RESULTS A. Xanthone chromatogram Under the optimal chromatogram conditions developed, xanthone was well separated from biological endogenous materials. Several trials have been conducted to determine the optimum conditions for separation and determination of xanthone by selecting the optimum wavelength. It was found that the maximum absorbance of xanthone is at 254 nm. Chromatograms obtained for a blank plasma sample and a plasma sample spiked with xanthone are shown in Fig. 2A and 2B. Fig. 2B shows the chromatogram of plasma spiked with xanthone (25 ug/ml). The run time was 12 min and xanthone retention time was at 9.46 min (Fig. 2B)