Reviewed: Gurrola-Díaz CM, García-López PM, Sánchez-Enríquez S, et al. Effects of Hibiscus sabdariffa extract powder and preventive treatment (diet) on the lipid profiles of patients with metabolic syndrome (MeSy). Phytomed. Jun 2010;17(7):500-505.

The anthocyanin-rich calyx (sepals on the flower) of Hibiscus (Hibiscus sabdariffa, Malvaceae) is used to make herbal teas in Mexico and elsewhere around the world. Hibiscus extracts have shown diuretic, laxative, antibacterial, antioxidant, antihypertensive, hypolipidemic, anti-atherosclerotic, and hypocholesterolemic effects. In this clinical study, researchers at the University of Guadalajara in Guadalajara, Mexico and the Instituto Tecnológico de Tlajomulco Jalisco herbarium in Tlajomulco de Zuñiga, Mexico studied the effect of a powdered hibiscus extract alone and combined with dietary changes on the lipid profile of metabolic syndrome patients, characterized by insulin resistance, obesity, hypertension, and dyslipidemia. Metabolic syndrome is considered to be a reversible clinical stage before its evolution to heart disease or Type 2 diabetes.

The authors enrolled 152 male and female subjects, aged 30-71 years, with or without metabolic syndrome diagnosed according to the criteria of the National Cholesterol Education Program (NCEP) Adult Treatment Panel (ATP)-III. The subjects with metabolic syndrome and the healthy control subjects were subdivided into 3 treatment groups: diet only, hibiscus extract only, and hibiscus extract plus diet. Biochemical evaluations were conducted at baseline and after 31 days of treatment.

For subjects receiving dietary modifications, the diets were individually formulated according to NCEP ATP-III guidelines. Those assigned the hibiscus extract took 1 capsule (100 mg) each day before breakfast. A botanist at the Instituto Tecnológico de Tlajomulco Jalisco herbarium authenticated hibiscus plants of the Tepalcatepec variety, and a voucher specimen was deposited. The researchers prepared the hibiscus extract by macerating fresh hibiscus calyces in 30% ethanol for 7 days and drying the extract into a powder. High performance liquid chromatography (HPLC) analysis showed that the extract contained 192.4 mg/g total anthocyanins, primarily delphinidin- and cyanidin-3-sambubiosides.

At baseline, there were 80 control group subjects and 72 subjects with metabolic syndrome enrolled in the study. There was a large number of withdrawals in both groups due to nonmedical reasons, which left 51 metabolic syndrome subjects and 73 control group subjects in the final data analysis.

The metabolic syndrome subjects who received the hibiscus extract experienced significant decreases compared to baseline in average values for glucose, total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C) (P<0.05 for all), as well as an increase in high-density lipoprotein cholesterol (HDL-C; P<0.001). Triglyceride levels decreased significantly compared to baseline in the control group patients who were treated by diet and those treated with hibiscus extract (P<0.01 for both), as well as metabolic syndrome patients treated with the hibiscus extract plus diet (P<0.001). Treatment with the hibiscus extract improved the triglyceride/HDL-C ratio in the control group and the metabolic syndrome group (P<0.01 and P<0.05, respectively). The control subjects who received dietary treatment and the metabolic syndrome subjects treated with hibiscus extract experienced significant intra-group absolute differences (final – baseline values) for TC (P=0.001 and P=0.050, respectively). The control subjects treated with hibiscus extract and the metabolic syndrome subjects treated with diet, hibiscus extract, and diet plus hibiscus extract showed significant intra-group absolute differences for HDL-C (P=0.047, P≤0.001, P≤0.001, and P≤0.01, respectively).

In addition, significant intra-group differences in the triglyceride/HDL-C ratio occurred in the control subjects who received the hibiscus extract and diet changes (P=0.002 and P=0.031, respectively), as well as the metabolic syndrome subjects who received the hibiscus extract and those who received the hibiscus extract plus diet (P=0.026 and P<0.001, respectively). Significant intra-group differences in triglyceride levels were observed in control subjects treated with diet and hibiscus extract (P=0.006 and P=0.002, respectively) and metabolic syndrome subjects who received hibiscus extract plus diet (P<0.001). The basal triglyceride levels of the metabolic syndrome patients who received hibiscus extract and hibiscus extract plus diet decreased significantly (P<0.001 for both).

There was a significant reduction in the metabolic syndrome patients with high cholesterol levels in the group that received hibiscus extract (P=0.033), as well as a reduction in hypertriglyceridemia in metabolic syndrome subjects treated with diet and those treated with hibiscus extract plus diet (P=0.032 and P=0.016, respectively). In addition, the authors observed a significant reduction in hypertension in the metabolic syndrome patients treated with hibiscus extract plus diet (P=0.031). Out of 16 metabolic syndrome patients with insulin resistance, eight had normal triglyceride/HDL-C ratios after treatment with hibiscus extract plus diet (P=0.004). Levels of urea, creatinine, alanine aminotransferase (ALT), and aspartate aminotransferase (AST) did not change significantly for any group, suggesting a good hepatic and renal safety profile. The authors did not report the presence or absence of adverse events during the study.

The hypolipidemic effect of hibiscus extract has been attributed to the presence of anthocyanins. The authors write that more research is needed to define the chemical profile of hibiscus extract and to determine the active constituent(s). The results of this study are in agreement with prior clinical trials indicating the cardiovascular benefits of hibiscus, including hypotensive and hypocholesterolemic effects. The authors conclude that hibiscus extract is a useful complementary therapy for patients with metabolic syndrome.

—Marissa Oppel-Sutter, MS