Water mediated TBAB catalyzed synthesis of spiro-indoline-pyrano[3,2-c]quinolines as α-amylase inhibitor and in silico studies

•TBAB catalysed green synthesis of spiro-indoline-pyrano[3,2-c]quinolines derivatives 4(a-ab).•Compounds 4g (IC50 = 73.82 ± 0.08 µg/ml) and 4h (IC50 = 76.65± 0.45 µg/ml) show significant α-amylase inhibition.•Single crystal structure evaluation of 4b shows a triclinic system with P1 space group.•Molecular docking studies of 4g and 4h reveals good H-bonding interaction with GLN63, HIS101 and ASP300 respectively.•In silico ADMET prediction of compounds 4g and 4h show the most promising drug-likeness properties.