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Determination of 5‐hydroxynaphthoquinones in phytotherapeutic Drosera preparations by differential pulse polarography
Author(s) -
Michelitsch Astrid,
Wurglics Mario,
SchubertZsilavecz Manfred,
Likussar Werner
Publication year - 1999
Publication title -
phytochemical analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 72
eISSN - 1099-1565
pISSN - 0958-0344
DOI - 10.1002/(sici)1099-1565(199903/04)10:2<64::aid-pca434>3.0.co;2-t
Subject(s) - polarography , chemistry , plumbagin , dropping mercury electrode , chromatography , buffer solution , methanol , phosphate buffered saline , analytical chemistry (journal) , electrode , electrochemistry , inorganic chemistry , botany , organic chemistry , biology
A differential pulse polarographic method is described for the determination of three pharmacologically active 5‐hydroxynaphthoquinones in Drosera ‐containing phytomedicines available on the Austrian market. The polarographic behaviours of plumbagin, 7‐methyljuglone and droserone were examined in various buffer systems in the pH‐range from 3.5 to 10.0. The compounds were reduced in a single reversible peak at the dropping mercury electrode. The differential pulse polarograms of the naphthoquinones showed distinct peaks in sodium acetate/acetic acid buffer:methanol solution, and a plot of peak height against concentration was found to be linear over the range 0.16–30.0 µg/ml for droserone, 0.06–8.0 µg/ml for plumbagin and 0.16–25.0 µg/ml for 7‐methyljuglone. The polarographic method was applied to determine the amounts of these naphthoquinones in three Drosera ‐containing phytomedicines. In one preparation the droserone concentrations, depending on the sample taken, were found to be 6.81 and 5.78 µg/ml, whilst in a second preparation the droserone concentrations were 1.87, 3.67 and 0.51 µg/ml. The content of plumbagin and 7‐methyljuglone was lower than the polarographic detection limit (0.4 µg/ml of each). In a third preparation neither droserone, plumbagin, nor 7‐methyljuglone were polarographically detectable (<0.2 µg/ml). Copyright © 1999 John Wiley & Sons, Ltd.