Background. Phenolic compounds are secondary plant metabolites, which occur in different parts of cell, according to they lipophilicity. The objective of this study was to determine differences in the content and stability of those compounds in herbal extract fractions marked by increasing lipophilicity. Material and methods. Eight herbal plants were analysed: basil, savory, lovage, lemon balm, peppermint, parsley, oregano and sage. Extracts were prepared from fresh plants harvested in late July, and they were separated into aqueous fractions and isolated with a 40% and 70% methanol solution on Cl8 silica gel. The total content of phenolics was determined using the Folin-Ciocalteu method directly after preparation and after three and six months of storage. Results. The stability of fresh herb extracts varied subject to plant species. The lemon balm leaf extract was most abundant in phenolic compounds and showed the highest polyphenol concentrations throughout the storage period. The greatest drop in phenolic compound levels was observed in parsley extracts. Following the separation of raw extracts into three fractions, the highest phenolic compound concentrations were noted in fractions isolated with a 40% methanol solution. The most dynamic changes in polyphenol content were reported in the initial period of storage (three months) regardless of the fraction’s lipophilicity. Compounds that were not degraded after this period were marked by high stability. Conclusions. Phenolic compounds found in herbal plants are hydrophilic to lipophilic substances which are stable compounds regardless of their affinity for water.
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