Photodynamic effect of hypericin on the conformation and catalytic activity of hemoglobin

Ultraviolet irradiation-dependent fluorescence enhancement of hemoglobin catalyzed by reactive oxygen species

Ultraviolet (UV) light has a potent effect on biological organisms. Hemoglobin, an oxygen-transport protein, plays an irreplaceable role in sustaining life of all vertebrates. In this study we scrutinize the effects of ultraviolet irradiation (UVI) as well as visible irradiation on the fluorescence characteristics of bovine hemoglobin (BHb) in vitro. Data show that UVI results in fluorescence enhancement of BHb in a dose-dependant manner. Furthermore, UVI-induced fluorescence enhancement is significantly increased when BHb is pretreated with hydrogen peroxide (H₂O₂), a type of reactive oxygen species (ROS). Meanwhile, The water-soluble antioxidant vitamin C suppresses this UVI-induced fluorescence enhancement. In contrast, green light irradiation does not lead to fluorescence enhancement of BHb no matter whether H₂O₂ is acting on the BHb solution or not. Taken together, these results indicate that catalysis of ROS and UVI-dependent irradiation play two key roles in the process of UVI-induced fluorescence enhancement of BHb.

Spectrophotometric study of the interaction between chlorotetracycline and bovine serum albumin using Eosin Y as site marker with the aid of chemometrics

Interaction of chlorotetracycline (CTC) with bovine serum albumin (BSA) was investigated under simulated physiological conditions by spectroscopy with the aid of multivariate curve resolution-alternating least squares (MCR-ALS). Eosin Y was selected as an alternative site I marker on the BSA to study the above molecular interaction. The binding of Eosin Y and CTC to BSA showed that CTC was displaced from CTC-BSA complex by Eosin Y, and Eosin Y-BSA complex was formed. However, the recorded fluorescence spectra of Eosin Y and Eosin Y-BSA overlapped and MCR-ALS was applied to resolve the two-way fluorescence spectra. From the resolved equilibrium concentration profiles, it was observed that Eosin Y competed with CTC in the binding process with BSA; it was also shown that the binding site of CTC on BSA was site I, and this was further confirmed by the fluorescence polarization method. Compared with some common site I markers for BSA, the fluorescence and UV-vis spectral shapes of the Eosin Y-BSA complex were quite different from that of Eosin Y, and this feature facilitated the investigation of the small molecule-BSA interaction.

A review of the antibacterial activity of Hypericum perforatum L

Hypericum perforatum L. (Hypericaceae) is a perennial herb that is commonly known as St. John's Wort. The plant has been valued for its important biological and chemical perspectives and its use in the treatment of infectious diseases has been documented in ethnobotanical reports. Most recent interest in H. perforatum has focused on its antidepressant effects, and only recently has its antimicrobial activity been evaluated against a number of bacterial and fungal strains. The present review gives a comprehensive summary of the ethnobotanical uses, chemical constituents and biological effects (antibacterial and antifungal) of this species. A comprehensive account of the chemical constituents including anthraquinone derivatives (naphthodianthrones), flavonoids, prenylated phloroglucinols, tannins and volatile oils is also included. Various types of preparations, ointments, creams and extracts prepared with and compounds isolated from this species have been found to possess a broad spectrum of biological and pharmacological effects such as antidepressant effects, wound-healing, antiviral and antimicrobial activity. The antibacterial activity of crude extracts can be related to the use of the herb as a wound healer in ancient times. The sole antibacterial principle isolated to date is a tetraketone, hyperforin, also thought to be responsible for the antidepressant activity of the herb. The available literature indicates that it has a higher antibacterial activity against Gram-positive than Gram-negative bacteria, and alcoholic extracts (methanolic/ethanolic) were shown to possess more pronounced activity than aqueous extracts. Based on the chemical and pharmacological characteristics of H. perforatum, we concluded that this species has beneficial therapeutic properties and has the potential for use as an effective adaptogenic herbal remedy.