Antioxidative iridoid glycosides from the sky flower (Duranta repens Linn).

Phytochemical investigations were performed on the EtOAc-soluble fraction of the whole plant of the sky flower (Duranta repens) which led to the isolation of the iridoid glycosides 1-6. Their structures were elucidated by both 1D and 2D NMR spectroscopic analysis. All the compounds showed potent antioxidative scavenging activity in four different tests, with half maximal inhibitory concentration (IC(50)) values in the range 0.481-0.719 mM against DPPH radicals, 4.07-17.21 µM for the hydroxyl radical (·OH) inhibitory activity test, 43.3-97.37 µM in the total reactive oxygen species (ROS) inhibitory activity test, and 3.39-18.94 µM in the peroxynitrite (ONOO(-)) scavenging activity test. Duranterectoside A (1) displayed the strongest scavenging potential with IC(50) values of (0.481 ± 0.06 mM, 4.07 ± 0.03, 43.30 ± 0.05, 3.39 ± 0.02 µM) for the DPPH radicals, ·OH inhibitory activity test, total ROS inhibitory activity test and the ONOO(-) scavenging activity test, respectively.

Xanthine oxidase/tyrosinase inhibiting, antioxidant, and antifungal oxindole alkaloids from Isatis costata.

Phytochemical investigations on the ethyl acetate soluble fraction of the whole plant of Isatis costata Linn. (Brassicaseae) led to the isolation of the oxindole alkaloids costinones A (1), B (2), isatinones A (3), B (4), indirubin (5), and trisindoline (6). Compounds 1-6 displayed significant to moderate inhibition against xanthine oxidase enzyme with IC50 values ranging from 90.3+/-0.06 to 179.6+/-0.04 microM, whereas the standard inhibitor of xanthine oxidase (allopurinol) had an IC(50) value of 7.4+/-0.07 microM. Compounds 1 (IC50 7.21+/-0.05 microM), 2 (IC50 9.40+/-0.03 microM), 3 (IC50 11.51+/-0.07 microM), 4 (IC50 12.53+/-0.06 microM), 5 (IC50 14.29+/-0.09 microM), and 6 (IC50 17.34+/-0.04 microM) exhibited pronounced activities when compared with the standard tyrosinase inhibitor L-mimosine (IC50 3.70+/-0.03 microM), along with DPPH radical scavenging activity with IC50 226, 270, 300, 320, 401, and 431 microM, respectively. The crude extract and compounds 1, 2, 5, and 6 showed significant antifungal activity against Trichophyton schoen leinii, Aspergillus niger, Candida albicans, Trichophyton simii, and Macrophomina phaseolina.

Two new anti-plasmodial flavonoid glycosides from Duranta repens.

The CHCl(3)-soluble fraction of the whole plant of Duranta repens showed anti-plasmodial activity against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum, with IC(50) values of 8.5 ± 0.9 and 10.2 ± 1.5 µg/mL, respectively. From this fraction, two new flavonoid glycosides, 7-O-α-d-glucopyranosyl-3,4'-dihydroxy-3'-(4-hydroxy-3-methylbutyl)-5,6-dimethoxyflavone (1) and 7-O-α-d-glucopyranosyl(6'''-p-hydroxcinnamoyl)-3,4'-dihydroxy-3'-(4-hydroxy-3-methylbutyl)-5,6-dimethoxyflavone (2), along with five known flavonoids, 3,7,4'-trihydroxy-3'-(4-hydroxy-3-methylbutyl)-5,6-dimethoxyflavone (3), 3,7-dihydroxy-3'-(4-hydroxy-3-methylbutyl)-5,6,4'-trimethoxyflavone (4), 5,7-dihydroxy-3'-(2-hydroxy-3-methyl-3-butenyl)-3,6,4'-trimethoxyflavone (5), 3,7-dihydroxy-3'-(2-hydroxy-3-methyl-3-buten-yl)-5,6,4'-trimethoxyflavone (6), and 7-O-α-d-glucopyranosyl-3,5-dihydroxy-3'-(4''-acetoxy-3''-methylbutyl)-6,4'-dimethoxyflavone (7), have been isolated as anti-plasmodial principles. Their structures were deduced by spectroscopic analysis including 1D and 2D NMR techniques. The compounds (1-7) showed potent anti-plasmodial activities against D6 and W2 strains of Plasmodium falciparum, with IC(50) values in the range of 5.2-13.5 µM and 5.9-13.1 µM, respectively.