Antibacterial activity of Ocimum sanctum L. fixed oil

Ocimum sanctum fixed oil showed good antibacterial activity against Staphylococcus aureus, Bacillus pumilus and Pseudomonas aeruginosa, where S. aureus was the most sensitive organism. Sesame and soyabean oils also showed moderate activity against S. aureus. Higher content of linolenic acid in O. sanctum fixed oil could contribute towards its antibacterial activity. The antibacterial activity combined with anti-inflammatory and analgesic activities of the oil, could make it useful in inflammatory disorder resulting from staphylococcal infection.     

Biological activities of Ocimum sanctum L. fixed oil--an overview

Seeds of Ocimum sanctum L. (Labiatae; popularly known as 'Tulsi' in Hindi and 'Holy Basil' in English) contain a pale yellow colored fixed oil. The oil possesses antiinflammatory activity due to dual inhibition of arachidonate metabolism supplemented by antihistaminic activity. The antiinflammatory activity is not dependent on the pituitary adrenal axis. The oil possesses antipyretic activity due to prostaglandin inhibition and peripherally acting analgesic activity. The oil has been found to be effective against formaldehyde or adjuvant induced arthritis and turpentine oil induced joint edema in animals. Lipoxygenase inhibitory, histamine antagonistic and antisecretory activities of the oil contribute towards antiulcer activity. The oil can inhibit enhancement of vascular capillary permeability and leucocyte migration following inflammatory stimulus. The LD50 of the oil is 42.5 ml/kg and long-term use of oil at 3 ml/kg dose does not produce any untoward effects in rats. The oil contains a-linolenic acid, an omega-3 fatty acid, which on metabolism produces eicosapentaenoic acid and the same appears to be responsible for the biological activity. The oil has hypotensive, anticoagulant and immunomodulatory activities. Antioxidant property of the oil renders metabolic inhibition, chemoprevention and hypolipidaemic activity. Presence of linolenic acid in the oil imparts antibacterial activity against Staphylococcus aureus. The oil alone or in combination with cloxacillin, a beta-lactamase resistant penicillin, has been found to be beneficial in bovine mastitis, an inflammatory disorder resulting from staphylococcal infection. Existence of anti-inflammatory, analgesic and antibacterial activities in single entity i.e. fixed oil appears to be unique.     

Ocimum sanctum essential oil inhibits virulence attributes in Candida albicans

Candida albicans is an opportunistic human fungal pathogen which causes disease mainly in immunocompromised patients. Activity of hydrolytic enzymes is essential for virulence of C. albicans and so is the capacity of these cells to undergo transition from yeast to mycelial form of growth. Ocimum sanctum is cultivated worldwide for its essential oil which exhibits medicinal properties. This work evaluates the anti-virulence activity of O. sanctum essential oil (OSEO) on 22 strains of C. albicans (including a standard strain ATCC 90028) isolated from both HIV positive and HIV negative patients. Candida isolates were exposed to sub-MICs of OSEO. In vitro secretion of proteinases and phospholipases was evaluated by plate assay containing BSA and egg yolk respectively. Morphological transition from yeast to filamentous form was monitored microscopically in LSM. For genetic analysis, respective genes associated with morphological transition (HWP1), proteinase (SAP1) and phospholipase (PLB2) were also investigated by Real Time PCR (qRT-PCR). Results were analyzed using Student's t-test. OSEO inhibits morphological transition in C. albicans and had a significant inhibitory effect on extracellular secretion of proteinases and phospholipases. Expression profile of respective selected genes associated with C. albicans virulence by qRT-PCR showed a reduced expression of HWP1, SAP1 and PLB2 genes in cells treated with sub-inhibitory concentrations of OSEO. This work suggests that OSEO inhibits morphological transition in C. albicans and decreases the secretion of hydrolytic enzymes involved in the early stage of infection as well as down regulates the associated genes. Further studies will assess the clinical application of OSEO and its constituents in the treatment of fungal infections.     

Effect of Ocimum sanctum Linn. on normal and dexamethasone suppressed wound healing

Ethanolic extract of leaves of O. sanctum was investigated for normal wound healing and dexamethasone depressed healing using incision, excision and dead space wound models in albino rats. The extract of O. sanctum significantly increased the wound breaking strength in incision wound model. The extract treated wounds were found to epithelialize faster and the rate of wound contraction was significantly increased as compared to control wounds. Significant increase in wet and dry granulation tissue weight, granulation tissue breaking strength and hydroxyproline content in dead space wound model was observed. The extract significantly decreased the antihealing activities of dexamethasone in all the wound models. The results indicated that the leaf extract promotes wound healing significantly and able to overcome the wound healing suppressing action of dexamethasone. Histological examination of granulation tissue to determine the pattern of lay-down for collagen confirmed the results.     

