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Lichen thalli of Platismatia glauca possesses a remarkable antimicrobial activity
Published: 30 October 2019 by MDPI AG in 5th International Electronic Conference on Medicinal Chemistry session Posters

The current study aimed to evaluate the antimicrobial properties of the methanolic extract of lichen thalli of Plastismatia glauca against some referenced bacterial and yeast strains. Disc diffusion test, minimum inhibitory (MIC) and minimum bactericidal (MBC) or minimum fungicidal (MFC) tests were carried out to evaluate the antimicrobial activity of lichen. All tested microorganisms exhibited varying degrees of susceptibility ranging from 18.5±1.0 to 11.0±0.0 mm zone of inhibition. It also showed high antifungal activity against the yeast Candida albicans (22.5±0.5 mm). The MIC, MBC and MFC were promising, with values as low as 3.125 to 12.5 mg/ml for MIC and 6.25 to 12.5 mg/ml for MBC and MFC. Accordingly, this lichen could be considered as a source of potential antimicrobial agents.

  • Open access
  • 13 Reads
Consumption of medicinal plants for central nervous system (CNS) disorders among university students in the Community of Madrid
Published: 30 October 2019 by MDPI AG in 5th International Electronic Conference on Medicinal Chemistry session ECMC-5

Anxiety and depression are two of the most common mental disorders of global population. These CNS diseases account for one out of every four consultations in primary health care centers. Between 1990 and 2013, the number of people suffering from these both diseases increased by around 50%. Medicinal plants consumption has a key role as an effective and safe alternative medicine to treat these CNS alterations.

A cross-sectional descriptive study was carried out to evaluate medicinal plants consumption for CNS disorders among university students aged 18-24 in the Community of Madrid using an ad hoc and previously validated survey. Results showed that approximately 47.75% of university students consumed medicinal plants to treat anxiety, 42.53 % to fall asleep and 1.49 % to treat symptoms related to depression. Medicinal plants consumption for CNS disorders was more frequent in women than in men. The most common medicinal plants used for these CNS disorders were Valeriana officinalis L. (31.33 %), Passiflora incarnata L. (5.96 %), Melissa oficinalis L. (2.98%) and Tila spp. (20.13 %) The most common consumption forms were herbal teas (71.63 %) and tablets/capsules (29.09%). These medicinal plants preparations were mainly acquired in pharmacies (51.45%) and supermarkets (39.54%). Finally, regarding risks and precautions, around 40% of university students consider that medicinal plants for CNS disorders are harmless and safety. Chi-squared test was used for statistically analysis.

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Biological evaluation of Cetrarioid clade as cholinesterase inhibitors
Published: 30 October 2019 by MDPI AG in 5th International Electronic Conference on Medicinal Chemistry session Posters

OBJECTIVE: Deficiencies in the neurotransmitter acetylcholine have been linked to the pathogenesis of Alzheimer's disease (AD). Therefore, cholinesterase inhibitors are potentially clinical effective for the symptomatic treatment of AD. Little is known about the neuroprotective activity of lichens as cholinesterase inhibitors. The aim of the present work is to evaluate for the first time the activity of five methanol extracts of lichens from Cetraroid clade: Cetraria commixta (Nyl.) Th.Fr, Cetraria crespoae (Barreno & Vazquez) Karnefelt, Cetraria cucullata (Bell.) Ach., Cetraria ericetorum. Opiz, Cetraria nivalis (L.) Ach and Asahinea scholanderi (Llano) as acetylcholinesterase (AchE) and butyrilcholinesterase (BchE) inhibitors.

METHODS: The AChE and BuChE activities were evaluated using the Ellman’s method at 25, 50 and 100 µg/ml methanol extract concentrations. Chemical analysis was performed using High Performance Liquid Chromatography (HPLC-UV).

RESULTS: Among all lichen extracts, Asahinea scholanderi was found the most potent AchE inhibitor (IC50 = 0.11 ± 0.006) followed by Cetraria nivalis (IC50 = 0.16 ± 0.013), Cetraria cucullata (IC50 = 0.18 ± 0.014). Regarding the action on BchE, Asahinea scholanderi was once again the most active lichen specie (IC50= 0.29 ± 0,004) followed by Cetraria cucullata (IC50= 0.31 ± 0,001) and Cetraria commixta (IC50= 0.49 ± 0,018). Since Asahinea scholanderi was the most active cholinesterase inhibitor, phytochemical analysis was performed. HPLC analysis of methanol extract revealed that the main compounds were α- and β-alectoronic, β-collatolic and usnic acid.

