What is holy basil

Holy basil also known as Tulsi or Ocimum sanctum L. (Ocimum tenuiflorum L.) is an aromatic shrub in the basil family Lamiaceae (tribe ocimeae) that is thought to have originated in north central India and now grows native throughout the eastern world tropics ¹⁾. Holy basil has been used as a medicinal plant for thousands of years in Indian traditional medicine Ayurveda and its allied herbalism disciplines for its diverse healing properties ²⁾. Holy basil plant is considered sacred and is worshipped in a sanctorum of its own in traditional Hindu temples, sacred groves, and households throughout the subcontinent and therefore its taxonomical synonym Ocimum sanctum L. is more popular in Indian scientific literature. Within Ayurveda, holy basil is known as “The Incomparable One,” “Mother Medicine of Nature” and “The Queen of Herbs,” and is revered as an “elixir of life” that is without equal for both its medicinal and spiritual properties ³⁾. Within India, holy basil has been adopted into spiritual rituals and lifestyle practices that provide a vast array of health benefits. This emerging science on holy basil, which reinforces ancient Ayurvedic wisdom, suggests that holy basil is a tonic for the body, mind and spirit that offers solutions to many modern day health problems ⁴⁾. A number of recent biochemical and physiological studies indicate that holy basil may possess antidiabetic ⁵⁾, antimicrobial ⁶⁾, anticancer ⁷⁾, adaptogenic ⁸⁾, and radioprotective ⁹⁾ properties. Daily consumption of holy basil is said to prevent disease, promote general health, wellbeing and longevity and assist in dealing with the stresses of daily life ¹⁰⁾. Holy basil is also credited with giving luster to the complexion, sweetness to the voice and fostering beauty, intelligence, stamina and a calm emotional disposition ¹¹⁾. In addition to these health-promoting properties, holy basil is recommended as a treatment for a range of conditions including anxiety, cough, asthma, diarrhea, fever, dysentery, arthritis, eye diseases, otalgia, indigestion, hiccups, vomiting, gastric, cardiac and genitourinary disorders, back pain, skin diseases, ringworm, insect, snake and scorpion bites and malaria ¹²⁾.

Holy basil is an erect, much branched subshrub, 30–60 cm tall with hairy stems and simple, opposite, green leaves that are strongly scented. Leaves have petioles and are ovate up-to 5 cm long, usually slightly toothed ¹³⁾. Recent molecular phylogenetic studies indicate that the tribe ocimeae is originated in tropical Asia and got introduced elsewhere ¹⁴⁾.

Figure 1. Holy basil (Ocimum sanctum L)

Holy basil phytochemical constituents

The chemical composition of holy basil is highly complex, containing many nutrients and other biologically active compounds, the proportions of which may vary considerably between strains and even among plants within the same field. Furthermore, the quantity of many of these constituents is significantly affected by differing growing, harvesting, processing and storage conditions that are not yet well understood ¹⁵⁾.

The nutritional and pharmacological properties of the whole herb in its natural form, as it has been traditionally used, result from synergistic interactions of many different active phytochemicals ¹⁶⁾. Consequently, the overall effects of holy basil cannot be fully duplicated with isolated compounds or extracts ¹⁷⁾. Because of its inherent botanical and biochemical complexity, holy basil standardization has, so far, eluded modern science. The holy basil leaf volatile oil ¹⁸⁾ contains eugenol (1-hydroxy-2-methoxy-4-allylbenzene [Figure 2]), euginal (also called eugenic acid), urosolic acid, carvacrol (5-isopropyl-2-methylphenol), linalool (3,7-dimethylocta-1,6-dien-3-ol), limatrol, caryophyllene (4,11,11-trimethyl-8-methylene-bicyclo[7.2.0]undec-4-ene), methyl carvicol (also called Estragol: 1-allyl-4-methoxybenzene) while the seed volatile oil have fatty acids and sitosterol; in addition, the seed mucilage contains some levels of sugars and the anthocyans are present in green leaves. The sugars are composed of xylose and polysaccharides ¹⁹⁾.

Although holy basil is known as a general vitalizer and increases physical endurance, it contains no caffeine or other stimulants ²⁰⁾. The stem and leaves of holy basil contain a variety of constituents that may have biological activity, including saponins, flavonoids, triterpenoids, and tannins ²¹⁾. In addition, the following phenolic actives have been identified, which also exhibit antioxidant and antiinflammatory activities, Rosmarinic acid ²²⁾. Two water-soluble flavonoids: Orientin (8-C-beta-glucopyranosyl-3’,4’,5,7-tetrahydroxyflav-2-en-3-one) and Vicenin (6-C-beta-D-xylopyranosyl-8-C-beta-D-glucopyranosyl apigenin), have shown to provide protection against radiation-induced chromosomal damage in human blood lymphocytes ²³⁾.

