Curcumin is also sensitive to light and is rapidly decolorized upon exposure to UV light [76, 77]. According to
Auslander et al., complete color loss of curcuminoid pigments in turmeric occured within three days of exposure to 900 footcandle of visible light [78]. Khurana and Ho reported that the dried powder form of curcumin was more stable to photooxidation as compared to the alcoholic extract [77]. In addition to that, the rate of curcumin photodegradation was influenced to a large extent by the nature of solvents used [77]. Tønnesen and Karlsen showed that stability of curcumin (as measured by halflife in various solvents) followed the decreasing trend: methanol (92.7 h) > ethyl acetate (15.1 h) > acetonitrile (6.3 h) > chloroform (2.7 h) [71]. It was probable that the significant protective or destabilizing effect of different solvents could be ascribed to the formation of inter and intramolecular bondings, which were solvent dependent [71]. Souza et al. found that the combination effect of air and light was more detrimental than light alone while the absorption of curcumin in water had no apparent effect on curcumin photostability [79]. In another study, the order of photochemical stability of different curcuminoid complexes in airsparged conditions in methanol was curcumin > demethoxycurcumin > bis demethoxycurcumin