Role of Photoactive Phytocompounds in Photodynamic Therapy of Cancer

Abstract

Cancer is one of the greatest life-threatening diseases conventionally treated using chemo- and radio-therapy. Photodynamic therapy (PDT) is a promising approach to eradicate different types of cancers. PDT requires the administration of photosensitisers (PSs) and photoactivation using a specific wavelength of light in the presence of molecular oxygen. This photoactivation exerts an anticancer effect via apoptosis, necrosis, and autophagy of cancer cells. Recently, various natural compounds that exhibit photosensitising potentials have been identified. Photoactive substances derived from medicinal plants have been found to be safe in comparison with synthetic compounds. Many articles have focused on PDT mechanisms and types of PSs, but limited attention has been paid to the phototoxic activities of phytocompounds. The reduced toxicity and side effects of natural compounds inspire the researchers to identify and use plant extracts or phytocompounds as a potent natural PS candidate for PDT. This review focusses on the importance of common photoactive groups (furanocoumarins, polyacetylenes, thiophenes, curcumins, alkaloids, and anthraquinones), their phototoxic effects, anticancer activity and use as a potent PS for an effective PDT outcome in the treatment of various cancers.

Strategies for Cancer Treatment Based on Photonic Nanomedicine

“…Photodynamic therapy (PDT) has been successfully employed in cancer treatment due to its ability to kill cancer cells through a localized generation of oxidative stress, preserving normal tissues [ 60 ]. It employs three individually distinct agents: the photosensitizer (PS), which is a photoactivatable drug, light (mainly lasers) [ 61 ], and molecular oxygen (O 2 ) [ 62 ]. During PDT, the cytotoxic species singlet molecular oxygen ( 1 O 2 *) and ROS are generated from a photodynamic process involving energy transfer from the PS in the triplet excited state to the ground state (O 2 ) upon light exposure.…”

“…Thus, PS localization is of fundamental importance in the success of PDT. In general, PDT is dependent on the chemical nature of PS, dosage, light source/intensity, and exposure time [ 62 ]. Different kinds of PS have been employed nowadays, allowing them to have affinity for different organelles/parts of the cells.…”

“…Usually, in PDT, the light wavelength ranges from 600 to 800 nm, including blue, red, and infrared lights. The right choice of light source depends on the nature of the tumor, chemical nature of PS (its absorption spectra), location and size [ 62 ].…”

Biophysical Characterization and Anticancer Activities of Photosensitive Phytoanthraquinones Represented by Hypericin and Its Model Compounds

“…However, their clinical applications have been limited by several imperfections such as accumulation in tissues, a lack of chemical purity, or low penetration [80]. Muniyandi et al [81] have published a comprehensive review article about the role of photoactive phytocompounds in PDT. Phototoxic effects, potential applications in the PDT of cancer of the main natural PSs groups (furanocoumarins, thiophenes, alkaloids, curcumins, polyacetylenes, and anthraquinones) have been described [81].…”

“…Muniyandi et al [81] have published a comprehensive review article about the role of photoactive phytocompounds in PDT. Phototoxic effects, potential applications in the PDT of cancer of the main natural PSs groups (furanocoumarins, thiophenes, alkaloids, curcumins, polyacetylenes, and anthraquinones) have been described [81]. Our paper focuses on the four anthraquinones, of which hypericin is the most promising PS in the PDT of cancer.…”