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Apocynum cannabinum: indices of anthocyanin production

Erica Ross, Ryan Edelen, Matthew Howes and Dana Dudle
Science Research Fellows and Biology Department, DePauw University
Summer 2006

There are three different indices reported in the primary literature (1999, 2003, and 2006) for converting data on light wavelengths to anthocyanin content of plant parts.  Each of the three indices produces different results.  The goal of our study was to compare anthocyanin content from each of the three indices to anthocyanin content from extraction and detection using an absorbance spectrophotometer.

We collected 50 Apocynum cannabinum plants in the DePauw Nature Park.  We collected five readings of each stem with a reflectance spectrophotometer.  We used a razor blade to remove the outer cortex of the stem and cut up 0.01 to 0.02 grams of tissue.  We placed the tissue in an eppendorf tube and extracted anthocyanins using acidified methanol.  We used an absorption spectrophotometer to measure anthocyanin concentrations based on absorption at 530 and 653 nm.

Results and Discussion
We found the strongest correlation between the absorbance of extracted samples and the 2003 index (r2 = 0.7393).  The correlations between the absorbance of extracted samples and the 1999 and 2006 indices were lower (r2 = 0.3464 and 0.4396).  The 2003 index was the most accurate index for reporting anthocyanin content.