By examination of the 8659 drugs recorded in the Comprehensive Medicinal Chemistry (CMC) database, 78 catecholics (including five pyrogallolics) were identified, of which 17 are currently prescribed by FDA. Through analyzing the substitutent patterns, ClogPs and O-H bond dissociation enthalpies (BDEs) of the catecholic drugs, some molecular features that may benefit circumventing the toxicity of catecholics were revealed: i) strong electron-donating substituents are excluded; ii) ClogP < 3; iii) an energy penalty exists for quinone formation. Besides, the present analyses also suggest that the clinical usage and dosage of currently prescribed catecholic drugs are of importance in designing or screening catecholic antioxidants.
This study aims at evaluating the anticancer effects of berberine hydrochloride (berberine) and d-limonene, alone and in combination, on human gastric carcinoma cell line MGC803 to determine whether berberine and d-limonene work synergistically and elucidate their mechanisms. MGC803 cells were treated with berberine and d-limonene, alone and in combination, for 24-48 h. The inhibitory effects of these drugs on growth were determined by MTT assay. The combination index and drug reduction index were calculated with the Chou-Talalay method based on the median-effect principle. Flow cytometry and laser scanning confocal microscopy were employed to evaluate the effects of both drugs on cell-cycle perturbation and apoptosis, generation of reactive oxygen species (ROS), mitochondrial membrane potential, and expression of Bcl-2 and caspase-3 in MGC803 cells. Berberine or d-limonene alone can inhibit the growth of MGC803 cells in a doseand time-dependent manner. Berberine and d-limonene at a combination ratio of 1:4 exhibited a synergistic effect on anti-MGC803 cells. The two drugs distinctly induced intracellular ROS generation, reduced the mitochondrial transmembrane potential (DCm), enhanced the expression of caspase-3, and decreased the expression of Bcl-2. The combination of berberine and d-limonene showed more remarkable effects compared with drugs used singly in MGC803 cells. The combination of berberine and d-limonene exerted synergistic anticancer effects on MGC803 cells by cell-cycle arrest, ROS production, and apoptosis induction through the mitochondria-mediated intrinsic pathway.KEY WORDS: anticancer apoptosis berberine d-limonene synergistic effect
As naturally occurring polyphenols, xanthones are rather active in scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. By means of quantum chemical calculation, we reveal that the activity difference of xanthones can be elucidated by their different O À H bond dissociation enthalpies (BDEs) and can be further explained in terms of electronic effect and intramolecular hydrogen bond effect of substituents. The unique structure of xanthones enables them to be promising antioxidants with advantages of rather low O À H BDE and relatively high ionization potential.
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