Figure 2. Holy basil eugenol (1-hydroxy-2-methoxy-4-allylbenzene)

Holy basil uses in Ayurveda and traditional medicine

Anti-anxiety and anti-depressant

The psychotherapeutic properties of holy basil have been explored in various animal experiments that reveal that holy basil has anti-anxiety and anti-depressant properties ²⁴⁾, with effects comparable to diazepam and antidepressants drugs ²⁵⁾. Animal studies further reveal that holy basil enhances memory and cognitive function ²⁶⁾ and protects against aging-induced memory deficits ²⁷⁾. Similarly, in human studies, holy basil has been observed to reduce stress, anxiety and depression ²⁸⁾, with a 6-week, randomized, double-blind, placebo-controlled study reporting that holy basil significantly improves general stress scores, sexual and sleep problems and symptoms such as forgetfulness and exhaustion ²⁹⁾.

While modern scientific studies suggest that holy basil is effective in treating a range of stressful conditions, within Ayurveda, holy basil is more commonly recommended as a preventive measure to enhance the ability to adapt to both psychological and physical stress and therefore prevent the development of stress-related diseases. To this end, many Ayurvedic practitioners recommend the regular consumption of holy basil tea as an essential lifestyle practice.

Liquid yoga

Regular consumption of holy basil tea may be compared with the regular practice of yoga, which can be considered “adaptogenic” through nurturing and nourishing the body — mind — spirit while fostering a sense of relaxation and wellbeing. In contrast, regular consumption of caffeinated beverages such a black and green tea (Camellia sinensis L.) and coffee (Coffea arabica L.) may be compared with more aerobic exercise, which confers health benefits through stimulation and activation.

Like yoga, holy basil has a calming effect that leads to clarity of thought, along with a more relaxed and calm disposition. The cognitive and memory-enhancing properties of holy basil therefore differ from those of caffeine-containing beverages such as coffee and tea, which heightens arousal and may cause physical and mental agitation. Furthermore, holy basil does not produce the same physical dependence as caffeine and can be safely consumed on a regular basis without the fear of withdrawal effects.

The drinking of tea and coffee has become an integral part of modern life and has been ritualized in many cultures to guide social interactions, set social agendas and invoke spiritual awareness. For example, sophisticated Asian tea ceremonies involve a whole set of rituals, tools and gestures that serve to transcend normal consciousness, while in the west the ritual of “afternoon tea” or “high tea” emphasizes the surroundings, equipment, manners and social circle. In less-formal situations, many people ritualize their morning cup of coffee and use the “meet-up for coffee” to arrange their social agendas, while the “tea break” is often built into the modern-day work routine. Yet, while tea and coffee have infiltrated their way into modern living, they have not yet attained the status that holy basil has within traditional Indian life.

Infection protection

holy basil has also been shown to be active against many animal pathogens, and this has led to holy basil being used in animal rearing to reduce infections in cows, poultry, goats, fish and silkworms. Holy basil’s activity against water-borne and food-borne pathogens further suggests that it can be used in the preservation of food stuffs ³⁰⁾ and herbal raw materials as well as for water purification ³¹⁾ and as a hand sanitizer ³²⁾.

Holy basil’s broad-spectrum activity, which includes activity against Streptococcus mutans, the organism responsible for tooth decay, further suggests that it can be used as a herbal mouth wash for treating bad breath, gum disease and mouth ulcers ³³⁾. This has been confirmed in clinical trials that have demonstrated that rinsing with holy basil is as effective as 0.2% Chlorhexidine and Listerine in reducing the levels of Streptococcus mutans ³⁴⁾ and that a herbal mouthwash that includes holy basil is preferred for its taste and convenience ³⁵⁾.

Holy basil’s unique combination of antibacterial antioxidant, anti-inflammatory and analgesic activities also makes it useful in wound healing ³⁶⁾. This is supported by experimental evidence that has shown that holy basil can increase wound-breaking strength and accelerate wound healing in laboratory animals. Holy basil has also been shown to have anti-ulcer and ulcer-healing activity that has been observed in many different animal models including aspirin-, indomethacin-, alcohol-, histamine-, reserpine-, serotonin-, acetic acid-, meloxicam-, cold restraint-, pyloric ligation- and stress-induced ulceration models ³⁷⁾. This anti-ulcer activity is attributed to multiple actions including the reduction of offensive factors such as acid-pepsin secretion and lipid peroxidation and the enhancement of gastric defensive factors such as mucin secretion, cellular mucus and longevity of mucosal cells ³⁸⁾.