Antidiabetic, antihypercholesterolaemic and antioxidant effect of Ocimum sanctum (Linn) seed oil

Antihyperlipidaemic and antioxidant effect of Ocimum sanctum Linn. seed oil (OSSO) was investigated in rabbits. Administration of OSSO (0.8 g/kg body weight/day) for four weeks, in cholesterol (100 mg/kg body weight/day) fed rabbits significantly decreased serum cholesterol, triacylglycerol and LDL-+VLDL-cholesterol as compared to untreated cholesterol fed group. There was significant fall in atherogenic index in OSSO treated group. In addition, treatment with OSSO decreased lipid peroxidation and increased reduced glutathione content in blood. Antidiabetic effect of O. sanctum seed oil was evaluated in alloxan diabetic rabbits. Two weeks treatment of diabetic rabbits with OSSO (0.8 gm/kg/day) showed no significant hypoglycaemic effect. Results of the present study show that OSSO has hypocholesterolaemic and antioxidant effects but it does not have antidiabetic effect.     

Antioxidant and radioprotective properties of an Ocimum sanctum polysaccharide

The antioxidant activity of two polysaccharides isolated from the Indian medicinal plants, Ocimum sanctum and Tinospora malabarica, was studied. Only the O. sanctum polysaccharide (OSP) showed significant activity. OSP could prevent oxidative damage to liposomal lipids and plasmid DNA induced by various oxidants such as iron, AAPH and gamma-radiation, besides scavenging important ROS such as the superoxide radical and hydrogen peroxide and inhibiting xanthine oxidase. In addition, OSP could prevent gamma-radiation-mediated cell deaths in mouse splenocytes.     

Effect of standardized extract of Ocimum sanctum Linn. on gastric mucosal offensive and defensive factors

The standardized methanolic extract of leaves of O. sanctum (OSE; eugenol content 5%) 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 OSE showed significant ulcer protection against ethanol and pyloric ligation-induced gastric ulcers, but was ineffective against aspirin-induced ulcers. OSE significantly healed ulcers induced by 50% acetic acid after 5 and 10 days treatment OSE (100 mg/kg) significantly inhibited the offensive acid-pepsin secretion and lipid peroxidation and increased the gastric defensive factors like mucin secretion, cellular mucus, and life span of mucosal cells and had antioxidant effect, but did not induce mucosal cell proliferation. The results indicate that the ulcer protective and healing effects of OSE may be due to its effects both on offensive and defensive mucosal factors.     

Endophytic Bacteria from Ocimum sanctum and Their Yield Enhancing Capabilities

Endophytes are beneficial microbes that reside intercellularly inside the plants. Interaction of endophytes with the host plants and their function within their host are important to address ecological relevance of endophyte. Four endophytic bacteria OS-9, OS-10, OS-11, and OS-12 were isolated from healthy leaves of Ocimum sanctum. These isolated microbes were screened in dual culture against various phytopathogenic fungi viz. Rhizoctonia solani, Sclerotium rolfsii, Fusarium solani, Alternaria solani, and Colletotrichum lindemuthianum. Of these, strain OS-9 was found to be antagonistic to R. solani, A. solani, F. solani, and C. lindemuthianum while OS-11 was found antagonistic against A. solani only. The growth-promoting benefits of the endophytes were initially evaluated in the glasshouse by inoculated seeds of O. sanctum. Treatment with endophytes OS-10 and OS-11 resulted in significant enhancement of growth as revealed by increase in fresh as well as dry weight. Further, field trials involving two genotypes OS Purple and CIM-Angana were conducted with strains OS-10 and OS-11. The growth-promoting effect was visible on both the genotypes tested as the endophytes significantly enhanced fresh herbage yield (t/ha). Interestingly, these endophytes increased the content of essential oil particularly in cultivar OS Purple and thereby increasing the total oil yields. Molecular characterization of strain OS-11 indicated the strain to be highly related to the type strain of Bacillus subtilis.     

