These protonated carbons and their bonded protons, which were determined unambiguously by the HMQC experiment, showed the presence of 20 carbons of a curcuminoid skeleton (Li et al., 2009). In addition, the deshielding of both the two olefinic carbons at δC 146.7 (C-2) and 176.1 (C-5) indicated their linkage to an oxygen atom. These observations with the presence of characteristic absorption bands in the IR (1665, 1598 cm−1) and UV (398, 295 nm) spectra, suggested the existence of a 3(2H)-furanone moiety instead of a linkage fragment (CCHCOCHC(OH)CHCH) like in curcuminoid derivatives ( Comte et al., 1996 and Gershenzon and Mabry, 1984)
These protonated carbons and their bonded protons, which were determined unambiguously by the HMQC experiment, showed the presence of 20 carbons of a curcuminoid skeleton (Li et al., 2009). In addition, the deshielding of both the two olefinic carbons at δC 146.7 (C-2) and 176.1 (C-5) indicated their linkage to an oxygen atom. These observations with the presence of characteristic absorption bands in the IR (1665, 1598 cm−1) and UV (398, 295 nm) spectra, suggested the existence of a 3(2H)-furanone moiety instead of a linkage fragment (CCHCOCHC(OH)CHCH) like in curcuminoid derivatives ( Comte et al., 1996 and Gershenzon and Mabry, 1984)
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