CONCLUSION: Our findings suggest that Asahinea scholanderi methanol extract display inhibitory activities against both AChE and BuChE, being a useful promising agent for AD treatment.

  • Open access
  • 12 Reads
Antioxidant capacity and cholinesterase inhibitory activity of Vulpicida pinastri lichen and its chemical composition
Published: 30 October 2019 by MDPI AG in 5th International Electronic Conference on Medicinal Chemistry session ECMC-5

This study reports for first time the antioxidant capacity and cholinesterase inhibitory activity of the methanol extract of the lichen Vulpicida pinastri (Scop.) J.E. Mattsson & M.J. Lai and its chemical composition. This lichen specie with a greenish yellow foliose thallus was collected in Puerto Alto del Peñon, Zamora (Spain). Antioxidant capacity was assessed by in vitro tests (DPPH, ORAC and FRAP), total phenolic content by Folin-Ciocalteu method, cholinesterase inhibitory activity by Ellman’s colorimetric method and chemical composition by HPLC-UV method. The results showed that the values for antioxidant capacity were IC50 283.7 ± 31.7 microg/ml for DPPH, 1.5 ± 0.1 micromol TE/mg dry extract for ORAC and 25.4 ± 2.3 micromol of Fe2+ eq/g sample for FRAP. Moreover, total phenolic content had a value of 48, 9 ±4.8 microg GA/mg. Furthermore, IC50 values were 0.19 ± 0.003 mg/mL for acetylcholinesterase inhibitory activity and 0.89 ± 0.018 mg/mL for butyrylcholinesterase inhibitory activity. Finally, the analysis of chemical composition revealed that the major secondary metabolites were vulpinic acid (9.3 ± 0.8), pinastric acid (41.9 ± 1.07) and usnic acid (36.5 ± 3.62). In conclusion, Vulpicida pinastri is a promising agent to further study for the prevention and treatment of Alzheimer’s disease based on its antioxidant and cholinesterase inhibitory activities.

  • Open access
  • 14 Reads
Optimization of 4-chloro-5-[5-(2-arylvinyl)-1,3,4-oxadiazol-2-yl]benzenesulfonamide structure towards anticancer activity
Published: 30 October 2019 by MDPI AG in 5th International Electronic Conference on Medicinal Chemistry session Posters

During our extensive research on anticancer activity of 2-mercaptobenznensulfonamide derivatives [1-5] we have found that a series of (E)-2-(benzylthio)-4-chloro-5-(5-styryl-1,3,4-oxadiazol-2-yl)benzenesulfonamide possesses a significant anti-tumor activity [5]. In presented studies, we decided to optimize hit-structure in order to determine the structure-activity relationships in this group of promising anticancer compounds. Therefore, we have tested the effect of the change of an aryl ring in the vinyl position (Ar), by synthesis of novel derivatives with diverse substituted aryl rings and 5- or 6-membered heterocyclic rings in that position. Secondly, we have checked the significance of the thiobenzyl substituent at the position 2 of the benzenesulfonamide scaffold by comparing compounds containing thiobenzyl substituent or chlorine atom.

Synthesized compounds 7-36 were tested using MTT assay towards their effect on growth of three human cancer cell lines: colon cancer HCT-116, breast cancer MCF-7 and cervical cancer HeLa as well as on noncancerous keratinocyte cell line HaCaT. Cell viability was measured after 72 h of incubation with tested compound in five concentrations 1 – 100 μM.

Analysis of the obtained results showed high cytostatic activity of derivatives based on the 2-(benzylthio)-4-chloro-benzenesulfonamide scaffold. On the other hand compounds based on 2,4-dichlorobenzenesulfonamide scaffold displayed considerable variety of activity strongly depending on type of aryl substituent in vinyl position. The most optimal configuration for compound 31 was the presence of 2‑nitrothiophene substituent and a lack of thiobenzyl moiety, which afforded with very high cytostatic activity in the IC50 range 0.5-4.5 μM (cisplatin 2.2-3.8 μM).

[1] A.Pogorzelska, B. Żołnowska, J. Sławiński, A. Kawiak, K. Szafrański, M. Belka, T. Bączek, Monatshefte Für Chemie - Chem. Mon. 149 (2018) 1885–1898.

