ched at C-3 on the skeleton of 4,2 ,four -trihydroxychalcone. Therefore, compound 17 was characterized as four,2 ,four -trihydroxy-3 -(3-hydroxy-3-methylbutyl)chalcone. Compound 19 was obtained as a pale yellow amorphous powder. Its molecular formula was established as C20 H24 O5 by its HRESIMS information ([M + Na]+ , calcd for C20 H24 O5 Na, 367.1521). Comparison with the 1 H- and 13 C-NMR information of 19 and ten revealed that the resonance signals for the methyl group at C-1 of ten have been absent in 19, suggesting the isoprene unit at C-3 of 19 was a 3-hydroxy-3-methylbutyl moiety (Tables 2 and 3). The connectivity of 3-hydroxy-3-methylbutyl moiety at C-3 was further secured by the HMBC correlations from H-1 (H 2.54) and H-2 (H 1.47) to C-3 (C 115.6). Compound 19 was as a result identified as four,two ,4 -trihydroxy-3 -(3-hydroxy-3-methylbutyl)dihyrochalcone. Structures of three other recognized compounds have been identified as brosimacutin M (18) [25], brosimacutin H (20) [26], and bavachromanol (21) [27,28] by comparing their spectral information with those reported within the literatures (Figures S74 76). However, absolute configuration of their hydroxyl groups remained undetermined due to the restricted quantities with the isolates. Further study may be essential to identify the absolute configuration in compounds 18, 20, and 21.Int. J. Mol. Sci. 2021, 22, x FOR PEER REVIEW8 ofInt. J. Mol. Sci. 2021, 22,information with those reported inside the literatures (Figures S74 76). Even so, absolute configuof ration of their hydroxyl groups remained undetermined resulting from the limited quantities8of 16 the isolates. Additional study may IL-2 Modulator custom synthesis possibly be essential to identify the absolute configuration in compounds 18, 20, and 21.2.three. Proposed Metabolic CYP1 Activator Biological Activity Pathways of Isobavachalcone (4) Catalyzed by A. niger KCCM 60332 two.3. Proposed Metabolic Pathways of Isobavachalcone (4) Catalyzed by A. niger KCCM 60332 Biotransformation of isobavachalcone (4) by the chosen fungal strain A. niger proBiotransformation of isobavachalcone (4) by the selected fungal strain A. niger developed metabolites 101 through hydrogenation, epoxidation, hydrolysis, reduction, cyduced metabolites 101 via hydrogenation, epoxidation, hydrolysis, reduction, cyclization, and alkylation (Figure 4). The prenyl substituent and ,-double bond were the clization, and alkylation (Figure four). The prenyl substituent and ,-double bond had been the major web sites for biotransformation by A. niger. big sites for biotransformation by A. niger.Figure four. Proposed metabolic pathways of four catalyzed by A. niger. Pathways a and b, represented by the arrows in red and Figure four. Proposed metabolic pathways of four catalyzed by A. niger. Pathways a and b, represented by the arrows in red and blue respectively, are proposed as two two routes to form aring in compound 19. Compound 22 is proposed as an blue respectively, are proposed as the the routes to form a brand new new ring in compound 19. Compound 22 is proposed as intermediate which could not be unambiguously identified in this study. study. an intermediate which couldn’t be unambiguously identified in thisRegarding the metabolic relationships these metabolites, 22 was was proposed as Regarding the metabolic relationships of of those metabolites, 22 proposed as a po- a tential intermediate which couldn’t be unambiguously identified in thisin this study. The possible intermediate which couldn’t be unambiguously identified study. The proposed intermediate 22 22 may very well be rationalized by initial epoxidation of the prenyl group proposed interm
