Structural elucidation of a novel pyrrolizidine alkaloid isolated from Crotalaria retusa L.

Pinto, Bryan Nickson Santana; Moura, Gabriella A.; Demuner, Antônio J.; Alvarenga, Elson S.

doi:10.1016/j.molstruc.2022.132394

Cited by 5 publications

(5 citation statements)

References 32 publications

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“…Honey samples from Ethiopia had the highest percentage of lycopsamine detection, with a 100% percentage of positive samples [24]. It is possible that the different PA levels and types in honey are due to the different climates, as studies have shown that the species of Camellia sinensis more easily spread and grow than other species in tropical or subtropical regions [27]. OTO-type senkirkine and clivorine are most common in honey [28].…”

Section: Status Of Pa Levels In Foodsmentioning

confidence: 99%

Levels, Toxic Effects, and Risk Assessment of Pyrrolizidine Alkaloids in Foods: A Review

Lu,

Qiu,

et al. 2024

Foods

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Pyrrolizidine alkaloids (PAs) are naturally occurring secondary metabolites of plants. To date, more than 660 types of PAs have been identified from an estimated 6000 plants, and approximately 120 of these PAs are hepatotoxic. As a result of PAs being found in spices, herbal teas, honey, and milk, PAs are considered contaminants in foods, posing a potential risk to human health. Here, we summarize the chemical structure, toxic effects, levels, and regulation of PAs in different countries to provide a better understanding of their toxicity and risk assessment. With recent research on the risk assessment of PAs, this review also discusses the challenges facing this field, aiming to provide a scientific basis for PA toxicity research and safety assessment.

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Section: Status Of Pa Levels In Foodsmentioning

confidence: 99%

Levels, Toxic Effects, and Risk Assessment of Pyrrolizidine Alkaloids in Foods: A Review

Lu,

Qiu,

et al. 2024

Foods

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“…29 A strategy that has gained prominence recently is the use of calculations based on quantum mechanics to simulate 1 H and 13 C NMR spectra. 24,25,[30][31][32] This is also driven by the growing computational power and user-friendly graphical interface software, that does not require expertise in programming languages. 33,34 Distinctive approaches can be used to calculate shielding tensors.…”

Section: Introductionmentioning

confidence: 99%

“…From the perspective of structural elucidation, a significant challenge is the unambiguous assignment of the relative configuration of structurally flexible molecules having several stereogenic centers 29 . A strategy that has gained prominence recently is the use of calculations based on quantum mechanics to simulate 1 H and 13 C NMR spectra 24,25,30–32 . This is also driven by the growing computational power and user‐friendly graphical interface software, that does not require expertise in programming languages 33,34 …”

Section: Introductionmentioning

confidence: 99%

Deciphering molecular structures: NMR spectroscopy and quantum mechanical insights of halogenated 4H‐Chromenediones

Martins,

Souto,

Hoye

et al. 2024

Magnetic Reson in Chemistry

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Sesquiterpene lactones (SL) represent a class of secondary metabolites found in the Asteraceae family, notable for their unique structures. The SL α‐santonin (1) and its derivatives are worthy of mention due to their diverse biological properties. Additionally, 4H‐chromenes and 4H‐chromones are appealing frameworks holding the capability to be used as structural motifs for new drugs. Furthermore, unambiguous structural elucidation is crucial for developing novel compounds for diverse applications. In this context, it is common to find in the literature molecules erroneously assigned. Therefore, the use of quantum mechanical calculations to simulate NMR chemical shifts has emerged as a valuable strategy. In this work, we conceived the synthesis of two halogenated 4H‐chromenediones derived from photosantonic acid (2), a photoproduct arising from irradiation of α‐santonin (1) in the ultraviolet region. The structure of the chlorinated and brominated products was determined by NMR analysis, with the aid of quantum mechanical calculations at the B3LYP/6‐311 + G(2d,p)//M062x/6‐31 + G(d,p) level of theory. All analyses were in agreement and led to the assignment of the brominated 4H‐chromene‐2,7‐dione as (3S,3aS,5aR,9bS)‐5a‐(2‐bromopropan‐2‐yl)‐3‐methyl‐3,3a,5,5a,8,9b‐hexahydro‐4H‐furo[2,3‐f]chromene‐2,7‐dione (11b) and of the chlorinated 4H‐chromene‐2,7‐dione as (3S,3aS,5aR,9bS)‐5a‐(2‐chloropropan‐2‐yl)‐3‐methyl‐3,3a,5,5a,8,9b‐hexahydro‐4H‐furo[2,3‐f]chromene‐2,7‐dione (12b). The diastereoselectivities of the reactions were explained based on products and intermediates formation energy calculated using B3LYP/6‐31 + G(d,p) as the level of theory. Structures 11b and 12b were identified as the thermodynamic and kinetic products of the reaction among all candidates. Consequently, the strategy utilized in this study is robust and successfully illustrates the use of quantum mechanical calculations in the structural elucidation of new compounds with potential applications as novel drugs or products.

