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Selected Scholars' Exclusive Papers on Natural Products Chemistry

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Natural Products Chemistry".

Deadline for manuscript submissions: closed (31 December 2023) | Viewed by 9660

Special Issue Editor

Special Issue Information

Dear Colleagues,

This Special Issue of Molecules is dedicated to recent advances and hot topics in the research area of natural products chemistry. It comprises a selection of exclusive papers contributed by invited reputable scholars, including the members of the Editorial Board as well as the Topical Advisory Panel of the Section Natural Products Chemistry. This Special Issue is meant to collect articles analyzing the new groundbreaking results of the invited scientists’ original research as well as timely review articles discussing key topics in the field. Thus, this Special Issue aims to represent our Section as an attractive open access publishing platform for all aspects of modern contemporary natural products chemistry.

Prof. Dr. Thomas J. Schmidt
Guest Editor

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Keywords

  • natural products (NPs)
  • secondary metabolites
  • isolation of NPs
  • structure elucidation of NPs
  • analytical characterization of NPs
  • analytical profiling of NPs
  • modern search methodologies for NPs
  • biological activity of NPs
  • natural drugs and drug leads
  • structure–activity relationships of NPs

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Published Papers (6 papers)

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Research

19 pages, 1024 KiB  
Article
Essential Oil Compounds in Combination with Conventional Antibiotics for Dermatology
by Shivar Simbu, Ané Orchard and Sandy van Vuuren
Molecules 2024, 29(6), 1225; https://doi.org/10.3390/molecules29061225 - 8 Mar 2024
Cited by 2 | Viewed by 1609
Abstract
Antimicrobial resistance has emerged as a significant threat to public health, prompting novel combinations comprising of natural sources such as essential oil compounds with conventional antibiotics. This study aimed to determine the possible interactions between six essential oil compounds with eight antibiotics/antifungals against [...] Read more.
Antimicrobial resistance has emerged as a significant threat to public health, prompting novel combinations comprising of natural sources such as essential oil compounds with conventional antibiotics. This study aimed to determine the possible interactions between six essential oil compounds with eight antibiotics/antifungals against six pathogens (Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Acinetobacter baumannii, Cutibacterium acnes, and Candida albicans) commonly implicated in skin infections. The minimum inhibitory concentrations (MICs) for the antibiotics and essential oil compounds were evaluated singularly and in combination using the broth microdilution assay. The fractional inhibitory concentrations (FIC) were calculated to determine the interactive profile of the combinations. The synergistic interactions (FIC ≤ 0.5) were further analysed at varying ratios and depicted on isobolograms. The toxicity of the synergistic combinations was determined using the brine shrimp lethality assay. Eight synergistic interactions were identified against the selected Gram-positive and P. aeruginosa pathogens, and the combinations also demonstrated a reduced toxicity. The combination of amoxicillin and eugenol demonstrated the lowest toxicity (LC50 = 1081 µg/mL) and the highest selectivity index (14.41) when in a 70:30 ratio. This study provides insight into the in vitro antimicrobial interactions of essential oil compounds and conventional antibiotics that can form a basis for newer therapies. Full article
(This article belongs to the Special Issue Selected Scholars' Exclusive Papers on Natural Products Chemistry)
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13 pages, 3231 KiB  
Article
TLC-Bioautography-Guided Isolation and Assessment of Antibacterial Compounds from Manuka (Leptospermum scoparium) Leaf and Branch Extracts
by Wenliang Xu, Danxia Shi, Kuanmin Chen and David G. Popovich
Molecules 2024, 29(3), 717; https://doi.org/10.3390/molecules29030717 - 4 Feb 2024
Cited by 1 | Viewed by 1465
Abstract
A rapid procedure for the targeted isolation of antibacterial compounds from Manuka (Leptospermum scoparium) leaf and branch extracts was described in this paper. Antibacterial compounds from three different Manuka samples collected from New Zealand and China were compared. The active compounds [...] Read more.
