Chlorophyll degradation in aqueous mediums induced by light and UV-B irradiation: An UHPLC-ESI-MS study

•UV radiation/illumination of chlorophyll leads to its irreversible degradation.•Photodegradation is governed by photon energy input.•Chlorophyll aggregation plays a protective role against UV radiation/illumination.•Chlorophyll photodegradation is accompanied by products formation.•Main chlorophyll products are pheophytin and hydroxy-pheophytin in early stages.

Irreversible chlorophyll degradation induced by continuous white light illumination and UV-B irradiation in the aqueous mediums (with 10%, 30% and 50% of methanol) was investigated using the ultrahigh liquid chromatography coupled with diode array and electrospray ionization mass spectrometry detectors (UHPLC-DAD-ESIMS). The degradation was governed by energy input of photons: higher energy of UV-B irradiation induced faster chlorophyll degradation and accordingly faster products formation in comparison to the white light treatment. Main light- or/and UV-B-induced products of chlorophyll in the aqueous mediums were hydroxy-pheophytin a, pheophytin a and hydroxy-lactone-pheophytin a, accompanied with the corresponding epimers. Chlorophylls aggregation dominant in the aqueous medium with the highest methanol content (50%) play a protective role against the UV-B radiation and white light illumination.