Objective:

2

To study the correlation between the color of Indigo Naturalis (powder and it's extracting solution) and effective components (indigo and indirubin) content.

Method:

2

The contents of indigo and indirubin in 27 batches of Indigo Naturalis were determined by HPLC

and the chromaticity values

L

*

a

*

and

b

*

of powder and extracting solution were determined by color colorimeter. SPSS 20.0 software was used to analyze the correlation and multiple linear regression between the content of active components and the chromaticity values of Indigo Naturalis.

Result:

2

By visual observing the appearance of the powder

we find that

as the powder color deepened

the brightness values (

L

*

) of the powder and extract were decreased

while the red-green value (

a

*

) were increased. The correlation analysis showed that the contents of indigo were negatively correlated with the brightness value (

L

*

) of the powder(

P

<

0.01)

and the correlation coefficient was-0.520

while they were positively correlated with the red-green value (

a

*

)(

P

<

0.01)

and the correlation coefficient was 0.567.The contents of indirubin were negatively correlated with the brightness value (

L

*

) of powder and extract (

P

<

0.01)

and the correlation coefficients were-0.635 and-0.580

respectively

while they were positive correlation with the red-green value (

a

*

) (

P

<

0.01)

and the correlation coefficient were 0.706 and 0.493

respectively.

Conclusion:

2

The darker the powder color of Indigo Naturalis

the higher the content of indigo and indirubin. The

L

*

and

a

*

values of indigo powder were more correlated with indigo and indirubin content than with the extracting solution. The color of powder was significantly correlated with the content of indigo and indirubin

which provided reference for rapid identification of Indigo Naturalis. The method of measuring the color of Indigo Naturalis by color colorimeter is stable

scientific and reliable.