Chapter 103 - Radioprotective Effects of the Ocimum Flavonoids Orientin and Vicenin: Observations from Preclinical Studies

Abstract

Radiotherapy is an important treatment modality for cancer and, depending on the stage of the tumor, its localization and general health of the patient, it may be used as a single modality or as an adjuvant along with surgery and/or chemotherapy. However, effective use of ionizing radiation is compromised by the side effects that result from radiation-induced damage to normal tissue. The use of radioprotective compounds, which can selectively protect normal tissues against radiation injury, is of immense use as, in association with protecting the normal tissue, it will also permit the use of higher doses of radiation to obtain better cancer control and a possible cure. However, to date no ideal radioprotectors are available as most synthetic compounds, including the Food and Drug Administration, USA, approved aminothiol, S-2-(3-aminopropyl-amino) ethyl phosphorothioic acid (WR-2721, amifostine, ethiophos (USA), or gammaphos (former USSR)), are toxic at their optimal concentrations. Obviously, there has been limited success of these agents in clinics, and this has necessitated the need for novel agents that are effective and non-toxic at their optimal therapeutic concentration(s). Plants have been a companion of humans since time immemorial, providing several useful drugs for the treatment of various ailments. Ocimum sanctum, commonly known as the Holy Basil, an aromatic herb belonging to the family Labiatae is an important medicinal and religious plant of India. The leaves and the stems have also been used since time immemorial in countless folk systems of medicine in Southeast Asia to treat various illnesses. Scientific studies carried out in the recent past have shown that the plant possesses anti-inflammatory, analgesic, antipyretic, antiasthmatic, antiemetic, diaphoretic, antidiabetic, hepatoprotective, hypotensive, hypolipidemic, antibacterial, antifungal, cardioprotective, antistress, anticancer and chemopreventive effects and validates ethnomedicinal uses. Exploratory studies performed in the past two decades have also shown that Tulsi and its flavonoids orientin and vicenin possess radioprotective effects. In this chapter, an attempt is made to summarize the radioprotective effects of the ocimum flavanoids.