Quality evaluation of health foods containing licorice in the Japanese Market

Abstract

Focusing on licorice, a highly used raw material in health foods, quantitative analysis of functional/medicinal components and a safety and functional evaluation was carried out for herbal medicines, health food ingredients, and so-called health foods. A functional component, glabridin, was detected in herbal medicines from Glycyrrhiza glabra and G. inflata, health food ingredients, and in commercially available health foods that contain licorice. Likewise, glycyrrhizin, a medicinal component, was detected in these sources, except in licorice oil extract. Estrogen activity in vitro was detected in some of the herbal medicines, health food ingredients, and in health foods containing licorice. In the in vivo study, liver weight in ovariectomized (OVX) mice treated with licorice oil extract was significantly higher than that in OVX and sham mice in a dose dependent manner. These results suggest that excessive intake of licorice oil extract from health foods should be avoided, even though these ingredients might be beneficial for medical use in order to maintain bone health in postmenopausal women. Measurement of hepatic cytochrome P-450 (CYP) activity, reproductive organ weight, and fat and bone mass in OVX mice was considered useful for evaluating the safety and efficacy of estrogenic health food ingredients derived from herbal medicines.

Keywords: BMD, bone mineral density; CAA, Consumer Affairs Agency; CYP, cytochrome P-450; Cytochrome P-450 (CYP); DGL, deglycyrrhizin; E2, 17β-estradiol; Estrogenic activity; FFC, Foods with Function Claims; FNFC, Foods with Nutrient Functional Claim; FOSHU, Foods for Specified Health Uses; HPLC, high-performance liquid chromatography; Health foods; Herbal medicines; Licorice; ORAC, oxygen radical absorption capacity; Safety assessment; TE, Trolox equivalent.

Graphical abstract

Fig. 1

Contents of glabridin and glycyrrhizin in licorice based products available in Japan were measured by HPLC with ultraviolet detection. Each bar represents the mean of the results (n = 2–3). Details of the samples are shown in Table 1. ND = not detected. Tr = trace.

Fig. 2

Contents of glabridin in licorice based products available in Japan were measured by HPLC with ultraviolet detection, and their antioxidant activities were measured by ORAC method. Each bar represents the mean of the results (n = 2). Details of the samples are shown in Table 1. ND = not detected. Tr = trace.

Fig. 3

Estrogenic activities of Premarin, glabridin and 50% ethanol extract of licorice based products. MCF-7 cells were transfected with 3XERE-TATA-luc and tk-Rluc, followed by incubation with control vehicle (Cont.), 10⁻¹⁰ M to 10^-8 M estrogen (E2), 1/1000 to 1/1 Premarin, 10^-8 M to 10^-6 M Grabridin or licorice based products. Relative luciferase activity was shown by mean ± S.E. The data were analyzed using one-way ANOVA followed by Turkey’s post hoc test, *, p < 0.05, **, p < 0.001, compared by cont.

Fig. 4

Body weight, abdominal fat, liver weight and uterine weight in ovariectomized mice. Values are expressed as mean ± SEM, n = 8; means with different letters differ, p < 0.05. The data were analyzed using one-way ANOVA, and differences among the groups were assessed by Tukey’s post hoc test. Sham-operated mice fed a control diet (Sham), ovariectomized mice fed a control diet (OVX), OVX mice fed a 0.39% licorice oil extract-supplemented diet (OVX+10 L), and OVX mice fed a 1.95% licorice oil extract-supplemented diet (OVX + 50 L).

Fig. 5

CYP mRNA expression in liver in ovariectomized mice. Values are expressed as mean ± SEM, n = 8; means with different letters differ, p < 0.05. The data were analyzed using one-way ANOVA, and differences among the groups were assessed by Tukey’s post hoc test. Sham-operated mice fed a control diet (Sham), ovariectomized mice fed a control diet (OVX), OVX mice fed a 0.39% licorice oil extract-supplemented diet (OVX+10 L), and OVX mice fed a 1.95% licorice oil extract-supplemented diet (OVX + 50 L).

Fig. 6

Bone mineral density of ovariectomized mice. Values are expressed as mean ± SEM, n = 8; means with different letters differ, p < 0.05. The data were analyzed using one-way ANOVA, and differences between groups were assessed by Tukey’s post hoc test. Sham-operated mice fed a control diet (Sham), ovariectomized mice fed a control diet (OVX), OVX mice fed a 0.39% licorice oil extract-supplemented diet (OVX+10 L), and OVX mice fed a 1.95% licorice oil extract-supplemented diet (OVX + 50 L).