Spectrophotometric determination of antiplasmodial cochloxanthins from roots of Cochlospermum planchonii Hook.f. (Bixaceae)

Abstract

The roots and leaves of Cochlospermum planchonii and C. tinctorium are widely used in Burkina Faso as medication for malaria treatment. The cochloxanthins, carotenoids, are - at least partially - responsible for the antimalarial activity of Cochlospermum spp.. Because of large variation of cochloxanthin contents in rhizomes and leaves of Cochlospermum spp., the available products are not always reliable. The gold standard method for the quantification of cochloxanthins is HPLC. However, HPLC is expensive, time consuming, and needs experienced personnel. Therefore, for quick analysis of Cochlospermum roots in local pharmacies and companies, we developed a spectrophotometric method that is inexpensive, fast, simple and robust. In our study, we produced ethanolic extracts of market samples of roots of Cochlospermum sp. from Burkina Faso and analysed them in parallel by HPLC and spectrophotometry. The two methods correlated well with an R2 > 0.95 (P < 0.001). However, spectrophotometry overestimated the samples by 10% compared to HPLC analyses. For the spectrophotometric method, the coefficients of variation inter day and intra days were 9% and 12.8%, respectively with a limit of detection (LOD) of 0.65 µg/g. A parallel test of the spectrophotometric assay in a 96 well microplate format showed a good correlation (R2 = 0.96) with conventional spectrophotometry. Variation of sample volumes in the wells did not influence the results, but extreme values were not correctly measured in the microplate reader. The new spectrophotometric method is well suitable for the analysis of cochloxanthins in Cochlospermum spp. roots; however, due to interfering absorbance, plant material containing chlorophyll cannot be analysed. Keywords: Carotenoids, Cochlospermum planchonii, Cochlospermum tinctorium, Cochloxanthins, HPLC, Spectrophotometry