Subphthalocyanines as fluorescence sensors for metal cations.

Subphthalocyanines (SubPcs) and their aza-analogues (SubTPyzPzs) are fluorophores with strong orange fluorescence emission; however, their sensing ability towards metal cations remains uncharted. To fill this gap, we have developed an efficient method for introducing aza-crown moieties at the axial position of SubPcs and SubTPyzPzs to investigate the structure-activity relationship for sensing alkali (Li+, Na+, K+) and alkaline earth metal (Ca2+, Mg2+, Ba2+) cations. SubPcs showed better photostability than SubTPyzPzs and even a commonly utilized dye, 6-carboxyfluorescein. Selectivity toward metal cations was driven by the size of the aza-crown, irrespective of the counter anion. The stoichiometry of binding was found to be 1 : 1 in all cases, and the interaction between SubPcs and cations was characterized by the corresponding apparent binding constants (Ka). Notably, an unusually strong interaction of all sensoric SubPcs with Ba2+ compared to other studied cations was demonstrated. The role of the surrounding environment, i.e. the addition of water or methanol, in sensing cations is shown in detail as well. Selectivity towards K+ over Na+ was demonstrated in aqueous media with SubPcs bearing the 1-aza-6-crown-18 moiety in Tween 80 micelles. In this case, a 5-fold increase of the fluorescence quantum yield was observed upon binding K+ ions. The high brightness, photostability, and sensing activity in aqueous media make SubPc macrocycles promising fluorophores for metal cation sensing.

Phytochemical Constituents, Biological Activities, and Health-Promoting Effects of the Melissa officinalis.

Medicinal plants are being used worldwide for centuries for their beneficial properties. Some of the most popular medicinal plants belong to the Melissa genus, and different health beneficial effects have already been identified for this genus. Among these species, in particular, the Melissa officinalis L. has been reported as having many biological activities, such as antioxidant, antimicrobial, antitumour, antiviral, antiallergic, anti-inflammatory, and also flatulence inhibiting effects. The beneficial properties of the Melissa officinalis, also known as "lemon balm herb", can be related to the bioactive compounds such as terpenoids, alcohols, rosmarinic acid, and phenolic antioxidants which are present in the plant. In this updated review, the botanical, geographical, nutritional, phytochemical, and traditional medical aspects of M. officinalis have been considered as well as in vitro and in vivo and clinically proven therapeutic properties have been reviewed with a special focus on health-promoting effects and possible perspective nutraceutical applications. To evidence the relevance of this plant in the research and completely assess the context, a literature quantitative research analysis has been performed indicating the great interest towards this plant for its beneficial properties.