Introduction: Raspberry leaves (Rubi idaei folium) are a source of flavonoids, gallic tannins, phenolcarboxylic acids, sterols, vitamin C and oligoelements (selenium, vanadium). The leaves are not mentioned by the scientific literature for their possible use in metabolic diseases (diabetes, dyslipidaemia, hyperuricaemia), but among their compounds, polyphenols, sterols and vitamin C might be responsible for these properties. The aim of the study was to determine the optimum time for harvesting the leaves, in order to obtain pharmacological active extracts, with the highest content of flavonoids, phenolcarboxylic acids and tannins.
Material and methods: Qualitative (specific chemical reactions and thin layer chromatography, TLC) and quantitative (spectrophotometric methods and high liquid chromatography, HPLC) analyses upon leaves, harvested at different stages of development (before and after blossom, at fruits’ ripening and at the end of vegetative state) were applied.
Results: Flavonoids, tannins and phenolcarboxylic acids were present in all vegetative states; rutin, hyperoside and chlorogenic acid were identified using TLC. The greatest amount of total polyphenols (16.0317 g% tannic acid), tannins (11.4376 g% tannic acid), flavonoids (2.6347 g% hyperoside) and phenolcarboxylic acids (2.4011 g% chlorogenic acid) were found in young leaves. Using HPLC, gallic, chlorogenic, caffeic, p-coumaric and ferulic acids, tannin, rutin, quercetin and catechin were identified in young leaves; rutin (0.0540 g%) and p-coumaric acid (0.03174 g%) were also quantified.
Conclusions: The highest content of flavonoids, phenolcarboxylic acids and tannins were found in leaves, harvested before blossom. The tannins content were higher, compared with scientific literature.