Effects of water stress on growth parameters, alkaloid content (galanthamine and lycorine), and antioxidant activities in summer snowflake (Leucojum aestivum L.)

Leucojum aestivum L. is a perennial bulbous plant belonging to the Amaryllidaceae family that contains two pharmaceutically significant alkaloids (galanthamine and lycorine). Galanthamine, an acetylcholinesterase inhibitor (AChEI), is an important treatment for Alzheimer's disease. Lycorine has potent antiretroviral, antimalarial, antimitotic, and cytotoxic properties. The aim of this investigation was to establish the effects of various water stress (WS) treatments on growth parameters, galanthamine and lycorine contents, non-enzymatic antioxidant activities (total phenol-flavonoid content and free radical (FR) scavenging activity), and enzymatic antioxidant activities [superoxide dismutase (SOD) and catalase (CAT)] in L. aestivum. The plants were grown for 7 weeks under different WS conditions. A control group (C), flooding stress (FS), and two different drought stress (DS) treatments were used: irrigation regime (IR) adjustment (25, 50, and 75%), and PEG 6000 (15, 30, and 45%). According to the obtained results, 50% IR produced the highest levels of galanthamine and lycorine in the bulbs and the highest levels of galanthamine in the leaves. In general, galanthamine and lycorine levels were increased with PEG treatments. On the other hand, galanthamine levels in the leaves and bulbs decreased with the treatment of FS. The best DPPH activity was observed in the 50% IR of the bulbs. The treatment with 50% IR enhanced the total phenolic and flavonoid content of both leaves and bulbs. The IR treatments reduced bulb SOD activity. An increase in CAT activity was detected in all bulb samples. In conclusion, 50% IR treatment has been considered the most effective in terms of pharmaceutical value.