Crystal Structures and Cytotoxicity of ent-Kaurane-Type Diterpenoids from Two Aspilia Species

Yaouba, Souaibou; Valkonen, Arto; Coghi, Paolo; Gao, Jiaying; Guantai, Eric M.; Derese, Solomon; Erdélyi, Máté; Yenesew, Abiy

doi:10.3390/molecules23123199

Cited by 9 publications

(13 citation statements)

References 41 publications

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“…( Asteraceae ) to investigate its potential antimicrobial activity and characterize the phytochemicals responsible for the bioactivity. A. pluriseta is locally known as Muuti (in Mbeere, Embu, and Kikuyu), Wuti (in Kamba), Ol-oiyabase (in Maasai), and Shilambila (in Luhya) communities of Kenya [ 40 ]. This plant is widely spread in East, Central, and Southern Africa, especially in open woodlands and grasslands [ 41 , 42 ].…”

Section: Introductionmentioning

confidence: 99%

Antimicrobial activity, phytochemical characterization and gas chromatography-mass spectrometry analysis of Aspilia pluriseta Schweinf. extracts

Njeru

Muema

2020

Heliyon

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Aspilia pluriseta is associated with various bioactivities, although with limited scientific justification. In this study, we evaluated the antimicrobial activity, and characterized the phytochemicals of root extracts of A. pluriseta aimed at validating its therapeutic potential. We used BACTEC MGIT™ 960 system to test for antitubercular activity, disc-diffusion together with the microdilution method to evaluate antimicrobial activities and qualitative phytochemical tests together with gas chromatography-mass spectrometry (GC-MS) analysis to determine the phytochemicals that associated with A. pluriseta extracts activity. We show that methanolic crude extract (at 1 g/mL) had high Mycobacterium tuberculosis (MTB) inhibitory activity (0 growth unit) and considerable potency against Escherichia coli (11.7 mm), Staphylococcus aureus (9.0 mm), and Candida albicans (7.7 mm). All the extract fractions exerted remarkable antimycobacterial activities with minimum inhibitory activity of between 6.26 – 25 μg/mL. The highest antimicrobial activity of petroleum ether and dichloromethane fraction was against E. coli at inhibition zone diameters of 8.3 mm, and 8.0 mm, respectively, while ethyl acetate fraction was against S. aureus with an inhibition zone of 8.7 mm. Methanolic fraction exhibited broad-spectrum activity against 87.5% of the tested microbes (inhibition zones 6.3–8.3 mm). Furthermore, we qualitatively detected terpenoids, alkaloids, and phenolics such as flavonoids, and anthraquinones in extract fractions. GC-MS analysis detected an abundance of fatty acid esters, 2-hydroxy-1-(hydroxymethyl) ethyl ester-hexadecanoic acid, and 2,3-dihydroxy propyl ester-octadecanoic acid and four alkanes. Taken together, we show that A. pluriseta extract fractions (especially ethyl acetate and methanolic fractions) have strong selective antitubercular activity, and thus, we scientifically validate the use of A. pluriseta as a potential source for the discovery of novel antitubercular agents.

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Section: Introductionmentioning

confidence: 99%

Antimicrobial activity, phytochemical characterization and gas chromatography-mass spectrometry analysis of Aspilia pluriseta Schweinf. extracts

Njeru

Muema

2020

Heliyon

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“…Eleven examples of real‐world CASE studies were examined using DFT analysis of J ‐couplings. Table shows structures that were elucidated by ACD/SE using the FSG algorithm.…”

Section: Resultsmentioning

confidence: 99%

Enhancing computer‐assisted structure elucidation with DFT analysis of J‐couplings

