances against antimicrobial resistant pathogens. In this study, we aimed to investigate antibacterial and antibiofilm activities of Posidonia oceanica (L.) Delile against Enterococcus faecalis ATCC 29212, Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922 and Klebsiella pneumoniae ATCC 700603 and several S. aureus clinical isolates obtained from medical devices, including patient urinary catheters and breast implant infections, with varying antibiotic recalcitrance profiles. The ethanolic and methanolic extracts from P. oceanica rhizome exhibited significant antibacterial activity against E. faecalis and S. aureus, as well as drug resistant S. aureus clinical isolates. Furthermore, significant antibiofilm activity was observed against S. aureus and E. faecalis treated with ER, MR1, and MR2. P. oceanica extracts also exhibited synergistic antimicrobial activity with ciprofloxacin against E. faecalis, sensitizing E. faecalis to a lower ciprofloxacin concentration. Collectively, our data demonstrate the selective antibacterial and antibiofilm activity of the extracts of P. oceanica against Gram-positive bacteria and clinical isolates along with potentiation of current antibiotics, which suggests that P. oceanica can be further investigated as a potential source for novel therapeutic options in the treatment of drug resistant bacterial infections.

Anticancer and antimicrobial evaluation of extract from brown algae Hormophysa cuneiformis

AIM

We investigated the antimicrobial and anticancer properties of an ethanol crude extract of Red Sea brown alga (Hormophysa cuneiformis) from Egypt.

METHODS

Extraction was achieved by mixing 100 g of sample powder with absolute ethanol, incubating at 37 °C overnight in a shaking incubator, and then collecting the extract. The extract's antimicrobial activity was tested using a well diffusion assay against the tested pathogens (Escherichia coli, Bacillus subtilis, Staphylococcus aureus, and Candida albicans) in comparison to commercial antibiotics. Anticancer activity was assessed using MTT assay on MCF-7, HepG-2, and HEP-2 cell lines. The anticancer mechanism of action against the HepG-2 cell line was investigated using cell cycle analysis, Annexin V, and antioxidant enzymes, in addition to transmission electron microscopy.

RESULTS

GC-MS phytoconstituent profile of the extract was dominant with fatty acids. A broad antimicrobial effect against all the pathogenic isolates of E. coli, S. aureus, B. subtitles, and C. albicans was demonstrated, especially at the high concentration in comparison to commercial antibiotics. The extract could inhibit the growth of the tested cell lines. We observed the most significant effect on HepG-2 cells, and the concentration of the extract played a role in the level of inhibition (IC50 of 44.6 ± 0.6 µg/ml). The extract had negligible effects on Vero normal cell lines at the lower concentration, with slight toxicity (90.8% viability) at the highest concentration (500 µg/ml). At this same concentration, the extract caused 80-92% inhibition of the cancer cell lines. The extract appears to have demonstrated promising effects on cancer cells. It induces programmed cell death (apoptosis), arrests the cell cycle, and affects the oxidative/antioxidant balance within the cells, potentially leading to the suppression or elimination of cancer cells. These findings are encouraging and may have implications for cancer treatment or further research in this area. More action of extract was seen against bacteria than fungi, with a wide antibacterial impact against all of the tested isolates, notably at the high concentration in comparison to conventional antibiotics.

CONCLUSION

According to the findings, H. cuneiformis may be a valuable source of chemicals that are both antimicrobial and anticancer.

Hamamelis virginiana L. Leaf Extracts Inhibit the Growth of Antibiotic-Resistant Gram-Positive and Gram-Negative Bacteria

Virginian witch hazel (WH; Hamamelis virginiana L.; family: Hamamelidaceae) is a North American plant that is used traditionally to treat a variety of ailments, including bacterial infections. Solvents of varying polarity (water, methanol, ethyl acetate, hexane and chloroform) were used to prepare extracts from this plant. Resuspensions of each extract in an aqueous solution were tested for growth-inhibitory activity against a panel of bacteria (including three antibiotic-resistant strains) using agar disc diffusion and broth microdilution assays. The ethyl acetate, hexane and chloroform extracts were completely ineffective. However, the water and methanolic extracts were good inhibitors of E. coli, ESBL E. coli, S. aureus, MRSA, K. pneumoniae and ESBL K. pneumoniae growth, with the methanolic extract generally displaying substantially greater potency than the other extracts. Combining the active extracts with selected conventional antibiotics potentiated the bacterial growth inhibition of some combinations, whilst other combinations remained non-interactive. No synergistic or antagonistic interactions were observed for any WH extracts/antibiotic combinations. Gas chromatography-mass spectrometry analysis of the extracts identified three molecules of interest that may contribute to the activities observed, including phthalane and two 1,3-dioxolane compounds. Putative modes of action of the active WH extracts and these molecules of interest are discussed herein.