Holy basil potential health benefits

Human clinical trials are lacking. In animal and in vitro experiments, effects of holy basil are largely attributed to antioxidant activity. Hypoglycemic activity and protective effects against noise stress have been studied, but clinical trials are lacking.

Holy basil dosage

Information is lacking. One clinical trial for hypoglycemic effect used 2.5 g leaves as dried powder in 200 mL water daily for 2 months.

Animal Studies (Pre-Clinical)

During the last two decades, holy basil has demonstrated various pre-clinical activities in animal models in vitro testing. Some such notable findings are reported here:

Antidiabetic

Ethanolic extract of holy basil significantly decreases the blood glucose, glycosylated hemoglobin and urea with a concomitant increase in glycogen, hemoglobin and protein in streptozotocin-induced diabetic rats ³⁹⁾. This extracts also resulted in an increase in insulin and peptide levels and glucose tolerance.

The constituents of holy basil leaf extracts have stimulatory effects on physiological pathways of insulin secretion, which may underlie its reported antidiabetic action ⁴⁰⁾.

Grover et al. ⁴¹⁾ suggested that treatment with holy basil extract for 30 days to normal rats fed with fructose for 30 days significantly lowered serum glucose level in comparison with control group. However, holy basil extract has no significant effect on hyperinsulinemia.

Ghosap et al. ⁴²⁾ unravel the possible mechanism of glucose-lowering activity of holy basil in male mice. The study suggested that holy basil decreases the serum concentration of both cortisol and glucose and also exhibited antiperoxidative effect. Therefore holy basil may potentially regulate corticosteroid- induced diabetic mellitus.

In another study the effect of holy basil on three important enzymes of carbohydrate metabolism [glucokinase (gk), hexokinase (hk) and phosphofructokinase (PFK) along with glycogen content of insulin-dependent (skeletal muscle and liver) and insulin-independent tissues (kidneys and brain) was studied by Vats et al ⁴³⁾ in streptozotocin (STZ, 65 mg/kg)-induced model of diabetes for 30 days in rats. Administration of holy basil extracts 200 mg/kg for 30 days lead to decrease in plasma glucose levels by approximately 9.06 and 24.4% on 15th and 30th day. holy basil significantly decreased renal but not liver weight (expressed as % of body weight) holy basil glycogen content in any tissue; also holy basil partially corrected the activity of glucokinase (gk), hexokinase (hk) and phosphofructokinase (PFK) distributed in the diabetic control.

holy basil (holy basil) leaf powder was fed at the 1% level in normal and diabetic rats for a period of one month and the result indicated a significant reduction in fasting blood sugar urogenic acid, total amino acids level. This observation indicates the hypoglycemic effect of holy basil in diabetic rats ⁴⁴⁾.

Chattopadyay also reported that oral administration of alcoholic extract of leaves of holy basil led to marked lowering of blood sugar level in normal, glucose-fed hyperglycemic and streptozotocin-induced diabetic rats ⁴⁵⁾. Furthermore, the extract potentiates the action of exogenous insulin in normal rats. The activity of the extract was 91.55 and 70.43% of that of Tolbutamide in normal and diabetic rats, respectively.

Cardiac activity

Oral feeding of hydroalcoholic extract of holy basil (100 mg/kg) to male Wister rats subjected to chronic-resistant stress (6 h/day for 21 days) significantly prevented the chronic-resistant stress/induced rise in plasma cAMP level, myocardial superoxide dismutase and catalase activities as well as the light microscopic changes in the myocardium ⁴⁶⁾.

Wister rats fed with fresh leaf homogenate of holy basil (50 and 100 mg/kg body weight) daily 30 days inhibit isoproterenol-induced changes in myocardial superoxide dismutase, glutathione peroxidase and reduced glutathione ⁴⁷⁾.

In another study effect of pre- and co-treatment of hydroalcoholic extract of holy basil at different doses (25, 50, 75, 100, 200 and 400 mg/kg) was investigated against isoproterenol (ISO, 20 mg/kg, Sc) myocardial infarction in rats. holy basil at the dose of 25, 50, 75 and 100 mg/kg significantly reduced glutathione (GSH), superoxide dismutase and LDH levels. In this study ⁴⁸⁾, it was observed that holy basil at the dose of 50 mg/kg was found to demonstrate maximum cardioprotective effect.

The generation of drug-induced oxygen radicals in heart cells led to cardiac lipid membrane peroxidation ⁴⁹⁾. Urosolic acid(UA) isolated from holy basil have been identified as a protector against Adriamycin (ADR)-induced lipid peroxidation. Protection with UA was 13 and 17% in liver and heart microsomes, respectively. On combination with oleanolic acid (OA) isolated from Eugenia jumbolata , it increased to 69%.