[2] B. Żołnowska, J. Sławiński, K. Szafrański, A. Angeli, C.T. Supuran, A. Kawiak, M. Wieczór, J. Zielińska, T. Bączek, S. Bartoszewska, Eur. J. Med. Chem. 143 (2018) 1931–1941.

[3] A. Pogorzelska, J. Sławiński, B. Żołnowska, K. Szafrański, A. Kawiak, J. Chojnacki, S. Ulenberg, J. Zielińska, T. Bączek, Eur. J. Med. Chem. 138 (2017).

[4] B. Żołnowska, J. Sławiński, A. Pogorzelska, K. Szafrański, A. Kawiak, G. Stasiłojć, M. Belka, J. Zielińska, T. Bączek, Chem. Biol. Drug Des. 90 (2017).

[5] J. Sławiński, K. Szafrański, A. Pogorzelska, B. Żołnowska, A. Kawiak, K. Macur, M. Belka, T. Bączek, Eur. J. Med. Chem. 132 (2017) 236–248.

  • Open access
  • 30 Reads
Anticancer Hybrid Combinations with phenolic compounds
Published: 30 October 2019 by MDPI AG in 5th International Electronic Conference on Medicinal Chemistry session Posters

Different types of treatments are being employed to overcome cancer, which is characterized by abnormal cell growth involving cell division without control. However, their usually lack of selectivity and the development of resistance result in limited efficacy or ineffectiveness of the therapies. For these reasons, seeking new treatment options for this disease is necessary. Nowadays, the acknowledge bioactive properties of some secondary metabolites such as polyphenols, have made antitumour hybrid combinations a promising therapeutic approach.

This work aims to provide a synopsis into Anticancer Hybrid Combinations involving phenolic compounds, focusing on their multi-target mechanisms of action and synergistic effects.

These combinations consist on the therapeutic mixture of synthetic drugs with chemically defined constituents from plants (secondary metabolites, in this case, phenolic compounds) aiming to increase the pharmacological activity of the formulation and simultaneously reduce the toxic side-effects of the drugs, interaction known as synergy.

Antitumour hybrid combinations are a promising therapeutic strategy to minimize adverse effects and to reduce cancer resistance to different treatments. At the same time, it shows selectivity to tumour cells and potentiate the activity of the drug that make them an interesting option to cure cancer.

References:
[1] Domínguez-Martin EM, Diaz-Lanza AM, Faustino CMC (2018) Curr Pharm Des 24, 4312-4333.
[2] Wagner H, Efferth T. (2017) Phytomedicine, 37, 1-3.
[3] Mahbub AA, Le Maitre CL, Haywood-Small S, Cross NA, Nicola Jordan-Mahy N (2019) Oncotarget 10, 4570-86
[4] Zhong C, Qiu S, Li J, Shen J, Zu Y, Shi J, Sui G (2019) Phytomedicine 59, 152921

  • Open access
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Synthesis, biological evaluation and membranotropic properties of quinoline-antimicrobial peptide conjugates as antibacterial drugs
Published: 30 October 2019 by MDPI AG in 5th International Electronic Conference on Medicinal Chemistry session ECMC-5

Tuberculosis and nosocomial infections are among the most frequent causes of death in the world. Mycobacteria such as Mycobacterium tuberculosis and ESKAPE bacteria are pathogens particularly implicated in these infectious diseases1. The lack of antibiotics with novel mode of action associated with the spread of drug resistant bacteria make the fight against these infections particularly challenging.

Using antimicrobial peptides (AMPs) to restore or to broaden antibacterial activity of antibiotics is an interesting strategy to fight resistant strains. For example, the conjugation between chloramphenicol and ubiquicidine29-41 gives a conjugate with increased activity against Escherichia coli and reduced toxicity against neutrophils compared to chloramphenicol alone 2.

During previous work on the development of new anti-infective drugs, we identified a series of quinolines active against Gram-positive bacteria such as Staphylococcus aureus and Enterococcus faecalis. Concerning Gram-negative bacteria, some of them were active on E.coli but not against Pseudomonas aeruginosa3,4. In order to broaden the antibacterial spectrum of this heterocycle core, we synthesized quinoline-based conjugates with short AMP sequences5. Their antibacterial activities against a panel of bacteria and mycobacteria will be discussed. Membranotropic properties study through tensiometry measures on bacterial mimetic membrane models was carried out to elucidate their mechanism of action.

