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Abstract The plant Calendula officinalis L. (marigold, belonging to the Asteraceae family) underwent foliar salicylic acid (SA) elicitation in both greenhouse and open-field experiments. Spectrophotometric analysis revealed variations in flavonoid levels in C. officinalis flowers from seven varieties cultivated in the greenhouse after applying four different concentrations of the elicitor (0.1–2 mM), with the highest flavonoid content observed at 1 mM SA. High-performance liquid chromatography with photodiode array and ion trap time-of-flight mass spectrometry (HPLC–PDA–IT–TOF–MS) analysis of the Golden Sea variety indicated significant changes in its phenolic profile, which contained 19 compounds in its original state and 35 compounds after 1–2 mM SA treatment. A total of 30 flavonols, primarily isorhamnetins, belonging to the quercetin and isorhamnetin series, were identified as acylated and non-acylated O-glycosides. Chromatographic separation of the SA-treated C. officinalis extract led to the isolation of a new flavonoid, identified using ultraviolet (UV) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and mass spectrometry (MS) as isorhamnetin 3-O-(4′′-O-acetyl-6′′-O-α-L-rhamnopyranosyl)-β-D-glucopyranoside (calendoside V). The application of 1 mM SA resulted in the 2.2-fold increase in flavonoid content in C. officinalis flowers compared to the control. This increase was primarily attributed to a greater accumulation of isorhamnetin glycosides, which increased by 129.3% compared to the control, while quercetin derivatives exhibited a more modest increase of 10.9%. A similar trend was observed in an open-field experiment, where increased flower productivity and flavonoid levels were noted, particularly in relation to isorhamnetin accumulation. The elicitation of C. officinalis with SA is a straightforward and cost-effective method for improving the quality of this medicinal plant and for producing raw materials with the desired composition.
Оленников et al. (Wed,) studied this question.