Application of chromatography and mass spectrometry to the characterization of cobalt, copper, manganese and molybdenum in Morinda Citrifolia

Studying Peptide-Metal Ion Complex Structures by Solution-State NMR

Metal chelation can provide structural stability and form reactive centers in metalloproteins. Approximately one third of known protein structures are metalloproteins, and metal binding, or the lack thereof, is often implicated in disease, making it necessary to be able to study these systems in detail. Peptide-metal complexes are both present in nature and can provide a means to focus on the binding region of a protein and control experimental variables to a high degree. Structural studies of peptide complexes with metal ions by nuclear magnetic resonance (NMR) were surveyed for all the essential metal complexes and many non-essential metal complexes. The various methods used to study each metal ion are presented together with examples of recent research. Many of these metal systems have been individually reviewed and this current overview of NMR studies of metallopeptide complexes aims to provide a basis for inspiration from structural studies and methodology applied in the field.

Characterization and Quantification of Luteolin-Metal Complexes in Aqueous Extract of Lonicerae Japonicae Flos and Huangshan Wild Chrysanthemum

Luteolin is a flavonoid compound widely found in vegetables, fruits, and medicinal plants. In this study, the reaction conditions for luteolin and five metal ions (Ca²⁺, Mg²⁺, Zn²⁺, Fe³⁺, and Cu²⁺) to form complexes in hot water were optimized, which was at a molar ratio of 1 : 1 for luteolin and metal ions at 90°C in a volume of 20 mL for 2 h, and the ability of luteolin to form complexes with Cu²⁺ was the strongest. The DPPH scavenging test showed that luteolin exerted a dose-dependent effect on the clearance of free radicals; luteolin-Cu²⁺ complexes and luteolin-Fe³⁺ complexes accentuated the clearance of free radicals. Furthermore, we used high performance liquid chromatography (HPLC) to analyze luteolin in samples from two medicinal plants, obtained from the dissolution of aqueous extracts in two different solvents. The results showed that the peak areas for luteolin in the samples dissolved in 20% formic acid-methanol were significantly larger than those from the samples dissolved in methanol alone, with increases in the peak area being 135.6% (Lonicerae Japonicae Flos), and 161.16% (Huangshan wild chrysanthemum). The aforementioned results indicate that complexes formed from organic compounds and metal ions are present in the decoction of a plant.

Properties and Applications of Morinda citrifolia (Noni): A Review

Morinda citrifolia commonly known as noni is a perennial plant originating in Southeast Asia, consumed over 2000 years. Due to its versatility of adaptation and use of the structures of the plant for different therapeutic purposes, noni attracted the attention of researchers from the pharmaceutical and food industry. Chemical and nutritional analyzes already performed in M. citrifolia reveal the existence of more than 200 phytochemical substances with bioactive properties such as acids, alcohols, phenols, saccharides, anthraquinones, carotenoids, esters, triterpenoids, flavonoids, glycosides, lactones, iridoids, ketones, lactones, lignans, nucleosides, triterpenides, sterols, and aromatic compounds. The high nutritional value of M. citrifolia may induce therapeutic effects, including antimicrobial and antioxidant properties. The main industrial products from this plant are beverages (juice drinks), powders (from dried fruits), oil (from seeds), and leaf powders. Biological and phytotherapeutic applications of M. citrifolia are promising, but more extensive studies are still required. Thus, this review aims to gather updated and comprehensive information on Morinda citrifolia, discussing its traditional use, biochemical, phytotherapics, and toxicological properties, as well as the recent advances in the processing and standardization of products derived from noni fruit.

ESI-TOF MS analysis of complexes formed between quercetin and five metal ions in hot water and a study into their DNA cleavage activity

Quercetin is a flavonoid compound widely found in vegetables, fruits, and medicinal plants. It has carbonyl and phenolic hydroxyl groups in its structure that can easily form complexes with metal ions. In this study, we reacted quercetin in water at 95 °C with five metal trace elements commonly found in plants, namely calcium, magnesium, zinc, iron(III), and copper. Each supernatant was then examined by electrospray ionization-time-of-flight mass spectrometry (ESI-TOF MS). The results showed that quercetin can form complexes with Ca²⁺, Mg²⁺, Zn²⁺, and Cu²⁺ in ratios of 2:1, 3:1, and 3:2. Interestingly, after reaction with Fe³⁺ in water at 95 °C, not only can quercetin‑iron(III) complexes be formed in ratios of 2:1 and 3:1, but small amounts of quercetin‑iron(II) complexes can also be formed in the same ratios. Furthermore, DNA cleavage experiments showed that when acting alone, quercetin and Cu²⁺ have weak or no cleavage effects on DNA, but the complex formed after reaction in hot water cleaves DNA in a time- and concentration-dependent manner. These results indicate that complexes may form between quercetin and a variety of metal trace elements in a water decoction of plants, and that these metal complexes may be the material basis for the health-promoting and therapeutic effects of edible or medicinal plants.

Mass spectrometry for the elucidation of the subtle molecular structure of biodegradable polymers and their degradation products

Contemporary reports by Polish authors on the application of mass spectrometric methods for the elucidation of the subtle molecular structure of biodegradable polymers and their degradation products will be presented. Special emphasis will be given to natural aliphatic (co)polyesters (PHA) and their synthetic analogues, formed through anionic ring-opening polymerization (ROP) of β-substituted β-lactones. Moreover, the application of MS techniques for the evaluation of the structure of biodegradable polymers obtained in ionic and coordination polymerization of cyclic ethers and esters as well as products of step-growth polymerization, in which bifunctional or multifunctional monomers react to form oligomers and eventually long chain polymers, will be discussed. Furthermore, the application of modern MS techniques for the assessment of polymer degradation products, frequently bearing characteristic end groups that can be revealed and differentiated by MS, will be discussed within the context of specific degradation pathways. Finally, recent Polish accomplishments in the area of mass spectrometry will be outlined.

Comparison of copper and zinc in vitro bioaccessibility from cyanobacteria rich in proteins and a synthetic supplement containing gluconate complexes: LC-MS mapping of bioaccessible copper complexes

An analytical procedure was proposed to estimate bioaccessibility of copper and zinc in Spirulina Pacifica tablets with respect to that of copper and zinc in gluconate complexes. Spirulina is the common name for diet supplements produced primarily from two species of cyanobacteria, namely Arthrospira platensis and Arthrospira maxima. Spirulina tablets are an excellent source of proteins, vitamins and minerals. To obtain information about the bioavailability of these elements, an in vitro bioaccessibility test was performed by application of a two-step protocol which simulated the gastric (pepsin) and intestinal (pancreatin) digestion. The species obtained were investigated by size exclusion chromatography on a chromatograph coupled to a mass spectrometer with inductively coupled plasma (SEC-ICP-MS) and an on-capillary liquid chromatograph coupled to an electrospray mass spectrometer (μ-HPLC-ESI-MS). Both copper and zinc were found to be highly bioaccessible in Spirulina tablets (90-111%) and those containing gluconate complexes (103% for Cu and 62% for Zn). In Spirulina tablets, copper was found to form two types of complex: (1) polar ones with glycine and aspartic acid and (2) more hydrophobic ones containing amino acids with cyclic hydrocarbons (phenylalanine, histidine, proline and tyrosine). Zinc and copper were also proved to form complexes during the digestion process with products of pepsin digestion, but the stability of these complexes is lower than that of the complexes formed in Spirulina. The results proving the involvement of proteins in the enhancement of copper and zinc bioaccessibility will be useful for the design of new copper and zinc supplements.