References:

  1. (a) WHO, Global tuberculosis report 2017; (b) Khan, H. A., Baig, F. K. & Mehboob. Nosocomial infections: Epidemiology, prevention, control and surveillance, Asian Pac. J. Trop. Biomed. 2017, 7, 478–482.
  2. (a) Arnusch et al. Enhanced Membrane Pore Formation through High-Affinity Targeted Antimicrobial Peptides. PLoS ONE 2012 7:e39768; (b) Chen et al. Bacteria-Targeting Conjugates Based on Antimicrobial Peptide for Bacteria Diagnosis and Therapy. Mol. Pharm. 2015, 12, 2505.
  3. Jonet, A.; Dassonville-Klimpt, A.; Sonnet, P.; Mullié, C. Side chain length is more important than stereochemistry in the antibacterial activity of enantiomerically pure 4-aminoalcohol quinoline derivatives. J. Antibiot. (Tokyo) 2013, 66, 683–686.
  4. Laumaillé, Dassonville-Klimpt, Peltier, Mullié, Andréjak, Da-Nascimento, Castelain, Sonnet, Synthesis and study of new quinolineaminoethanols as anti-bacterial drugs, Pharmaceuticals 2019, 12(2), 91.
  5. Strøm, M. B. et al. The Pharmacophore of Short Cationic Antibacterial Peptides, 2003, 46, 3–6.

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  • 24 Reads
Antibacterial activity of apigenin, luteolin, and their C-glucosides
Published: 30 October 2019 by MDPI AG in 5th International Electronic Conference on Medicinal Chemistry session ECMC-5

Apigenin (4′,5,7-trihydroxyflavone) and luteolin (3′,4′,5,7-tetrahydroxyflavone) are among the most widely distributed flavone aglycones in flowering plants. These metabolites often occur in the form of O- and C-glycosides. In this group, four C-glucosides pay special attention: vitexin (apigenin 8-C-glucoside) and isovitexin (apigenin 6-C-glucoside) as well as orientin (luteolin 8-C-glucoside) and isoorientin (luteolin 6-C-glucoside). The above-mentioned compounds show various biological activities, including antioxidant, anti-inflammatory, immunomodulatory, anticancer as well as neuro-, cardio-, and hepatoprotective effects. The aim of the present work was to determine the antibacterial activity of these flavones.

In the in vitro tests, there were investigated clinical strains of two Gram-positive (Staphylococcus aureus, Enterococcus faecalis) and Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa). The antimicrobial activity of chosen substances was determined by the micro-dilution method according to recommendations of the Clinical and Laboratory Standards Institute (CLSI). Curcumin was used as a positive control.

Our results exhibited a relatively low sensitivity of the tested strains to the plant metabolites. In the case of curcumin – natural compound with known strong antibacterial effect, the minimal inhibitory concentration (MIC) for all species of bacteria was 500 μg/mL. The same level of biological activity was observed for apigenin, luteolin, and their glucosides against E. coli and P. aeruginosa. Among Gram-positive bacteria, the obtained results showed significant variability. Strains of S. aureus demonstrated a weak sensitivity to apigenin (MIC = 500-1000 μg/mL), and were resistant to its derivatives: vitexin and isovitexin (>1000 μg/mL). Additionally, these compounds poorly inhibited the growth of E. faecalis (1000 μg/mL). In turn, luteolin and its C-glucosides (orientin, isoorientin) reached the same values of the MICs: moderate against S. aureus (500 μg/mL) and weak for E. faecalis (1000 μg/mL).

Our research points to the problem of varied sensitivity and even resistance of some clinical strains of common pathogens to the widespread natural plant compounds, such as flavonoids and other phenolics (e.g., curcumin). It is interesting that apigenin, luteolin, and their C-glucosides were generally more potent against Gram-negative bacteria than Gram-positive ones. A pair of analysed flavone aglycones has a very similar chemical structure, and they did not differ significantly in the antibacterial activity. Similarly, the presence and location of the sugar group in the flavone glucosides usually did not affect the values of the MICs.

  • Open access
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In vitro antimicrobial effect of curcumin
Published: 30 October 2019 by MDPI AG in 5th International Electronic Conference on Medicinal Chemistry session ECMC-5

Curcumin is a major phenolic constituent of turmeric (Curcuma longa L.) rhizomes. This substance has been described as an anti-inflammatory, antibacterial, and antifungal agent. Unfortunately, the literature data concerning its antimicrobial activity provide very diverse results. Moreover, some of them are doubtful, especially when curcumin has been dissolved in chemical compounds inhibiting bacterial growth: ethanol or methanol. Therefore, the purpose of the present work was to carry out comparative analyses of the antimicrobial activity of curcumin using recommendations prepared by the Clinical and Laboratory Standards Institute (CLSI).

