Light-Activated Phytochemicals in Photodynamic Therapy for Cancer: A Mini Review

Light-Activated Phytochemicals in Photodynamic
Therapy for Cancer: A Mini Review
Blassan P. George, PhD, and Heidi Abrahamse, PhD
Abstract
Background: Cancer is a serious life-threatening disease often thought
of as a deadly and painful disease with
no permanent cure. With the advancement of medical science, there have
been several clinically approved
treatment options developed over the past decade. Photodynamic therapy
(PDT) is one such approved mini-
mally invasive light-based therapeutic option for many cancers.
Selection of a suitable photosensitizer (PS) is
an important step in PDT for improved therapeutic outcomes. Efforts to
discover more efficient PSs continue
for optimal PDT.
Objective: This review discusses the available natural PS of plant
origin, the role of phytochemicals in the
application of PDT of cancer, specific localization of PS in various
cell organelles, and photochemical reactions.
Materials and methods: Owing to the substantial side effects, many
biomedical research fields are currently
focusing on natural compounds with chemotherapeutic potential with
environmentally sustainable green approaches.
Medicinal plant extracts have been used since ancient times for the
treatment of various ailments. Plants are a natural
source of many bioactive compounds with pharmaceutical potential and
there have been some efforts made to
discover potential new compounds from plants with photosensitizing
properties for effective PDT outcomes.
Results and conclusions: The PDT application in the current scenario
raises some questions, such as most
effective PS, its administration, the time of irradiation, light source,
sensitivity of cells toward PS, and so forth.
PDT effects can be direct or indirect. Owing to the direct effect of the
PDT, most of the tumoral mass is
destroyed. In the cancer cells that were not directly affected,
secondary effects such as vascular effects,
apoptosis induction, inflammation, and generation of an immune response
may occur; however, the complex
nature of PDT tissue response is not fully established.
Keywords: phytochemicals, cancer, photosensitizers, photodynamic
therapy, photochemical reactions, sub-
cellular localization
Introduction
More than half of all approved medical applied drugs
or drugs currently studied in clinical trials are de-
rived from plant sources. 1 The combination of photodynamic
therapy (PDT) with phytochemicals is effective in enhancing
PDT outcomes and overcoming drug resistance compared
with the monotherapy regime. Hence, further investigation of
potential herbal agents in cancer PDT is necessary. One of the
most well-known first choice natural photosensitizers (PSs)
isolated from the plant Hypericum perforatum is Hypericin.
The phototoxic properties of Hypericin can be improved by
combining it wit