Hibiscus sabdariffa L. (Hs, roselle; Malvaceae) has been used traditionally as a food, in herbal drinks, in hot and cold beverages, as a flavouring agent in the food industry and as a herbal medicine. In vitro and in vivo studies as well as some clinical trials provide some evidence mostly for phytochemically poorly characterised Hs extracts. Extracts showed antibacterial, anti-oxidant, nephro- and hepato-protective, renal/diuretic effect, effects on lipid metabolism (anti-cholesterol), anti-diabetic and anti-hypertensive effects among others. This might be linked to strong antioxidant activities, inhibition of α-glucosidase and α-amylase, inhibition of angiotensin-converting enzymes (ACE), and direct vaso-relaxant effect or calcium channel modulation. Phenolic acids (esp. protocatechuic acid), organic acid (hydroxycitric acid and hibiscus acid) and anthocyanins (delphinidin-3-sambubioside and cyanidin-3-sambubioside) are likely to contribute to the reported effects. More well designed controlled clinical trials are needed which use phytochemically characterised preparations. Hs has an excellent safety and tolerability record.
S. herba extract displays an anti-inflammatory effect on different models of rodent colitis that could be attributed to its immunomodulatory properties.
Objective Induction of CYP3A by St. John's wort (SJW) products with high hyperforin content is well described. Since CYP3A induction is mediated by hyperforin in a concentration-dependent manner, and SJW preparations differ significantly in hyperforin content, the aim of the study was to evaluate the effect of an SJW powder with low hyperforin content on CYP3A function. Methods Twenty healthy male volunteers received an SJW powder with low hyperforin content for 2 weeks. Midazolam plasma concentration time profiles were characterized after a single oral dose of 7.5 mg midazolam on the day before and on the 14th day of SJW medication. Results Midazolam AUC 0-∞ slightly decreased from 124.0 ± 62.5 ng/ml·h at baseline to 105.6 ± 53.2 ng/ml·h after SJW (P < 0.05), representing a mean 11.3% decrease (95% CI: −22.8 to 0.21). No significant change in midazolam C max , t 1/2 and t max was observed. For all pharmacokinetic parameters, the 90% CI for the geometric mean ratio of treatment over baseline were within the no-effect boundaries of 0.70-1.43. Conclusion Administration of an SJW product with low hyperforin content resulted in a mild induction of CYP3A not considered clinically relevant.
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