Hi friends,
I prepared a curcumin nanosuspension via 3.5mg of curcumin into 25 mg tween, 80, 700 mg ethanol, 750 mg aloevera and 1078 mg water via bath soniacation method. Then, it was centrifuged and its supernatant was evaluated for untrapped drug in nanosuspension. the size of particle was about 200 nm. The absorbance of untrapped curcumin was 3.80 while the absorbance of 3.5 mg/ml curcumin/ethanol was 3.18. It shows higher absorption than whole curcumin used. How it is possible? I used blank for both of them. How can I evaluate its entrapment efficacy?
Dear Shima,
It might be related to instability of curcumin. Please read the following:
Journal of Pharmaceutical and Biomedical Analysis
Volume 15, Issue 12, August 1997, Pages 1867–1876
Stability of curcumin in buffer solutions and characterization of its degradation products
Abstract
The degradation kinetics of curcumin under various pH conditions and the stability of curcumin in physiological matrices were investigated. When curcumin was incubated in 0.1 M phosphate buffer and serum-free medium, pH 7.2 at 37°C, about 90% decomposed within 30 min. A series of pH conditions ranging from 3 to 10 were tested and the result showed that decomposition was pH-dependent and occurred faster at neutral-basic conditions. It is more stable in cell culture medium containing 10% fetal calf serum and in human blood; less than 20% of curcumin decomposed within 1 h, and after incubation for 8 h, about 50% of curcumin is still remained. Trans-6-(4′-hydroxy-3′-methoxyphenyl)-2,4-dioxo-5-hexenal was predicted as major degradation product and vanillin, ferulic acid, feruloyl methane were identified as minor degradation products. The amount of vanillin increased with incubation time.
Hoping this will be helpful,
Rafik
Yes to the above. Also -- you may be observing diffraction (light scatter) from the nanoparticles; this would appear to add to the apparent absorbance! -- I hope you are not observing these absorbances in 1 cm pathlength cells; 3.8 absorbance is usually well into the spectrometer "noise" region .... If it's a (raw) 1.6 in 0.5 cm cells, you should still be OK on signal:noise (assuming your reference-cuvette buffer is low-absorbance!). If it's diffraction, you'll see a change especially in the low-nm end of the spectrum, on the absorbance-spectrum shape. Try overlaying your spectra, appropriately individually scaled so as to match the maxima, and examine critically.
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