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Revisiting the absolute chirality and polymorphism of (-)-Istanbulin A
Luz Arancibia1, Mariana Naspi1, Graciela Pucci2
1Departamento de Química, Química Orgánica, Universidad Nacional de la Patagonia San Juan Bosco, km 4, s/n°, Comodoro Rivadavia, Chubut 9000, Argentina.
Acta Crystallographica. Section C, Structural Chemistry
|September 5, 2020
Summary
The natural product (-)-Istanbulin A, a sesquiterpene lactone from Senecio filaginoides, was structurally characterized as a new polymorph (form II). Its antimicrobial and antifungal activities were evaluated for future applications.
Area of Science:
- Natural Product Chemistry
- Organic Chemistry
- Crystallography
Background:
- Senecio filaginoides DC, an Argentinian plant species, is a source of natural products.
- Terpenoids, specifically sesquiterpene lactones, are a diverse class of natural compounds with potential bioactivity.
Purpose of the Study:
- To isolate, characterize, and determine the absolute configuration of (-)-Istanbulin A from Senecio filaginoides.
- To identify (-)-Istanbulin A as a new polymorph (form II) and compare it to the known form I.
- To evaluate the antimicrobial and antifungal activities of (-)-Istanbulin A, form II.
Main Methods:
- Isolation of (-)-Istanbulin A from plant material.
- Single-crystal X-ray diffraction for structural and absolute configuration determination.
- 1D and 2D Nuclear Magnetic Resonance (NMR) spectroscopy.
- High-Resolution Electrospray Ionization Mass Spectrometry (HR-ESI-MS).
- Antimicrobial and antifungal activity assays.
Main Results:
- (-)-Istanbulin A was isolated and its structure confirmed as a sesquiterpene lactone with an eremophilanolide skeleton and 4S,5R,8R,10S chirality.
- The compound was identified as a new polymorph, designated form II, distinct from the previously reported form I.
- Spectroscopic data (NMR, HR-ESI-MS) corroborated the structural findings.
- The chirality of Istanbulin A was revisited based on structural data and literature review.
- Preliminary antimicrobial and antifungal activities of form II were established.
Conclusions:
- The detailed structural elucidation of (-)-Istanbulin A, form II, provides a foundation for understanding its chemical properties.
- Identification of a new polymorph highlights the importance of crystal form in natural product characterization.
- The evaluated bioactivities establish a reference point for future research and potential applications of specific Istanbulin A polymorphs.
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