Arabian Primrose leaf extract mediated synthesis of silver nanoparticles: their industrial and biomedical applications.

The present study encompasses green synthesis of silver nanoparticles (AgNPs) using aqueous leaf extract of Arabian Primrose within 6 min of reaction at 60 °C, pH 7 and their characterisation using physico-chemical analytical techniques. UV-Visible spectroscopy elucidated the surface plasmon resonance around 420 nm. FESEM and TEM images revealed that AgNPs were spherical with average diameter 10-60 nm. XRD pattern confirmed their crystalline nature. The leaf extract rich in phenolics and flavonoids was subjected to GC-MS analysis that identified bioactive compounds helping in reduction and stabilisation of AgNPs. The synthesised AgNPs possessed high anti-oxidant potential against DPPH and H2O2 radicals. Incidentally, the AgNPs acted as excellent nanocatalyst towards borohydride reduction and degradation of structurally different organic dyes. The AgNPs also exhibited selective colorimetric sensing of hazardous mercuric, ferric ions and ammonia. Such AgNPs were cytotoxic against HeLa cells (IC50 7.18 µg/mL) and compatible towards normal L20B cells. These AgNPs showed effective anti-microbial activity against different human pathogens tested (bacterial and fungal). This is probably the first report of AgNPs synthesis using Arabian Primrose leaf extract showing strong anti-oxidant, catalytic, biosensing, anti-cancer and anti-microbial activities and find remarkable applications in medical, industrial and ecological sectors.

Biocontrol of mosquito vectors through herbal-derived silver nanoparticles: prospects and challenges.

Mosquitoes spread several life-threatening diseases such as malaria, filaria, dengue, Japanese encephalitis, West Nile fever, chikungunya, and yellow fever and are associated with millions of deaths every year across the world. However, insecticides of synthetic origin are conventionally used for controlling various vector-borne diseases but they have various associated drawbacks like impact on non-targeted species, negative effects on the environment, and development of resistance in vector species by alteration of the target site. Plant extracts, phytochemicals, and their nanoformulations can serve as ovipositional attractants, insect growth regulators, larvicides, and repellents with least effects on the environment. Such plant-derived products exhibit broad-spectrum resistance against various mosquito species and are relatively cheaper, environmentally safer, biodegradable, easily accessible, and are non-toxic to non-targeted organisms. Therefore, in this review article, the current knowledge of phytochemical sources exhibiting larvicidal activity and their variations in response to solvents used for their extraction is underlined. Also, different methods such as physical, chemical, and biological for silver nanoparticle (AgNPs) synthesis, their mechanism of synthesis using plant extract, their potent larvicidal activity, and the possible mechanism by which these particles kill mosquito larvae are discussed. In addition, constraints related to commercialization of nanoherbal products at government and academic or research level and barriers from laboratory experiments to field trial have also been discussed. This comprehensive information can be gainfully employed for the development of herbal larvicidal formulations and nanopesticides against insecticide-resistant vector species in the near future. Graphical abstract.

Green synthesis of silver nanoparticles using Indian Belladonna extract and their potential antioxidant, anti-inflammatory, anticancer and larvicidal activities.

KEY MESSAGE: Atropa acuminata aqueous leaf extract biosynthesized silver nanoparticles showed strong antioxidant, anticancerous (HeLa cells) and anti-inflammatory activities. Besides, this bio syn-AgNP also proved effective against mosquito vectors causing malaria, dengue and filariasis. Present study highlights eco-friendly and sustainable approach for the synthesis of silver nanoparticles (AgNP) using aqueous leaf extract of A. acuminata, a critically endangered medicinal herb. The addition of 1 mM silver nitrate to aqueous leaf extract resulted in the synthesis of AgNP when solution was heated at 60 °C for 30 min at pH 7. Absorption band at 428 nm, as shown by UV-Vis spectroscopy confirmed the synthesis of AgNP. XRD patterns revealed the crystalline nature of AgNP and TEM analysis showed that most of the nanoparticles were spherical in shape. Zeta potential of AgNP was found to be - 33.5 mV which confirmed their high stability. FT-IR investigations confirmed the presence of different functional groups involved in the reduction and capping of AgNP. The synthesized AgNP showed effective DPPH (IC50-16.08 µg/mL), H2O2 (IC50-25.40 µg/mL), and superoxide (IC50-21.12 µg/mL) radical scavenging activities. These plant-AgNP showed significant inhibition of albumin denaturation (IC50-12.98 µg/mL) and antiproteinase activity (IC50-18.401 µg/mL). Besides, biosynthesized AgNP were found to have strong inhibitory effect against a cervical cancer (HeLa) cell line (IC50-5.418 µg/mL) as well as larvicidal activity against 3rd instar larvae of Anopheles stephensi (LC50-18.9 ppm, LC90-40.18 ppm), Aedes aegypti (LC50-12.395 ppm, LC90-36.34 ppm) and Culex quinquefasciatus (LC50-17.76 ppm, LC90-30.82 ppm) and were found to be non-toxic against normal cell line (HEK 293), and a non-target organism (Mesocyclops thermocyclopoides). This is the first report on the synthesis of AgNP using aqueous leaf extract of A. acuminata, validating their strong therapeutic potential.

