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Background: The fractionation of the n-hexane phase of the EtOH extract from the leaves of Duguetia lanceolata (Annonaceae) led to the identification of the sesquiterpene (–)-cyclocolorenone. Objective: Chemical characterization, including determination of the absolute stereochemistry, and in vitro evaluation of antileishmanial activity of the sesquiterpene (–)-cyclocolorenone, isolated from D. lanceolata, were carried out. Methods: (–)-Cyclocolorenone was isolated from D. lanceolata leaves using different chromato-graphic steps and its structure was defined by analysis of NMR and ESI-HRMS data. Additionally, the absolute configuration of (–)-cyclocolorenone was ambiguously assigned by means of vibra-tional circular dichroism (VCD). Antileishmanial activity of (–)-cyclocolorenone was evaluated on promastigote and amastigote forms of Leishmania (Leishmania) amazonensis. The integrity of the cell membrane of L. (L.) amazonensis was analyzed using the SYTOX green probe. Results: (–)-(1R,6S,7R,10R)-Cyclocolorenone displayed activity against promastigotes and amastigotes forms of L. (L.) amazonensis with IC50 of 4.54 and 28.44 , respectively. Further-more, this compound was non-toxic in J774 macrophage cells (CC50 > 458.71 ) with a selectivi-ty index > 100 (promastigotes) and > 32.2 (amastigotes). Additionally, (–)-cyclocolorenone was ob-served to target the parasite cell membrane. Conclusion: Obtained data suggested that (–)-cyclocolorenone, in which absolute configuration was determined, can be considered as a scaffold for the development of new drugs for the treatment of leishmaniasis.

Vibrational circular dichroism (VCD) is one of the most powerful techniques to assess stereochemistry of chiral molecules in solution state. The need for quantum chemical calculations to interpret experimental data, however, has precluded its widespread use by non-experts. Herein, we propose the search and validation of IR and VCD spectral markers to circumvent the requirement of DFT calculations allowing for absolute configuration assignments even in complex mixtures. To that end, a combination of visual inspection and machine learning based methods is used. Monoterpene mixtures are selected for this proof-of-concept study.

The fractionation of the n-hexane phase of the EtOH extract from the leaves of Duguetia lanceolata (Annonaceae) led to the identification of the sesquiterpene (-)-cyclocolorenone.Chemical characterization, including determination of the absolute stereochemistry, and in vitro evaluation of antileishmanial activity of the sesquiterpene (-)-cyclocolorenone, isolated from D. lanceolata, were carried out.(-)-Cyclocolorenone was isolated from D. lanceolata leaves using different chromatographic steps and its structure was defined by analysis of NMR and ESI-HRMS data. Additionally, the absolute configuration of (-)-cyclocolorenone was ambiguously assigned by means of vibrational circular dichroism (VCD). Antileishmanial activity of (-)-cyclocolorenone was evaluated on promastigote and amastigote forms of Leishmania (Leishmania) amazonensis. The integrity of the cell membrane of L. (L.) amazonensis was analyzed using the SYTOX green probe.(-)-(1R,6S,7R,10R)-Cyclocolorenone displayed activity against promastigotes and amastigotes forms of L. (L.) amazonensis with ICObtained data suggested that (-)-cyclocolorenone, in which absolute configuration was determined, can be considered as a scaffold for the development of new drugs for the treatment of leishmaniasis.

Microbial strains isolated from extreme and understudied environments, such as caves, are still poorly investigated for the production of bioactive secondary metabolites. Investigation of the ethyl acetate extract from the growth medium produced by the soil-derived fungus Aspergillus sp. SDC28, isolated from a Brazilian cave, yielded two anthraquinones: versicolorin C (1) and versiconol (2). The complete assignment of nuclear magnetic resonance and mass spectroscopic data of 1 and 2 was performed for the first time. Moreover, the yet unreported absolute configuration of both compounds was unambiguously established by analysis of experimental and theoretical electronic circular dichroism data. Vibrational circular dichroism was also applied to confirm the absolute stereochemistry of 2. Compounds 1 and 2 showed cytotoxic activity against human ovarian cancer cells (OVCAR3).