Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA172

Poster Communications

Mechanism of the Hypotensive Effect of Hibiscus sabdariffa Tea: A Double-Blind Study

F. B. Mojiminiyi1, O. I. Oyeniran2, I. A. Abubakar3, G. O. Igbokwe4, E. E. Igbokwe1, Y. J. Oyeniyi5, S. A. Isezuo6

1. Physiology, Usman Danfodio University, Sokoto, Nigeria. 2. Physiology, Nile University of Nigeria, Abuja, Nigeria. 3. Veterinary Parasitology & Entomology, Usman Danfodio University, Sokoto, Nigeria. 4. c/o Physiology, Usman Danfodio University, Sokoto, Nigeria. 5. Pharmaceutics, Usman Danfodio University, Sokoto, Nigeria. 6. Medicine, Usman Danfodio University, Sokoto, Nigeria.


Hibiscus sabdariffa tea (HST) has been reported to lower blood pressure (BP) in pre-hypertensive and mildly hypertensive subjects1 due to its anthocyanin, polyphenol and hibiscus acid contents.2 Findings from an open study suggest that Hibiscus sabdariffa extract lowers BP by dampening the sympathetic nervous system (SNS).3 Since open studies may be subjective, the present study was designed to examine this problem using a randomized double-blind placebo-controlled approach. Following ethical approval and informed consent, the cold pressor test (CPT) was performed in healthy human subjects before and after the oral administration of 200mg/kg HST (n=20) or a food colourant (FC; n=20) which served as placebo. The basal BP and pulse rate (PR) were determined, then each subject immersed one hand into iced water (4oC) just above the wrist for 1-2 minutes and the BP and PR responses were measured. Experiments were performed in accordance with the Principles of the Declaration of Helsinki. Mean arterial pressure (MAP) was taken as representative BP. Results are expressed as Mean±SEM. Paired T test was used to analyze the data within the HST and FC groups while unpaired T test was used to analyze the difference between the HST and FC groups. When three or more groups were compared, ANOVA with repeated measures was used. P<0.05 was considered significant. The peak MAP and PR obtained during the CPT in the absence of FC (94.2±1.7mmHg and 77.6±1.2 beats/min) were significantly higher than the basal values (83.3±1.8mmHg and 69.2±1.4 respectively; P<0.05). In the presence of FC these parameters rose significantly (100±1.8mmHg and 82.9±1.2 beats/min; P<0.05) compared to its absence. The peak MAP and PR obtained during the CPT without HST (105.1±2.8 mmHg and 82.3±2.0 beats/min) were significantly higher than the corresponding basal values (90.8±3.0mmHg and 72.8±2.0 beats/min; P < 0.05). These parameters fell significantly when the subjects received HST (97.3±2.6mmHg and 77.1±2.0 beats/min; P<0.05) compared to its absence. In the presence of HST, CPT-induced changes (ΔMAP=7.0±1.3mmHg; ΔPR=4.3±0.6 beats/min) were significantly reduced compared to its absence (ΔMAP=14.4±1.6mmHg, ΔPR=9.5±1.1 beats/min; P<0.0001 respectively). However, in the presence of FC, the changes (ΔMAP=16.9±1.7mmHg, ΔPR=14.0±1.4 beats/min) were significantly higher than in its absence (ΔMAP=10.4±1.4mmHg, ΔPR= 8.4±1.1 beats/min; P<0.0001 respectively). These results suggest that CPT-induced activation of the SNS was attenuated by HST but aggravated by FC. It is concluded that the hypotensive effect of HST may occur through the reduction of SNS activation while FC may further activate it. Hence FC may neither be an inert placebo nor be innocuous.

Where applicable, experiments conform with Society ethical requirements