Bioengineering of Piper longum L. extract mediated silver nanoparticles and their potential biomedical applications.

The present investigation highlights the strong antioxidant, anticancer and larvicidal potential of green synthesized silver nanoparticles (AgNPs) using aqueous leaf extract of Piper longum L. for their diverse therapeutic applications. The optimum conditions for the synthesis of AgNPs were recorded as 1 mM AgNO3, 60 ±â€¯2 °C at pH 6 for 120 min. Synthesized AgNPs proved to be highly stable and monodispersed as characterized through various techniques. UV-Vis spectrum of biosynthesized AgNPs showed a maximum absorption peak at 420 nm. Field emission-Scanning electron microscopy (FE-SEM) and High resolution-Transmission electron microscopy (HR-TEM) micrographs showed the spherical shape of AgNPs with mean diameter size of 28.8 nm. Existence of crystallographic AgNPs was proved by X-ray diffraction (XRD) pattern analysis. Presence of phenolics, terpenoids and flavonoids compounds which act as bioreducing agents were confirmed by Fourier-transform infrared spectroscopy (FTIR) analysis. Furthermore, the AgNPs and leaf extracts prepared individually in different solvents such as methanol, ethyl acetate, chloroform, hexane and aqueous were assessed for their bio-efficacies. AgNPs showed the enhanced antioxidant (IC50 67.56 µg) and radical-scavenging activities (IC50 196.8 µg) as compared to the crude leaf extracts. Anticancer activity revealed the strong and dose-dependent cytotoxic effect of AgNPs against the HeLa cells showing maximum IC50 value being 5.27 µg/mL after 24 h and was also found to be non-toxic to normal cells (HEK). The AgNPs induced the fragmentation of DNA in the cells, indicating the occurrence of apoptosis and necrosis. Subsequently, an efficient larvae mortality was also recorded against Anopheles stephensi having LC50 and LC90 values being 8.969 and 16.102 ppm, followed by Aedes aegypti (LC50;14.791 and LC90;28.526 ppm) and Culex quinquefasciatus (LC50;18.662 and LC90;40.903 ppm) after 72 h of exposure. Besides, they showed no toxicity against Mesocyclops thermocyclopoides (non-target organism). This is the first report showing strong anti-tumorous and larvicidal activity of AgNPs synthesized using P. longum leaf extract against cervical cancer cell line and mosquito vectors causing dengue, malaria and filariasis. Based on our findings, we suggest that AgNPs derived using P. longum leaf extract possessed excellent anti-cancerous and mosquito larvicidal potential and therefore, can be bioprospected further for the management of these hazardous health diseases. This study has given a new insight for the novel drug designing after conducting experiments on the in vivo models.

Fabrication of silver nanoparticles using Arnebia hispidissima (Lehm.) A. DC. root extract and unravelling their potential biomedical applications.

