Abstract
The aim of this study was to quantify the levels of flavonoids (rutin, myricetin, quercetin, kaempferol) and phenolic acids (gallic, p-coumaric, rosmarinic, syringic, caffeic, chlorogenic, ellagic, ferulic) in lemon balm (Melissa officinalis L.) commonly used as a culinary, aromatic and medicinal herb. A rapid and reliable HPLC procedure was developed to determine the phenolic compounds in methanolic extracts, infusions and tinctures prepared from lemon balm. Except for myricetin and quercetin, as well as ellagic, gallic and rosmarinic acids, higher levels of the analytes under study were determined in the methanolic extracts (up to 22 mg/g of dry weight, DW), than in infusions (up to 5 mg/g DW). Tinctures were the poorest in flavonoids and phenolic acids (below 550 μg/g DW), except for ellagic and rosmarinic acids, which were quantified in tinctures at higher levels (mg/g DW). To sum up, the flavonoids were extracted more effectively in the infusions and tinctures than the phenolic acids. Statistically significant correlations were found between phenolic acids, possibly owing to similar biochemical pathways of the compounds. The hierarchical cluster and principal component analyses have also shown that the samples of lemon balm could be differentiated based on the levels of flavonoids and phenolic acids.