From folk-medicine to the laboratory: a multidisciplinary study approach on Agrimonia eupatoria L. collected in Valle Imagna (BG, North of Italy)

Between November 2021 and November 2022, an ethnobotanical investigation was conducted through open interviews in Valle Imagna (BG, North of Italy) on different fields of use (medicinal, food, veterinary, domestic, etc.) and involving a total of 109 local informants (20-96 years old). Concerning the therapeutic field, which was among the most relevant, the most treated pathologies were related to skin diseases and traumas. In this category, Agrimonia eupatoria L. (Rosaceae) was noteworthy as anti-inflammatory and wound healing agent for the external treatment of wounds and cuts. Its leaves were directly placed on the wound or infused in water for the application of compresses of the herbal tea, specifically for wounds that were ‘hard to treat otherwise’. The use of this species was recollected only by some of the elderly people interviewed and the plant itself was known only by its vernacular name (Erba del Vinil). The bond with the territory prompted us to choose this species for further laboratory investigations. First, extensive bibliographic research highlighted that this plant has been little studied from a micromorphological point of view (1). Therefore, leaf samples from fresh plants were collected in loco in August 2022 and July 2023, fixed and subjected to the standard procedures for the observations under Scanning Electron and Light Microscopy. Concerning the glandular indumentum two trichomes morphotypes were observed: capitate with 1-celled rounded head and 2-celled capitate with cylindrical head, consistent with Type I and Type II hairs described in other subspecies of different origin (1). Furthermore, we observed two types of non-glandular hairs, already described in the nominal species: curved trichomes and straight trichomes of variable length forming variable angles with respect to the epidermis. The histochemical investigation proved that both capitates were responsible for the production of terpenes; the cylindrical capitates also positively responded to polyphenols. Regarding the phytochemical investigation, we followed the field and bibliographic data collected and we decided to perform investigations on epicuticular depositions on the leaves’ surface and on infusion and decoction-like preparations. Samples of leaves and whole epigeal parts of A. eupatoria were collected in loco in July 2023 and dried in a cool and aerated place. The characterization of phenolic compounds was carried out by means of liquid chromatography and mass spectrometry (LC-ESI-MS/MS) on 2 epicuticular extracts (water at 35°C, water at 100°C) and on 4 tissue extracts (infusion and decoction of leaves and whole plants). From this analysis, a total of 34 molecules was identified. Specifically, Luteolin 7-O-glucoside, Catechin, and Epicatechin were common to all the 6 extracts. Bibliographic research highlighted the potential correlation between some of these molecules and anti-inflammatory and wound healing activities (2,3). Additionally, we performed analyses through gas chromatography and mass spectrometry (GC-MS) on an acetonic epicuticular extract from leaves of the same harvest batch to investigate the apolar fraction. A total of 37 compounds was identified. Among these, 4 sesquiterpenoids (2-Methyl-β-ionone; Hedycaryol; 2,4,4-Trimethyl-3-(3-oxobutyl)cyclohex-2-enone; Zerumbone) and 2 diterpenoids (1-Naphthalenepropanol, α-ethenyldecahydro-α,5,5,8a-tetramethyl-2-methylene-, [1S-[1α(S*),4aβ,8aα]]-; Methyl levopimarate). Further phytochemical investigations on the VOCs produced and excreted by fresh leaves, as well as a survey on tradition-related biological activities are currently in progress. Although preliminary, these results hold a particular interest specifically because of the strong bond with the traditional use of agrimony described in Valle Imagna.