Ocimum sanctum (Holy Basil, Tulsi, Tulasi, Kemangen) belongs to Lamiaceae (Mint family). A tropical, much branched, annual herb, up to 18 inches tall; it grows into a low bush. The tulsi considered sacred by the Hindus, has small leaves with a strong smell and purple flowers. In several ancient systems of medicine including Ayurveda, Greek, Roman, Siddha and Unani, ocimum has vast number of therapeutic aoolications such as in cardiopathy, haemopathy, leucoderma, asthma, bronchitis, catarrhal fever, otalgia, hepatopathy, lumbago, hiccups, ophthalmia, gastropathy, genitourinary disorders, ringworm, verminosis, skin diseases, etc.

Antimicrobial action against drug-resistant strains: Osimum sanctum extract was found to be active against multidrug-resistant strains of Staphylococcus aureus that are also resistant to common beta lactam antibiotics. Similarly, ocimum was found to be active against resistant Neisseria gonorrhea straains. Moderate activity was observed against the multidrug-resistant Salmonella typhi. Ocimum was also tested against enteric pathogens by the gar diffusion method. Aqueous extract showed wider zone inhibition compared to alcoholic extracts. Klesbiella, E. coli, proteus and Staphylococcus aureus were inhibited.

Effects on Central Nervous System: An ethanol extract of ocimum prolonged the time of lost reflex in mice due to pentobarbital, decreased the recovery time and severity of electroshock- and phenyltetrazole-indced convulsions and decreased apomorphine-induced fighting time and ambulation in "open field" trials. Antistressor proprty of the plant against acute and chronic noise sytress in rats has also been demonstrated. Acute noise stress caused leukopenia, ncreased corticosterone level and enhanced neutrophil functions. Prior treatment with ocimum brought back stress-altered parameters to normal levels. At high doses occimum extract increased swimming time suggesting a CNS stimulant and/or antistress activity. The effect was comparable to that of desipramine, an antidepressant drug.

Long term hypoperfusion (a model for cerebrovascular insufficiency in dementia) caused altered exploratory behavior in open-field testing and memory deficits. Pretreatment with ocimum significantly prevented the structural sand functional disturbances

Diabetes: Oral administration of ocimum extract led to marked lowering of blood sugar in normal, glucose-fed hyperglycemic, and streptozotocin-induced diabetic rats. A randomizzed, placebo-controlled, cross over single blind human trial indicated a significant decrease in fasting and postprandial blood glucose levels by 17.6% and 7.3%, respectively. Urine glucose levels showed a similar trend. Further, ocimum has aldose reductase activity, which may help in reducing the complications of diabetes such as cataract, retinopathy, etc.

Antioxidant Action: Tulsi has been credited with antioxidant, antiinflammatory, and cognitive enhancing properties. Tulsi extract has shown nitric oxide scavenging activity in a dose-dependent manner. In one study the effect of ocimum in cerebral reperfusion injury and long term hypoperfusion has been described. Ocimum pretreatment prevented the reperfusion-induced lipid peroxidation and superoxide dismutase (SOD) activity. Hypoperfusion caused cellular edema, gliosis and perivascular inflammatory infiltrate. Ocimum treatment prevented these structural and functional disorders. Another study showed that ocimum prevented isoproterenol-induced myocardial necrosis in rats which would normally deplete myocardial SOD and glutathione peroxidase (GPx). Ocimum has also been shown to offer significant protection against radiation lethality and chromosomal abberations in vivo which are believed to be associated with its antioxidant ability.Extracts obtained by different processes have been assayed for free radical scavenging activities by the chemiluminiscence method. Peroxy radicals were generated from 2,2'-azobis(2-amidinopropane)dihydrochloride, superoxide radical from xanthine/xanthine oxidase and hydroxyl radical from xanthine/xanthine oxidase/FeCl3/EDTA. Potent activity against these radical s was demonstrated.

Antifertility Properties: It would be of great value to develop plant-derived fertility inhibitors that are selective for reproductive systems and enzymes. Many plants including ocimum have been screened for the fertility inhibiting effect in the male. Of the 1600 plants tested, 90 showed positive semen coagulating properties. Ocimum extract fed to albino rats for 48 days showed decreased total sperm count, sperm motility and forward velocity. The anti-androgenic property of ocimum was found to be reversible, as all parameters returned to normal levels 2 weeks after cessation of treatment. Another study on male Wistar rats showed decreased sexual activity during the period of treatment. However, high doses (400 mg/kg) were needed for this effect. Yet another study evaluated the anti-fertilizing, antizygotic, blastocystotoxic, antiimplantation and early abortifacient activities. Ocimum extract showed encouraging results. None of the rats delivered to experimental rats showed evidence of teratogenicity up to an age of 1 month.

Cancer: Anticancer and chemopreventive properties of ocimum have been reported. Topical application of ocimum extract significantly reduced the cumulative number of papillomas in 7,12-dimethylbenz(a)anthracene-induced skin papillomagenesis in rats. A significant 2-fold elevation of reduced glutathione content in the skin increased glutathione S-transferase activity was also observed. Rat hepatocytes pretreated with ocimum and then with DMBA showed significant reduction in DMBA-DNA adducts. Pretreatment with 500 micrograms of the extract caused a 93% reduction in the mean values of DMBA-DNA adducts. Similar effects were also noted with DMBA-induced hamster bucchal pouch carcinogenesis. Another study showed increased activities of cytochrome p450, cytochrome b5, aryl hydrocarbon hydroxylase and glutathione S-transferase, all of which are important in the detoxification of carcinogens and mutagens.