Evaluation of nootropic potential of Ocimum sanctum Linn. in mice

Dementia is one of the age related mental problems and a characteristic symptom of various neurodegenerative disorders including Alzheimer's disease. Certain drugs like diazepam, barbiturates and alcohol disrupt learning and memory in animals and man. However, a new class of drugs known as nootropic agents is now used in situations where there is organic disorder in learning abilities. The present work was undertaken to assess the potential of O. sanctum extract as a nootropic and anti-amnesic agent in mice. Aqueous extract of dried whole plant of O. sanctum ameliorated the amnesic effect of scopolamine (0.4 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. O. sanctum extract decreased transfer latency and increased step down latency, when compared to control (piracetam treated), scopolamine and aged groups of mice significantly. O. sanctum preparations could of beneficial in the treatment of cognitive disorders such as dementia and Alzheimer's disease.     

Enhancing antidiabetic and antimicrobial performance of Ocimum basilicum,and Ocimum sanctum (L.) using silver nanoparticles

The role of silver nanoparticles (AgNps) is an attractive proposition for advancing modern diabetes therapies and applied science. Stable AgNps with a size range of 3–25 nm were synthesized using aqueous leaf extracts from Ocimum basilicum, Ocimum sanctum, and in combination. The concentration of the extracts facilitated the reduction of silver nitrate that led to the rapid formation of AgNps at room temperature, indicating a higher reaction rate as opposed to harsh chemical methods, and high conversion energy usually involved in the synthesis. The size, shape and elemental analysis were carried out using UV–Visible spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX), dynamic light scattering (DLS), and zeta potential whilst, Fourier transform infrared (FTIR) supported by gas chromatography mass spectroscopy (GC–MS) was used to identify the type of capping agents. Inhibition of α-amylase and α-glucosidase enzymes retards the rate of carbohydrate digestion, thereby provides an alternative and a less evasive strategy of reducing postprandial hyperglycaemia in diabetic patients. The AgNps derived from O. sanctum and O. basilicum, respectively displayed an inhibitory effect at 89.31 ± 5.32%, and 79.74 ± 9.51%, respectively, against Bacillus stearothermophilus α-glucosidase enzyme model, indicating an enhanced biocatalytic potential compared to their respective crude extracts and the control. Furthermore, the emerging rate of infections in diabetic patients validates the need for the discovery of dual diabetes therapies. As a result, the bioderived AgNps displayed antimicrobial activity against bacterial species Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Salmonella species.     

Mechanism of action of antiinflammatory effect of fixed oil of Ocimum basilicum Linn

Fixed oil of O. basilicum was found to possess significant antiinflammatory activity against carrageenan and different other mediator-induced paw edema in rats. Significant inhibitory effect was also observed in castor oil-induced diarrhoea in rats. It also inhibited arachidonic acid- and leukotriene-induced paw edema. The results of antiinflammatory activity of O. basilicum support the dual inhibition of arachidonate metabolism as indicated by its activity in inflammation models that are insensitive to selective cyclooxygenase inhibitors. On the basis of these findings, it possible to conclude that O. basilicum may be a useful antiinflammatory agent which block both cyclooxygenase and lipoxygenase pathways of arachidonic acid metabolism.     

Microwave assisted extraction of ursolic acid and oleanolic acid from Ocimum sanctum

Present study deals with the microwave assisted extraction (MAE) of ursolic acid (UA) and oleanolic acid (OA) from Ocimum sanctum leaves. UA and OA have been reported to possess significant medicinal properties. Various experimental parameters such as selection of solvent, solvent composition, irradiation time, microwave power, solid to solvent ratio, preleaching time and number of cycles were investigated to optimize the extraction process. Under optimum conditions of irradiation time (3 min), microwave power (272 W), solid to solvent ratio (1:30), preleaching time (10 min), maximum UA and OA has been extracted in one extraction cycle with ethanol: water (80:20) as a solvent. Maximum 86.76 and 89.64% of UA and OA was extracted under above mentioned optimized experimental conditions. MAE was also compared with the batch and ultrasound assisted extraction (UAE) method. As compared to batch and UAE, higher extraction yield of these important phytochemicals have been obtained through MAE in only 3 min.     

Changes in growth and photosynthetic characteristics of Ocimum sanctum under growth regulator treatments

A field experiment was conducted to investigate the effect of growth regulators on growth characteristics such as root length,shoot length,total leaf area,number of inflorescence per plant,number of flower per inflorescence,whole plant fresh weight and whole plant dry weight.Photosynthetic characteristics were also analyzed based on the same experiment.For this,various photosynthetic pigment contents such as chlorophyll,carotenoid,anthocyanin and xanthophyll content were calculated.The conventional growth regulator abscisic acid (ABA) and non-conventional growth regulator triazole compound paclobutrazol (PBZ) were used.Root length increased due to growth regulator treatment,but shoot length decreased.Leaf area was decreased due to growth regulator treatment.The number of inflorescence increased in ABA treated plants,but it was decreased in PBZ treated plants.In ABA treated plants,the number of flowers per inflorescence was increased.In PBZ treated plants the number of inflorescence was reduced.The whole plant fresh weight (FW) and dry weight (DW) were increased in ABA and PBZ treated plants.There was an increase in chlorophyll content in growth regulator treated plants compared to control,and it was more in PBZ treated plants.The carotenoid content was also increased in ABA and PBZ treated plants.     

