Spectrophotometric assessment of leaf UV-B absorbing compounds and chemically determined total phenolic levels are strongly correlated

Investigations concerning the two major ecological roles of phenolics use different methods to quantify these compounds (phenolics as antiherbivores, Folin-Ciocalteu chemical assay; phenolics as UV-B screening pigments, UV-B absorbance). Yet, comparisons of the corresponding results are not possible, since an empirical correlation between the two methods is lacking. In the present study, significant regressions between total phenolic levels (chemically determined with the Folin-Ciocalteu method) and leaf UV-B absorbing capacity (assessed from simple absorbance measurements of methanolic extracts at 300 nm) were found in all seven plant species tested, yet interspecies differences in regression equations were evident. Provided that a standard curve between UV-absorbance versus total phenolic levels is established for each test plant, the latter could be predicted from the former. The UV-absorbance method is preferable because it is time-saving, simpler, and less costly. Given the strong regression between ...

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