Modulation of indole alkaloid composition in Vinca minor

Abstract

Changes in the content and the composition of natural compounds always results from the balance of their biosynthesis, allocation, and degradation. These three processes are influenced differentially by various developmental and environmental factors. In consequence, the overall impact of these influences on the spectrum and the content of the secondary metabolites might be very complex and multifarious. However, these considerations open novel doors for manifold and deliberate approaches to change the secondary metabolism, to improve and optimize the search for novel pharmacologically active compounds. With respect to environmental factors, various stress situations and the concomitant consideration of the developmental stage of the plant, seems to be most promising approaches. Since these conjunctures are governed by various signal transduction chains, the application of corresponding growth regulators or signal transducers should augment plant chemodiversity and thus promote phytochemical drug discovery. In this context, the most promising candidates are methyl jasmonate (MeJA), hydrogen peroxide (H2O2) and salicylic acid (SA). The scope of the current study was to investigate the impact of exogenous application of growth regulators as a novel approach to modify the composition of active components in medicinal plants. Accordingly, mature Vinca minor plants of defined physiological status were used as a model system to investigate the effect of elicitation by signal transducers. The vividly demonstrate that such approaches indeed lead to massive qualitative as well as quantitative variations in the content of bioactive compounds. MeJA and H2O2 induces the conversion of vincamine to 9-methoxyvincamine and of vincadifformine to minovincinine and further on to minovincine. Based on the concomitant application of enzyme inhibitors, it could be deduced that in V. minor these reactions are catalyzed by cytochrome P450 enzymes. The discovery of 9-methoxyvincamine as a novel natural product underlines that even extensively studied plants such as V. minor might still be an auspicious source for the generation of novel phytochemical drugs. These coherences highlight that the utilization of growth regulators or signal transducers, especially of MeJA, and the consideration of different developmental stages, could be a promising tool for altering and diversifying the composition of active substances even in well investigated medicinal plants.