1H NMR spectra of trypsin inhibitors from seeds of Cucurbitaceae plants. Resonance signals of methyl groups.

1H NMR spectra (250 MHz) of four trypsin inhibitors isolated from seeds of Cucurbitaceae plants were studied. It was found that structural differences between the inhibitors from the genus Cucurbita and from the genus Cucumis consist, among others, in the presence in the former group of a valine residue strongly shielded from the solvent.