Wound healing activity

Shetty et al. ⁵⁰⁾ evaluated the wound healing effect of aqueous extract of holy basil in rats. Wound-breaking strength in incision wound model, epithelization period and percent wound concentration in excision wound model were studied owing to increased per cent wound contraction. Holy basil may be useful in the management of abnormal healing such as keloids and hypertropic scars.

Ethanolic extract of leaves of holy basil was investigated for normal wound healing and dexamethasone-depressed healing ⁵¹⁾.The extract significantly increased the wound breaking strength, wound epithelializes fast and wound contraction was significantly increased along with increase in wet and dry granulation tissue weight and granulation tissue breaking strength. The extract also significantly decreases the anti-healing activities of dexamethasone in all wound healing models.

Radio-protective effect

Radio-protective effect of aqueous extract of holy basil (40 mg/kg, for 15 days) in mice exposed to high doses (3.7 MBq) of oral 131 iodine was investigated by studying the organ weights, lipid peroxidation and antioxidant defense enzyme in various target organs like liver, kidney, salivary glands and stomach at 24 h after exposure ⁵²⁾. Pretreatment with holy basil in radioiodine-exposed group showed significant reduction in lipid peroxidation in both kidney and salivary glands. In liver, reduced glutathione (GSH) levels showed significant reduction after radiation exposure while pretreatment with holy basil exhibited less depletion in GSH level even after 131 iodine exposure. However, no such changes were observed in the stomach. The results indicate the possibility of using aqueous extract of holy basil for ameliorating 131 iodine induced damage to the salivary glands.

Two polysaccharides isolated from holy basil could prevent oxidative damage to liposomal lipids and plasmid DNA induced by various oxidants such as iron, AAPH and gamma radiation ⁵³⁾.

Vrinda et al. ⁵⁴⁾ reported that two water-soluble flavonoids, Orientin (Ot) and Vicenin (Vc), isolated from the leaves of holy basil provide significant protection against radiation, lethality and chromosomal aberration in vivo. In order to select the most effective drug concentration, fresh whole blood was exposed to 4 Gy of cobalt-60 gamma radiation with holy basil without a 30 min pretreatment with 6.25, 12.5, 15, 17.5 and 20 micron of Ot/Vc in micronucleus test. Radiation significantly increased the micronucleus (MN) frequently. Pretreatment with either Ot or Vc at all concentration-dependent manner, with optimum effect at 17.5 μm.

The effect of aqueous extract of leaves of holy basil against radiation lethality[30] and chromosome damage was studied by radiation-induced lipid peroxidation in liver. Adult Swiss mice were injected with 10 mg/kg of gamma radiation 30 min after last injection. Glutathione (GSH) and the antioxidant enzymes glutathione transferase (GST), reductase (GSRx), peroxidase (GSPx) and superoxide dismutase (SOD) as well as lipid peroxide (LPx) activity were estimated in the liver at 15 min, 30 min, 1, 2, 4 and 8 h post-treatment. Aqueous extract itself increased the GSH and enzymes significantly above normal level, whereas radiation significantly reduced all the values and significantly increased the lipid peroxidation rate, reaching a maximum value at 2 h after exposure (3.5 times of control). Aqueous extract significantly reduced the lipid peroxidation and accelerated recovery to normal levels.

In a comparative study of radioprotection by ocimum flavonoids and synthetic aminothiol protectors in mouse showed Ocimum flavonoids as promising human radiation protectant ⁵⁵⁾. In this study, adult Swiss mice were injected intraperitoneally with 50 μg/kg body weight of Orientin (OT) or vicenin (Vc) 20 mg/kg body weight of 2-ercaptopropionyl glycine (MPG) 150 mg/kg body weight of WR2721 and exposed to whole body irradiation of 2 Gy gamma radiation 30 min later. After 24 hours, chromosomal aberrations were studied in the bone marrow of the femur by routine metaphase preparation after colchicines treatment. Pretreatment with all the protective compounds resulted in a significant reduction in the percentage of aberrant metaphases. Vicenin produced the maximum reduction in per cent aberrant cells while MPG was the least effective; OT and WR-2721 showed an almost similar effect.

Ganasoundari et al. ⁵⁶⁾ investigated the radio-protective effect of the leaf extract of holy basil (OE) in combination with WR-2721 (WR) on mouse bone marrow. Adult Swiss mice were injected intraperitoneally with OE (10 mg/kg for five consecutive days) alone or 100-400 mg/kg WR (Single dose) holy basil combination of the two and whole body was exposed to 4.5Gy gamma irradiation (RT). Metaphase plates were prepared from femur bone marrow on days 1, 2, 7 and 14 post-treatment and chromosomal aberrations were scored. Pretreatment with leaf extract of holy basil or WR individually resulted in a significant decrease in aberrant cells as well as different types of aberrations. The combination of the two further enhanced this effect; resulting in a two-fold increase in the protection factors (PF = 6.68) compared to 400 mg/kg WR alone.

