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Hesperidin and hesperetin are polyphenols that can be found predominantly in citrus fruits. They possess a variety of pharmacological properties such as neuroprotective and antidiabetic activity. However, the bioavailability of these compounds is limited due to low solubility and restricts their use as pro-healthy agents. This paper described the limitations resulting from the low bioavailability of the presented compounds and gathered the methods aiming at its improvement. Moreover, this work reviewed studies providing pieces of evidence for neuroprotective and antidiabetic properties of hesperidin and hesperetin as well as providing a detailed look into the significance of reported modes of action in chronic diseases. On account of a well-documented pro-healthy activity, it is important to look for ways to overcome the problem of poor bioavailability.

The nanostructure of poly(acrylic acid) (PAA) adsorption layer on the surface of mesoporous-activated carbon HPA obtained by physical activation of residue after supercritical extraction of hops was characterized. This characterization has been done based on the analysis of determination of adsorbed polymer amount, surface charge density, and zeta potential of solid particles (without and in the PAA presence). The SEM, thermogravimetric, FTIR, and MS techniques have allowed one to examine the solid surface morphology and specify different kinds of HPA surface groups. The effects of solution pH, as well as polymer molecular weight and concentration, were studied. The obtained results indicated that the highest adsorption on the activated carbon surface was exhibited by PAA with lower molecular weight (i.e., 2000 Da) at pH 3. Under such conditions, polymeric adsorption layer is composed of nanosized PAA coils (slightly negatively charged) which are densely packed on the positive surface of HPA. Additionally, the adsorption of polymeric macromolecules into solid pores is possible.

Residues after supercritical extraction of hops were chosen as activated bio-carbons precursor. The actual adsorbent was prepared by physical activation of the starting material. Some amount of the activated bio-carbon was divided into two parts. One of them was washed with distilled water, while the other part of the activated bio-carbon was washed first with a 5% solution of HCl and then with distilled water. The activated bio-carbons obtained were subjected to textural characterization and determination of pH and the content of surface oxygen groups. Carbonaceous adsorbents obtained were tested for removal of gas pollutant of acidic character (nitrogen dioxide) and liquid organic (methylene blue) and inorganic (iodine) pollutants. The maximum sorption capacity of the carbonaceous adsorbents towards iodine was 1395 mg/g, while towards methylene blue it was 238 mg/g. The results have shown that physical activation of the residue after supercritical extraction of hops is possible to be used as precursor of activated bio-carbons showing high adsorption capacity towards nitrogen dioxide reaching a maximum of 72.1 mg/g. The effectiveness of nitrogen dioxide removal depends on bio-carbons preparation and the conditions of adsorption.