The bioactive monoterpene indole alkaloid N,β-D-glucopyranosyl vincosamide is regulated by irradiance quality and development in Psychotria leiocarpa

Leaves of Psychotria leiocarpa accumulate a major shoot-specific indole alkaloid, N,beta-D-glucopyranosyl vincosamide (GPV), which has antioxidant, but no apparent antifeedant or allelopathic activity. The species is tolerant to high doses of UV-B, possibly due to constitutive GPV accumulation in leaves. In seedlings, GPV accumulation is induced by white light in a photosynthesis independent fashion. To better understand the regulation of the in planta GPV pool, detailed alkaloid profiles were examined. Light shift tests confirmed that GPV accumulation is light dependent. GPV was tightly regulated in its organ distribution, with highest concentrations in reproductive structures. Far-red and blue wavelengths promoted GPV accumulation without clear correlation with carbohydrate or protein concentrations or dry biomass in seedlings, thus indicating direct effects of light. Since light conditions are often associated with higher oxidative stress, light-induced accumulation of GPV may contribute to maintain redox balance. In vitro, GPV was an overall more effective antioxidant compared to closely related alkaloids. Indirect evidence of potential antioxidant properties of GPV in vivo was obtained by application of GPV on leaves of UV sensitive species exposed to high doses of UV-B, which significantly improved tolerance to this stress. In contrast to the known constitutive accumulation of GPV in leaves, the alkaloid concentration proved to be highly dynamic, changing during development, reproductive organogenesis and seedling irradiance treatments. Data further support a role for GPV as an oxidative stress protectant and provide a means to improve alkaloid yields in plant biomass for pharmacological applications. (C) 2016 Elsevier B.V. All rights reserved.