Determination of oxalic acid in herbal medicines by semi-micro hydrophilic interaction liquid chromatography coupled with electrochemical detection.

In this study, the determination of oxalic acid in herbal medicines was performed by using a hydrophilic interaction liquid chromatography coupled with electrochemical detection (HILIC-ECD) method. A semi-micro column packed with amide-silica particles and an acetonitrile-30 mM phosphate buffer (pH 6.8) mixture (65:35, v/v) were used as the stationary and mobile phases, respectively, in the HILIC-ECD. A potential of + 1.1 V vs. Ag/AgCl was applied to a glassy carbon working electrode. The ratio of the peak height of oxalic acid to that of the internal standard (synephrine) was proportional to the concentration of 0.45 µg L-1 to 1.8 mg L-1 with a correlation coefficient of 0.999. The detection limit (signal-to-noise ratio, S/N = 3) of oxalic acid was 0.17 µg L-1. By the HILIC-ECD, the oxalic acid content in crude drugs and Kampo medicine extract granules (Zingiberis Rhizoma Processum, Pinelliae Tuber, Sho-seiryu-to, Hange-shashin-to, etc.) were determined with less than 2.9% relative standard deviation (RSD, n = 6), and their recoveries were more than 88.7% with less than 3.3% RSD (n = 6). In conclusion, we demonstrated that the HILIC-ECD performed measurements that were quite selective, accurate, and precise for the determination of oxalic acid in herbal medicines.

[An analysis of the ingredients in decoctions and extracts of Kampo medicines: Amounts of baicalin and baicalein in Kampo medicines containing Scutellariae Radix].

AIM: Kampo medicines containing Scutellariae Radix (the root of Scutellaria baicalensis Georgi; SR) sometimes cause serious adverse effects, including interstitial pneumonia and liver dysfunction. Baicalin (BL) is the major active component of SR and is presumed to be responsible for the adverse effects. We analyzed the amounts of BL in Kampo medicines to better understand how they can be used safely. METHODS: We determined the amounts of BL in 28 Kampo decoctions containing SR (recommended daily dose: 1.5-4 g/day) and corresponding Kampo extract products by high-performance liquid chromatography. RESULTS: The amounts of BL in the Kampo decoctions were 1.7-4.0-fold higher than those of the corresponding Kampo extract products. Inter-product variations in the amounts of BL in Shosaikoto, Otsujito, Daisaikoto, Saibokuto, Orengedokuto, and Saireito Kampo extracts from various companies were also examined. Significant differences in the amounts of BL were observed for Shosaikoto, Otsujito, Daisaikoto, and Saibokuto extract products (up to 2.6, 1.6, 1.5, and 1.3-fold differences, respectively), whereas no significant differences were observed for Orengedokuto and Saireito extract products. CONCLUSIONS: Because the Kampo decoctions containing SR that we examined contained 1.7-4.0 times as much BL as the corresponding Kampo extract products, medical doctors and pharmacists should be aware that Kampo decoctions containing SR might cause more severe side effects than corresponding Kampo extract products. Furthermore, we recommend that the amounts of BL and its aglycone, baicalein (BA), in Kampo extract products be made known to practitioners and patients.