The present study reports the biosynthesis of silver nanoparticles using aqueous root extract of Arnebia hispidissima. They were prepared by adding 10 mL root extract in 90 mL silver nitrate (0.5 mM) solution and heating at 60 ± 2 °C for 12 min at pH 7.5. Characterization of the biosynthesized silver nanoparticles was done using UV-Visible spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray analysis, transmission electron microscopy, X-ray diffraction analysis, dynamic light scattering measurements and Fourier-transform infrared spectroscopy. The synthesized silver nanoparticles were crystalline in nature exhibiting different shapes like sphere, rod, triangle, hexagon and polygon. Their zeta potential was -23.6 mV confirming their high stability. Fourier-transform infrared spectroscopy analysis showed the presence of phenolics, flavonoids and proteins as reducing, capping and stabilizing agents. The synthesized nanoparticles showed effective in vitro anti-oxidant activity against DPPH (IC50 = 9.86 µg/mL) and H2O2 (IC50 = 53.78 µg/mL) radicals. The nanoparticles showed dose-dependent cytotoxicity against HeLa (cervical cancer, IC50 = 4.44 µg/mL) cells and were non-toxic towards normal L20 B cells (non-malignant mouse cell line). They also exhibited strong anti-microbial activity against Candida albicans, Candida tropicalis, Geotrichum candidum (fungal strains); Escherichia coli, Staphylococcus aureus, Enterococcus faecalis, Klebsiella pneumoniae (bacterial strains). This is the first report of synthesis of silver nanoparticles using A. hispidissima root extract validating their bioefficacy against HeLa cancer cells and diverse microorganisms.

Green synthesis of silver nanoparticles using Holarrhena antidysenterica (L.) Wall.bark extract and their larvicidal activity against dengue and filariasis vectors.

The present study was carried out to evaluate the larvicidal potential of methanol, hexane, acetone, chloroform, and aqueous bark extracts of Holarrhena antidysenterica (L.) Wall. and silver nanoparticles (AgNPs) synthesized using aqueous bark extract against the third instar larvae of Aedes aegypti L. and Culex quinquefasciatus Say. AgNPs were prepared by adding 10 ml of aqueous bark extract in 90 ml of 1 mM silver nitrate (AgNO3) solution. After 5 min of mixing, a change in color from yellow to dark brown occurred indicating the synthesis of AgNPs. Their further characterization was done through ultraviolet-visible spectroscopy (UV-Vis), X-ray diffraction analysis (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR). UV-Vis spectrum of synthesized AgNPs showed a maximum absorption peak at 420 nm wavelength. Crystalline nature of AgNPs was confirmed by the presence of characteristic Bragg reflection peaks in XRD pattern. TEM images have shown that most of the AgNPs were spherical in shape with an average size of 32 nm. FT-IR spectrum of AgNPs showed prominent absorbance peaks at 1012.2 (C-O) and 3439.44 cm-1 (O-H) which represent the major constituents of phenolics, terpenoids, and flavonoids compounds. LC-MS analysis of the bark extract confirmed the presence of carbonyl and hydroxyl functional groups which were directly correlated with FT-IR results. These AgNPs were assayed against different mosquito vectors, and the maximum mortality was recorded against the larvae of A. aegypti with LC50 and LC90 values being 5.53 and 12.01 ppm, respectively. For C. quinquefasciatus, LC50 and LC90 values were 9.3 and 19.24 ppm, respectively, after 72 h of exposure. Bark extracts prepared in different solvents such as methanol, chloroform, hexane, acetone, and water showed moderate larvicidal activity against A. aegypti their respective LC50 values being 71.74, 94.25, 102.25, 618.82, and 353.65 ppm and LC90 values being 217.36, 222.24, 277.82, 1056.36, and 609.37 ppm. For C. quinquefasciatus, their LC50 values were 69.43, 112.39, 73.73, 597.74, and 334.75 ppm and LC90 values of 170.58, 299.76, 227.48, 1576.98, and 861.45 ppm, respectively, after 72 h of treatment. AgNPs proved to be nontoxic against the non-target aquatic organism, Mesocyclops thermocyclopoides Harada when exposed for 24, 48, and 72 h. The results showed that bark extract-derived AgNPs have extremely high larvicidal potential compared to other organic solvents as well as aqueous bark extract alone. These AgNPs, therefore, can be used safely for the control of dengue and filarial vectors that cause severe human health hazards.

Effects of salinity and drought on growth, ionic relations, compatible solutes and activation of antioxidant systems in oleander (Nerium oleander L.).

