Moving toward a more sustainable development, a pivotal role is played by circular economy and a smarter waste management. Industrial wastes from plants offer a wide spectrum of possibilities for their valorization, still being enriched in high added-value molecules, such as secondary metabolites (SMs). The current review provides an overview of the most common SM classes (chemical structures, classification, biological activities) present in different plant waste/by-products and their potential use in various fields. A bibliographic survey was carried out, taking into account 99 research articles (from 2006 to 2020), summarizing all the information about waste type, its plant source, industrial sector of provenience, contained SMs, reported bioactivities, and proposals for its valorization. This survey highlighted that a great deal of the current publications are focused on the exploitation of plant wastes in human healthcare and food (including cosmetic, pharmaceutical, nutraceutical and food additives). However, as summarized in this review, plant SMs also possess an enormous potential for further uses. Accordingly, an increasing number of investigations on neglected plant matrices and their use in areas such as veterinary science or agriculture are expected, considering also the need to implement “greener” practices in the latter sector.

Castanea sativa cultivation has been present in Mediterranean regions since ancient times. In order to promote a circular economy, it is of great importance to valorize chestnut groves’ by-products. In this study, leaves and spiny burs from twenty-four Castanea trees were analyzed by ¹H NMR metabolomics to provide an overview of their phytochemical profile. The Orthogonal Projections to Latent Structures Discriminant Analysis (OPLS-DA) performed on these data allowed us to distinguish ‘Marrone’ from ‘Castagna’, since the latter were generally more enriched with secondary metabolites, in particular, flavonoids (astragalin, isorhamnetin glucoside, and myricitrin) were dominant. Knowing that microglia are involved in mediating the oxidative and inflammatory response of the central nervous system, the potential anti-inflammatory effects of extracts derived from leaves and spiny burs were evaluated in a neuroinflammatory cell model: BV-2 microglia cells. The tested extracts showed cytoprotective activity (at 0.1 and 0.5 mg/mL) after inflammation induction by 5 µg/mL lipopolysaccharide (LPS). In addition, the transcriptional levels of IL-1β, TNF-α, and NF-kB expression induced by LPS were significantly decreased by cell incubation with spiny burs and leaves extracts. Taken together, the obtained results are promising and represent an important step to encourage recycling and valorization of chestnut byproducts, usually considered “waste”.

Valorization of wild plants to obtain botanical ingredients could be a strategy for sustainable production of cosmetics. This study aimed to select the rosehip extract containing the greatest amounts of bioactive compounds and to encapsulate it in vesicular systems capable of protecting their own antioxidant activity. Chemical analysis of Rosa canina L. extracts was performed by LC-DAD-MS/MS and ¹H-NMR and vitamins, phenolic compounds, sugars, and organic acids were detected as the main compounds of the extracts. Liposomes, prepared by the film hydration method, together with hyalurosomes and ethosomes, obtained by the ethanol injection method, were characterized in terms of vesicle size, polydispersity index, entrapment efficiency, zeta potential, in vitro release and biocompatibility on WS1 fibroblasts. Among all types of vesicular systems, ethosomes proved to be the most promising nanocarriers showing nanometric size (196 ± 1 nm), narrow polydispersity (0.20 ± 0.02), good entrapment efficiency (92.30 ± 0.02%), and negative zeta potential (−37.36 ± 0.55 mV). Moreover, ethosomes showed good stability over time, a slow release of polyphenols compared with free extract, and they were not cytotoxic. In conclusion, ethosomes could be innovative carriers for the encapsulation of rosehip extract.

The antioxidant activity of supercritical CO2 extracts of H.\ud italicum dried flower heads derived from the commercial drug\ud and from plants grown in different areas of north-east Italy\ud with different culturing conditions was determined. In particular,\ud the characterization of the antioxidant activity was made by the DPPH and b-carotene bleaching test methods. The four kind of H. italicum extracts were also tested for their ability to scavenger superoxide radicals. All extracts showed, although with different importance, an antioxidant activity with all the methods performed. The supercritical extracts obtained from commercial dried H. italicum flower heads and from dried flower heads belonging to wild plants exhibited the highest activity. These results established H. italicum supercritical extracts as important antioxidant solvent-free matrices in alimentary (i.e., dietary, nutraceutical, flavouring) and cosmetic fields, as well as the value of coastal Mediterranean areas to serve as an exploitable source of important plant matrices

Alkaloids present in plants of the Amaryllidaceae family are secondary metabolites of high biological interest, possessing a wide range of pharmacological activities. In the search for new plant-derived compounds with antimicrobial activities, two alkaloid extracts obtained from bulbs and leaves of Pancratium illyricum L., a plant of the Amarillydaceae family, were tested for their effect on bacterial and yeast growth. The broth microdilution susceptibility test was applied to study the effect of plant extracts on the growth of reference bacterial strains and Candida albicans reference and clinical isolates strains. Extracts obtained from the different parts of the plant were tested and compared with the pure components identified in the extracts. Since matrix metalloproteinase enzymes play a role in the dissemination process of Candida albicans, the effect of the bulb extract and pure alkaloids on in vitro collagenase activity was tested. Cell viability test was carried out on human embryo lung fibroblasts (HEL 299). Whilst both extracts did not show any inhibitory activity against neither Gram positive nor Gram negative bacteria, a strong antifungal activity was detected, in particular for the bulb extract. All clinical isolates were susceptible to the growth inhibitory activity of the bulb extract, with endpoint IC50 values ranging from 1.22 to 78 μg/mL. The pure alkaloids lycorine and vittatine, identified as components of the extract, were also assayed for their capacity of inhibiting the yeast growth, and lycorine turned very active, with endpoint IC50 values ranging from 0.89 to 28.5 μg/mL. A potent inhibition of the in vitro collagenase activity was found in the presence of the bulb extract, and this effect was much higher than that exerted by the pure alkaloids. Viability of cell lines tested was not affected by the extract. Taken together, results suggest that the extract of Pancratium illyricum may act as antifungal agent both directly on the yeast growth and by altering the tissue invasion process.