Comparative larvicidal activity of different species of Ocimum against Culex quinquefasciatus

Larvicidal Activity and Phytochemical Profiling of Sweet Basil (Ocimum basilicum L.) Leaf Extract against Asian Tiger Mosquito (Aedes albopictus)

Applying larvicides to interrupt a mosquito’s life cycle is an important strategy for vector control. This study was conducted to evaluate the larvicidal properties of the hexane extract of sweet basil (Ocimum basilicum L.; family Lamiaceae) leaves against the wild strain of Asian tiger mosquito, Aedes albopictus (Skuse). Third instar larvae (20 larvae/replicate, n = 3) were exposed to different concentrations of the extract (6.25–200 µg/mL), and the mortality rate was recorded. Probit analysis showed that the median lethal concentration and 95% lethal concentration of the extract were 16.0 (10.9–22.1) and 53.0 (34.6–136.8) µg/mL, respectively, after 24 h exposure. Only the fractions F3, F4, and F5 from the column chromatography displayed high mortality rates of 91.7–100% at 25.0 µg/mL after 24 h exposure. Subsequent column chromatography from the pooled fraction yielded two active subfractions, H-F345-S2 and H-F345-S3, with mortality rates of 100% and 98.3 ± 2.9%, respectively, at 12.5 µg/mL. Gas chromatography–mass spectrometry analysis unveiled that methyl chavicol, 2-(2-butoxyethoxy)ethanol, cedrelanol, methyl eugenol, 2,4,di-tert-butylphenol, and phytol were the major components in both subfractions with some of them being reported as larvicidal compounds. The results suggest that sweet basil has substantial larvicidal activity against Ae. albopictus mosquito and is a potential source of naturally derived larvicide.

Mosquitoes Larvicidal Activity of Ocimum kilimandscharicum Oil Formulation under Laboratory and Field-Simulated Conditions

Mosquitoes are vectors of many severe diseases, including malaria, yellow as well as dengue fever, and lymphatic filariasis. The use of synthetic chemical insecticides for mosquito control has been associated with resistance development and detrimental human, and ecological effects. For a safer alternative, the emulsified Ocimum kilimandscharicum oil formulation was evaluated for its larvicidal activity. The oil was analyzed by GC and GC/MS. The formulations were evaluated against third instar mosquito larvae in the laboratory and later compared with Bacillus thuringiensis subsp. israelensis against An. gambiae under field-simulated conditions. Thirty-nine compounds were identified in the oil, the main ones being D-camphor (36.6%) and limonene (18.6%). The formulation showed significant larval mortalities against An. gambiae and An. arabiensis larvae with LC50 of 0.07 and 0.31 ppm, respectively, at 24 h. Under the field-simulated trial, within 24 h, the formulation showed 98% mortality while Bti had achieved 54%. On day three, it caused 100% mortality while Bti achieved 76.5%. The high bioactivity and sublethal toxic effects to offspring of treated mosquito larvae, in terms of disruption of larval morphological aspects, suggest the high potential of the formulation as a botanical larvicide. The formulation, thus, may provide a valuable alternative for the effective and eco-friendly control of disease vectors.

Essential Oils Extracted from Different Species of the Lamiaceae Plant Family as Prospective Bioagents against Several Detrimental Pests

On the basis of the side effects of detrimental synthetic chemicals, introducing healthy, available, and effective bioagents for pest management is critical. Due to this circumstance, several studies have been conducted that evaluate the pesticidal potency of plant-derived essential oils. This review presents the pesticidal efficiency of essential oils isolated from different genera of the Lamiaceae family including Agastache Gronovius, Hyptis Jacquin, Lavandula L., Lepechinia Willdenow, Mentha L., Melissa L., Ocimum L., Origanum L., Perilla L., Perovskia Kar., Phlomis L., Rosmarinus L., Salvia L., Satureja L., Teucrium L., Thymus L., Zataria Boissier, and Zhumeria Rech. Along with acute toxicity, the sublethal effects were illustrated such as repellency, antifeedant activity, and adverse effects on the protein, lipid, and carbohydrate contents, and on the esterase and glutathione S-transferase enzymes. Chemical profiles of the introduced essential oils and the pesticidal effects of their main components have also been documented including terpenes (hydrocarbon monoterpene, monoterpenoid, hydrocarbon sesquiterpene, and sesquiterpenoid) and aliphatic phenylpropanoid. Consequently, the essential oils of the Lamiaceae plant family and their main components, especially monoterpenoid ones with several bioeffects and multiple modes of action against different groups of damaging insects and mites, are considered to be safe, available, and efficient alternatives to the harmful synthetic pesticides.

