A capillary zone electrophoresis method for the quantitative determination of hypoxoside in commercial formulations of African potato (Hypoxis hemerocallidea).

Hypoxoside is a norlignan diglucoside present in the corms of African potato, Hypoxis hemerocallidea, used as a popular African traditional medicine for its nutritional and immune boosting properties. A specific analytical method employing capillary zone electrophoresis has been developed and validated for the quantitative determination of this analyte. Sulfafurazole was used as internal standard, and electrophoretic separation of both analytes could be achieved within 12 min. Linearity of the method was established within the range 5-60 microg/mL and provided a high degree of accuracy (100 +/- 3%). The recovery of the method was found to be 100 +/- 5% and the RSDs of the intra- and inter-day precision were better than 5.19 and 2.52%, respectively. The limits of detection and quantification were calculated to be 0.5 and 2 microg/mL, respectively. The described method was used for the analysis and quality control of two commercially available products containing African potato. The method can also be used to determine product stability since it could separate the hypoxoside peak from its degraded products obtained from degradation studies.

In vitro evaluation of human cytochrome P450 and P-glycoprotein-mediated metabolism of some phytochemicals in extracts and formulations of African potato.

African potato (Hypoxis hemerocallidea, AP) is a traditional herbal medicine widely used as an immune booster and also for the treatment of various ailments such as urinary diseases, prostrate hypertrophy and cancer. Amongst the chemical components contained in AP, the norlignan glycoside, hypoxoside (HYP) is purported to be the most important phytochemical in terms of AP's medicinal value. Additional constituents in AP include the sterols, beta-sitosterol (BSS), stigmasterol (STG), and the stanol, stigmastanol (STN). The potential of extracts of AP, AP formulations as well as HYP, its aglycone rooperol (ROP) and the sterols to inhibit in vitro metabolism of drug marker substrates by human cytochrome P450 (CYP) enzymes such as CYP3A4, 3A5 and CYP19 were investigated. Samples were also assessed for their effect on drug transport proteins such as P-glycoprotein (P-gp). The effects on CYP-mediated metabolism were studied by fluorometric microtitre plate assay. The potential interaction with P-gp was investigated by measuring the efflux of the fluorescent dye rhodamine 123 (Rh 123) in the CaCo-2 (colon carcinoma) cell line. Various extracts of AP, AP formulations, only STG and the norlignans, in particular the aglycone ROP, exhibited inhibitory effects on CYP3A4-, 3A5- and 19-mediated metabolism. The extracts and the formulations that contained a significant amount of HYP showed high induction of P-gp compared to the positive control, ritonavir. Whilst extrapolation of the current in vitro findings to clinical effects may well be considered speculative, these in vitro data should be heeded as a signal of possible in vivo interactions. Appropriate measures are therefore necessary to explore the possibility of such in vitro-in vivo correlations.

Investigation of the antioxidant activity of African potato (Hypoxis hemerocallidea).

African potato (AP) is widely used as an immune booster for the treatment of various ailments. The norlignan glycoside hypoxoside, a major phytoconstituent of AP, its aglycon rooperol, and an aqueous preparation of lyophilized AP corms were screened for in vitro antioxidant activity using the DPPH (1,1-diphenyl-2-picryl hydrazine) and FRAP (ferric reducing ability of plasma) tests. Inhibition of quinolinic acid (QA) induced lipid peroxidation in rat liver tissue was studied in vitro using the thiobarbituric assay (TBA). Superoxide free radical scavenging activity was determined by the nitroblue tetrazolium assay. An isocratic HPLC method was developed to quantitatively determine both hypoxoside and rooperol concurrently. While rooperol and AP extracts reduced QA-induced lipid peroxidation in rat liver homogenates and significantly scavenged the superoxide anion at pharmacological doses, in comparison, hypoxoside was virtually devoid of activity. Since hypoxoside is converted to rooperol in vivo following administration of AP, the results indicate that the hypoxoside component in AP could have value as an antioxidant prodrug.

High-performance liquid chromatographic method for the quantitative determination of Hypoxoside in African potato (Hypoxis hemerocallidea) and in commercial products containing the plant material and/or its extracts.

Hypoxoside is a norlignan diglucoside present in the corms of African potato (Hypoxis hemerocallidea). The latter is used as a popular African traditional medicine for it's nutritional and immune-boosting properties. A reverse phase high-performance liquid chromatography method was developed and validated for the determination of hypoxoside using a mobile phase consisting of acetonitrile:water (20:80, v/v). The method was linear throughout the range of 10-100 microg/mL and provided a high degree of accuracy (100 +/- 4%). The recovery of the method was found to be 100 +/- 5%, and the precision of the study, % relative standard deviation intraday and interday (over three separate days), was better than 6.15 and 5.64%, respectively. The limits of detection and quantification were calculated to be 0.75 and 3.5 microg/mL, respectively. This method was applied to the analysis and quality control of African potato corms as well as 12 commercially available products. The daily intake of hypoxoside through traditionally prepared African potato decoction was also evaluated.