Phytochemical composition, bioactive properties, and toxicological profile of Tetrapleura tetraptera

The use of medicinal plants has gained renewed wide popularity in Africa, Asia, and most parts of the world because of the decreasing efficacy of synthetic drugs. Thus, natural products serve as a potent source of alternative remedy. Tetrapleura tetraptera is a medicinal plant with cultural and traditional significance in West Africa. In addition to the plant being commonly used as a spice in the preparation of traditional spicy food for postpartum care it is also widely used to constitute herbal concoctions and decoctions for treatment of diseases. This review aimed to provide an up-to-date information on the ethnomedicinal uses, pharmacological activities and phytoconstituents of T. tetraptera. Preclinical studies regarding the plant's toxicity profile were also reviewed. For this updated review, literature search was done on PubMed, Science Direct, Wiley, and Google Scholar databases using the relevant keywords. The review used a total of 106 papers that met the inclusion criteria from January 1989 - February 2022 and summarised the bioactivities that have been reported for the rich phytoconstituents of T. tetraptera studied using various chemical methods. Considering the huge report, the review focused on the antimicrobial and antiinflammatory activities of the plant extracts and isolated compounds. Aridan, aridanin and several bioactive compounds of T. tetraptera have shown pharmacological activities though their mechanisms of action are yet to be fully understood. This study also highlighted the influence of plant parts and extraction solvents on its biological activities. It also presented data on the toxicological profile of the plant extracts using different models. From cultural uses to modern pharmacological research the bioactive compounds of T. tetraptera have proved effective in infectious disease management. We hope that this paper provided a robust summary of the biological activities and toxicological profile of T. tetraptera, thus calling for more research into the pharmacological and pharmacokinetic activities of natural products to help combat the growing threat of drug resistance and provide guidelines for their ethnomedicinal uses.

Optimization Method for Phenolic Compounds Extraction from Medicinal Plant (Juniperus procera) and Phytochemicals Screening

Juniperus procera is a natural source of bioactive compounds with the potential of antitumor, antimicrobial, insecticidal, antifungal, and antioxidant activities. An optimization method was developed for total phenolic content (TPC), total flavonoid content (TFC), and total tannin content (TTC) in leaf and seed extract of Juniperus procera. Organic solvents (methanol (99.8%), ethanol (99%), and acetone (99.5%)), and deionized water (DI) were used for extraction. The estimation of TPC, TFC, and TTC in plant materials was carried out using UV-spectrophotometer and HPLC with the standards gallic acid, quercetin, and tannic acid. Recovery of TPC in leaf extract ranged from 2.9 to 9.7 mg GAE/g DW, TFC from 0.9 to 5.9 mg QE/g DW, and TTC ranged from 1.5 to 4.3 mg TA/g DW while the TPC value in the seed extract ranged from 0.53 to 2.6 mg GAE/g DW, TFC from 0.5 to 1.6 mg QE/g DW, and TTC ranged from 0.5 to 1.4 mg TA/g DW. This result revealed that methanol is the best solvent for recovery of the TPC value (9.7 mg) from leaf extract in comparison to other solvents. Ethanol recorded the highest result of TFC (5.9 mg) in leaf extract among the solvents whereas acetone was the best for TTC yield recovery from leaf extract (4.3 mg). In the case of the seed extract, ethanol was the best solvent for both TPC (2.6 mg), and TFC (1.6 mg) recovery in comparison to other solvents. Total tannin content in methanol resulted in significant recovery from seed extract (1.4 mg). Separation and quantification of gallic acid, quercetin, and tannic acid in plant materials were undertaken using HPLC. Gallic acid in leaf and seed of J. procera ranged from 6.6 to 9.2, 6.5 to 7.2 µg/g DW, quercetin from 6.3 to 18.2, 0.9 to 4.2 µg/g DW, and tannic acid from 16.2 to 29.3, 6.6 to 9.3 µg/g DW, respectively. Solvents have shown a significant effect in the extraction of phenolic compounds. Moreover, phytochemicals in plant materials were identified using GC-MS and resulted in very important bioactive compounds, which include anti-inflammatory, antibacterial, and antitumor agents such as ferruginol, phenanthrene, and n-hexadecanoic acid. In conclusion, the optimal solvent for extraction depends on the part of the plant material and the compounds that are to be isolated.