Anticonvulsant potential of holy basil, Ocimum sanctum Linn., and its cultures

Callus cultures from stem of O. sanctum were induced on slightly modified Murashige and Skoog's (MS) medium and supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D, 1-2 ppm) and kinetin (kn, 1 ppm). Different extractives of stem, leaf and stem callus of O. sanctum were tested for anticonvulsant activity against standard drug phenytoin using maximal electroshock (MES) model. Ethanol and chloroform extractives of stem, leaf and stem calli were effective in preventing tonic convulsions induced by transcorneal electroshock.     

Cardioprotective potential of Ocimum sanctum in isoproterenol induced myocardial infarction in rats

Myocardial infarction (MI was produced in rats with 85, 200 and 300 mg/kg of isoproterenol (ISO) administered subcutaneously (sc) twice at an interval of 24 h. Shift in antioxidant parameters, lactate dehydrogenase (LDH) together with morphological and histopathological changes were investigated. Two hundred mg/kg ISO dose was selected for the present study as this dose offered significant alteration in biochemical parameters along with moderate necrosis in heart. Effect of pre and cotreatment of hydroalcoholic extract of Ocimum sanctum (Os) at different doses (25, 50, 75, 100, 200 and 400 mg/kg) was investigated against ISO (200 mg/kg) induced myocardial infarction in rats. Modulation of various biochemical parameters and membrane integrity was studied. Os at the dose of 25, 50, 75 and 100 mg/kg reduced significantly glutathione (GSH), superoxide dismutase (SOD) and LDH levels. It also inhibited the lipid peroxidation as observed by the reduced thiobarbituric acid reactive substances (TBARS) levels. In the present study Os at the dose of 50 mg/kg was found to demonstrate maximum cardioprotective effect. Above results were further confirmed by histopathological findings. Thus from the present study it is concluded that Os may be of therapeutic and prophylactic value in the treatment of MI.     

Fungal Endophyte Diversity and Bioactivity in the Indian Medicinal Plant Ocimum sanctum Linn

Endophytic mycopopulation isolated from India’s Queen of herbs Tulsi (Ocimum sanctum) were explored and investigated for their diversity and antiphytopathogenic activity against widespread plant pathogens Botrytis cinerea, Sclerotinia sclerotiorum, Rhizoctonia solani and Fusarium oxysporum. 90 fungal isolates, representing 17 genera were recovered from 313 disease-free and surface sterilised plant segments (leaf and stem tissues) from three different geographic locations (Delhi, Hyderabad and Mukteshwar) during distinct sampling times in consequent years 2010 and 2011 in India. Fungal endophytes were subjected to molecular identification based on rDNA ITS sequence analysis. Plant pathogens such as F. verticillioides, B. maydis, C. coarctatum, R. bataticola, Hypoxylon sp., Diaporthe phaseolorum, Alternaria tenuissima and A. alternata have occurred as endophyte only during second sampling (second sampling in 2011) in the present study. Bi-plot generated by principal component analysis suggested tissue specificity of certain fungal endophytes. Dendrogram revealed species abundance as a function of mean temperature of the location at the time of sampling. Shannon diversity in the first collection is highest in Hyderabad leaf tissues (H'' = 1.907) whereas in second collection it was highest from leaf tissues of Delhi (H'' = 1.846). Mukteshwar (altitude: 7500 feet) reported least isolation rate in second collection. Nearly 23% of the total fungal isolates were considered as potent biocontrol agent. Hexane extract of M. phaseolina recovered from Hyderabad in first collection demonstrated highest activity against S. sclerotiorum with IC₅₀ value of 0.38 mg/ml. Additionally, its components 2H-pyran-2-one, 5,6-dihydro-6-pentyl and palmitic acid, methyl ester as reported by GC-MS Chromatogram upon evaluation for their antiphytopathogenic activity exhibited IC₅₀ value of 1.002 and 0.662 against respectively S. sclerotiorum indicating their significant role in antiphytopathogenic activity of hexane extract. The production of 2H-pyran-2-one, 5,6-dihydro-6-pentyl from M. phaseolina, an endophytic fungus is being reported for the first time.