Genotoxicity

In vivo cytogenetic assay in Allium cepa root tip cells has been carried out to detect the modifying effect of holy basil aqueous leaf extract against chromium (Cr) and mercury (Hg)-induced genotoxicity ⁵⁷⁾. It was observed that the roots post-treated with the leaf extract showed highly significant recovery in mitotic index and chromosomal aberrations. When compared to pre-treated (Cr/Hg) samples, the lower doses of the leaf extract were found to be more effective than the higher doses.

Immu-21, a poly-herbal formulation containing holy basil and other herbal extracts when given at 100 mg per kg daily over 7 days and 300 mg/kg daily over 14 days inhibited both cyclophosphamide (40 mg/kg intraperitoneal)-induced classical and non-classical chromosomal aberration (40–60% of control) ⁵⁸⁾. This also reduces the increase in micronuclei in the bone marrow erythrocytes of mice treated with cyclophosphamide.

Antioxidant

The antioxidant capacity of essential oils obtained by steam hydrodistillation from holy basil was evaluated using a high-performance liquid chromatography (HPLC) based hypoxanthine xanthine oxidase and OPPH assays ⁵⁹⁾. In hypoxanthine xanthine oxidase assay, strong antioxidant capacity was evident from holy basil (IC50 = 0.46 μL/ml).

In another study the aqueous extract of holy basil significantly increases the activity of anti-oxidant enzymes such as superoxide dismutase, catalase level in extract-treated group compared to control ⁶⁰⁾.

Aqueous extract of holy basil inhibit the hypercholesterolemia-induced erythrocyte lipid peroxidation activity in a dose-dependent manner in male albino rabbits ⁶¹⁾. Oral feeding also provides significant leaver and aortic tissue protection from hypercholestrolemia-induced peroxidative damage.

The effect of methanolic extract of holy basil leaves in cerebral reperfusion injury as well as long-term hypoperfusion was studied by Yanpallewar et al. ⁶²⁾. Holy basil pretreatment (200 mg/kg/day for 7 days) prevented reperfusion-induced rise in lipid peroxidation and superoxide dismutase. Holy basil pretreatment also stabilized the levels of tissue total sulfhydryl group during reperfusion.

Hypolipidemic

Administration of holy basil seed oil (0.8 gm/kg body weight/day) for four weeks, in cholesterol-fed (100 mg/kg body weight/day) rabbits significantly decreases serum cholesterol, triacylglycerol and LDL + VLDL cholesterol as compared to untreated cholesterol-fed group suggesting the hypo-cholesterolemic activity of holy basil ⁶³⁾.

Fresh leaves of holy basil mixed 1 and 2 g in 100 gm of diet given for four weeks brought about significant changes in the lipid of normal albino rabbits ⁶⁴⁾. This resulted in significant lowering in serum total cholesterol, triglyceride, phospholipids and LDL-cholesterol level and significant increase in the HDL-cholesterol and total fecal sterol contents.

Antimicrobial

Singh et al. ⁶⁵⁾ in his study suggested that higher content of linoleic acid in holy basil fixed oil could contribute towards its antibacterial activity. The holy basil oil show good antibacterial activity against Staphylococcus aureus, Bacillus pumius and Pseudomonas aeruginosa, where S. aureus was the most sensitive organism.

Geeta et al. ⁶⁶⁾ studied that the aqueous extract of holy basil (60 mg/kg) show wide zones of inhibition compared to alcoholic extract against Klebsiella, E. coli, Proteus, S. aureus and Candida albicans when studied by agar diffusion method. Alcoholic extract showed wider zone for Vibrio cholerae.

Effect on gene transcription

The genes that have direct role in artherogenesis include LDRL, LxRalpha, PPARs, CD-36 because these genes control lipid metabolism, cytotoxin production and cellular activity within the arterial wall. To know whether or not the polyphenols extracted from holy basil have any effect on the transcription of these genes, Kaul et al. ⁶⁷⁾ cultured human mononuclear cells in the presence of polyphenols extracted from holy basil Transcriptional expression of these genes was measured by using RT-PCR and SCION IMAGE analysis software. These polyphenolic extracts were found to have the inherent capacity to inhibit the transcriptional expression of these genes.

Gastroprotective

The standardized methanolic extract of leaves of holy basil given in doses of 50–200 mg/kg orally twice daily for five days showed dose-dependent ulcer protective effect against cold-restraint stress-induced gastric ulcers. Optimal effective dose (100 mg/kg) of holy basil extract showed significant ulcer protection against ethanol and pyloric ligation induced gastric ulcer but was ineffective against aspirin-induced ulcer ⁶⁸⁾. Holy basil extract (100 mg/kg) also inhibits the offensive acid pepsin secretion and lipid peroxidation and increases the gastric defensive factors like mucin secretion, cellular mucus and lifespan of mucosal cells.