Nerium oleander is an ornamental species of high aesthetic value, grown in arid and semi-arid regions because of its drought tolerance, which is also considered as relatively resistant to salt; yet the biochemical and molecular mechanisms underlying oleander's stress tolerance remain largely unknown. To investigate these mechanisms, one-year-old oleander seedlings were exposed to 15 and 30 days of treatment with increasing salt concentrations, up to 800 mM NaCl, and to complete withholding of irrigation; growth parameters and biochemical markers characteristic of conserved stress-response pathways were then determined in stressed and control plants. Strong water deficit and salt stress both caused inhibition of growth, degradation of photosynthetic pigments, a slight (but statistically significant) increase in the leaf levels of specific osmolytes, and induction of oxidative stress-as indicated by the accumulation of malondialdehyde (MDA), a reliable oxidative stress marker-accompanied by increases in the levels of total phenolic compounds and antioxidant flavonoids and in the specific activities of ascorbate peroxidase (APX) and glutathione reductase (GR). High salinity, in addition, induced accumulation of Na+ and Cl- in roots and leaves and the activation of superoxide dismutase (SOD) and catalase (CAT) activities. Apart from anatomical adaptations that protect oleander from leaf dehydration at moderate levels of stress, our results indicate that tolerance of this species to salinity and water deficit is based on the constitutive accumulation in leaves of high concentrations of soluble carbohydrates and, to a lesser extent, of glycine betaine, and in the activation of the aforementioned antioxidant systems. Moreover, regarding specifically salt stress, mechanisms efficiently blocking transport of toxic ions from the roots to the aerial parts of the plant appear to contribute to a large extent to tolerance in Nerium oleander.

Strong Anti-tumorous Potential of Nardostachys jatamansi Rhizome Extract on Glioblastoma and In Silico Analysis of its Molecular Drug Targets.

BACKGROUND: Glioblastoma has been reckoned as the prime cause of death due to brain tumours, being the most invasive and lethal. Available treatment options, i.e. surgery, radiotherapy, chemotherapy and targeted therapies are not effective in improving prognosis, so an alternate therapy is insistent. Plant based drugs are efficient due to their synergistic action, multi-targeted approach and least side effects. METHODS: The anti-tumorous potential of Nardostachys jatamansi rhizome extract (NJRE) on U87 MG cell line was evaluated through various in vitro and in silico bio-analytical tools. RESULTS: NJRE had a strong anti-proliferative effect on U87 MG cells, Its IC50 was 33.73±3.5, 30.59±3.4 and 28.39±2.9 µg/mL, respectively after 24, 48 and 72 h. NJRE at 30 µg/mL induced DNA fragmentation, indicating apoptosis, early apoptosis began in the cells at 20 µg/mL, whereas higher doses exhibited late apoptosis as revealed by dual fluorescence staining. NJRE at 60 and 80 µg /mL caused a G0/G1 arrest and at 20 and 40 µg/mL showed excessive nucleation and mitotic catastrophe in the cells. Immuno-blotting validated the apoptotic mode of cell death through intrinsic pathway. NJRE was harmless to normal cells. In silico docking of NJRE marker compounds: oroselol, jatamansinol, nardostachysin, jatamansinone and nardosinone have revealed their synergistic and multi-targeted interactions with Vestigial endothelial growth factor receptor 2 (VEGFR2), Cyclin dependent kinase 2 (CDK2), B-cell lymphoma 2 (BCL2) and Epidermal growth factor receptor (EGFR). CONCLUSION: A strong dose specific and time dependent anti-tumorous potential of NJRE on U87 MG cells was seen. The extract can be used for the development of safe and multi-targeted therapy to manage glioblastoma, which has not been reported earlier.

Assessment of Antioxidant Enzyme Activity and Mineral Nutrients in Response to NaCl Stress and its Amelioration Through Glutathione in Chickpea.

