In this work, we assess the potential of waste products of Phlegrean mandarin (Citrus reticulata Blanco), namely seeds and peel, to be reutilized as a source of bioactive compounds beneficial for the human diet. Starting from the evidence that the by-products of this specific cultivar are the most powerful sources of antioxidants compared to pulp, we have investigated if and how the bioactive compounds in peel and seeds may be affected by fruit ripening. Three stages of fruit ripening have been considered in our study: unripe fruits = UF, semi-ripe fruits = SRF, ripe fruits = RF. The overall results indicated that RF showed the highest concentration of antioxidants. Among fruit components, peel was the richest in total antioxidant capacity, total polyphenol content, total flavonoids, total chlorophylls and carotenoids, while seeds exhibited the highest concentration of total condensed tannins and ascorbic acid. The liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay indicates the occurrence, in peel extracts, of 28 phenolic compounds, mainly flavonoids (FLs); in seeds, 34 derivatives were present in the first stage (UF), which diminish to 24 during the ripening process. Our data indicated that the content of phytochemicals in citrus strongly varies among the fruit components and depends on the ripening stage. The higher antioxidant activity of peel and seeds, especially in RF, encourage a potential use of by-products of this specific citrus cultivar for industrial or pharmacological applications. However, to maximize the occurrence of desired bioactive compounds, it is important also to consider the ripening stage at which fruits must be collected.

Chemical compounds within tea (Camellia sinensis) are characterized by an extensive heterogeneity; some of them are crucial for their protective and defensive role in plants, and are closely connected to the benefits that the consumption of tea can provide. This paper is mainly focused on the characterization of polyphenols (secondary metabolites generally involved in defense against ultraviolet radiation and aggression by pathogens) and metals, extracted from nine Chinese tea samples, by integrating different mass spectrometry methodologies, LC-MS/MS in multiple reaction monitoring (MRM) and inductively coupled plasma mass spectrometry (ICP-MS). Our approach allowed to identify and compare forty polyphenols differently distributed in tea infusions at various fermentation levels. The exploration of polyphenols with nutraceutical potential in tea infusions can widely benefit especially tea-oriented populations. The worldwide consumption of tea requires at the same time a careful monitoring of metals released during the infusion of tea leaves. Metal analysis can provide the identification of many healthy minerals such as potassium, sodium, calcium, magnesium, differently affected by the fermentation of leaves. Our results allowed us: (i) to draw up a polyphenols profile of tea leaves subjected to different fermentation processes; (ii) to identify and quantify metals released from tea leaves during infusion. In this way, we obtained a molecular fingerprint useful for both nutraceutical applications and food control/typization, as well as for frauds detection and counterfeiting.

The electroanalytical field has exploited great advantages in using paper-based substrates, even if the word "paper" might be general. In fact, the mainly adopted paper-based substrates are often chromatographic and office ones. They are characterized by the following main features (and drawbacks): chromatographic paper is well-established for storing reagents/ treating samples, but the sensitivity compared to traditional screen-printed ones is lower (due to porosity), while office paper represents a sustainable alternative to plastic (with similar sensitivity), but its porosity is not enough to load reagents. To overcome the limitations that might arise due to the adoption of a type of individual paper-based substrate, herein, we describe for the first time the development of a two-dimensional merged paper-based device for electrochemical copper ion detection in serum. In this work, we report a novel configuration to produce an integrated all-in-one electrochemical device, in which no additional working medium has to be added by the end user and the sensitivity can be tuned by rapid preconcentration on porous paper, with the advantage of making the platform adaptable to real matrix scenarios. The novel architecture has been obtained by combining office paper to screen-print a sustainable and robust electrochemical strip and a chromatographic disk to (1) store the reagents, (2) collect real samples, and (3) preconcentrate the analyte of interest. The novel sensing platform has allowed us to obtain a detection limit for copper ions down to 4 ppb in all the solutions that have been investigated, namely, standard solutions and serum, and a repeatability of ca. 10% has been obtained. Inductively coupled plasma-mass spectrometry measurements confirmed the satisfactory correlation.

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