Toxicological Activity of Some Plant Essential Oils Against Tribolium castaneum and Culex pipiens Larvae

In the present work, essential oils (EOs) from Schinus terebinthifolius (ripe and unripe fruits and leaves), Origanum majorana (air-dried aerial parts), and Psidium guajava (leaves) were assayed for their insecticidal activity against red flour beetle (Tribolium castaneum) and Culex mosquito larvae (Culex pipiens). Several components were identified in the EOs using Gas chromatography–mass spectrometry (GC/MS), of which Δ-3-carene (25.9%), γ-terpinene (19.4), and γ-elemene (7.1%) were the major ones in S. terebinthifolius ripe fruits, α-pinene (48.9%), germacrene D (12.9%), and α-thujene (7.7%) in S. terebinthifolius unripe fruits, γ-elemene (11.7%), spathulenol (10.1%), β-elemene (9.2%), and p-cymene (9.1%) in S. terebinthifolius leaves, α-pinene (25.5%), (E)-caryophyllene (15.7%), (E)-nerolidol (16.7%), and cedran-8-ol (8.8%) in P. guajava leaves, and terpinen-4-ol (21.7%), γ-terpinene (16.5%), and sabinene (10.1%) in O. majorana air-dried aerial parts. The lethal concentration (LC50) was calculated for tested EOs at different time periods (after 6, 12, 24, 48, and 72 h). After 6 h of treatment, the LC50 was 33.3 and 6.8 µg/L air for S. terebinthifolius ripe and unripe fruits, respectively, and >40 µg/L air for EOs of S. terebinthifolius leaves, O. majoranaair-dried aerial parts, and P. guajava leaves. After 24 h of treatment, the LC50 was 4.2, <2, 5, >40, and 6.1 µg/L air for EOs of S. terebinthifolius ripe fruits and leaves, O. majorana leaves, and P. guajava leaves, respectively. On the other hand, the LC50 values decreased when the exposed period was increased to 72 h, and were <2 µg/L air for EOs of S. terebinthifolius ripe fruits, unripe fruits, and leaves along with P. guajava leaves, respectively, and 37.912 for EO of O. majorana leaves. The LC50 value after 24 h of exposure of S. terebinthifolius unripe fruit EO was under 2 µg/L air, which means that the EO of S. terebinthifolius ripe fruit had a strong effect on adult T. castaneum adults compared to other tested EOs using the fumigation method. The present data confirm that the EOs of O. majorana leaves and S. terebinthifolius unripe fruits and leaves were more effective as larvicide than the EOs of S. terebinthifolius ripe fruits and P. guajava leaves on C. pipiens at a higher concentration (100 mg/L) when applied by the dipping method. EOs from S. terebinthifolius unripe or ripe fruits and leaves and P. guajava leaves were more effective as adulticide than EO of O. majorana leaves against T. castaneum when applied by the fumigant method.

Tulsi - Ocimum sanctum: A herb for all reasons

The predominant cause of global morbidity and mortality is lifestyle-related chronic diseases, many of which can be addressed through Ayurveda with its focus on healthy lifestyle practices and regular consumption of adaptogenic herbs. Of all the herbs used within Ayurveda, tulsi (Ocimum sanctum Linn) is preeminent, and scientific research is now confirming its beneficial effects. There is mounting evidence that tulsi can address physical, chemical, metabolic and psychological stress through a unique combination of pharmacological actions. Tulsi has been found to protect organs and tissues against chemical stress from industrial pollutants and heavy metals, and physical stress from prolonged physical exertion, ischemia, physical restraint and exposure to cold and excessive noise. Tulsi has also been shown to counter metabolic stress through normalization of blood glucose, blood pressure and lipid levels, and psychological stress through positive effects on memory and cognitive function and through its anxiolytic and anti-depressant properties. Tulsi's broad-spectrum antimicrobial activity, which includes activity against a range of human and animal pathogens, suggests it can be used as a hand sanitizer, mouthwash and water purifier as well as in animal rearing, wound healing, the preservation of food stuffs and herbal raw materials and traveler's health. Cultivation of tulsi plants has both spiritual and practical significance that connects the grower to the creative powers of nature, and organic cultivation offers solutions for food security, rural poverty, hunger, environmental degradation and climate change. The use of tulsi in daily rituals is a testament to Ayurvedic wisdom and provides an example of ancient knowledge offering solutions to modern problems.