A UHPLC-DAD method for quantification of curcuminoids and piperine in food supplements based on Curcuma longa extract and evaluation of their biological activity on the Hep-2 cell lines

This study deals with the determination of bioactive compounds in Curcuma longa extract with addition of piperine to enhance the bioavailability of curcuminoids. The supplements containing bioactive phytochemicals including curcumin, demethoxycurcumin, bisdemethoxycurcumin, tetrahydrocurcumin, and piperine were quantified by ultra-high performance liquid chromatography method with diode array detection using an Ascentis Express RP-Amide column with 2.7 µm core-shell particles. The chromatographic analysis was performed at 30 °C with a run time of 12.5 min. Ultrasound-assisted solid-liquid extraction was applied to herbal extracts prior to analysis. The validated method yielded recoveries ranging from 91.52 ± 0.54–97.23 ± 0.54 %, and the limit of detection from 0.02 to 0.06 µg/mL. The content of curcuminoids and piperine in food supplements was alarmingly low, ranging from 1.04 % to 81.22 % of the declared content. The biological activity and cytotoxic properties of Curcuma longa extracts on the Hep-2 cell lines from a laryngeal carcinoma using Neutral Red assay and WST-1 proliferation test were also evaluated and positively correlated with the content of curcuminoids in individual preparations after 48 h. The supplement containing the lowest level of curcuminoids showed negligible cytotoxicity for Hep-2 cell lines while those containing the highest level of curcuminoids showed significant cytotoxicity.