Hypericin in photobiological assays: An overview.

Hypericin is considered a potent photosensitizer for use in antitumor and antimicrobial photodynamic therapy (PDT). This review presents the primary biological results obtained with hypericin in photodynamic therapy applications, such as photodynamic cancer treatment, photoinactivation of microorganisms (PDI), tissue scarring, and photo diagnosis. We present a compilation of in vitro results that have been published thus far; for these studies, we highlight the hypericin concentration, light dose, and other experimental conditions to evaluate the efficiency of photodynamic treatment like cell death, cell viability, or cell proliferation. The results indicate that different hypericin phototoxicity levels can be observed according to the specific light dose and concentration. Furthermore, it was shown that cellular localization and cell death mechanisms (apoptosis and necrosis) are dependent on the cell type.

Comparative in vitro study of photodynamic activity of hypericin and hypericinates in MCF-7 cells.

In this work we present a comparative in vitro study of photodynamic activity between hypericin (HYP) and some hypericinates (hypericin ionic pair with lysine or N-methylglucamine) in human mammary adenocarcinoma cells (MCF-7). The toxicity and phototoxicity of hypericin and hypericinates were compared, as well as their cellular uptake and localization and mutagenic, genotoxic and clonogenic capacity. Our results demonstrate that different cationic moieties promote differences in the hypericinate solubility in a biological environment, and can influence the cellular localization and the phototoxicity of the photosensitizer. It was verified that hypericinates have better efficiency to generate singlet oxygen than HYP, and a lower aggregation in biological medium. In vitro assays have shown that HYP and the hypericinates are able to permeate the MCF-7 cell membrane and accumulated in organelles near the nucleus. The difference in location, however, was not determinant to the cell death mechanism, and a higher prevalence of apoptosis for all studied compounds occurred. The photodynamic studies indicated that hypericinates were more effective than HYP and were able to inhibit the formation of cellular colonies, suggesting a possible ability to prevent the recurrence of tumors. It also appears that all compounds have relative safety for mutagenicity and genotoxicity, which opens up a further safe route for application in in vivo studies.