Structural features guided "fishing" strategy to identification of flavonoids from lotus plumule in a self-built data "pool" by ultra-high performance liquid chromatography coupled with hybrid quadrupole-orbitrap high resolution mass spectrometry.

Lotus plumule, a traditional Chinese medicine, has significant pharmaceutical value to treat various health problems. Flavonoids are important bioactive ingredients in lotus plumule. In this study, we proposed an efficient "fishing" strategy to profile and identify non-targeted flavonoids from lotus plumule aqueous extract based on a self-built mass data "pool" with an untargeted mass data acquisition method in order to acquire comprehensive structural information of flavonoids in lotus plumule. This mass data acquisition method was applied by ultra-high performance liquid chromatography coupled with hybrid quadrupole orbitrap high-resolution mass spectrometry (UHPLC/Q-orbitrap HRMS) executed in full MS/dd-MS2 mode with different collision energies in positive ionization mode. The self-built targeted data "pool" was constructed by the basic structure of flavonoids in lotus plumule, such as odd quasi-molecular ions, C6-C3-C6 skeleton, molecular weight limit. The "molecule lures" of fishing are characterized by molecular features, fragmental patterns, characteristic fragments ions, relative abundance and retention times. More importantly, the special "lures" of PredRet (the tool of predicting the retention times) and ClogP (the calculated lipophilicity parameter) were adopted to distinguish some isomers and some compounds whose mass spectra are difficult to determine with no reference substances. The "fished" flavonoids were further confirmed by their molecular features and fragmental patterns. This developed analysis method was successfully applied to profile 29 flavonoids compounds in the aqueous extract of lotus plumule, and 3 of them were recognized for the first time in lotus plumule. To our knowledge, this is the first analytical screening methods without standard samples to systematically identify flavonoids in lotus plumule.

Fluorescent probes for the detection of magnesium ions (Mg2+): from design to application.

Magnesium ions (Mg2+) play essential roles in various physiological and pathological processes, its abnormal homeostasis in cells is related to many diseases, such as diabetes, neuromuscular disorders, hypertension and other cardiovascular disorders. Investigation on the regulation of magnesium in cellular processes has attracted considerable interest in the past several decades. Among those reported strategies, fluorescent imaging technology has become a powerful and cost-effective tool for the real-time monitoring of magnesium distribution, uptake and trafficking, due to its superior features of high sensitivity and non-invasiveness, as well as excellent spatial and temporal fidelity. Herein, we critically summarize the progresses in the intracellular magnesium detection with fluorescent imaging probes. Our discussion focuses on the recent contributions concerning fluorescent imaging probes for mapping magnesium in biological processes. All the candidates are organized according to their acceptor structures. The sensing mechanisms of fluorescent probes are also highly taken into account. Challenges, trends and prospects of fluorescent imaging technology in magnesium detection are also set forth.