Lamiaceae extracts as a source of phytochemicals with promissory antioxidant properties
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resumo
Plant extracts have been used over years due to their marked healing properties. Primitive societies
used them not only as botanical preparations for therapeutic uses, but also as prophylaxis and for
psychological effects. Despite the recognized millenary health evidences, numerous phytochemicals
responsible for those benefits remain unknown. Among the heterogeneous group of secondary
metabolites, phenolic compounds have been pointed out as relevant bioactive phytochemicals [1-3].
Furthermore, the culinary uses of different plant species associated to their biological activities
highlight them as potential functional foods.
The aim of the present work was to evaluate the antioxidant potential of aqueous (infusion and
decoction) and methanol/water (80:20, v/v) extracts of three Lamiaceae plant species used with
culinary and medicinal purposes, Origanum vulgare L. (oregano), Thymus vulgaris L. (thyme) and
Salvia officinalis L. (sage), and to relate it with the phenolic profile assessed by HPLC-DADESI/
MS.
In general, aqueous extracts evidenced the highest antioxidant potential (lipid peroxidation inhibition
free radicals scavenging activity and reducing power). This potential seems to be related with the
abundance in phenolic compounds, once sage that showed the highest antioxidant activity, also gave
the highest concentration both in phenolic acid derivatives and flavonoids, followed by thyme and
oregano.
In all the studied samples, rosmarinic acid and luteolin derivatives (especially luteolin 7-Oglucuronide
and luteolin 7-O-glucoside) were the most abundant phenolic acid derivatives and
flavonoids, respectively. Other abundant phenolic compounds present in these matrices were
apigenin derivatives (in oregano and sage), hesperetin and eriodictyol derivatives (in thyme),
hispidulin glucuronide (in sage), caffeic acid dimers, trimers and tetramers (in sage), and lithospermic
acid A (a caffeic acid tetramer), quercetin and kaempferol derivatives (in oregano and thyme).
Overall, flavonoids followed by phenolic acid derivatives were the classes involved in the antioxidant
potential of the tested Lamiaceae extracts. These species might be used as functional foods, but more
studies are necessary in order to elucidate the mechanisms of action involved, as well as the
bioavailability of the different phenolic compounds and related metabolic pathways.