A rapid procedure for the targeted isolation of antibacterial compounds from Manuka (Leptospermum scoparium) leaf and branch extracts was described in this paper. Antibacterial compounds from three different Manuka samples collected from New Zealand and China were compared. The active compounds were targeted by TLC-bioautography against S. aureus and were identified by HR-ESI-MS, and -MS/MS analysis in conjunction with Compound Discoverer 3.3. The major antibacterial component, grandiflorone, was identified, along with 20 β-triketones, flavonoids, and phloroglucinol derivatives. To verify the software identification, grandiflorone underwent purification via column chromatography, and its structure was elucidated through NMR analysis, ultimately confirming its identity as grandiflorone. This study successfully demonstrated that the leaves and branches remaining after Manuka essential oil distillation serve as excellent source for extracting grandiflorone. Additionally, we proposed an improved TLC-bioautography protocol for evaluating the antibacterial efficacy on solid surfaces, which is suitable for both S. aureus and E. coli. The minimum effective dose (MED) of grandiflorone was observed to be 0.29–0.59 μg/cm2 against S. aureus and 2.34–4.68 μg/cm2 against E. coli, respectively. Furthermore, the synthetic plant growth retardant, paclobutrazol, was isolated from the samples obtained in China. It is hypothesized that this compound may disrupt the synthesis pathway of triketones, consequently diminishing the antibacterial efficacy of Chinese Manuka extract in comparison to that of New Zealand. Full article
(This article belongs to the Special Issue Selected Scholars' Exclusive Papers on Natural Products Chemistry)
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21 pages, 3280 KiB  
Article
Extraction Optimization and Qualitative/Quantitative Determination of Bioactive Abietane-Type Diterpenes from Three Salvia Species (Common Sage, Greek Sage and Rosemary) by 1H-qNMR
by Panagiotis Kallimanis, Prokopios Magiatis, Angeliki Panagiotopoulou, Kostas Ioannidis and Ioanna Chinou
Molecules 2024, 29(3), 625; https://doi.org/10.3390/molecules29030625 - 28 Jan 2024
Cited by 2 | Viewed by 1421
Abstract
The objective of this study was the optimization of the extraction process and the qualitative and quantitative determination of the bioactive metabolites: 12-O-methylcarnosic acid (12MCA), carnosic acid (CA), carnosol (CS), 7-O-methyl-epi-rosmanol (7MER) and rosmanol (RO) in infusions, [...] Read more.
The objective of this study was the optimization of the extraction process and the qualitative and quantitative determination of the bioactive metabolites: 12-O-methylcarnosic acid (12MCA), carnosic acid (CA), carnosol (CS), 7-O-methyl-epi-rosmanol (7MER) and rosmanol (RO) in infusions, decoctions, turbulent flow extracts, tinctures and oleolites from three Salvia species: Salvia officinalis L. (common sage, SO), Salvia fruticosa Mill. (Greek sage, SF) and Salvia rosmarinus Spenn (syn Rosmarinus officinalis L.) (rosemary, SR), using Quantitative Proton Nuclear Magnetic Resonance Spectroscopy (1H-qNMR). Regarding the aqueous extracts, decoctions appeared to be richer sources of the studied metabolites than infusions among the three plants. For SR, the turbulent flow extraction under heating was the most efficient one. The optimum time for the preparation of decoctions was found to be 5 min for SF and SO and 15 min for SR. It is noteworthy that SR tinctures were not stable in time due to decomposition of the abietane-type diterpenes CA and CS because of the polar solvent used for their preparation. Contrary to this finding, the oleolites of SR appeared to be very stable. Olive oil as a solvent for extraction was very protective for the contained abietane-type diterpenes. A preliminary stability study on the effect of the storage time of the SF on the abietane-type diterpenes content showed that the total quantity of abietanes decreased by 16.51% and 40.79% after 12 and 36 months, respectively. The results of this investigation also demonstrated that 1H-qNMR is very useful for the analysis of sensitive metabolites, like abietane-type diterpenes, that can be influenced by solvents used in chromatographic analysis. Full article
(This article belongs to the Special Issue Selected Scholars' Exclusive Papers on Natural Products Chemistry)
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14 pages, 2723 KiB  
Article
NMR and Docking Calculations Reveal Novel Atomistic Selectivity of a Synthetic High-Affinity Free Fatty Acid vs. Free Fatty Acids in Sudlow’s Drug Binding Sites in Human Serum Albumin
by Themistoklis Venianakis, Alexandra Primikyri, Till Opatz, Stefan Petry, Georgios Papamokos and Ioannis P. Gerothanassis
Molecules 2023, 28(24), 7991; https://doi.org/10.3390/molecules28247991 - 7 Dec 2023
Cited by 4 | Viewed by 1300
Abstract
Saturation transfer difference (STD), inter-ligand NOEs (INPHARMA NMR), and docking calculations are reported for investigating specific binding sites of the high-affinity synthetic 7-nitrobenz-2-oxa-1,3-diazoyl-4-C12 fatty acid (NBD-C12 FA) with non-labeled human serum albumin (HSA) and in competition with the drugs warfarin and [...] Read more.
Saturation transfer difference (STD), inter-ligand NOEs (INPHARMA NMR), and docking calculations are reported for investigating specific binding sites of the high-affinity synthetic 7-nitrobenz-2-oxa-1,3-diazoyl-4-C12 fatty acid (NBD-C12 FA) with non-labeled human serum albumin (HSA) and in competition with the drugs warfarin and ibuprofen. A limited number of negative interligand NOEs between NBD-C12 FA and warfarin were interpreted in terms of a short-range allosteric competitive binding in the wide Sudlow’s binding site II (FA7) of NBD-C12 FA with Ser-202, Lys-199, and Trp-214 and warfarin with Arg-218 and Arg-222. In contrast, the significant number of interligand NOEs between NBD-C12 FA and ibuprofen were interpreted in terms of a competitive binding mode in Sudlow’s binding site I (FA3 and FA4) with Ser-342, Arg-348, Arg-485, Arg-410, and Tyr-411. NBD-C12 FA has the unique structural properties, compared to short-, medium-, and long-chain saturated and unsaturated natural free fatty acids, of interacting with well-defined structures with amino acids of both the internal and external polar anchor sites in Sudlow’s binding site I and with amino acids in both FA3 and FA4 in Sudlow’s binding site II. The NBD-C12 FA, therefore, interacts with novel structural characteristics in the drug binding sites I and II and can be regarded as a prototype molecule for drug development. Full article
