Chemical Components from the Stems of Pueraria lobata and Their Tyrosinase Inhibitory Activity

Phytochemical investigation of the stems of Pueraria lobata (Wild) Ohwi (Leguminosae), led to the isolation of eighteen known compounds: β-amyrone (1), (+)-pinoresinol (2), (+)-syringaresinol (3) (+)-syringaresinol-O-β-D-glucoside (4), (+)-lariciresinol (5), (-)-tuberosin (6), naringenin (7), liquiritigenin (8), isoliquiritigenin (9) genistein (10), daidzein (11) daidzin (12) daidzein 4',7-diglucoside (13) 2,4,4'-trihydroxy deoxybenzoin (14), S-(+)-1-hydroxy-3-(4-hydroxyphenyl)-1-(4-hydroxy-2-methoxy-phenyl)propan-2-one (15), methyl 2-O-β-D-glucopyranosylbenzoate (16), pyromeconic acid 3-O-β-D-glucopyranoside 6'-(O-4''-hydroxy-3-methoxybenzoate) (17), and allantion (18). The chemical structures of these compounds were elucidated from spectroscopic data and by comparison of those data with previously published results. The effects of isolated compounds on mushroom tyrosinase enzymatic activity were screened. The results indicated that, chloroform extract of P. lobata stems turned out to be having tyrosinase inhibitory effect, and only compounds 5, 8, 9, and 11 showed enzyme inhibitory activity, with IC₅₀ values of 21.49 ± 4.44, 25.24 ± 6.79, 4.85 ± 2.29, and 17.50 ± 1.29 µM, respectively, in comparison with these of positive control, kojic acid (IC₅₀ 12.28 ± 2.72 µM). The results suggest that P. lobata stems extract as well as its chemical components may represent as potential candidates for tyrosinase inhibitors.

Phytochemical Constituents from the Aerial Part of Ducrosia ismaelis Asch

Phytochemical investigation of the aerial components of Ducrosia ismaelis Asch. led to the isolation of six known compounds, psoralen (1), isopsoralen (2), cnidioside A (3), (-)-syringaresinol-O-beta-D-glucopyranoside (4), (E)-plicatin B (5), trilinolein (6). The chemical structures of these compounds were elucidated from spectroscopic data and by comparison of these data with previously published results. The antioxidant, anti-osteoporotic and cardiovascular related activities of the isolated compounds were assessed using oxygen radical absorbance capacity (ORAC), reducing capacity, tartrate-resistant acid phosphatase (TRAP), and soluble epoxide hydrolase (sEH) inhibitory activity assays. Compounds (3-5) showed potent peroxyl radical-scavenging capacities with ORAC values of 11.06 +/- 0.39, 7.98 +/- 0.10, and 13.99 +/- 0.06 Trolox equivalent (TE) at concentrations of 10 microM, respectively. Only compounds 4 and 5 was able to significantly reduce Cu2+ ions, with a reduction value of 9.06 +/- 0.32 and 4.61 +/- 0.00 microM Trolox Equivalent (TE) at a concentration of 10 microM. Compound 5 at 10 microM exhibited a potent inhibitory effect on osteoclastic TRAP activity with a TRAP value of 86.05 +/- 6.55% of the control. Compounds 1, 3 and 5 potently inhibited sEH activity with IC50 values of 41.6 4.9, 16.0 1.1, and 49.0 5.7 microM, respectively.