Bioactive compounds in herbal infusions

Herbal teas are very popular and known as important source of biologically activecompounds. Some of popular Latvian herbal teas: Calendula (Calendula officinalis L.),Matricaria chamomilla (Matricaria chamomilla), Lady's-mantle (Alchemilla vulgaris L.),Jasmine (Jasminum officinale L.), Yarrow (Achillea millefolium L.) and Linden flowers(Tilia spp.) were selected for analysis. This study was carried out with the aim to investigate theeffect of extraction time (10, 15, 20 min) on the content of total flavonoids and total phenols aswell as antioxidant activity of herbal tea extracts. The infusions were prepared by usual domesticpreparation technique using ground air-dried plant materials and boiling deionized water(0.055 µS cm-1) for extraction. Content of total flavonoids, total phenols and antioxidant activitywas determined spectrophotometrically. Dry matter content was determined in lyophilized herbalinfusions. The obtained results indicated that extraction time did not affected the content ofbiologically active compounds in the herbal infusions significantly (P > 0.05). The highest levelof flavonoids was found in Jasmine and Lady's-mantle infusions (average104.98 ± 9.21 mg quercetin equivalent 100 g-1and 115.28 ± 5.25 QE mg 100 g-1respectivelly),while the lowest was determined in Matricaria chamomilla extract – (average70.10 ± 4.68 QE mg 100 g-1). Lady's-mantle tea contained the largest amount of total phenols(average 4126.62 ± 26.24 mg gallic acid equivalents 100g-1), the lowest – Calendula tea1828.04 ± 10.37 mg GAE 100 g-1). Data analysis showed a close linear positive correlationbetween the content of total flavonoids and total phenols in herbal infusions (R2 = 0.872;r = 0.934) with the probability of 99%. In general, all samples tested in this study, demonstratedhigh level of antioxidant activity (from 75.04 to 91.54 mmol Trolox equivalents 100 g-1). Resultsof the present experiments demonstrated that content of dry matter in analysed herbal teas wassignificantly different (P < 0.05).