Zur Biogenese der Betacyane: Versuche mit [2‐¹⁴C]‐Dopaxanthin

Abstract

On the biogenesis of betacyanins. Expaiments with [2‐ 14 C]‐dopaxanthine Labelled dopaxanthine is prepared from betanin by a double exchange procedure replacing first its cyclodopa part by diethylamine and effecting the second exchange with 2‐[ 14 C]‐dopa on the purified intermediate ‘DEA‐betalain’; the specific activity delivered with the dopa allowed accurate determination of ϵ in the electronic spectrum of dopaxanthine (λ max 488 nm, ϵ = 41.800). The C(2)‐labelled dopaxanthine is incubated into the fruits of Opuntia bergeriana . The incorporation rates into betanin are found to correspond approximately to those obtained in earlier experiments with labelled dopa alone: Only 1‐‐5% of the label showed up in the cyclodopa moiety of the betanin (which is isolated as cyclodopa‐glucoside) whereas 99‐‐95% of the radioactivity was associated with the betalamic acid part (recovered in form of indicaxanthine).