Amomum villosum, (Amomi Fructus) (Amomi Fructus)

Ding, Min, Wu, Sheng-Li, Hu, Jing, He, Xiao-Feng, Huang, Xiao-Yan, Li, Tian-Ze, Ma, Yun-Bao, Zhang, Xue-Mei & Geng, Chang-An, 2022, Norlignans as potent GLP- 1 secretagogues from the fruits of Amomum villosum, Phytochemistry (113204) 199, pp. 1-8 : 3-4

2.3. Antidiabetic effects of A. villosum on db/db mice

The antidiabetic effects of A. villosum were assayed on db/db mice for the amelioration of random blood glucose, fasting blood glucose, plasma insulin and leptin levels, oral glucose tolerance, and insulin tolerance ( Fig. 5 ). The db/db mice were orally administrated with metformin (200 mg /kg) and A. villosum (400 and 200 mg /kg) daily for four weeks. At the fourth week, the random blood glucose of the A. villosum (200 mg /kg) group was obviously decreased, which was equivalent to the positive control, metformin (200 mg /kg) at the same dose. Whereas, the highdose group (400 mg /kg) showed no significant variation compared with the vehicle group, although the random blood glucose maintained the decreased tendency. Different from metformin, A. villosum did not influence the fasting blood glucose at the tested doses of 400 and 200 mg /kg. At the fourth week, both the plasma insulin and leptin levels in db/db mice were obviously increased by metformin (200 mg /kg), whereas A. villosum only in 200 mg /kg dosage showed a promotion in insulin levels. Besides, A. villosum had little influence on the blood glucose in oral glucose tolerance test (OGTT) and insulin tolerance test (ITT), as well as the body weight and food intake during the four-week treatment. As a comparison, metformin (200 mg /kg) could alleviate the blood glucose in OGTT and ITT tests. This study suggested that A. villosum showed hypoglycemic effects on db/db mice by promoting insulin secretion, which might have a different mechanism of action with metformin.

2.4. GLP-1 secretion stimulative activity

The EtOH extract and EtOAc fraction of A. villosum were assayed for their stimulative effects on GLP-1 secretion in STC-1 cells ( Fig. 6 ). At the concentration of 50.0 μ g/mL, the EtOH extract could stimulate GLP-1 secretion by 100.1%. After extracted with EtOAc, the obtained EtOAc part showed higher activity with promotion rates of 156.2% (25.0 μ g/ mL) and 273.9% (50.0 μ g/mL). Compounds 1–4 were assayed for their GLP-1 stimulative effects at concentrations of 12.5 and 25.0 μ M, of which amovillosumin A (1) showed the highest activity in stimulating GLP-1 secretion by 166.9% and 375.1%, more potent than the positive control, oleoylethanolamide (OEA, 163.1%, 25.0 μ M). Also, amovillosumin B (2) obviously increased the GLP-1 secretion by 62.7% (12.5 μ M) and 222.7% (25.0 μ M), comparable to the positive control. Whereas, amovillosumins C (3) and D (4) were inactive at the tested concentrations ( Table 3 ). Compounds 1 – 4 possessed similar structures with the main difference at two phenyl rings. Thus, the substitution patterns (1 ′,3 ′ - and 3,4,5-subsititution) at phenyl rings might play key roles in maintaining GLP-1 stimulative activity.

3. Conclusions

In this study, the fruits of A. villosum were first revealed with hypoglycemic effects on db/db mice by promoting insulin secretion. Guided by GLP-1 secretion assay, four new norlignans, amovillosumins A‒D (1–4), were isolated from the EtOAc fraction. The subsequent chiral resolution gave rise to three pairs of enantiomers, 1a/1b, 2a/2b, and 3a/3b, whose absolute configurations were determined by ECD calculation. Amovillosumins A (1) and B (2) could stimulate GLP-1 secretion by 375.1% and 222.7% at 25.0 μ M, and 166.9% and 62.7% at 12.5 μ M, representing a new type of GLP-1 secretagogues. This investigation provides new clues for understanding the antidiabetic effects of A. villosum and the active norlignans as promising GLP-1 secretagogues.

Figures

Fig. 5. Antidiabetic effects of A. villosum on db/db mice, (A–E) random blood glucose (0–4 weeks), (F) fasting blood glucose (4th week), (G) plasma insulin level, (H) plasma leptin level, (I) OGTT, (J) ITT, (K) food intake, and (L) body weight. Data were presented as mean ±SDs (n =8). *p <0.05, **p <0.01 vs Vehicle, ##p <0.01, ###p <0.001, ####p <0.0001 vs Lean.

Fig. 6. The stimulation of fractions and compounds on GLP-1 secretion. Oleoylethanolamide (OEA) was used as positive control. Data were expressed as mean ± SD (n = 3). **p <0.01, ***p <0.001.