Banana plant as a source of valuable antimicrobial compounds and its current applications in the food sector

Bananas (Musaceae) are one of the world's most common fruit crops and the oldest medicinal plants that are used to treat a variety of infections. There has been recent interest in elucidating the efficiency of the naturally active ingredients, particularly the antimicrobials, in this plant. This review begins with a short background of the banana plant and its cultivars as well as a brief description of its parts. Different experimental tests of the antimicrobial effects and the responsible bioactive compounds of the banana part extracts are then elaborated. A variety of recent and evolving applications of banana parts in the development of functional bakery, dairy, beverage, and meat products as a wheat substitute, fiber/prebiotic source, fat/sucrose substitute, and natural antioxidant are also discussed. Finally, the recent challenges and opportunities presented by different banana parts in creating bio-packaging materials and bactericidal nanoparticles are addressed. This plant contains a variety of antimicrobial substances, including dopamine, gentisic acid, ferulic acid, lupeol, and 3-carene. However, few studies have been conducted on its use as a bio-preservative in food products; it should also be seen as a natural source of both antimicrobial and antioxidant agents. It offers a potentially simple eco-friendly alternative to antibacterial and fungicidal agents rather than chemicals. Low cost, reliable methods for purifying these compounds from banana waste could be useful for food storage and creating more value-added bio-packaging products for perishable food goods.

Hybrid Molecules Development: A Versatile Landscape for the Control of Antifungal Drug Resistance: A Review

Hybrid molecule approach of drug design has become popular due to advantages such as delayed resistance, reduced toxicity, ease of treatment of co-infection and lower cost of preclinical evaluation. Antifungal drugs currently available for the treatment of fungal diseases suffer a major side effect of drug resistance. Hybrid drugs development is one of the approaches that has been employed to control microbial resistance. Their antifungal activity is influenced by their design. This review is focused on hybrid molecules exhibiting antifungal properties to guide scientists in search of more efficient drugs for the treatment of fungal diseases.

Synthesis, Characterization, X-Ray Crystallography, and Antileishmanial Activities of N-Linked and O-Linked Glycopyranosides

Novel N-linked 5a–e and O-linked glycopyranosides 7a–e were synthesized in high yield from commercially available L-tartaric acid containing two asymmetric centers and C2 axis of symmetry. The compound L-tartaric acid was completely protected and then partially hydrolyzed to get the monoester, which upon treatment with different amino and hydroxyl derivatives of glycopyranoses gave the desired amides and esters. The synthesized derivatives were purified by chromatography and characterized by spectroanalytical techniques. The structure of compound 7c in the series was supported by X-ray analysis. Leishmanicidal activities of compounds 5a–e and 7a–e were investigated which showed moderate to good activities.

Desktop NMR spectroscopy for real-time monitoring of an acetalization reaction in comparison with gas chromatography and NMR at 9.4 T

Monitoring of chemical reactions in real-time is in demand for process control. Different methods such as gas chromatography (GC), mass spectroscopy, infrared spectroscopy, and nuclear magnetic resonance (NMR) are used for that purpose. The current state-of-the-art compact NMR systems provide a useful method to employ with various reaction conditions for studying chemical reactions inside the fume hood at the chemical workplace. In the present study, an acetalization reaction was investigated with compact NMR spectroscopy in real-time. Acetalization is used for multistep synthesis of the variety of organic compounds to protect particular chemical groups. A compact 1 T NMR spectrometer with a permanent magnet was employed to monitor the acid catalyzed acetalization of the p-nitrobenzaldehyde with ethylene glycol. The concentrations of both reactant and product were followed by peak integrals in single-scan ¹H NMR spectra as a function of time. The reaction conditions were varied in terms of temperature, agitation speed, catalyst loading, and feed concentrations in order to determine the activation energy with the help of a pseudo-homogeneous kinetic model. For low molar ratios of aldehyde and glycol, the equilibrium conversions were lower than for the stoichiometric ratio. Increasing catalyst concentration leads to faster conversion. The data obtained with low-field NMR spectroscopy were compared with data from GC and NMR spectroscopy at 9.4 T acquired in batch mode by extracting samples at regular time intervals. The reaction kinetics followed by either method agreed well. The activation energies for forward and backward reactions were determined by real-time monitoring with compact NMR at 1 T were 48 ± 5 and 60 ± 4 kJ/mol, respectively. The activation energies obtained with gas chromatography for forward and backward reactions were 48 ± 4 and 51 ± 4 kJ/mol. The equilibrium constant decreases with increasing temperature as expected for an exothermic reaction. The impact of dense sampling with online NMR and sparse sampling with GC was observed on the kinetic outcome using the same kinetic model. Graphical abstract Acetalization reaction kinetics were monitored with real-time desktop NMR spectroscopy at 1 T. Each data point was obtained at regular intervals with a single shot in 15 s. The kinetics was compared with sparsely sampled data obtained with GC and NMR at 9.4 T.

