Supplementary Materialsmolecules-25-00240-s001. molecular information about commercially available medicines [8], 87% of medicines contain nitrogen and 37% contain sulfur. Thus, both nitrogen and sulfur are important constituents of most medicines. The identification of natural products containing nitrogen is relatively simple, and we have utilized several developed methods that can be used to discover nitrogen compounds in microbial cultures. For example, staurosporine, neoxaline, CP-724714 tyrosianse inhibitor and pyrindicin were discovered using Dragendorffs reagent, which can be used to detect tertiary or quaternary amines [1,2,3,4,5,9,10]. Trichothioneic acid, which contains an ergothioneine moiety, was HDAC7 discovered by nitrogen rule screening [11]. By contrast, with the exception of ultrahigh resolution CP-724714 tyrosianse inhibitor mass spectrometry [12,13], screening methods for sulfur compounds have not been reported. This report aims to help establish a simple means of screening for sulfur compounds. Molybdenum (Mo)-catalyzed oxidation with hydrogen peroxide (H2O2) was first reported in 1984 by Trost et al. [14]. Under basic conditions, this reaction preferentially oxygenates secondary alcohols followed by olefin epoxidation and primary alcohol oxidation. In a subsequent report, Trost et al. [15] described the Mo-catalyzed oxidation of sulfides. During the synthesis of the 20-member macrolide CP-724714 tyrosianse inhibitor laulimalide, sulfide is oxygenated to sulfone by Mo-catalyzed oxidation under neutral conditions in ethanol. This oxidation proceeds more readily than olefin epoxidation and primary or secondary alcohol oxidation [16]. Therefore, Mo-catalyzed oxidation may allow the identification of sulfur compounds from microbial cultures when combined with liquid chromatography-mass spectrometry (LC/MS). In this study, we report the establishment of a screening method for sulfur compounds based on Mo-catalyzed oxidation (MoS-screening) and LC/MS. 2. Dialogue and LEADS TO determine the suitability of Mo-catalyzed oxidation for the recognition of sulfur substances, methanol solutions of many known microbial substances including sulfur, such as for example outovirin A [17], nanaomycin K [18], and lactacystin [19,20] (Shape S1), had been oxygenated with (NH4)6Mo7O244H2O and 30% H2O2. After 6 h of shaking at space temperatures, both non-oxidized and oxidation examples were examined by LC/MS. The LC/MS circumstances are demonstrated in Desk S1. For outovirin A, which consists of a diketopiperazine bridged with a sulfur atom, an oxidative item was recognized at a retention period of 12.55 min (= 497 [M + H]+), indicating an increased polarity compared to the original compound (retention time 13.44 min, = 481 [M + H]+) (Shape S2A). This total result shows that the Mo-catalyzed oxidation of outovirin A leads to sulfinyl outovirin A. Likewise, Mo-catalyzed oxidation of nanaomycin K, which consists of an ergothioneine moiety, yielded a sulfonyl item (12.08 min, = 580 [M + H]+) at a lesser retention time than that of nanaomycin K (13.38 min, = 548 [M + H]+) (Shape S2B). Shape S2A(ii) and B(iv) show that Mo-catalyzed oxidation of outovirin A or nanaomycin K results in the complete replacement of the LC peaks corresponding to the original compounds with those corresponding to the oxidized products. By contrast, no peaks were detected after the oxidation of lactacystin, which contains an [M + H]+) are shown in Table 1. Each peak in the non-oxidized chromatogram (Figure 1A, peaks 1C6) was identified by its UV absorption spectrum (Figure S3) and mass-to-charge ratio as a corresponding compound in Table 1. In the chromatogram of the oxidized sample (Figure 1B), peaks 1 (11.56 min), 2 (11.16 min), and 4 (7.10 min) were identified as tanzawaic acid B, beauvericin, and acremolin B, respectively, by their UV absorption spectra (data not shown), mass-to-charge ratios, and retention times. Peaks 5 (6.52 min) and 6 (6.45 min) were not detected after oxidation, while peaks 5a, 6a, and 6b appeared only after oxidation (Figure 1B). Peaks 6a (5.62 min) and 6b (6.21 min) yielded pseudomolecular ion peaks at = 564 and 580 [M + H]+, respectively, and the same absorption spectrum as that of peak 6 (nanaomycin K). Peak 5a (5.72 min) gave a pseudomolecular ion peak at = 497 [M + H]+ and exhibited the same UV absorption spectrum CP-724714 tyrosianse inhibitor as peak 5 (outovirin A). Thus, peaks 5a,.