Influence of Hibiscus sabdariffa (Gongura) on the levels of circulatory lipid peroxidation products and liver marker enzymes in experimental hyperammonemia

In vitro modulation of cytochrome P450 isozymes and pharmacokinetics of caffeine by extracts of Hibiscus sabdariffa Linn calyx

Background Hibiscus sabdariffa beverage (HSB) is widely consumed as a medicinal herb and sometimes used concomitantly with drugs. This study evaluated the in vitro inhibitory potential of the aqueous extract of H. sabdariffa calyces (AEHS) on selected cytochrome P450 (CYP) isozymes and the effect of HSB on the pharmacokinetics of caffeine in vivo. Methods In vitro inhibitions of eight major CYP isozymes by AEHS were estimated by monitoring CYP-specific model reactions of 10 CYP probe substrates using N-in-one assay method. Subsequently, an open, randomized, two-period crossover design was used to evaluate the effect of HSB on the pharmacokinetics of single-dose 200 mg caffeine in six healthy human volunteers. Blood samples were obtained at specific times over a 24 h period. Probe drugs and metabolites were analyzed in their respective matrices with ultra-performance liquid chromatography/mass spectrometer/mass spectrometer and reversed-phase high-performance liquid chromatography/ultraviolet detection. Results The H. sabdariffa aqueous extract weakly inhibited the selected CYP isozymes in vitro, with IC50 of >100 μgmL-1 in the order of CYP1A2 > CYP2C8 > CYP2B6 >> CYP2D6 > CYP2C19 > CYP3A4 > CYP2A6 > CYP2C9. HSB decreased terminal t1/2 and Tmax of caffeine by 13.6% and 13.0%, respectively, and increased Cmax by 10.3%. Point estimates of primary pharmacokinetic endpoints, Cmax = 1.142 (90% confidence interval (CI) = 0.882, 1.480) and AUC0-∞ = 0.992 (90% CI = 0.745, 1.320), were outside the 90% CI of 0.8-1.25 bioequivalence limits. Conclusion The aqueous extract of H. sabdariffa weakly inhibited eight CYP isozymes in vitro, but HSB modified the exposure to caffeine in human. Caution should be exercised in administering HSB with caffeine or similar substrates of CYP1A2 until more clinical data are available.

Effect of Hibiscus sabdariffa L. dried calyx ethanol extract on fat absorption-excretion, and body weight implication in rats

The effect of Hibiscus sabdariffa L. (Hs) calyx extract on fat absorption-excretion and body weight in rats, was investigated. Rats were fed with either a basal diet (SDC = Control diet) or the same diet supplemented with Hs extracts at 5%, 10% and 15% (SD₅, SD₁₀ and SD₁₅). Only SD₅ did not show significant increases in weight, food consumption and efficiency compared to SD_C. The opposite occurred in SD₁₅ group which showed a significant decrease for these three parameters. The SD₁₀ responses were similar to SD₁₅, with the exception of food consumption. In both SD_C and SD₅ groups, no body weight loss was observed; however, only in the latter group was there a significantly greater amount of fatty acids found in feces. A collateral effect emerging from the study is that components of Hs extract at the intermediate and greater concentrations used in this experiment could be considered possible antiobesity agents.