The balm of Norway spruce (Picea abies (L.) H. Karst., Pinaceae) has been used in European folk medicine as a wound healing agent since centuries. Several clinical trials already examined its wound healing and antimicrobial properties confirming its empirical use. However, scientific data concerning the active constituents, their mode of action and the quantitative composition of this natural product are scarce.
This study therefore aimed at isolating and identifying constituents and examining potential positive effects on re-epithelialization. For isolation and structural elucidation of constituents preparative TLC, flash chromatography and HPLC-UV-DAD on normal phase and reversed phase material, as well as LC-MS, 1D- and 2D-NMR were employed. In vitro bioactivity was characterized in human keratinocytes (HaCaT): the resazurin conversion assay served to detect cytotoxicity of the compounds/extract; monitoring the closure of a gap in a confluent keratinocyte monolayer (scratch assay) revealed an influence of fractions/compounds on migration and proliferation and thus re-epithelialization.
Pure compounds from Norway spruce balm were isolated from an extract enriched in carboxylic acids and comprised several diterpenoid resin acids of the abietic-type and the pimaric-type, phenolic acids like coumaric acid, caffeic acid and ferulic acid, as well as a labdane type diterpene (abienol) and a lignan (pinoresinol).
The average non-toxic concentration range was determined between 0,1-10 µg/mL. The resin acids, abienol and pinoresinol were able to induce a significantly faster closure of the cell free area in the scratch assay compared to the vehicle control. The constituents showed an activity at concentrations of 0,3-3 µM (resin acids) and 3-30 µM (labdane diterpene and lignan).
Overall, this study provides first insight into the constituents of Norway spruce balm and their potential influence on re-epithelialization during the wound healing process.