Dharmani et al. ⁶⁹⁾ evaluated the anti-ulcerogenic activity in cold-restraint, aspirin, alcohol, pyloric ligation induced gastric ulcer models in rats, histamine-induced duodenal ulcer in guinea pigs and ulcer healing activity in acetic acid induced (AC) chronic ulcer model. Osimum sanctum L. at a dose of 100 mg/kg was found to be effective in cold-restraint (65.07%), aspirin (63.49%), alcohol (53.87%), pyloric ligation (62.06%) and histamine (61.76%) induced ulcer models and significantly reduced free, total acidity and peptic activity by 72.58, 58.63 and 57.6%, respectively, and increased mucin secretion by 34.61% conclusively holy basil could act as a potent therapeutic agent against peptic ulcer disease.

The antiulcerogenic property of holy basil was studied in pyloric-ligated and aspirin-treated rats ⁷⁰⁾. The holy basil extract of reduced ulcer index, free and total acidity on acute and chronic administration seven days pretreatment increased the mucus secretion also. So it may be concluded that holy basil extract has anti-ulcerogenic property against experimental ulcers and it is due to its ability to reduce acid secretion and increase mucus secretion.

Immunomodulatory effect

Immunotherapeutic potential of aqueous extract of holy basil leaf in bovine sub-clinical mastitis was investigated after intramammary infusion of aqueous extract ⁷¹⁾. The results revealed that the aqueous extract of holy basil treatment reduced the total bacterial count and increased neutrophil and lymphocyte counts with enhanced phagocytic activity and phagocytic index.

In another study, the immunomodulatory effect of holy basil seed oil was evaluated in both non-stressed and stressed animals ⁷²⁾. Holy basil seed oil (3 ml/kg, intraperitoneal) produced a significant increase in anti-sheep red blood cells antibody titer and a decrease in percentage histamine release from peritoneal mast cell of sensitized rats (humoral immune responses) and decrease in food pad thickness and percentage leucocyte migration inhibition (cell-mediated immune responses). Co-administration of diazepam (1 mg/kg, subcutaneously), a benzodiazepine with holy basil seed oil (1 mg/kg, intraperitoneal) enhanced the effect of holy basil seed oil on resistant stress induced changes in both humoral and cell-mediated immune responses. Further, flumazenil (5 mg/kg, intraperitoneal) a central benzodiazepine receptor antagonist inhibited the immunomodulatory action of holy basil seed oil on resistant stress induced immune responsiveness. Thus, holy basil seed oil apparatus to modulate both humoral and cell-mediated immune responsiveness and these immunomodulatory effects may be mediated by GABAnergic pathway.

Godhwani et al. ⁷³⁾ investigated the immunoregulatory profile of methanolic extract and an aqueous suspension of holy basil leaves to antigenic challenge of Salmonella typhosa and sheep erythrocytes by quantifying agglutinating antibodies employing the Widal agglutination and sheep erythrocyte agglutination tests and E-rosette formation in albino rats. The data of the study indicate an immunostimulation of humoral immunogenic response as represented by an increase in antibody titer in both the Widal and sheep erythrocyte agglutination tests as well as by cellular immunologic response represented by E-rosette formation and lymphocytosis.

Sexually transmitted disease

Extract of holy basil caused inhibition of Neisseria gonorrhoeae clinical isolates and WHO organization strains ⁷⁴⁾. The activity is comparable to penicillin and ciprofloxacin.

Effect on central nervous system

Different extracts of stem, leaf and stem callus (induced on slightly modified Murashige and Skoog’s medium and supplemented with 2,4-dichlorophenonyacetic acid and kinetin) were tested for anticonvulsant activity by maximal electroshock model using Phenytoin as standard ⁷⁵⁾. It was observed that ethanol and chloroform extractives of stem, leaf and stem calli were effective in preventing tonic convulsions induced by transcorneal electroshock.

Ethanolic extract of leaves of holy basil prolonged the time of lost reflex in mice due to pentobarbital, decreased the recovery time and severity of electroshock and pentylenetetrazole-induced convulsions and decreased apomorphine-induced fighting time and ambulation in ‘open field’ studies ⁷⁶⁾. In the forced swimming behavioral despair model, the extract lowered immobility in a manner comparable to Imipramine. This action was blocked by haloperidol and sulpiride, indicating a possible action involving dopaminergic neurons. In similar studies, there was a synergistic action when the extract was combined with bromocriptine, a potent Dopamine 2-receptor agonist.

