Despite curcumin has been proved to possess antimalarial effects, the underlying mechanism remains to be elucidated. In this letter, the active site binding modes of curcumin in PfATP6, an important antimalarial target, were investigated using computational docking. It was revealed that curcumin interacts with PfATP6 mainly through hydrophobic interactions and hydrogen bonds. Moreover, the theoretically predicted binding affinity implies that curcumin can efficiently inhibit PfATP6, which gains some deeper insights into the antimalarial mechanism of curcumin.The efficient inhibition of curcumin to PfATP6 may be involved in its antimalarial mechanism.

The triplet excited (T1) state characters of α-terthienyl (α-T) have been investigated using density functional theory calculations, based on which, its photosensitization mechanisms were explored. Primarily, the direct oxidation to the DNA bases by the T1 state α-T through the electron transfer is not thermodynamically feasible. Secondly, 1O2 can be photogenerated both in benzene and water through the direct energy transfer from the T1 state α-T to 3O2, while O2- can only be formed in water through the electron transfer from the T1 state α-T or α-T− to 3O2.

Benzo[a]pyrene (BaP) possesses photosensitive activity and can photogenerate reactive oxygen species (ROS), which have been postulated to be involved in the BaP induced oxidative DNA damage. Therefore, in the present work, a thermodynamic analysis on the ROS-photogenerating mechanisms of BaP was performed on the basis of quantum chemical calculations. It was revealed that: (i) the 1O2-generating pathway involves direct energy transfer from triplet excited state BaP to 3O2 both in benzene and water; (ii) BaP gives birth to O2− through two pathways in water, i.e., electron transfer from triplet excited state BaP or anion radical of BaP to 3O2.

By means of quantum chemical calculations, the deactivating reactions of triplet excited state C60 by β-carotene were explored from the thermodynamic point of view. The solvent effect on the deactivating mechanisms was also discussed. Primarily, the energy transfer from triplet excited state C60 to β-carotene is feasible both in benzene and water. Secondly, β-carotene may also deactivate triplet excited state C60 through electron transfer from ground state β-carotene to triplet excited state C60 or from triplet excited state β-carotene to triplet excited state C60 in water, while only the latter pathway is thermodynamically favorable in benzene.

In this work, mechanisms of both the singlet and triplet state riboflavin (RF) quenching by 3-hydroxypyridine (3-HP) and 4-hydroxypyridine (4-HP) have been investigated by employing quantum chemical calculations. It was revealed that both the direct electron transfer and H-atom transfer pathways, i.e., (i) direct electron transfer from zwitterionic forms of 3-HP and 4-HP to excited state RF; (ii) H-atom transfer from enol forms of 3-HP and 4-HP to excited state RF, are thermodynamically favorable to be involved in the excited state RF quenching by 3-HP and 4-HP. The present results provide some deeper insights into the photooxidation of hydroxypyridine-based pesticides in the presence of natural photosensitizers.

The quenching mechanisms of both the singlet and triplet state riboflavin (RF) by dopamine (DP) were investigated by means of density functional theory calculations in this communication. It was found that both the direct electron transfer and H-atom transfer pathways are thermodynamically feasible for the singlet state RF quenching by DP, while only the H-atom transfer pathway is involved in the triplet state RF quenching by DP.

In this communication, time-dependent density functional theory (TD-DFT) calculations are employed to investigate the triplet excited state properties of porphyrin-related photosensitizers, including free base porphyrin (FBP), free base chlorine (FBC) and porphyrazine (PZ), based on which, the photosensitization mechanisms of the three molecules have been explored. It was revealed that the three photosensitizers can photogenerate 1O2 through direct energy transfer between T1 state photosensitizers and 3O2 both in benzene and water, while the photosensitizers can give birth to O2- only in aqueous solution and the O2--generating pathways are different among the three molecules.

