The Theoretical and Experimental Insights into the Radical Scavenging Activity of Rubiadin.

Rubiadin (RBD), an anthraquinone derivative, is obtained from Rubia cordifolia, a plant species classified under the Rubiaceae family. Rubiadin has proven beneficial properties, such as anticancer, neuroprotective, anti-inflammatory, and antidiabetic activity. The antioxidant activity of this molecule was suggested by some experimental results but has not been clearly established thus far. In this study, we employ DFT calculations to comprehensively assess the mechanism and kinetics of the HO•/HOO• radical scavenging activity of this compound in relation to solvents. RBD showed moderate HO• radical scavenging activity, with rate constants of 2.95 × 108 and 1.82 × 1010 M-1 s-1 in lipid and polar media, respectively. In the aqueous solution, the compound exhibited remarkable superoxide anion radical scavenging activity (k = 4.93 × 108 M-1 s-1) but modest HOO• antiradical activity. RBD also showed promising antiradical activity against a variety of radicals (CCl3O•, CCl3OO•, NO2, SO4•-, and N3•), while experimental and computational results confirmed that RBD has moderate activity in DPPH/ABTS•+ assays. Thus, RBD is predicted to be a good, albeit selective, radical scavenger.

Four New Stilbene Derivatives Isolated from Gnetum latifolium var. funiculare Markgr. and Their Inhibition of NO Production in LPS-activated RAW264.7 Cells.

Gnetum latifolium var. funiculare Markgr. is a medicinal plant and widely distributed in mountainous areas of Vietnam. Phytochemical investigation on the trunks of this plant afforded eight stilbene derivatives (1-8) including for new compounds (1-4). Their structures were determined based on extensive analyses of HR-ESI-MS, 1D and 2D NMR spectra. Among the isolates, compounds 1-3 showed moderate NO production inhibition in LPS-activated RAW264.7 cells with the IC50 values ranging from 46.81 to 68.10 µM, compounds 4 and 6 showed weak effects with the IC50 values of 96.57 and 79.46 µM, respectively, compared to that of the positive control compound, dexamethasone (IC50 14.20 µM).

Feruloylmonotropeins: promising natural antioxidants in Paederia scandens.

Paederia scandens (Lour.) is a widely used medicinal herb in Vietnam, China, India, and Japan for the treatment of a variety of conditions, including toothache, chest pains, piles, and spleen inflammation. There is broad interest in identifying the composition of its extracts and confirming their numerous biological activities, including anti-nociceptive, antiviral, and anticancer properties. Two iridoid glucosides obtained from the MeOH extract of P. scandens, 6'-O-E-feruloylmonotropein (6-FMT) and 10'-O-E-feruloylmonotropein (10-FMT), are potential antioxidants based on their structure. In this study, the hydroperoxyl scavenging activity of 6-FMT and 10-FMT was examined in silico by using density functional theory. These FMTs are predicted to be weak antioxidants in non-polar environments, whereas a good HOO˙ scavenging activity is expected in polar environments (pH = 7.4) with k overall = 3.66 × 107 M-1 s-1 and 9.45 × 106 M-1 s-1, respectively. This activity is better than many common antioxidants such as trolox and nearly equivalent to ascorbic acid and resveratrol. The hydroperoxyl scavenging activity was exerted mainly by the di-anion form of FMTs in water at physiological pH following the single electron transfer mechanism. The results suggest that FMTs are promising natural antioxidants in aqueous physiological environments.