Abstract
Amaryllidaceae alkaloids are of notable pharmacological relevance. For instance, galanthamine is used in the treatment of Alzheimer's disease, while other alkaloids (lycorine, crinine, etc.) derived from Amaryllidaceae plants are also of great interest because they exhibit antitumour, antiviral, antibacterial, antifungal, antimalarial, analgesic and cytotoxic properties. Phenolic acids comprise a group of natural bioactive substances that have commercial value in the cosmetic, food and medicinal industries due to their antioxidant, anticancer, anti-inflammatory and cardioprotective potential. In the present study, the effect of temperature (15, 20, 25 and 30 °C) on Amaryllidaceae alkaloid and phenolic acid biosynthesis in Leucojum aestivum in vitro plant cultures was investigated. The highest diversity of alkaloids (i.e., galanthamine, crinan-3-ol, demethylmaritidine, crinine, 11-hydroxyvitattine, lycorine, epiisohaemanthamine, chlidanthine) was noted in plants cultured at 30 °C. By contrast, ismine and tazettine were only present in plants cultured at 15 °C. Temperatures of 20 °C and 30 °C were found to stimulate galanthamine accumulation. The highest lycorine content was noted in plants grown at temperatures of 15 and 30 °C, and it was negatively correlated with the expression of the gene that encodes the cytochrome P450 96T (CYP96T) enzyme which catalyses a key step in the biosynthesis of different types of Amaryllidaceae alkaloids. This observation may reflect temperature-induced shifts in metabolic flux among different branches of Amaryllidaceae alkaloid biosynthesis. The observed stimulating effect of a 15 °C temperature on the chlorogenic, caffeic, p-coumaric, sinapic, ferulic and isoferulic acid content was in line with the highest expression of a gene that encodes the tyrosine decarboxylase (TYDC) enzyme, which is involved in plant stress response mechanisms. At 30 °C, however, the highest content of the caffeic, vanillic, p-coumaric and isoferulic acids was noted.