Nootropic agents are a new class of drugs used in situations where there is organic disorder in learning abilities. Joshi and Parle ⁷⁷⁾ assessed the potential of holy basil extract as a nootropic and anti-amensic agent in mice. Aqueous extract of derived whole plant of holy basil ameliorated the amensic effect of scopolamine (0.04 mg/kg), diazepam (1 mg/kg) and aging-induced memory deficits in mice. Elevated plus maze and passive avoidance paradigm served as the exteroceptive behavioral models. holy basil extract decreased transfer latency and increased step-down latency, when compared to control (piracetam-treated), scopolamine and aged groups of mice significantly. So holy basil preparation could be beneficial in the treatment of cognitive disorders such as dementia and Alzheimer’s disease.

Methanolic extract of holy basil root extract at a dose of 400 mg/kg intraperitoneal increases the swimming time of mouse in a despair swim test model, suggesting a central nervous system stimulant and/or anti-stress activity of holy basil ⁷⁸⁾.

Analgesic effect

The analgesic activity of alcoholic leaf extract of holy basil (50, 100 mg/kg, ip; 50, 100, 200 mg/kg, oral) was tested in mice using glacial acetic acid induced writhing test ⁷⁹⁾. Holy basil reduced the number of writhes. Holy basil (50, 100 mg/kg intraperitoneal) also increased the tail withdrawal latency in mice.

Anti-fertility

Benzene extract of holy basil leaves have a reversible anti-fertility effect, as holy basil extract (250 mg/kg body weight) for 48 days decreases the total sperm count, sperm motility and forward velocity ⁸⁰⁾. The percentage of abnormal sperm increased in caudal epididymal fluid and the fructose content decreased in the caudal plasma of the epididymis and the seminal vesicles. All these parameters returned to normal two week after the withdrawal of the treatment.

Anthelmintic activity

The anthelmintic activity of the essential oil from holy basil was evaluated by Caenorhabditis elegance model ⁸¹⁾. Eugenol exhibited an ED50 of 62.1 μg/ml and being the predominant component of the essential oil, it was suggested as the putative anthelmintic principle.

Antiinflammatory

Compounds isolated from holy basil extract, Civsilineol, Civsimavatine , Isothymonin, Apigenin, Rosavinic acid and Eugenol were observed for their anti-inflammatory activity or cyclooxygenase inhibitory activity ⁸²⁾. Eugenol demonstrated 97% cyclooxygenase-1 inhibitory activity when assayed at 1000 μM concentration (pn). Civsilineol, Civsimavitin, Isothymonin, Apigenin and Rosavinic acid displayed 37, 50, 37, 65 and 58% cyclooxygenase-1 inhibitory activity, respectively, when assayed at 1000 μM concentrations. The activities of these compounds were comparable to Ibuprofen, Naproxen and aspirin at 10, 10 and 1000 μM concentrations.

Singh in his study ⁸³⁾ reported that linoleic acid present in different amount in the fixed oil of different species of holy basil has the capacity to block both the cyclooxygenase and lipoxygenase pathways of arachidonate metabolism and could be responsible for the anti-inflammatory activity.

A methanolic extract and an aqueous suspension of holy basil (500 mg/kg) inhibited acute as well as chronic inflammation in rats as tested by carrageenin-induced pedal edema and cratonoil -induced granuloma and exudates, respectively, and the response was comparable to the response observed with 300 mg/kg of sodium salicylate ⁸⁴⁾. Both the extract and suspension showed analgesic activity in mouse hot plate procedure, and the methanol extract caused an increase in tail withdrawal reaction time of a sub-analgesic dose of morphine. Both preparations reduced typhoid–paratyphoid A–B vaccine-induced pyrexia. The antipyretic action of methanol extract and aqueous suspension was weak and of shorter duration than that of 300 mg/kg sodium salicylate.

Anticancer

Fresh holy basil leaf paste (topically) aqueous and ethanolic extract (orally) for their chemopreventive activity against 7,12-dimethylbenzaanthracene (DMBA) induced (0.5%) hamster buccal pouch carcinogenesis ⁸⁵⁾. Incidence of papillomas and squamous cell carcinomas were significantly reduced and increased the survival rate in the topically applied leaf paste and orally administered extracts to animals. Histopathological observation made on the mucosa confirmed the profound effect of the orally administered aqueous extract than other.

