Studies on curcumin and curcuminoids. XXXIX. Photophysical properties of bisdemethoxycurcumin.
Bottom Line: The steady-state absorption and fluorescence, as well as the time-resolved fluorescence properties of bisdemethoxycurcumin dissolved in several solvents differing in polarity and H-bonding capability were measured.The bisdemethoxycurcumin decay mechanisms from the S(1) state were discussed and compared with those of curcumin.The differences in S(1) dynamics observed between bisdemethoxy-curcumin and curcumin could be ascribed to a difference in H-bond acceptor/donor properties of the phenolic OH and a difference in strength of the intramolecular H-bond in the keto-enol moiety within the two molecules.
Affiliation: Department of Physics and Mathematics, University of Insubria and C.N.I.S.M.-C.N.R., Via Valleggio, 11- 22100 Como, Italy. email@example.comShow MeSH
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Mentions: The yellow orange pigment derived from the rhizome of the plant Curcuma longa L., (turmeric) consists of three diarylheptanoids: curcumin (CURC), demethoxy-curcumin (DMC), and bisdemethoxy-curcumin (bisDMC) (Fig. 1). The demethoxy- and bidemethoxy compounds can amount to nearly 40% of what is known as commercially available curcumin . In some turmeric extracts bisdemethoxycurcumin is even shown to be the major constituent . Curcumin is by far the most investigated curcuminoid, although some comparative studies on the naturally occurring curcuminoids have been performed. A constantly increasing number of publications have shown that curcumin displays notable effects not only as an anti-inflammatory compound [3–5] and a potent antioxidant [4, 5], but also as a chemopreventive [6, 7] and chemotherapeutic [8, 9] agent. Moreover, it seems to have a potential in the treatment of Alzheimer disease  and cystic fibrosis , as well as being considered a model substance for the treatment of HIV-infections [12–14] and as an immune-stimulating agent . CURC was shown to be significantly more effective than DMC [15, 16], which in turn is more effective than bisDMC, as an antioxidant. The molecular mechanisms underlying the antioxidant effects are still not fully understood, but it is apparent that, even if the major antioxidant activity has been associated to electron withdrawal from the keto-enol group to the phenolic hydroxyl moieties, the phenolic methoxy substituents also play a significant role [15–18]. Moreover, CURC is both a powerful metal chelating agent and an efficient radical scavenger. Metal chelation occurs at the central keto-enol group, and is strongly affected by the enol proton mobility and acidity . Scavenging effects are connected with the formation of phenoxyl radicals  that are formed by deprotonation of the phenolic hydroxyl groups . In spite of the fact that the methoxy phenolic substituents are not directly involved in either metal chelation or radical scavenging, DMC has been proven to be less effective than CURC, and bisDMC to be almost inactive, with respect to both of these biologically relevant activities . Finally, the three compounds vary dramatically in their ability to suppress the nuclear cell factor κB activation in vitro : CURC is by far the most efficient suppressor while bisDMC is almost inert. This is relevant with respect to their chemopreventive and chemotherapeutic potentials.Fig. 1
Affiliation: Department of Physics and Mathematics, University of Insubria and C.N.I.S.M.-C.N.R., Via Valleggio, 11- 22100 Como, Italy. firstname.lastname@example.org