Quality assessment of marketed food supplements and herbal tea products of olive leaf in Turkey

Abstract

Inthis study,qualitative and quantitative analysis of commercially available food supplements composed of olive leaf extract and herbal tea products containing olive leaf were evaluated by High-Performance Thin-Layer Chromatography (HPTLC) and anewly developed and validated High-Performance Liquid Chromatographic (HPLC) method for their quality assessment.In addition, leaves of two varieties of Olea europaeaL. (var. europaeaand var. sylvestris) grown in Turkeywhich were assigned as reference plant materialsand their chemical compositions were also comparatively analyzed by HPTLC. ThenHPTLC fingerprints of reference plant materialswere compared to the marketed olive leaf samples. For quantification of oleuropein and luteolin 7-O-glucoside(L7G)contents in the samples, a simple and fast HPLCmethod was developedand validated.Consequently, in water and hydroalcoholic extracts of O. europaeavar. europaea leaves,oleuropeincontents were found to be 15.89% (w/w) and 15.84% (w/w), whileL7G contentswere0.75% and 1.23%, respectively. For the reference materials, oleuropein in O. europaeaL.var. sylvestrisleaves wasfound to be 12.77% (w/w, in water extract) and 12.36%(w/w, in hydroalcoholic extract),while the concentrationof L7G was0.51% (w/w) and 0.83% (w/w) in water and hydroalcoholic extracts, respectively. Qualitative analysis of the commercial products revealed that fraud was detected in threeof eight olive leaf herbal tea bag brands and two of ten olive leaf food supplements.These samples were found either devoid of oleuropein orthey haddifferent HPTLC fingerprint profiles than the reference samples.