The agriculture and horticulture industries generate many by-products while processing commodities, leading to significant environmental and societal dilemmas. Bioactive compounds obtained from by-products of plants are also known as ingredients in traditional medicines and the food industry due to their potential health benefits for humans as antioxidant, anti-inflammatory, and antimicrobial agents. On the other hand, an extensive array of colorants from natural sources has been scrutinized recently in different sectors to mitigate the negative ecological impacts of synthetic dyes, especially in modern textile manufacturing. Approaching these matters, this paper reviews various chemical compositions of plant secondary metabolites, including flavonoids, tannins, phenolic acids, essential oils, tulipalins, and factors that influence the isolation process. Moreover, the article offers an updated view of the advanced technologies for extraction, focusing on eco-friendly solvents such as water, supercritical carbon dioxide, and deep eutectic solvents. Eventually, a comparison of different extraction methods is highlighted to devise the most appropriate strategy for industries. Graphical abstract

The purpose of this study was to elucidate the structures and functional properties of tannin- and lignin-derived nano- and microparticles and the coatings prepared from them. Nanoparticles prepared from technical lignins and water-insoluble tannin obtained from softwood bark showed large differences in the suspension testing of antibacterial efficacy against methicillin-resistant Staphylococcus aureus (MRSA) bacteria. A common factor among the most effective lignin nanoparticles was a relatively low molar mass of the lignin, but that alone did not guarantee high efficacy. Tannin nanoparticles showed good antibacterial activity both in suspension testing and as coatings applied onto cellulose. The nanoparticles of nitrogen-modified tannin and the small microparticles of nitrogen-modified kraft lignin exhibited promising flame-retardant parameters when applied as coatings on cellulose. These results illustrate the potential of nano- and microsized particles of unmodified and chemically modified polyphenols to provide functional coatings to cellulosic substrates for environments and applications with high hygiene and fire safety requirements.

This study examined how plant residues from Norway maple (Acer platanoides) and silver birch (Betula pendula), and extraction conditions, affect polyphenol recovery, considering their antimicrobial potential. Three extraction methods were conducted in this study: Hot Solvent Extraction (HSE), Autoclave Extraction (AE), and Subcritical Acidified Water Extraction (SAWE). Extraction efficiency was evaluated by determining total phenolic content (TPC), total flavonoid content (TFC), and antimicrobial activity against Staphylococcus aureus. Principal Component Analysis (PCA) was further applied to explore the relationships between process parameters and extract properties. Although extraction yield generally increased with temperature and pressure, TPC and TFC did not follow the same trend, indicating that phenolic recovery was governed not only by process severity but also by extraction mechanisms and operating conditions. Maple leaf extracts consistently exhibited higher phenolic and flavonoid contents than birch leaf extracts. The highest TPC and TFC values for maple leaves were achieved using HSE, which reached 346.8 ± 4.8 mg GAE g⁻¹ DE and 110 ± 2.5 mg CE g⁻¹ DE, respectively. In contrast, the lowest values were observed under SAWE at 120 °C. PCA and correlation analyses revealed a strong association between TPC and antimicrobial activity. Maple extracts exhibited markedly stronger inhibition of S. aureus than birch extracts, with the highest antibacterial activity observed for SAWE extracts produced at 120–160 °C and 40 bar, followed by a decline at 180 °C.