Design, synthesis and structure-activity studies of amino acids conjugated quinazolinone-Schiff's bases as potential antioxidant and anti-inflammatory agents

A novel series of amino acids conjugated quinazolinone-Schiff's bases were synthesized and characterized by analytical and spectroscopic methods. All the synthesized analogues (8–43) and the intermediates (1–7) were screened for their in vitro antioxidant and anti-inflammatory activities. Antioxidant activities were determined by three different in vitro assays such as DPPH, ABTS and DMPD cation radical activity methods. Compounds 15, 16, 23–25, 30–34 and 39–43 shows potent antioxidants compared to standards gallic acid and ascorbic acid in all the three antioxidants methods. Compounds 9–11, 18–20, 27–29 and 36–38 showed potent anti-inflammatory activity compared to standards indomethacin and ibuprofen. Preliminary structure-activity relationship revealed that the tryptophan and phenylalanine derived compounds with electron donating groups (OH and OCH₃) were found to be excellent antioxidant activity compared to glycine and alanine derivatives. Tryptophan and phenylalanine containing compounds with electron withdrawing groups (Cl, NO₂ and F) were found to be excellent anti-inflammatory agents.