Aromatic and medicinal raw plant materials and their derivatives: evaluation of potential biological activities by bio-guided fractionation approaches

Aromatic and medicinal plants are a rich source of bioactive compounds, including essential oils (EOs), complex mixtures of volatile metabolites with promising applications in the pharmaceutical, food, and cosmetic sectors. This PhD project aimed to investigate the biological activities of EOs through a bio-guided fractionation approach integrating chemical characterization (GC-FID and GC-MS), in vitro bioassays, fractionation, evaluation of pure compounds, cell-based studies, and application-oriented investigations. The first part of the project focused on the inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), two key therapeutic targets in Alzheimer's disease. Fifty-nine EOs from twenty botanical families were chemically characterized and screened for inhibitory activity. Most EOs were active against at least one enzyme, showing marked selectivity. EOs rich in 1,8-cineole exhibited the strongest AChE inhibition, which was mainly attributable to this compound. In contrast, cardamom EO showed dual AChE/BChE inhibitory activity. Bio-guided fractionation demonstrated that its oxygenated fraction was responsible for the activity, while further investigations revealed that the overall inhibitory effect resulted from the combined contribution of major and minor constituents. A similar synergistic behaviour was observed for peppermint EO, whose BChE inhibitory activity depended on the interaction between principal and minor compounds. Preliminary studies on neuronal cell lines confirmed the inhibitory potential of both cardamom and peppermint EOs while demonstrating a favourable safety profile at the tested concentrations. A second study investigated the EO of Lippia origanoides Kunth as a multitarget agent for type 2 diabetes and Alzheimer's disease. The EO exhibited inhibitory activity against AChE, BChE, α-glucosidase, lipase, and tyrosinase, together with significant antioxidant activity. Although carvacrol was identified as the major constituent, it was unable to fully explain the biological activity of the whole EO. Bio-guided fractionation demonstrated that both the oxygenated and hydrocarbon fractions contributed to the overall activity, highlighting the importance of synergistic interactions within the phytocomplex. The potential application of EOs as natural food preservatives was also investigated. Among the tested samples, Origanum vulgare EO displayed the strongest antimicrobial activity against microorganisms associated with tomato sauce spoilage. The oxygenated fraction was identified as the main contributor to the antimicrobial effect, while microencapsulation successfully preserved EO activity during storage, allowing effective microbial control at lower concentrations and reducing potential sensory impact. Finally, a pullulan-based film containing an EO blend was developed for the topical treatment of acne vulgaris. The formulation showed bactericidal activity against Cutibacterium acnes and Staphylococcus aureus, while preserving the commensal Staphylococcus epidermidis, thus supporting skin microbiota balance. The functionalized film retained antimicrobial activity after incorporation of the EO blend and exhibited physicochemical properties suitable for topical applications. Overall, this work demonstrates that essential oils act as multitarget phytocomplexes whose biological activities arise from the cooperative interaction of multiple constituents rather than from a single dominant compound. The bio-guided fractionation strategy proved to be an effective tool for identifying the compounds responsible for biological activity and elucidating their interactions, providing a solid foundation for the development of innovative EO-based applications in the pharmaceutical, food, and cosmetic fields