Prasbar et al. ⁸⁶⁾ in their study reported that holy basil leaf extract blocks or suppresses the events associated with chemical carcinogenesis by inhibiting metabolic activation of the carcinogen. In this study, primary cultures of rat hepatocytes were treated with 0–500 μg of holy basil extract for 24 h and then with 7,12-dimethaylbenz[a] anthracene (DMBA, 10 or 50 μg) for 18 h. Cells were then harvested and their DNA was isolated and analyzed by 32p post-labeling. A significant reduction in the levels of DMBA/DNA adducts was observed in all cultures pretreated with holy basil extract. Hepatocytes that were treated with the highest dose of extract (500 μg) showed a maximum reduction of 93% in the mean values of DMBA/DNA adducts. This suggests the inhibition of metabolic activation of carcinogen.

The chemopreventive activity of holy basil seed oil of holy basil was evaluated against subsequently injected 20-methyl cholanthrene-induced fibrosarcoma tumors in the thigh region of Swiss albino mice ⁸⁷⁾. Supplementation of maximal-tolerated dose (100 μl/kg body wt.) of the oil significantly reduced 20-methaylcholathrene-induced tumor incidence and tumor volume. The enhanced survival rate and delay in tumor incidence was observed in seed oil supplemented mice. Liver enzymatic, non-enzymatic antioxidants and lipid peroxidation end product, malondialdehyde level were significantly modulated with oil treatment as compared to untreated 20-methylcholathrene injected mice. The chemopreventive efficacy of 100 μl/kg holy basil seed oil was comparable to that of 80 mg/kg vitamin E.

Thyroid activity

The extract of holy basil leaf extract on the changes in the concentrations of serum Triiodothyronine (T3), Thyronine (T4) and serum cholesterol were investigated ⁸⁸⁾. Holy basil leaf extract at the dose of 0.5 g/kg body weight for 15 days significantly decreased serum T4 concentration; however, no marked changes were observed in serum T3 level, T3/T4 ratio and in the concentration of serum cholesterol. It appears that holy basil leaf extract is antithyroidic in nature.

Miscellaneous activity

Graded dose of 100, 150, 200 and 400 mg/kg of holy basil leaves extract significantly decreases the sexual behavioral score in adult male Wistar rats ⁸⁹⁾. Broadband white noise exposure (100 dB) in Wistar strain male albino rats significantly increased the level of dopamine (DA), serotonin (5-HT) and 5-HT turnover in many of the discrete brain regions during sub-chronic noise exposure (4 h daily, 15 days). In acute (4 h for 1 day) and chronic noise exposures (4 h daily for 30 days) the levels were significantly altered in certain region ⁹⁰⁾. The intraperitoneal administration of 70% ethanolic extract of holy basil at dosage of 100 mg/kg body weight to animals subjected to noise exposure has prevented the noise-induced increase in neurotransmitter levels without affecting the normal levels. This suggests that holy basil can be a probable herbal remedy for noise-induced biogenic amine alterations. Gupta ⁹¹⁾ studied the anticataract effect of holy basil extract on selenite-induced cataract (25 micromole/kg body weight) in 9 day old rat pups. Holy basil (5 and 10 mg/kg body wt.) injected intraperitoneally 4 h prior to selenite challenge reduces the incidence of selenite cataract by 20 and 60%, respectively, and prevented protein insolubilization as well.

Halder et al. ⁹²⁾ found aqueous extract of holy basil as the most effective aldose reductase inhibitor with a significant inhibition of 38.05% considering the aldose reductase activity of normal rat lenses as 100%. The IC50 value was found to be 20 μg/ml.

Holy basil extract (10 mg/kg body wt., oral) before and after mercury (HgCl2) intoxication (5 mg/kg body wt.) showed a significant decrease in lipid peroxidation ⁹³⁾. Serum glutamate pyruvate transaminase (SGPT) activities compared to HgCl2-induced values suggests that holy basil extract provides protection against HgCl2-induced toxicity in mice.

Holy basil fixed oil increases blood clotting time and percentage increase was comparable to aspirin and could be due to inhibition of platelet aggregation ⁹⁴⁾. Holy basil oil also increased pentobarbitone-induced sleeping time in rats indicating probable inhibitory effect of holy basil oil towards cytochromic enzyme responsible for hepatic metabolism of pentobarbitone.

Noise stress causes leucopenia, increased corticosterone level and enhances the neutrophil functions as indicated by increase in the candida phagocytosis and nitro blue tetrazolium reduction ⁹⁵⁾. Pre-treatment with the holy basil extract brought back the stress altered values to normal levels indicating the stress alleviating effect of holy basil.

Holy basil side effects

Information is limited. Few adverse reactions were noted in a Cochrane review of holy basil studies ⁹⁶⁾. Reversible inhibition of spermatogenesis, and decreased total sperm count and motility have been demonstrated in mice. Two animal studies suggested that large amounts of holy basil might negatively affect fertility ⁹⁷⁾, ⁹⁸⁾. Safety during pregnancy and lactation has not been investigated; until more is known, holy basil should probably be avoided at those times ⁹⁹⁾.