A. Rygula and P. Miskowiec
298
components of the plant matrix. Simultaneously, lignin and carotenoids distribution
were detected with 1,607 cm
−1
and 1525 cm
−1
signals as marker bands, respectively.
the spectacular results of the flavonoid mapping together with carotenoid analyses was published in ref. [71] (Fig. 10.9). the hCA method, calculated for fullrange spectra, was used to analyses of the Raman maps that allowed to discriminate within the flavonoids between the flavonols and anthocyanins. Additionally,
based on the integrated band intensity, the relative concentrations of these dyes
were shown. As the marker bands, two regions were defined: 1,550–1,588 cm
−1
for
flavonols and 1,225–1,272 cm
−1
for anthocyanins. the sensitivity of hCA allows to
discriminate within the flavonoids group between the similar moieties classified to
the flavonols and anthocyanins.
Flavonoid components usually do not give so clear and distinctive spectra like
e.g. carotenoids. Nevertheless, the in situ quantitative analysis is possible. the
quantification of aspalathin and nothofagin in green rooibos ( Aspalathus linearis)
was performed with Ft-Raman spectroscopy together with flavonoid mapping in
plant mentioned above [66]. the Ft-Raman calibration for aspalathin model resulted in R
2
= 0.87 (SECv = 0.53 g/100 g) whilst for nothofagin showed R
2
= 0.78
(SECv—0.14 g/100 g). the last result is relatively satisfactory because nothofagin
is presented in small amounts in dried rooibos (0.067–1.23 g/100 g), contrary to
aspalathin content which is about 0.60–10.59 g/100 g. In order to apply the PLS
regression mode, the whole range of spectrum was selected and the model for the
prediction was not improved if only marker bands were calculated.
A few analysis have been carried out for extracted dyes. Quercetin is one of the
most popular dietary flavonols occurring in vegetables i.e. onion. the determination of quercetin in the methanol and ethanol extract from an onion peels was carried out by RS with 488 nm laser [93]. What is characteristic, the solvent was used
as the internal standard to remove experimental factors disturbing the analysis. For
quantitative analysis, the Raman bands of quercetin at 600 cm
−1
and ethanol at
884 cm
−1
were used. the analogous analysis was carried for quercetins using AtR
FtIR spectroscopy [94].
detection of anthocyanins and their glycosides [95] was not accompanied by
a quantitative analysis and only the spectra of anthocyanins derivatives in dependence of the glycolysation and excitation wavelength was studied.
Lu et al. [96, 97] carried out the Ft-IR spectroscopic analysis for onions and
shallots, which are characterized by high amount of flavonoids and compared them
with the results obtained with the typical analytical methods for phenolic content
and total antioxidant capacity (the Folin–Ciocalteu assay, 2,2-diphenyl-picrylhydrazyl (dPPh) assay, trolox equivalent antioxidant capacity (tEAC) assay and ferric
reducing antioxidant power (FRAP) assay). As a result, correlation coefficient > 0.95
was obtained, with standard errors of calibration (SEC) and standard errors of crossvalidation (SECv) less than 2.85. moreover, cluster analysis and discriminant function analysis (dFA) differentiated varieties of onions and shallot based upon infrared
spectral features.
298
components of the plant matrix. Simultaneously, lignin and carotenoids distribution
were detected with 1,607 cm
−1
and 1525 cm
−1
signals as marker bands, respectively.
the spectacular results of the flavonoid mapping together with carotenoid analyses was published in ref. [71] (Fig. 10.9). the hCA method, calculated for fullrange spectra, was used to analyses of the Raman maps that allowed to discriminate within the flavonoids between the flavonols and anthocyanins. Additionally,
based on the integrated band intensity, the relative concentrations of these dyes
were shown. As the marker bands, two regions were defined: 1,550–1,588 cm
−1
for
flavonols and 1,225–1,272 cm
−1
for anthocyanins. the sensitivity of hCA allows to
discriminate within the flavonoids group between the similar moieties classified to
the flavonols and anthocyanins.
Flavonoid components usually do not give so clear and distinctive spectra like
e.g. carotenoids. Nevertheless, the in situ quantitative analysis is possible. the
quantification of aspalathin and nothofagin in green rooibos ( Aspalathus linearis)
was performed with Ft-Raman spectroscopy together with flavonoid mapping in
plant mentioned above [66]. the Ft-Raman calibration for aspalathin model resulted in R
2
= 0.87 (SECv = 0.53 g/100 g) whilst for nothofagin showed R
2
= 0.78
(SECv—0.14 g/100 g). the last result is relatively satisfactory because nothofagin
is presented in small amounts in dried rooibos (0.067–1.23 g/100 g), contrary to
aspalathin content which is about 0.60–10.59 g/100 g. In order to apply the PLS
regression mode, the whole range of spectrum was selected and the model for the
prediction was not improved if only marker bands were calculated.
A few analysis have been carried out for extracted dyes. Quercetin is one of the
most popular dietary flavonols occurring in vegetables i.e. onion. the determination of quercetin in the methanol and ethanol extract from an onion peels was carried out by RS with 488 nm laser [93]. What is characteristic, the solvent was used
as the internal standard to remove experimental factors disturbing the analysis. For
quantitative analysis, the Raman bands of quercetin at 600 cm
−1
and ethanol at
884 cm
−1
were used. the analogous analysis was carried for quercetins using AtR
FtIR spectroscopy [94].
detection of anthocyanins and their glycosides [95] was not accompanied by
a quantitative analysis and only the spectra of anthocyanins derivatives in dependence of the glycolysation and excitation wavelength was studied.
Lu et al. [96, 97] carried out the Ft-IR spectroscopic analysis for onions and
shallots, which are characterized by high amount of flavonoids and compared them
with the results obtained with the typical analytical methods for phenolic content
and total antioxidant capacity (the Folin–Ciocalteu assay, 2,2-diphenyl-picrylhydrazyl (dPPh) assay, trolox equivalent antioxidant capacity (tEAC) assay and ferric
reducing antioxidant power (FRAP) assay). As a result, correlation coefficient > 0.95
was obtained, with standard errors of calibration (SEC) and standard errors of crossvalidation (SECv) less than 2.85. moreover, cluster analysis and discriminant function analysis (dFA) differentiated varieties of onions and shallot based upon infrared
spectral features.