Crystal structure of 5''-benzyl-idene-1'-methyl-4'-phenyl-tri-spiro-[ace-naphthyl-ene-1,2'-pyrrolidine-3',1''-cyclo-hexane-3'',2'''-[1,3]dioxane]-2,6''-dione

In the title compound, C36H31NO4, two spiro links connect the methyl-substituted pyrrolidine ring to the ace-naphthyl-ene and cyclo-hexa-none rings. The cyclo-hexa-none ring is further connected to the dioxalane ring by a third spiro junction. The five-membered ring of the ace-naphthylen-1-one ring system adopts a flattened envelope conformation with the ketonic C atom as flap, whereas the dioxalane and pyrrolidine rings each have a twist conformation. The cyclo-hexa-none ring assumes a boat conformation. Three intra-molecular C-H⋯O hydrogen bonds involving both ketonic O atoms as acceptors are present. In the crystal, C-H⋯O hydrogen bonds connect centrosymmetrically related mol-ecule into chains parallel to the b axis, forming rings of R 2 (2)(10)and R 2 (2)(8) graph-set motifs.

Crystal structure of 5''-(4-chloro-benzyl-idene)-4'-(4-chloro-phen-yl)-1'-methyltri-spiro[acenapthylene-1,2'-pyrrolidine-3',1''-cyclo-hexane-3'',2'''-[1,3]dioxane]-2(1H),6''-dione

In the title compound, C36H29Cl2NO4, two spiro links connect the methyl-substituted pyrrolidine ring to the ace-naphthyl-ene and cyclo-hexa-none rings. The cyclo-hexa-none ring is further connected to the dioxalane ring by a third spiro junction. The five-membered ring of the ace-naphthylen-1-one ring system adopts a flattened envelope conformation, with the ketonic C atom as the flap, whereas the dioxalane and pyrrolidine rings each have a twist conformation. The cyclo-hexenone ring assumes a boat conformation. An intra-molecular C-H⋯O hydrogen-bond inter-action is present. In the crystal, mol-ecules are linked by non-classical C-H⋯O hydrogen bonds, forming chains extending parallel to the a axis.

Gas chromatography-mass spectroscopy analysis of bioactive petalostigma extracts: Toxicity, antibacterial and antiviral activities

Background:

Petalostigma pubescens and Petalostigma triloculare were common components of pharmacopeia's of multiple Australian Aboriginal tribal groupings which traditionally inhabited the areas in which they grow. Among these groups, they had a myriad of medicinal uses in treating a wide variety of bacterial, fungal and viral infections. This study was undertaken to test P. pubescens and P. triloculare leaf and fruit extracts for the ability to inhibit bacterial and viral growth and thus validate Australian Aboriginal usage of these plants in treating bacterial and fungal diseases.

Materials and Methods:

P. pubescens, and P. triloculare leaves and fruit were extracted and tested for antimicrobial, antiviral activity and toxicity. The bioactive extracts were further examined by RP-HPLC and GC-MS to identify the component compounds.

Results:

The methanol, water and ethyl acetate leaf and fruit extracts of displayed potent antibacterial activity. The methanol and ethyl acetate extracts displayed the broadest specificity, inhibiting the growth of 10 of the 14 bacteria tested (71%) for the leaf extract and 9 of the 14 bacteria tested (64%) for the fruit extracts. The water extracts also had broad spectrum antibacterial activity, inhibiting the growth of 8 (57%) and 7 (50%) of the 14 bacteria tested, respectively. All antibacterial extracts were approximately equally effective against Gram-positive and Gram-negative bacteria, inhibiting the growth of 50-75% of the bacteria tested. The methanol, water and ethyl acetate extracts also displayed antiviral activity in the MS2 plaque reduction assay. The methanol and water extracts inhibited 26.6-49.0% and 85.4-97.2% of MS2 plaque formation, respectively, with the fruit extracts being more potent inhibitors. All ethyl acetate extracts inhibited 100% of MS2 plaque formation. All extracts were also non-toxic or of low toxicity. Analysis of these extracts by RP-HPLC showed that the P. triloculare ethyl acetate fruit extract was the least complex of the bioactive extracts. Subsequent analysis of this extract by GC-MS revealed that it contained 9 main compounds: acetic acid; 2,2-dimethoxybutane; 4-methyl-1,3-dioxane; decane; unadecane; 2-furanmethanol; 1,2-benzenediol; 1,2,3-benzenetriol; and benzoic acid.

Conclusion:

These studies validate Australian Aboriginal therapeutic usage of Petalostigma species and indicate their medicinal potential.