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“…Contém em sua estrutura átomos de nitrogênio situados em anéis (cíclicos), responsáveis pelo caráter alcalino desses compostos(PINTO et al, 2022a). São produzidos através do metabolismo de plantas e microrganismos, desempenhando importante papel na defesa desses seres vivos.…”

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“…cos, como o Ultravioleta-Visível (UV), Infravermelho (IV), Raman e Ressonância Magnética Nuclear (RMN). A RMN é uma das ferramentas mais poderosas para a determinação estrutural de compostos orgânicos (TEIXEIRA; ALVARENGA, 2016), porém muitas estruturas orgânicas de produtos naturais são complexas e de difícil interpretação, necessitando de ferramentas complementares que auxiliem na proposição de estruturas corretas a partir das técnicas espectroscópicas(PINTO et al, 2022a). Essas ferramentas envolvem o uso de programas computacionais e cálculos teóricos baseados em mecânica quântica(ALVARENGA et al, 2019a).Cálculos teóricos de deslocamento de RMN têm sido utilizados para determinar e/ou confirmar a estereoquímica de estruturas de produtos naturais, muitas vezes assinaladas erroneamente na literatura (TEIXEIRA; ALVARENGA, 2016).…”

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Cálculos teóricos como ferramenta complementar para a elucidação estrutural do novo alcaloide pirrolizidínico isolado de crotalaria paulina

Baia

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A área de produtos naturais tem sido alvo de muitas pesquisas envolvendo isolamento, caracterização e quantificação de substâncias bioativas, com potenciais aplicações na indústria farmacêutica e agroquímica. Um dos desafios encontrados nos estudos de produtos naturais é a identificação estrutural dos compostos orgânicos constituintes, muitas vezes de difícil interpretação pelos métodos espectroscópicos tradicionais. Por isso, existem relatos de estruturas assinaladas erroneamente na literatura e que necessitam de revisão. Embora a ressonância magnética nuclear (RMN) seja uma das ferramentas mais poderosas utilizadas para a elucidação estrutural, ainda existem limitações associadas à purificação da amostra, erros sistemáticos e moléculas complexas que demandam o auxílio de protocolos complementares para a correta identificação. Neste sentido, a química computacional se apresenta como uma ferramenta útil para os químicos orgânicos, permitindo o estudo de parâmetros de RMN através de cálculos teóricos, com obtenção de dados calculados que podem ser comparados com os dados experimentais da molécula estudada. Vários métodos estatísticos são encontrados na literatura para avaliar a qualidade do ajuste dos dados, como o CP3, DP4 e DP4+. Enquanto o método CP3 analisa dois conjuntos de dados experimentais com duas estruturas candidatas, os métodos DP4 e DP4+ analisam um conjunto disponível de dados experimentais com duas ou mais estruturas candidatas, indicando aquela que mais se aproxima dos dados experimentais. Esse trabalho descreve detalhadamente a elucidação estrutural de um novo alcaloide pirrolizidínico (AP) isolado da planta Crotalaria paulina, com o auxílio de experimentos de RMN e cálculos teóricos, envolvendo a Teoria do Funcional da Densidade (DFT) e o método estatístico DP4+. Oito possíveis estereoisômeros para o AP foram avaliados por meio dessas ferramentas, indicando que a etilmetilcrotalina (estrutura candidata 3) é a estrutura correta para esse produto natural. Palavras-chave: Elucidação estrutural. Produtos naturais. Química computacional. Cálculos teóricos. Crotalaria paulina.

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Structural elucidation of a novel pyrrolizidine alkaloid isolated from Crotalaria retusa L.

Cited by 5 publications

References 32 publications

Levels, Toxic Effects, and Risk Assessment of Pyrrolizidine Alkaloids in Foods: A Review

Levels, Toxic Effects, and Risk Assessment of Pyrrolizidine Alkaloids in Foods: A Review

Deciphering molecular structures: NMR spectroscopy and quantum mechanical insights of halogenated 4H‐Chromenediones

Cálculos teóricos como ferramenta complementar para a elucidação estrutural do novo alcaloide pirrolizidínico isolado de crotalaria paulina

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