Radioprotective, anticarcinogenic and antioxidant properties of the Indian holy basil, Ocimum sanctum (Tulasi).

Ocimum sanctum (Sanskrit: Tulasi; English: holy basil; family: Labiatae), is found throughout the semi­ tropical and tropical parts of India. It is grown in the gardens and is worshipped as a sacred plant by the Hindus. The medicinal value of this plant is known for millennia. The different parts of the plant are traditionally used in the Ayurveda and Siddha systems for the treatment of diverse ailments like infections, skin diseases, hepatic disorders, common cold and cough, malarial fever and as an antidote for snake bite and scorpion stingl. The Santal tribe uses the plant in fever, dropsy,. vomit�ng, constipation, cough, postnatal complamts, etc . O. sanctum is also used as an ingredient of herbal preparations with other medicinal plants. Investigations on its pharmacological and therapeutic properties during the past decades have led to a number of publications. Literature on the ethnobotany, pharmacognosy and pharmacology of Ocimum sp. has been extensively reviewed by Satyavati and co-workersl. Water extract of the leaves was reported to have a hypotensive action in dogs3. A 50 % ethanolic extract of O. sanctum leaves showed hypoglycemic effect in rats and antispasmodic activity in guinea pigs4. The ether extract and essential oil of the leaves exhibited antibacterial activity against a number of bacterial species5-8• The essential oil also exhibited antifungal . . 79 C aCtivIty'. rude extracts from the young leaves and plant showed antiviral activity against some common plant viruses like papaya leaf reduction virus 10, top . . f II 2 necrosIs VIruS 0 pea and bean mosaic virus I . The acetone extract of the plant showed insecticidal activity against Spodoptera litura13, while the water extract has nematicidal activiti4• The anti-stress effect of the plant has been reported in mice and ratsl5-19 H t t ' .. . epa opro ectIve actIvIty of the extract against carbon tetrachloride toxicity20 and paracetamol induced damage21 have been demonstrated. A methanol extract and an aqueous suspension of 0. sanctum leaves were found to have anti-inflammatory and analgesic22 and immuno­ stimulatory23 properties. Aqueous extract of the leaves and pure eugenol, which is a constituent of the extract, were reported to reduce the biochemical and membrane changes induced by restraint stress in t 24 0 . ra s . Clmum sanctum extract also protected against experimental ulcers, which was related to its ability to reduce acid secretion and increase mucus secretion25. The essential oil of O. sanctum was observed to have anti-inflammatory26.27 and anti-ulcer28 activities in rats. Oral feeding of Ocimum leaf powder for one month was found to reduce fasting blood sugar and cholesterol levels in blood, liver and heart of rats; the results indicated a hypoglycemic and hypolipidemic effect in diabetic rats29. A preliminary clinical trial showed that treatment with the aqueous extract of O. sanctum leaves gave a higher survival rate among patients suffering from viral encephalitis than in patients given steroid treatmeneo. Oral administration of 250 g of dried leaf powder daily for 6 weeks reduced the blood pressure in hypertensive patients31. There has been a high interest in the radioprotective, anticarcinogenic and antioxidant properties of this plant in the recent years . The present paper attempts to review the publications on these topics.