Dear Dr Galani,

I have attached my recent work hopefully that  help you in the calculation of the pigment.

Best regards

Aly

Article Effect of Roselle Calyces Extract on the Chemical and Sensor...

Article Effect of Roselle Calyces Concentrate with Other Ingredients...

You can measure a standard anthocyanin and work a standard curve then you can measure the conc. of anthocyanin in extract by applying absorption on standard curve. 

Good morning Galani,

I agree with Usama Ramadhan. To evaluate total anthocyanins using Optical Density, the first step is to establish a calibration curve at a given  wavelength. In my opinion, the wavelength most appropriate is 535 nm, because most of the anthocyanins are their maximum absorption at this wavelength. 

To establish the calibration curve, you must have standarts of anthocyanins (e.g., malvidin-3-glucoside), and then prepare solutions of growing concentration, e.g.: 10 mg/L, 50 mg/L, ..., 100 mg/L. Then you mesure the OD of these solutions, and draw the calibration curve (conc. vs. OD).

Once you have this curve, you can mesure the OD at 535 nm of an unknown solution, and have the concentration of anthocyanins of the unknown solution (expressed in malvidin-3-glucoside).