Inhibition of key enzymes linked to type 2 diabetes by compounds isolated from Aframomum melegueta fruit

Figures & data

Figure 1. Structures of compounds 1–4 isolated from A. melegueta.

Table 1. ¹H and ¹³C NMR data of compounds 1–4 isolated from A. melegueta (more details in the supplementary data file).

Pos.	1 (^1H)	1 (^13C)	2 (^1H)	2 (^13C)	3 (^1H)	3 (^13C)	Pos.	4 (^1H)	4 (^13C)
1	2.74–2.78 m	29.0	2.80–2.81 m	31.3	2.64–2.65 m	29.1	1	1.54–1.56 m	38.4
2	2.61–2.65 m	44.5	2.80–2.81 m	41.9	2.58–2.60 m	45.2	2	1.25–1.27 m	27.2
3		210.9		200.1		211.4	3	3.19 dd (J = 10.7, 4.1 Hz)	79.0
4	2.29–2.33 m	43.1	6.05 d (J = 15.9 Hz)	130.3	2.39–2.41 m	49.4	4		38.8
5	1.47–1.52 m	23.7	6.76–6.80 m	148.1	3.91–3.94 m	67.7	5	0.69 bs	55.2
6	1.19–1.25 m	31.6	2.12–2.16 m	32.4	1.13–1.34 m	36.6	6	1.29–1.32 m; 1.49–1.51 m	18.3
7	1.19–1.25 m	29.5	1.38–1.42 m	27.7	1.13–1.34 m	31.7	7	1.36–1.40 m	32.6
8	1.19–1.25 m	29.1	1.21–1.27 m	29.9	1.13–1.34 m	25.1	8		39.3
9	1.19–1.25 m	22.6	1.21–1.27 m	22.4	1.13–1.34 m	22.5	9	1.55–1.56 m	47.6
10	0.82 t (J = 6.8 Hz)	14.0	0.84 t (J = 6.7 Hz)	13.9	0.75 t (J = 6.8 Hz)	14.0	10		37.1
1′		133.0		133.1		132.6	11	1.94–1.96 m	22.9
2′	6.63 d (J = 1.8 Hz)	111.2	6.66 d (J = 1.8 Hz)	111.2	6.54 d (J = 1.8 Hz)	111.4	12	5.25 bs	122.6
3′		146.6		146.5		146.9	13		143.6
4′		144.0		143.9		144.0	14		41.6
5′	6.75 d (J = 8.0)	114.5	6.78 d (J = 8.1 Hz)	114.4	6.65 d (J = 8.0 Hz)	114.8	15	1.65–1.68 m; 1.02–1.08 m	27.7
6′	6.59 dd (J = 8.0, 1.8 Hz)	120.7	6.63 dd (J = 8.1, 1.8 Hz)	120.8	6.47 dd (J = 8.0, 1.8 Hz)	120.6	16	1.82–1.85 m; 1.05–1.07 m	23.4
7′	3.78 s	55.8	3.81 s	55.8	3.64 s	55.7	17		46.5
							18	2.79 dd (J = 13.5, 4.0 Hz)	41.0
							19	1.58–1.60 m	45.9
							20		30.7
							21	1.38–1.42 m	33.8
							22	1.72–1.76 m; 1.52–1.55 m	32.4
							23	0.95 s	28.1
							24	0.75 s	15.5
							25	0.89 s	15.3
							26	0.72 s	17.1
							27	1.10 s	25.9
							28		183.3
							29	0.88 s	33.1
							30	0.90 s	23.6

Figure 2. α-Amylase (A) and α-glucosidase (B) inhibitions (%) of compounds isolated from A. melegueta fruit. Data are presented as mean ± SD of triplicate determinations. a–e Values with different letters presented for a given concentration for each extract are significantly different from each other.

Table 2. IC₅₀ values of bioactive compounds isolated from the A. melegueta fruit in antidiabetic models.

	IC50 (μM)
Compounds	α-amylase inhibition	α-glucosidase inhibition
6-Paradol (1)	664.56 ± 11.58^d	243.32 ± 6.65^d
6-Shagaol (2)	443.17 ± 1.38^c	326.11 ± 5.60^e
6-Gingerol (3)	81.78 ± 7.79^a	21.55 ± 0.45^b
Oleanolic acid (4)	91.72 ± 1.63^b	17.35 ± 0.88^a
Acarbose	85.15 ± 5.56^a,b	82.15 ± 2.42^c

Data are presented as mean ± SD values of triplicate determinations.

^a–eDifferent superscript letters presented within a column for a given parameter are significantly different from each other (Tukey’s-HSD multiple range posthoc test, p < 0.05).

Figure 3. Lineweaver-Burke plots for α-amylase (A) and α-glucosidase (B) in the absence and presence of the inhibitors (bioactive compounds).

Table 3. Kinetic analysis of α-amylase and α-glucosidase inhibition by compounds isolated from the fruit of A. melegueta in antidiabetic models.

	α-Amylase inhibition			α-Glucosidase inhibition
Compounds	KM (%)	Vmax (μmol/min)	Ki (μg/mL)	KM (mM)	Vmax (μmol/min)	Ki (μg/mL)
Control	0.06	35.65		1.10	471.56
A. melegueta
6-Paradol (1)	0.06	15.60	23.29	1.10	81.20	6.24
6-Shagaol (2)	0.09	24.10	62.33	1.10	55.70	4.02
6-Gingerol (3)	0.06	16.73	26.46	1.10	123.10	7.83
Oleanolic acid (4)	0.13	273.00	59.25	1.10	64.20	4.73