In the present work, we investigated the photophysical and photosensitive properties and further explored the substituent effects on these properties of a series of anthraquinones by means of theoretical calculations. It is revealed that comparing with the parent 9,10-anthraquinone (AQ), the substitutents red-shifted the absorption spectra and lowered the ET1 of anthraquinones considerably. Moreover, the present results also provide some deeper insights into the photosensitization mechanisms of anthraquinones, that is, although anthraquinones can photo-generate 1O2 through direct energy transfer in both non-polar and polar solvents, they give birth to O2- through electron transfer only in polar solvents, and it is the anthraquinones anions (generated from autoionization) that are responsible for the O2--generation.

In this study, the photosensitization mechanisms of riboflavin (RF) are explored by means of time-dependent density functional theory calculations. The results indicate that RF can photo-generate various reactive oxygen species and the corresponding reaction pathways are schemed. The solvent effects on the photosensitization mechanisms of RF are also discussed.

An increasing number of studies show that alterations in intestinal microbiota are linked with metabolic diseases. Here, we propose that intestinal microbiota regulation by polyphenols may be an important mechanism underlying their therapeutic benefits for metabolic diseases. This helps elucidate the intriguing pharmacology of polyphenols and optimize the treatment of metabolic diseases.

The natural product curcumin has gained considerable attention in recent years for its multiple pharmacological activities, but more efforts are needed to understand how curcumin can have these pharmacological effects considering its low bioavailability. In addition, it is unclear how curcumin exerts inhibitory effects against numerous enzymes, especially those that cannot accommodate curcumin within recognized binding pockets. By analyzing the similarities between the biological activities of curcumin and its degradation products against diseases such as Alzheimer's disease and cancer, as well as the preferential inhibition of some enzymes by degradation products, it appears that the bioactive degradation products may contribute to the pharmacological effects of curcumin. This possibility should be given full attention when elucidating the pharmacology of this promising natural product for various diseases.

IntroductionParkinson's disease (PD) and osteoporosis are common diseases which affect a substantial portion of the elderly population. Accumulating evidence supports that PD patients have a high risk for osteoporosis in recent years. The purpose of the present study is to perform a meta-analysis on the risk of osteoporosis and bone mineral density (BMD) levels in PD patients.MethodsWe searched all articles indexed in Medline, SciVerse Scopus and Cochrane Library published up to January 2012 concerning the association between PD and risk of osteoporosis or BMD levels. In total, 15 studies were included in the meta-analysis.ResultsThe results indicated that PD patients are at higher risk for osteoporosis (summary OR = 1.18, 95% CI = [1.09, 1.27]) than healthy controls. The gender subgroup analysis suggested that PD male patients have a higher risk for osteoporosis than female patients (female patients: summary OR = 1.16, 95% CI = [1.07, 1.26]; male patients: summary OR = 2.44, 95% CI = [1.37, 4.34]). Further meta-analysis showed that PD patients have a lower hip, lumbar spine and femoral neck BMD than healthy controls. The gender subgroup analysis found a lower BMD in PD female patients than controls, while no obvious difference was observed in PD male patients and controls.ConclusionsThis meta-analysis suggested that PD patients are at higher risk for osteoporosis and have lower BMD levels than healthy controls overall.Highlights► Increasing evidence supports that PD patients have a high risk for osteoporosis. ► We performed a meta-analysis on osteoporosis risk and BMD levels in PD patients. ► PD patients are at higher risk for osteoporosis than healthy controls. ► PD patients have lower BMD levels than controls overall.

Contradicting outcomes have been observed in numerous studies investigating the benefits of vitamin E supplements in the context of neurodegenerative diseases. By reviewing epidemiological studies and clinical trials, it is found that dietary intake of vitamin E exhibits beneficial effects on neurodegeneration, whereas α-tocopherol supplements failed in most interventional trials. Potential reasons for why α-tocopherol supplements exhibit disappointing effects, especially compared with dietary intake, are put forward and implications for future studies are discussed.