Phenolic compounds in decoction, infusion and hydroalcoholic extract of cultivated thyme (Thymus vulgaris L.) with bioactive properties
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resumo
The use of medicinal plants as prevention or treatment of various conditions has, recently, sparked an increasing
interest for scientific researchers that have been studying their biological properties [1]. Thymus vulgaris L. can
provide a wide source of biomolecules, such phenolic compounds that have been referred to as antioxidants [2] and
antimicrobials [3]. Several studies report chemical composition and antioxidant properties of thyme, but mostly of
essential oils [4,5].
In the present work, the bioactive properties of decoction, infusion and hydroalcoholic extracts of cultivated thyme
were evaluated, and further characterized in terms of phenolic composition. The antioxidant activity was assessed by
four in vitro assays: reducing power, free radicals scavenging activity, beta-carotene bleaching inhibition and lipid
peroxidation inhibition in brain cell homogenates. Antimicrobial activity was assessed against gram-positive
(Staphylococcus aureus and Staphylococcus epidermidis) and gram-negative (Escherichia coli, Klebsiella spp.,
Pseudomonas aeruginosa, Enterococcus aerogenes, Proteus vulgaris and Enterobacter sakazaki1) bacteria was also
evaluated. Phenolic compounds characterization was performed by HPLC-DAD-ESI/MS.
The decoction showed the highest concentration in phenolic compounds (either phenolic acids or flavonoids),
followed by infusion and hydroalcoholic extract. In general, the samples were effective against gram-positive and
gram-negative bacteria, although decoction presented the most pronounced effect. This sample also gave the highest
radical scavenging activity and reducing power. Rosmarinic acid (in all the preparations), luteolin 7-0-glucoside (in the
hydroalcoholic extract) and luteolin 7 -0-glucuronide (in the infusion and decoction) were the main phenolic acid and
flavonoid, respectively. The results obtained support the idea that compounds with strong antioxidant and antibacterial
activities are also water-soluble. Furthermore, the use of infusion and decoction of thyme, by both internal and
external use, at recommended doses, is safe and no adverse reactions have been described.
