Optimization of Supercritical CO_(2) Extraction of Curcumin by Response Surface Methodology and Its Antioxidant Activity

[Objectives]This study was conducted to establish a mathematical model for supercritical CO_(2) extraction of curcumin.[Methods]With ginger as the experimental raw material,a quadratic polynomial mathematical model of the yield of curcumin extracted by supercritical CO_(2) was established by response surface methodology(RSM).The validity of the mathematical model was verified,and the effects of extraction temperature(60-70℃),pressure(30-50 MPa)and time(70-90 min)on curcumin yield were analyzed.[Results]According to the model,the process parameters were optimized.Taking curcumin yield as the index,the optimal process conditions for supercritical CO_(2) extraction obtained were:temperature 62.6℃,pressure 37.7 MPa,time 82.9 min,under which the yield of curcumin was as high as 7.34%.Under the optimal extraction conditions,curcumin had a certain reducing capacity,and showed strong scavenging capacities to·OH,O_(2)^(-)·and DPPH,and its IC_(50) values were 9.40,9.03 and 8.04 mg/ml,respectively.Therefore,it is feasible to extract curcumin from ginger using supercritical CO_(2).[Conclusions]This study provides a theoretical basis for the development and utilization of curcumin.

Rare-Earth Doping Graphitic Carbon Nitride Endows Distinctive Multiple Emissions with Large Stokes Shifts

Two-dimensional(2D)graphitic carbon nitride(g-C_(3)N_(4))possesses a unique geometric configuration featuring a superimposed heterocyclic sp2 carbon and nitrogen framework.Its fluorescence may be attributed to π-π^(*),lone pair(LP)-π^(*),or LP-δ^(*)transitions.So far,the manipulation of its fluorescence emissions is largely unexploited and remains challenging.Herein,for the first time,rare-earth doping into the backbone structure of a g-C_(3)N_(4) framework under microwave agitation endows unprecedented fluorescence nature,with the emergence of two exceptional new fluorescence emissions in the 450-700 nm range.With terbium-doped g-C_(3)N_(4):Tb as a representative,these emissions exhibit distinctive features,that is,very sharp fluorescence peaks with narrow full width at half maximum(FWHM)(peak width at half-height)of<12 nm,quantumyields of 2.3±0.0% and 7.6±0.1% for the new emissions at λ_(ex)/λ_(em)=290/490 nm,and 290/545 nm,respectively;and a large Stokes shift of>200 nm.These features of g-C_(3)N_(4):Tb are most advantageous for applications in various fields,as demonstrated by(1)tracking biodistribution of g-C_(3)N_(4) in vivo with mass spectrometric imaging where the doped terbium serves as a tag,(2)a biometrics study facilitating the identification of an individual through fingerprint,and(3)anti-counterfeiting with g-C_(3)N_(4)∶Tb as a dual-functional marker to facilitate fluorescence and mass spectrometric imaging.