Antioxidants and carbohydrate content in infusions and microwave extracts from eight medicinal plants

Abstract

The aims of the current research were to evaluate and to compare the antioxidant activity and the content of total phenolic, flavonoids and fructan content in infusions and microwave-assisted extracts from eight herbs: rosehip (Rosa canina L.), peppermint (Mentha piperita L.), thyme (Thymus vulgaris L.), coltsfoot (Tussilago farfara L.), dandelion (Taraxacum officinale Web.), elecampane (Inula helenium L.), great burdock (Arctium lappa L.) and echinacea (Echinacea purpurea Moench.). The total phenolic contents, total flavonoids and antioxidant activity were evaluated by Folin-Ciocalteau, Al(NO3)3 methods and DPPH assays. The total fructans and sugars were determined by resorcinol and HPLC-RID methods. Infusion and microwave-assisted extraction (MAE) were evaluated as efficient methods for preparation of herbal drinks. The highest values of biologically active substances and antioxidant activity were found in MAE herbal extracts. Coltsfoot, thyme and great burdock extracts demonstrated the highest content of total phenolic and flavonoids. Coltsfoot and thyme extracts showed the highest antioxidant activity (334 mM TEg-1 and 287 mM TEg-1dw, respectively). Fructans were found in coltsfoot (4.6%) and echinacea (3.9 %) leaves, in great burdock, dandelion and elecampane roots - 14 %, 34% and 44% dw, respectively. Elecampane and dandelion roots were evaluated as sources of prebiotic inulin.