Curcumin reactions

The effect of those ions most frequently present in soils on the boron determinations is shown in Table 12.1. The interference of iron at concentrations higher than 7xlO 5M can be eliminated as the chloro complex by extraction with methyl isobutyl ketone. The total elimination of iron III was not necessary as the phosphoric acid masked the residual iron III in the boric acid-curcumin reaction. 

Two colorimetric methods are recommended for boron analysis. One is the curcumin method, where the sample is acidified and evaporated after addition of curcumin reagent. A red product called rosocyanine remains it is dissolved in 95 wt % ethanol and measured photometrically. Nitrate concentrations >20 mg/L interfere with this method. Another colorimetric method is based upon the reaction between boron and carminic acid in concentrated sulfuric acid to form a bluish-red or blue product. Boron concentrations can also be deterrnined by atomic absorption spectroscopy with a nitrous oxide—acetjiene flame or graphite furnace. Atomic emission with an argon plasma source can also be used for boron measurement. 

Antioxidant capacities of common individual curcuminoids were determined in vitro by phosphomolybdenum and linoleic acid peroxidation methods. Antioxidant capacities expressed as ascorbic acid equivalents (pmol/g) were 3099 for curcumin, 2833 for demethoxycurcumin, and 2677 for bisdemethoxycurcumin at concentrations of 50 ppm. The same order of antioxidant activity (curcumin > demethoxycurcumin > bisdemethoxycurcumin) was observed when compared with BHT (buty-lated hydroxyl toluene) in linoleic peroxidation tests. The antioxidant activity of curcumin in the presence of ethyl linoleate was demonstrated and six reaction products were identified and structurally characterized. The mechanism proposed for this activity consisted of an oxidative coupling reaction at the 3 position of the curcumin with the lipid and a subsequent intramolecular Diels-Alder reaction. ... 

Also, boron can be analyzed by colorimetry techniques (APHA, AWWA, and WEF. 1999. Standard Methods for the Examination of Water and Wastewater, 20th ed. Washington DC American Public Health Association). Boron in acidified aqueous phase reacts with curcumin to form a red-colored product, roso-cyanine. Presence of calcium and magnesium at high concentrations can interfere in the test. Another colorimetric measurement involves the reaction of boron with carmine or carminic acid in concentrated sulfuric acid. The color of the solution changes from bright red to bluish red or blue, depending on boron concentration. 

Several clinical trails are reported with curcumin in cancer patients around the world. Some of our recent review [Anand et al., 2008 Goel et al., 2007 Kunnumakkara et al., 2008] gives a detailed description of the clinical trials with curcumin, which are summarized in Table 16.2. An early clinical trial evaluated the effectiveness of topical application of a curcumin ointment in patients with external cancerous lesions. Patients with cancers of oral cavity (37 patients), breast (7 patients), vulva (4 patients), skin (3 patients), and miscellaneous unspecified sites (11 patients) were enrolled in this study. Remarkable symptomatic relief was observed in this study with the reduction in smell in 90% of the cases, reduction in itching in almost all cases, and reduction in exudates in 70% of cases. Reduction in lesion size and pain was observed in about 10% of the cases and only one melanoma (scalp) patient showed an adverse effect of local itching, which may be due to the allergic reaction to curcumin. 

Barik A, Mishra B, Shen L, Mohan H, Kadam RM, Dutta S, Zhang HY, Priyadarsini KI. 2005. Evaluation of a new copper(II)-curcumin complex as superoxide dismutase mimic and its free radical reactions. Free Radio Biol Med 39 811-822. 

Priyadarsini KI, Maity DK, Naik GH, Kumar MS, Unnikrishnan MK, Satav JG, Mohan H. 2003. Role of phenolic O-H and methylene hydrogen on the free radical reactions and antioxidant activity of curcumin. Free Radio Biol Med 35 475-484. 

Priyadarsini Kl. (1999) Free radical reactions of curcumin in model membranes. 

The /3-diketone moiety in conjugation with the phenolic groups contributes greatly to the anti-inflammatory and anti-tumor activity of curcumin/ The rate constants for the reactions of several oxidizing free radicals with quercetin and curcumin are given in Table 2. 

Mishra B, Priyadarsini KI, Bhide MK, Kadam RM, Mohan H. (2004) Reactions of superoxide radicals with curcumin Probable mechanisms by optical spectroscopy and EPR. Free Radio Re 38 355-362. 

Could a truly imstable product be labeled stable as a result of testing using an inappropriate source In theory this is possible, especially with Option 2, if the compound or degradation products that sensitize the reaction absorb mainly in the "gap" (380-420 nm), e.g., curcumin or bilirubin. As mentioned above, it is important to combine the results with knowledge already obtained from other tests before labeling and packaging decisions are made. 

Pavolini (118) who prepared curcumin by condensation of acetylacetone with vanilline. He observed that Knoevenagel condensation, one of the main side reactions, could be suppressed by adding boric oxide. This method was further developed by Pabon (119) who first prepared a complex from acetylacetone and boric anhydride and reacted the product with vanilline in the presence of triisopropyl borate and butylamine. Yields calculated on vanilline were thus improved from 10% to 80%. Besides several other indutrial applications (120-123) the method was also used for the synthesis of dihydroyashabushiketol (6) (11) and the tetramethylether of oregonin (11) (14). By selective alkylation of acetylacetone at C-3 Pedersen and associates exploited the above method for the preparation of a series of non-natural diaiylheptanoids substituted at C-4 (124). 

The sensitivity of the method and the reproducibility of the results obtained depend on the quality of the curcumin reagent, and on rigorous observance of the reaction conditions (temperature, time, reagent quantities) [23-25]. Commercial curcumin samples differ considerably in quality. Under the most favourable conditions, the molar absorptivity of rosocyanin is 1.8-10 at A,max = 550 nm (a = 16.6). 

Curcumin has both antioxidant and pro-oxidant effects in oxygen radical reactions, acting as a scavenger of hydroxy radicals or a catalyst in the formation of hydroxy radicals, depending on the experimental conditions [18-20]. The antioxidant effect of curcumin presumably arises from scavenging of biological free radicals. 

Figure 2. Reaction Meebanisin for Curcumin Acting as a Free Radical Scavenger...

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