Combined approach including affinity crystallography revealed dihydrowogonin bound to GSTO3S hydrophobic site. (A) Normalized inhibition of esterase activity with substrates CMFDA and MUA is shown. Fractions 46–47 min that inhibited both activities were selected for further analysis. (B) MS analysis in positive (bottom panel) and negative (top panel) modes revealed two major compounds. (C) 1H-NMR spectrum showed the structural features of flavanones. Affinity crystallography allowed the elucidation of the flavanone dihydrowogonin. Its 1H-NMR data37 are indeed found on the spectrum of the mixture: numbers in parenthesis are the typical chemical shifts for dihydrowogonin and numbers in blue correspond to the values obtained in the present study. Integration values of 2 methoxy groups allowed to evaluate maximum abundance of dihydrowogonin in the fractions (numbers in red). (D) Electron density of dihydrowogonin in structure of GSTO3S crystallized in presence of 46-47 eluate. The map shown is a 2mFo-DFc composite omit map contoured at 1 σ. (E) Chemical structure of dihydrowogonin.