Determination of adrenergic agonists from extracts and herbal products of Citrus aurantium L. var. amara by LC.

The purpose of this study was to set up a HPLC method to separate adrenergic amines (dl-octopamine, dl-synephrine and tyramine) and to determine their content in fruits, extracts and herbal products of Citrus aurantium L. var. amara. A rapid method for the quantitative analysis of these amines is described, based on their separation by RP-HPLC technique with UV detection. The analysis were conducted on a Lichrospher RP-18 column at room temperature, using a mobile phase consisting of 0.02 M citric acid-0.02 M NaH2PO4 (7:3 v/v) and adjusted to a final pH of 3. The detection was at 220 nm. Since some of these amines are chiral compounds and their enantiomers showed different pharmacological activity, the direct separation of synephrine enantiomers was carried out with HPLC on a beta-cyclodextrin stationary phase. The mobile phase consisted of methanol-NaH2PO4 25 mM pH 3.5 (20:80 v/v) and tetrabutylammonium hydrogen sulfate 10 mM in ratio of 30:70 v/v in isocratic condition and the detection was at 220 nm. The two proposed methods were applied to the analysis of fruits, extracts and herbal products of C. aurantium L. var. amara. Taking into account that some authors have reported that l-synephrine may be converted into its d-form by high temperature, this optical isomerization was monitored by the same HPLC method used for the separation of enantiomers.