Binding of Clitoria ternatea L. flower extract with α-amylase simultaneously monitored at two wavelengths using a photon streaming time-resolved fluorescence approach

The binding of an extract from the flowers of Clitoria ternatea L. to the digestive enzyme α-amylase was investigated. This extract is a mixture of flavonoids, including anthocyanins, and has been previously shown to inhibit the activity this enzyme. This has implications for modulating starch digestion. Since the extract contains a mixture of flavonoids, including anthocyanins, in order to investigate the kinetics, we made use of time-resolved fluorescence to simultaneously monitor two different emission bands emanating from the extract. This measurement was enabled by the use of a “photon streaming” approach and changes in fluorescence lifetime and intensity were used to follow the interaction. A longer wavelength band (655nm) was ascribed to anthocyanins in the mixture and these were observed to bind at a rate an order of magnitude slower than other flavonoids present in the extract, monitored at a shorter wavelength (485 nm). Changes in the fluorescence emission of the extract upon binding were further assessed by the use of decay associated spectra.