By-products from medicinal and aromatic plants: from tradition to innovation

The Ph.D. project focused on characterizing selected species of medicinal and aromatic plants (MAPs) and valorisation of their bioactive compounds for health or environmental applications. Specifically, the objective was to utilize parts of plants typically considered waste: 1) the aerial part of a medicinal plant (Peucedanum), traditionally known for its roots/rhizomes’ medicinal properties; 2) the less valuable fronds of an aromatic plant (Eucalyptus), a species recently cultivated for ornamental purposes as well. The goal was to bridge traditional historical uses with new applications, emphasizing the recovery of waste material that remains a rich source of compounds with significant biological activities and potential uses across various sectors. 1) The first topic of the project was the study of the species Peucedaum ostruthium (L.) W.D.J. Koch (Apiaceae), selected among the alpine medicinal plants documented in ethnobotanical research conducted in the Aosta Valley side of the Gran Paradiso National Park. It was investigated from micromorphological, phytochemical, and pharmacological perspectives. The antioxidant and anti-inflammatory properties, inhibitory activities against enzymes involved in the skin's extracellular matrix degradation, and cicatrizing abilities of hydroalcoholic extracts obtained from both rhizomes and leaves were evaluated. Tests, conducted through cell-free enzymatic techniques and in vitro cell cultures, were aimed at scientifically validating the medicinal properties reported in traditional medicine. The rhizomes of P. ostruthium have a long tradition of medicinal use and have been known as 'Divinum remedium' since the 18th century, considered a panacea for various ailments. They were included in the BELFRIT list (2018) for regulating digestive function, bronchial secretion fluidity, and as a tonic for relieving physical and mental fatigue. Additionally, in the Aosta Valley (Italy), leaves are claimed to treat skin diseases (such as wounds, infections, and insect bites), muscular inflammations, and hematomas. Scientific validation of the traditional uses of both parts of the plant is crucial for incorporating their extracts into new herbal medicinal products. Moreover, collected data suggest the potential dermatologic use of the leaves of this species, which represent a considerable biomass currently underexploited or not exploited at all. 2) The second main topic of this project concerned the valorisation of by-products obtained from several Eucalyptus species (Myrtaceae). The cultivation of Eucalyptus is widespread globally and has been increasingly extended to Italy. Particularly in Liguria, several Eucalyptus species are cultivated for their foliage, which is cut and sold in Northern Europe for floral compositions. Eucalyptus plantations undergo constant pruning to maintain the production of juvenile branches that are more suitable for the market. Consequently, floriculture generates large volumes of waste biomass annually, mainly consisting of pruned fronds that are typically burned or buried for disposal. However, this by-product retains rich bioactive compounds that could be recovered and used in the organic farming sector. The leaves of E. gunnii Hook.f., E. pulverulenta Sims cv 'Baby blue' E. cinerea F. Muell. Ex Benth, and E. nicholii Maiden and Blakely were micromorphologically characterized, and their essential oils (EOs) were phytochemically evaluated. Subsequently, these EOs were tested for their phytotoxic and antimicrobial activities to evaluate their potential use as bioherbicides and biocontrollers. In addition, a review was conducted to evaluate the potential activities of the Eucalyptus EOs as repellents, insecticides, and acaricides, with applications in human and animal health, food storage, and crop protection sectors. Essential oils represent valuable alternatives to synthetic herbicides and pest controllers, being biodegradable and safe for humans and the environment. From this perspective, utilizing these waste biomasses aligns with the principles of the circular economy.