Temporal variation of tannins (galloylglucoses), flavonols and anthocyanins in leaves of Eucalyptus nitens seedlings : implications for light attenuation and antioxidant activities

Abstract

Leaves of Eucalyptus nitens (Deane & Maiden) Maidenwere sampled during establishment of seedlings that were deprived of nutrientsor fertilised at planting. Extracts were analysed for polyphenolic compoundsusing high pressure liquid chromatography (HPLC) in conjunction with UV diodearray and electrospray ionisation mass spectrometry (ESI-MS) with negative iondetection as well as direct MS injection. The presence of quercetin, rutin,sideroxylonal A and B andpenta-galloylglucose were confirmed by comparison with standards. Othergalloylglucoses were identified by first principles. Galloylglucoses comprisedabout 75% of polyphenolics. Quercetin and various quercetin glycosidescomprised ca 85% of flavonols. The anthocyanins,cyanidin-3-glycoside and cyanidin-3,5-diglycoside were identified from directinjection MS data. HPLC–ESI-MS was found to be a superior analyticaltechnique compared to conventional HPLC–UV diode array detection due toco-elution of peaks under UV. Temporal variation of anthocyanins may berelated to the severity of cold-induced photoinhibition. Changes ingalloylglucoses and flavonols were similar with time and related to levels offoliar nitrogen. The suitability of HPLC–ESI-MS for the study of foliarpolyphenolics, the phenolic constitution of E. nitensfoliage, and temporal variation of the phenolic constituents during a seedlingestablishment period of 29 weeks are demonstrated.