In the study, there were tested six Gram-positive (Enterococcus faecalis, Staphylococcus aureus, methicillin-resistant S. aureus /MRSA/, S. epidermidis, Streptococcus agalactiae, S. pyogenes) and five Gram-negative bacteria (Acinetobacter lwoffii, Escherichia coli, Klebsiella oxytoca, Proteus mirabilis, Pseudomonas aeruginosa) as well as pathogenic fungus Candida albicans. For each species, four clinical strains were used. The minimal inhibitory concentrations (MICs) of curcumin were determined by the micro-dilution method described in details in our previous publications [1,2]. Curcumin was dissolved in 40% water solution of dimethyl sulfoxide (DMSO), which in this concentration has not antimicrobial effect.

In vitro analyses have shown a large diverse of curcumin activity. This plant metabolite did not inhibit the growth of C. albicans, MRSA, S. agalactiae, and P. mirabilis (MICs >1000 μg/mL), while it demonstrated very strong effect on strains of S. epidermidis (MICs: 15.6-31.25 μg/mL) and S. pyogenes (62.5-125 μg/mL). Curcumin sensitivity was also observed for A. lwoffii (125-250 μg/mL), P. aeruginosa (250-500 μg/mL) as well as E. coli and K. oxytoca (500-1000 μg/mL). Among S. aureus and E. faecalis strains, we found both resistant (MICs >1000 μg/mL) and sensitive (500 μg/mL) bacteria.

Summarizing our study, curcumin belongs to the potent natural antibacterial agents of plant origin, but its activity varies greatly depending on the species and even the bacterial strain. The above-mentioned compound was very strong against S. epidermidis and S. pyogenes, and at the same time it had weak or no activity on other Gram-positive bacteria. In the case of Gram-negative ones, curcumin exhibited moderate, weak or none antibacterial effect.

[1] Karpiński T.M. Efficacy of octenidine against Pseudomonas aeruginosa strains. Eur J Biol Res. 2019, 9, 135-140.

[2] Karpiński T.M., Adamczak A. Fucoxanthin - an antibacterial carotenoid. Antioxidants 2019; 8(8): 239.

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Cytotoxic activity of coleon diterpenoids from Plectranthus mutabilis codd
Published: 30 October 2019 by MDPI AG in 5th International Electronic Conference on Medicinal Chemistry session ECMC-5

Plectranthus species have been traditionally used to combat different types of cancer due to their anti-tumour properties [1]. The cytotoxicity screenings have identified Plectranthus plants as potential sources of antitumor lead compounds. Abietane diterpenoids have been reported as the main constituents of some species in this genus and are responsible for its potential therapeutic value [2]. These naturally occurring compounds display a vast array of biological activities including cytotoxic and antiproliferative activities against human tumour cells [3]. The objective of this study was to evaluate the biological activity of sixteen Plectranthus spp. acetonic extracts and identify the bioactive compounds in the most effective extracts. P. mutabilis had the highest extraction yield (30.03%, dry weight % w/w). All extracts were screened for their general toxicity using the Artemia salina model [4]. Thus, the antitumor activity of the five most toxic extracts was explored in three different cancer cell lines: HCT116, MCF-7 and NCI-H460. P. mutabilis with high cytotoxic activity was subjected to a bio-guided fractionation using the A. salina general toxicity assay. Column chromatography on silica or polyamide, with gradient systems of increasing polarity allowed to achieve the diterpenoid coleon U (1) and 8α,9α-epoxycoleon U quinone (2). The complete structure characterization was done mainly by 1D- and 2D-NMR, and comparison with literature data. Compound 1 showed moderate cytotoxicity on sensitive and resistant (ABCB1 overexpressing) human colon adenocarcinoma and normal cell lines showing slight selectivity towards resistant cells. Moreover, this compound is not an inhibitor of ABCB1 transporter based on the intracellular accumulation of the ABCB1 substrate rhodamine 123. Further phytochemical studies are ongoing.

References

[1]. Diogo et al, (2019). ACS Omega 31; 4(5): 8094–8103.

[2]. Burmistrova et al, (2013). Journal of Natural Products 10-1021

[3]. Santos-Rebelo et al, (2018). Pharmaceutics 10(4): 216

[4]. Epole et al, (2017). Biomed Biopharm Res. (14) 1: 95-108

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