Identification of crypto- and neochlorogenic lactones as potent xanthine oxidase inhibitors in roasted coffee beans

Figures & data

Fig. 1. Chemical structures of chlorogenic acids (1–3) and identified lactone derivatives (4–8).

Fig. 2. XO inhibitory activities of boiling water extracts (0.3 and 0.6 mg mL⁻¹) from green, dried, and roasted coffee beans.

Note: Data are expressed at the mean ± SD (n = 3).

*Significant against control (t-test, p < 0.05).

Fig. 3. XO inhibitory activities of eluted fractions (0.15 mg mL⁻¹) from size-exclusion chromatography of roasted coffee bean extract.

Note: Data are expressed at the mean ± SD (n = 3).

*Significant against control (t-test, p < 0.05).

Fig. 4. HPLC analytical profile of active fraction 7 from size-exclusion chromatography of roasted coffee bean extracts.

Note: HPLC conditions: column, Cosmosil 5C18-ARII (250 × 2.0 mm i.d.); solvent, 1% acetic acid in H₂O–CH₃CN (85:15); flow rate of 0.5 mL min⁻¹.

Table 1. XO inhibitory activities of chlorogenic acids, isolated compounds, and allopurinol (positive control).

Compound	Percent inhibition at 1000 μmol L^−1(mean ± SD)^a	IC50 (μmol L^−1)
1	22.5 ± 4.5^d	–^c
2	16.8 ± 0.9^d	–
3	32.9 ± 1.8^d	–
B (4)	38.8 ± 2.7^d	–
C (5 + 6 (3:1 mixture))	50.2 ± 2.7^d	–
D (7)	81.0 ± 2.4^d	210
E (8)	70.1 ± 2.3^d	360
Allopurinol	53.8 ± 2.8^b^,^d	–

^a n = 3.

^b Data at the concentration of 1.0 μmol L⁻¹.

^c Not determined.

^d Significant inhibition against control (t-test, p < 0.05).

Fig. 5. HPLC analytical profiles of extracts from green, dried, and roasted coffee beans.

Note: HPLC conditions: column, Cosmosil 5C18-AR-II (250 × 4.6 mm i.d.); solvent, (A): 1% acetic acid in H₂O, (B): CH₃CN; gradient conditions [percent of solvent B (time)], 5% (0 min), 45% (40 min), 100% (50–55 min); flow rate, 1.0 mL min⁻¹.