The aim of this work is to evaluate the vibrational and structural properties of N-acetyl-l-cysteine (NAC), and its molecular structure and electronic properties in relation to the action of thiol and amine groups at different pH.
Two new metabolites containing a 1-oxa-7-azaspiro[4.4]non-2-ene-4,6-dione core, pseurotin A1 (1) and A2 (2), as well as pseurotin A (3), were isolated from the holothurian-derived fungus Aspergillus fumigatus WFZ-25. These compounds were determined using extensive analysis of their spectroscopic data, including 1D and 2D NMR, HR-ESI-MS, and circular dichroism (CD) experiments.
Two new sesquiterpenes, named aristoyunnolin I (1) and J (2), together with eight known compounds (3 - 10) were isolated from the roots of Aristolochia yunnanensis. Compounds 1 and 2 feature a rare hydroazulene-type sesquiterpene skeleton and represent the third and fourth examples of this kind found in nature. The structures were determined from spectroscopic data, and the absolute configurations of 1 - 3 were assigned by comparing experimental with simulated electronic circular dichroism (ECD) spectra. Compounds 1, 2, 6 - 10 were isolated from this plant for the first time. The cytotoxic activities of 1 - 10 were evaluated against P-388 and A-549 cell lines. Only compounds 4 and 5 showed moderate activity with IC50 values ranging from 12.0 to 18.2 μM.
A Raman, SERS and UV-circular dichroism spectroscopic study of N-acetyl-l-cysteine in aqueous solutions