Synthesis, Crystal Structure, Antioxidant, and α-Glucosidase Inhibitory Activities of Methoxy-substituted Benzohydrazide Derivatives

Abstract

Eight methoxy substituted at the benzylidene moiety benzohydrazide derivatives [R = 2-OCH₃ (1), 3-OCH₃ (2), 4-OCH₃ (3), 2,3-(OCH₃)₂ (4), 3,4-(OCH₃)₂ (5), 2,4,5-(OCH₃)₃ (6), 2,4,6-(OCH₃)₃ (7), and 3,4,5-(OCH₃)₃ (8)] were synthesized and characterized by ¹H NMR, FT-IR and UV-Vis spectroscopy. The crystal structure of 4 was determined by single crystal X-ray diffraction (sp. gr. Pbca, Z = 8). The molecule is slightly twisted with the dihedral angle between the two phenyl rings being 9.33(14)°. The methoxy group at the ortho position is twisted [C–O–C–C angle is–109.2(3)°] whereas the other at meta position is co-planar with the attached benzene ring. In the crystal packing, the molecules are linked into two-dimensional network parallel to the (001) plane by O–H···O, O–H···N, and N–H···O hydrogen bonds. Compounds 1–8 were evaluated for an antioxidant and α-glucosidase inhibitory activities and the results suggested that the −OCH₃ substituent was ineffective for bioactivity enhancement.