Buevich

Elyashberg²

2020

Magnetic Reson in Chemistry

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Computer-assisted structure elucidation (CASE) is the class of expert systems that derives molecular structures primarily from one-dimensional and twodimensional nuclear magnetic resonance data. Contemporary CASE systems, including Advanced Chemistry Development/Structure Elucidator (ACD/SE), consider cross-peaks in heteronuclear multiple bond coherence (HMBC) and correlation spectroscopy (COSY) spectra as two-or three-bond correlations by default. However, four and more bond correlations (nonstandard correlations [NSCs]) could be present in these spectra too. The indiscriminate addition of NSCs to the CASE computations is prohibitively expensive. To address this problem, the ACD/SE program performs a logical analysis of observed correlations and determines the minimum number of NSCs. Guided by this information, a more efficient fuzzy structure generation (FSG) algorithm is subsequently applied. Until now, the FSG algorithm was utilized without any verification of the reliability of found NSCs. Here, we report a verification method for NSCs based on the relationship between NSCs and J-couplings computed with high accuracy density functional theory (DFT) methods. We used the example of strychnine to show that 41 (32%) of 8-Hz HMBC crosspeaks were NSCs and were consistent with 4-6 J CH couplings greater than 0.3 Hz. This cutoff value was largely confirmed by the analysis of NSCs in 11 realworld natural products elucidated by ACD/SE. Additionally, utilizing the example of the CASE study of cleospinol A, we showed that the DFT-computed J-couplings of NSCs can distinctively differentiate the correct structure among six proposed isomers. The proposed approach of NSC verification should further improve the robustness of CASE analysis and can help reveal potential problems with reported experimental data.

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“…Preparation of 16α-hydroxy-ent-kauran-19-oic acid (2d), 16α-methoxy-ent-kauran-19-oic acid (2e) was performed using acid-catalysed hydroxylation and methoxylation, respectively (Cavalcanti et al 2009). For these reactions, amounts of 50 mg were applied instead of 1 g and the resulting products were identified by comparison of their MS and NMR data to literature (Chen et al 2000;Yaouba et al 2018).…”

Section: Monohydroxy and Methoxy Derivativesmentioning

confidence: 99%

Biological Activities of Two Major Copaiba Diterpenoids and Their Semi-synthetic Derivatives

Çiçek

Wenzel‐Storjohann

Girreser

et al. 2020

Rev. Bras. Farmacogn.

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The oleoresin of Copaifera reticulata Ducke, Fabaceae, is a traditional Brazilian remedy used for a wide range of applications. Commonly named copaiba, the oleoresin has been found to exhibit strong antimicrobial effects in our previous study, which could be attributed to some of its diterpenoid constituents. In order to find new biological activities and to eventually enhance the before observed effects, (−)-polyalthic acid (1) and kaurenoic acid (2), together with eight prepared semi-synthetic derivatives (1a-1c and 2a-2e) were evaluated for their cytotoxic, antibacterial and antifungal properties. Regarding the gram-positive bacteria Enterococcus faecium and methicillin-resistant Staphylococcus aureus, we found that both the exocylic methylene group and the carboxyl group were crucial for the activity against these two clinically relevant bacterial strains. Investigation of the antifungal activity, in contrast, showed that the carboxyl group is unnecessary for the effect against the dermatophytes Trichophyton rubrum and Cryptococcus neoformans, indicated by low micromolar IC 50 values for both (−)-polyalthic acid diethylamide (1a) as well as (−)-polyalthic acid methyl ester (1b). Apart from studying the biological activity, the structure of one semi-synthetic derivative, compound 1c, is being reported for the first time. During the course of the structure elucidation of the new compound, we discovered inconsistencies regarding the stereochemistry of polyalthic acid and its stereoisomers, which we clarified in the present work.

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Crystal Structures and Cytotoxicity of ent-Kaurane-Type Diterpenoids from Two Aspilia Species

Cited by 9 publications

References 41 publications

Antimicrobial activity, phytochemical characterization and gas chromatography-mass spectrometry analysis of Aspilia pluriseta Schweinf. extracts

Antimicrobial activity, phytochemical characterization and gas chromatography-mass spectrometry analysis of Aspilia pluriseta Schweinf. extracts

Enhancing computer‐assisted structure elucidation with DFT analysis of J‐couplings

Biological Activities of Two Major Copaiba Diterpenoids and Their Semi-synthetic Derivatives

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