Alkaloids and antioxidant mechanisms in galls: insights from Peumus boldus-Dasineura sp. interactions.

Abstract

The alkaloids present in Peumus boldus Molina (Monimiaceae), a tree native to Chile, are well known for their antioxidant properties. Given that Dasineura sp. (Cecidomyiidae) induces galls in stems of this tree and that alkaloid dynamics in this interaction remain largely unexplored, we hypothesize that stem alkaloids help maintain redox balance within galls. However, the composition and accumulation of alkaloids may be altered by gall-inducing insects, ultimately reducing the in vitro antioxidant activity of the host organ. Alkaloid changes in P. boldus stems across growth and development (GDG), maturation (MG), and senescence (SG) stages were analysed with Dragendorff's reagent for qualitative detection, and gas chromatography-mass spectrometry was used for quantitative analysis. Antioxidant activity was assessed via DPPH and ABTS assays. Nongalled stems (NGS) served as control. Histochemical analyses revealed a redistribution of alkaloids, which initially concentrated on nutritive and peripheral tissues then shifted toward surrounding gall tissues in later stages. Alkaloids detected were isoquinoline derivatives, mainly aporphines, with variations in composition and relative abundance, depending on organ and gall stage. Eleven alkaloids were found in NGS, 13 in GDG, 11 in MG, and 15 in SG. Only three alkaloids were present across all the samples. Antioxidant activity varied significantly among extracts: NGS had highest activity, MG lowest, and SG intermediate values - comparable to those of controls in the ABTS assay. Alkaloids in P. boldus stems are involved in maintaining redox balance in Dasineura sp. galls, but their altered accumulation and composition across gall development stages leads to a decline in antioxidant activity.