Phenolic compounds (PCs) are widespread secondary metabolites with potent biological activity. Their sources are mainly plants from cultivated and natural states, providing valuable protective and health-promoting extracts. The wide biological activity of PCs (antioxidant, anti-inflammatory, antimicrobial, antiatherosclerotic, antidiabetic, antiallergic, prebiotic, antimutagenic) means that new sources of PCs are constantly being sought, as exemplified by extracting these compounds from tissue culture or agricultural by-products. Plant phenols show marked qualitative and quantitative variation not only at different genetic levels (between and within species and clones) but also between different physiological and developmental stages. Assessing genetic and seasonal variations in phenolic content and activity allows for selecting the best time to harvest the plant. Learning about the causes of PCs’ variability and putting this knowledge into practice can significantly increase PCs’ yields and extract the most valuable compounds. The health-promoting properties resulting from consuming products rich in plant PCs are undeniable, so it is worth promoting high-phenolic products as a regular diet. This paper presents an overview of different sources of PCs for use as potential therapeutic alternatives. Additionally, factors of variation in the phenolic complex at the genome and ontogeny levels, relevant in practical terms and as a basis for further scientific research, are presented.

Fresh fruit and vegetables are highly utilized commodities by health-conscious consumers and represent a prominent segment in the functional and nutritional food sector. However, food processing is causing significant loss of nutritional components, and the generation of waste is creating serious economic and environmental problems. Fruit and vegetables encompass husk, peels, pods, pomace, seeds, and stems, which are usually discarded, despite being known to contain potentially beneficial compounds, such as carotenoids, dietary fibers, enzymes, and polyphenols. The emerging interest in the food industry in the nutritional and biofunctional constituents of polyphenols has prompted the utilization of fruit and vegetable waste for developing enriched and functional foods, with applications in the pharmaceutical industry. Moreover, the utilization of waste for developing diverse and crucial bioactive commodities is a fundamental step in sustainable development. Furthermore, it provides evidence regarding the applicability of fruit and vegetable waste in different food formulations especially bakery, jam, and meat based products.

Medicinal aromatic plants (MAPs) are a rich and diverse source of traditional and modern medicines. Aromatic plants contain valuable essential oils that exhibit numerous biological activities. Essential oils are used in pharmaceutical production, cosmetics, and food preservation to ensure the microbiological stability of products. Plants from the Lamiaceae family, including Origanum vulgare L., are a source of raw materials with antimicrobial and antioxidant properties, and they can be utilized in the production of new drugs and other bioproducts. Oregano is an example of a plant with great potential, known for its traditional health-related and culinary applications and its growing significance in the production of medicines, cosmetics, antiseptics, and preservatives. This work aims to consolidate the current research results on the occurrence, acquisition, use, and medicinal and dietary value of common oregano and oregano essential oil. The obtained results indicate that oregano is a valuable medicinal and culinary plant, serving as a source of natural antiseptics and protective agents. Oregano essential oil, rich in thymol and carvacrol, has a number of health-promoting properties. These compounds (also present in extracts) exhibit significant antioxidant, anti-inflammatory, antiangiogenic, anticancer, and antimicrobial activities. The research findings highlight the promising role of these compounds as potential structures in the search for new antimicrobial and antibiofilm agents.

Antimicrobial resistance (AMR) is a global public health problem, and the rapid rise in AMR is attributed to the inappropriate and/or overuse of antibiotics. Therefore, alternative antimicrobial agents, including those of natural origin, are being sought for the development of new drugs. The purpose of our study was to analyze the chemical composition, and antimicrobial and antioxidant activities of four oregano essential oils (OEOs) from Poland, Europe, Turkey and the USA. The antimicrobial activity (AMA) was evaluated using 23 strains, including Gram-positive bacteria, Gram-negative bacteria and Candida species. The antioxidant activity (AA) of essential oils (EOs) was determined by the DPPH method. The main component of the EOs tested was carvacrol (76.64–85.70%). The highest amount of this compound was determined in the Polish OEO. The OEOs we tested showed antimicrobial resistance, which was especially strong against fungi (MIC = 0.06–0.25 mg/mL⁻¹). These products also showed high AA (71.42–80.44%). OEOs high in carvacrol should be the subject of further research as potential antimicrobial and antioxidant agents.

Currently, the potential utilization of fruits and vegetable waste as a source of micronutrients and antioxidants has increased. The present study, therefore, aimed to determine the antimicrobial and anti-inflammatory activities of Citrus nobilis peel extract. A modified solvent evaporation technique was employed for peel extract preparation. For effective utilization of the natural product, quantitative analysis of phenolic compounds was carried out using liquid chromatography and mass spectroscopy technique. Phenolic and flavonoids were present in high amounts, while β-carotene and lycopene were present in vestigial amounts. The antimicrobial efficiency of peel extract was evaluated against four bacterial strains including Staphylococcus aureus (MTCC 3160), Klebsiella pneumoniae (MTCC 3384), Pseudomonas aeruginosa (MTCC 2295), and Salmonella typhimurium (MTCC 1254), and one fungal strain Candida albicans (MTCC 183), and zone of inhibition was comparable to the positive control streptomycin and amphotericin B, respectively. The extract of Citrus nobilis peels showed effective anti-inflammatory activity during human red blood cell membrane stabilization (HRBC) and albumin denaturation assay. The extracts also exhibited 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity ranging from 53.46 to 81.13%. Therefore, the obtained results suggest that Citrus nobilis peel could be used as an excellent source of polyphenols and transformed into value-added products.

The herbal material of Coriandrum sativum is the fruit. Fresh herb is also used as an aromatic spice. The aim of the present study was to evaluate the content and chemical composition of coriander herb obtained at different plant growth stages. Coriander plants were grown in a glasshouse, the herb was harvested at the initial stage of flowering and from regrowing shoots. Essential oil extraction from the herb was performed by the hydrodistillation method, whereas the assessment of the chemical composition – using GC-MS method. The examined material contained 0.17–0.29 ml × 100g-1 of essential oil, depending on the stage of plant development when the harvest was done. 61 (generative phase) and 65 (vegetative phase) compounds were found in the examined coriander oil. The essential oil from the coriander herb contained the highest amount of aliphatic aldehydes, among which was decanal, E-2-dodecanol and E-2-decenol had the highest percentages. The contents of most aliphatic aldehydes decreased with each subsequent harvest of the herb. In addition to the above-mentioned aliphatic aldehydes, the presence of linalool, phytol, and oleic acid was found in the essential oil extracted from the coriander herb.