Antimicrobial and phytochemical analyses of European Larch resins and essential oils

Abstract

Malignant fungating wounds (MFW) affect 5 to 14% of oncology patients and to date there is no standard therapy to manage these wounds [1], [2]. Pinaceae resins have been investigated as promising wound healing agents [3] – Larix decidua resin has already been described for MFW treatment [4]. This study aimed to compare the non-volatile chemical composition of nine different Larch resins as well as their essential oil composition, using GC-MS, GC-FID and HPTLC as analytical tools. The antimicrobial potential was evaluated by agar diffusion test, using wound and skin bacterial strains. HPTLC results showed a similar qualitative profile for all resins. Using three different mobile phases, several diterpenes could be separated. The GC-MS confirmed the resinsʼ similarity, and 4 compounds were identified using authentic standards: larixyl acetate, isopimaric acid, abietic acid, and dehydroabietic acid. GC-FID analysis of the resinsʼ essential oils obtained by hydrodistillation revealed a consistent profile for all samples, allowing for the identification of alpha-pinene, beta-pinene and 3-carene, being alpha-pinene the major compound (825.3 – 896.7 µL/mL) in all oils. However, although the chemical profile was related in all samples, their antibacterial activity differed substantially. Results were promising for one essential oil (inhibition zones for all tested strains ~ 25 mm). Smaller inhibition zones were also seen for four other oils. In conclusion, our results showed that Larch resins from different manufacturers presented similar chemical profiles by HPTLC, GC-MS and GC-FID. Further investigation is ongoing to evaluate the biological activities and wound healing properties of Larix decidua from different harvest collections.