Chitosan is a cationic natural polysaccharide, which has emerged as an increasingly interesting biomaterialover the past few years. It constitutes a novel perspective in drug delivery systems and nanocarriers’ formulations due to its beneficial properties, including biocompatibility, biodegradability and low toxicity. The potentiality of chemical or enzymatic modifications of the biopolymer, as well as its complementary use with other polymers, further attract the scientific community, offering improved and combined properties in the final materials. As a result, chitosan has been extensively used as a matrix for the encapsulation of several valuable compounds. In this review article, the advantageous character of chitosan as a matrix for nanosystemsis presented, focusing on the encapsulation of natural products. A five-year literature review is attempted covering the use of chitosan and modified chitosan as matrices and coatings for the encapsulation of natural extracts, essential oils or pure naturally occurring bioactive compounds are discussed.

Aurones are minor flavonoids that possess a wide variety of bioactivity, including antioxidant, anticancer, and enzyme inhibitory activity. L-proline-based natural deep eutectic solvents (NaDES) were synthesized and applied as solvents and catalysts for the Knoevenagel condensation reaction between benzofuranone and substituted benzaldehydes to produce aurones in high yields and purity. The reaction between benzofuranone and vanillin served as the model reaction. After screening three NaDESs, and testing microwave, as well as ultrasound as energy sources, we concluded that the optimum results are obtained using L-proline/glycerol 1:2 as catalyst and solvent and ultrasound irradiation. The scope of the reaction was evaluated using a variety of benzaldehydes, and the corresponding aurones were obtained in moderate to satisfactory yields (57–89%) and high purity. An important additional feature of the described methodology is the recyclability and reusability of the NaDES, which was recycled and effectively reused after 6 cycles.

2′-hydroxy-chalcones are naturally occurring compounds with a wide array of bioactivity. In an effort to delineate the structural features that favor antioxidant and lipoxygenase (LOX) inhibitory activity, the design, synthesis, and bioactivity profile of a series of 2′-hydroxy-chalcones bearing diverse substituents on rings A and B, are presented. Among all the synthesized derivatives, chalcone 4b, bearing two hydroxyl substituents on ring B, was found to possess the best combined activity (82.4% DPPH radical scavenging ability, 82.3% inhibition of lipid peroxidation, and satisfactory LOX inhibition value (IC₅₀ = 70 μM). Chalcone 3c, possessing a methoxymethylene substituent on ring A, and three methoxy groups on ring B, exhibited the most promising LOX inhibitory activity (IC₅₀ = 45 μM). A combination of in silico techniques were utilized in an effort to explore the crucial binding characteristics of the most active compound 3c and its analogue 3b, to LOX. A common H-bond interaction pattern, orienting the hydroxyl and carbonyl groups of the aromatic ring A towards Asp768 and Asn128, respectively, was observed. Regarding the analogue 3c, the bulky (-OMOM) group does not seem to participate in a direct binding, but it induces an orientation capable to form H-bonds between the methoxy groups of the aromatic ring B with Trp130 and Gly247.

The extraction of valuable phytochemicals from natural sources is an important and constantly evolving research area. Zingiber officinale Roscoe (ginger) contains high amounts of bioactive phytochemicals, which are desirable due to their significant properties. In this work, the ability of different natural deep eutectic solvents (NaDESs) to serve as green solvents for the preparation of high added value extracts from ginger is explored, in combination with ultrasound assisted extraction. The method was optimized by applying a response surface methodology using the NaDES Bet/La/W (1:2:2.5). Three independent variables, namely the extraction time, ultrasound power and NaDES-to-dry-ginger ratio, were investigated by employing a 17-run three-level Box–Behnken Design (BBD) in order to study the correlation between the extraction conditions and the quality of the obtained extracts. The optimum conditions (in order to achieve simultaneously maximum total phenolic content and antioxidant activity), were found to be 23.8 min extraction time, 60 Watt and NaDES/ginger 25:1 w/w. In the optimum conditions the DPPH radical scavenging ability of the extracts was found to reach IC₅₀ = 18.16 mg/mL after 120 min, whereas the TPC was 20.10 ± 0.26 mg GAE/g of dry ginger. The green methodology was also compared with the extraction using conventional solvents. All the obtained extracts were evaluated for their antioxidant activity and their total phenolic content, while the extract derived by the optimum extraction conditions was further investigated for its ability to bind to calf thymus DNA (ctDNA).

In this work, the privileged scaffold of 4-hydroxy-2quinolinone is investigated through the synthesis of carboxamides and hybrid derivatives, as well as through their bioactivity evaluation, focusing on the ability of the molecules to inhibit the soybean LOX, as an indication of their anti-inflammatory activity. Twenty-one quinolinone carboxamides, seven novel hybrid compounds consisting of the quinolinone moiety and selected cinnamic or benzoic acid derivatives, as well as three reverse amides are synthesized and classified as multi-target agents according to their LOX inhibitory and antioxidant activity. Among all the synthesized analogues, quinolinone–carboxamide compounds 3h and 3s, which are introduced for the first time in the literature, exhibited the best LOX inhibitory activity (IC₅₀ = 10 μM). Furthermore, carboxamide 3g and quinolinone hybrid with acetylated ferulic acid 11e emerged as multi-target agents, revealing combined antioxidant and LOX inhibitory activity (3g: IC₅₀ = 27.5 μM for LOX inhibition, 100% inhibition of lipid peroxidation, 67.7% ability to scavenge hydroxyl radicals and 72.4% in the ABTS radical cation decolorization assay; 11e: IC₅₀ = 52 μM for LOX inhibition and 97% inhibition of lipid peroxidation). The in silico docking results revealed that the synthetic carboxamide analogues 3h and 3s and NDGA (the reference compound) bind at the same alternative binding site in a similar binding mode.

Flavanones and their biochemical precursors, chalcones, are naturally occurring compounds and consist of privileged scaffolds used in drug discovery due to their wide range of biological activities. In this work, two novel flavanones (3 and 4), the arylidene flavanone 5, and the chalcone 6, displaying structural analogies with butylated hydroxytoluene (BHT), were synthesized via an aldol reaction. According to the antioxidant activity studies of the synthesized flavanones, the arylidene flavanone 5 was the most potent antioxidant (70.8% interaction with DPPH radical and 77.4% inhibition of lipid peroxidation). In addition, the ability of the synthesized compounds to bind with ctDNA was measured via UV-spectroscopy, revealing that chalcone 6 has the strongest interaction with DNA (K_b = 5.0 $\times$ 10⁻³ M⁻¹), while molecular docking was exploited to simulate the compound-DNA complexes. In an effort to explore the conformational features of the novel synthetic flavanones (3 and 4), arylidene flavanone 5, and chalcone 6, theoretical calculations were applied and the calculation of their physicochemical properties was also performed.