(This article belongs to the Special Issue Selected Scholars' Exclusive Papers on Natural Products Chemistry)
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16 pages, 1078 KiB  
Article
Chemical Composition of Essential Oils and Supercritical Carbon Dioxide Extracts from Amomum kravanh, Citrus hystrix and Piper nigrum ‘Kampot’
by Vihanova Katerina, Urbanova Klara, Nguon Samnang and Kokoska Ladislav
Molecules 2023, 28(23), 7748; https://doi.org/10.3390/molecules28237748 - 24 Nov 2023
Viewed by 1762
Abstract
The fruits of Amomum kravanh, Citrus hystrix and Piper nigrum ‘Kampot’ are traditionally used as spices in Cambodian cuisine. In this study, the chemical composition of essential oils (EOs) and supercritical CO2 extracts from all three species was determined using GC-MS, [...] Read more.
The fruits of Amomum kravanh, Citrus hystrix and Piper nigrum ‘Kampot’ are traditionally used as spices in Cambodian cuisine. In this study, the chemical composition of essential oils (EOs) and supercritical CO2 extracts from all three species was determined using GC-MS, with two columns of different polarity (HP-5/DB-HeavyWAX). Differences between the chemical profile of the EOs and CO2 extracts were observed for all species. The greatest difference was detected in A. kravanh EO containing mainly eucalyptol (78.8/72.6%), while the CO2 extract was rich in fatty acids (13/55.92%) and long-chain alkanes (25.55/9.54%). Furthermore, the results for the CO2 extract of this species differed, where tricosane (14.74%) and oleic acid (29.26%) were the main compounds identified when utilizing the HP-5 or DB-HeavyWAX columns, respectively. Moreover, the EO and CO2 extract from P. nigrum ‘Kampot’ fruits and the CO2 extract from C. hystrix fruit peel, containing respective amounts 34.84/39.55% (for EO) and 54.21/55.86% (for CO2 extract) of β-caryophyllene and 30.2/28.9% of β-pinene, were isolated and analyzed for the first time. Generally, these findings suggest that supercritical CO2 could potentially be used for the extraction of all three spices. Nevertheless, further research determining the most efficient extraction parameters is required before its commercial application. Full article
(This article belongs to the Special Issue Selected Scholars' Exclusive Papers on Natural Products Chemistry)
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12 pages, 1060 KiB  
Article
Nutritional Composition and Odor-Contributing Volatile Compounds of the Edible Mushroom Cantharellus alborufescens
by Mohaddeseh Moghaddam, Masoomeh Ghobad-Nejhad, Thomas Stegemann, Serhat Sezai Çiçek, Christian Zidorn and Majid Javanmard
Molecules 2023, 28(22), 7516; https://doi.org/10.3390/molecules28227516 - 10 Nov 2023
Viewed by 1473
Abstract
Chanterelles are one of the most highly valued wild edible mushroom genera worldwide. This work aimed to investigate the nutritional characteristics and volatile compounds’ profile of Cantharellus alborufescens for the first time. Proximate analysis was performed according to the Association of Official Agricultural [...] Read more.
Chanterelles are one of the most highly valued wild edible mushroom genera worldwide. This work aimed to investigate the nutritional characteristics and volatile compounds’ profile of Cantharellus alborufescens for the first time. Proximate analysis was performed according to the Association of Official Agricultural Chemists, while the mineral contents and the volatile compounds were determined using ICP-MS and GC-MS, respectively. C. alborufescens had an average of 25.8% protein, 5.5% fat, 12.7% ash, and 55.9% carbohydrates, including 11.4% fiber per dw of mushroom. Further analyses of the fat and protein contents revealed high amounts of polyunsaturated fatty acids as well as monosodium glutamate-like amino acids. Linoleic acid (42.0% of fat) and oleic acid (28.6% of fat) were the major fatty acids, while leucine (1.2%) and lysine (0.9%) were the most abundant essential amino acids. The results showed that C. alborufescens contained 3.1 µg/g vitamin D2 and 4.9 mg/g vitamin E per dw, as well as notable quantities of macro- and microelements, such as potassium, calcium, magnesium, and iron. GC-MS analysis revealed various volatile compounds such as acetaldehyde, n-hexanal, 3-methylbutanal, 1-octen-3-ol, etc. In conclusion, this study supports the use of C. alborufescens as a food rich in fiber and vitamin E, with a suitable amount of protein and other nutrients. Full article
(This article belongs to the Special Issue Selected Scholars' Exclusive Papers on Natural Products Chemistry)
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