Salinity stress has been reckoned as one of the major threat towards crop productivity as it causes significant decline in the yield. The impact of NaCl stress (0, 1, 10, 50, 100 and 200 mg L(-1)) as well as glutathione (10 mg L(-1)) either alone or in combination has been evaluated on the induction of multiple shoots, antioxidant enzymes' activity, lipid peroxidation, relative permeability, concentration of nutrients, photosynthetic pigments, protein and proline content of nodal segments of chickpea after 14 days of culture. The antioxidant enzyme activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX) and glutathione reductase (GR) were found to be increased under salt stress as well as glutathione-supplemented medium. A significant decrease in the concentrations of chlorophylls a, b, total chlorophyll and carotenoid was observed under salt stress. Concentrations of nitrogen, phosphorus, potassium, calcium, carbon, magnesium and sulphur showed an initial increase up to 10 mg L(-1) NaCl, but a decline was seen at higher NaCl levels. Proline content and malondialdehyde concentration were found to be increased under salt stress. Three isoforms of SOD, one of CAT and four of GPX were expressed during native polyacrylamide gel electrophoresis (PAGE) analysis. However, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of the stressed nodal explants revealed the over-expression of several polypeptide bands related to NaCl stress. These findings for the first time suggest that glutathione (GSH) helps in ameliorating NaCl stress in nodal explants of chickpea by manipulating various biochemical and physiological responses of plants.

In vitro enhancement of psoralen as an important anticancer compound in Psoralea corylifolia through precursor feeding.

CONTEXT: Psoralea corylifolia L. (Fabacese) is rich source of bioactive compounds, which endows the plant with immense value for its use in pharmaceuticals, health, and body-care products. OBJECTIVE: The current study was designed (i) for the determination of psoralen from callus derived from different plant parts, and (ii) for the enhancement of psoralen in in vitro condition with the treatment of various psoralen pathway precursors. MATERIALS AND METHODS: B5 media were employed for raising the cultures from different plant parts such as leaf, node, root, and green seeds. Cotyledons' calluses were derived from cotyledon of green seeds that were elicited on MS + 10 µM BA + 5 µM IBA medium supplemented at 0.1, 1, 2.5, 5, 25, and 50 mg/L of various psoralen pathway precursors such as umbelliferone, cinnamic acid, and NADPH. The method for extraction of psoralen was modified from the Singh method and the content of psoralen was measured using HPLC. RESULTS: HPLC analysis of callus derived from different parts of P. corylifolia revealed that a maximum of psoralen (2601.8 µg/g fresh wt.) was recorded in cotyledons' callus. Cotyledonary callus was chosen for the enhancement of psoralens because of higher amount of psoralen in it. In vitro evaluation showed that all the precursors enhanced the psoralen amount dramatically so that the optimum amount of psoralen (2518.8 µg/g fresh wt.) was obtained at 2.5 mg/L cinnamic acid. DISCUSSION AND CONCLUSION: The results obtained indicate that cinnamic acid is one of the important precursors of psoralen pathway that induced a maximum amount of psoralen with in vitro conditions.

Strong larvicidal potential of Artemisia annua leaf extract against malaria (Anopheles stephensi Liston) and dengue (Aedes aegypti L.) vectors and bioassay-driven isolation of the marker compounds.

Malaria and dengue are the two most important vector-borne human diseases caused by mosquito vectors Anopheles stephensi and Aedes aegypti, respectively. Of the various strategies adopted for eliminating these diseases, controlling of vectors through herbs has been reckoned as one of the important measures for preventing their resurgence. Artemisia annua leaf chloroform extract when tried against larvae of A. stephensi and A. aegypti has shown a strong larvicidal activity against both of these vectors, their respective LC50 and LC90 values being 0.84 and 4.91 ppm for A. stephensi and 0.67 and 5.84 ppm for A. aegypti. The crude extract when separated through column chromatography using petroleum ether-ethyl acetate gradient (0-100%) yielded 76 fractions which were pooled into three different active fractions A, B and C on the basis of same or nearly similar R f values. The aforesaid pooled fractions when assayed against the larvae of A. stephensi too reported a strong larvicidal activity. The respective marker compound purified from the individual fractions A, B and C, were Artemisinin, Arteannuin B and Artemisinic acid, as confirmed and characterized through FT-IR and NMR. This is our first report of strong mortality of A. annua leaf chloroform extract against vectors of two deadly diseases. This technology can be scaled up for commercial exploitation.

Bioassay of Artemisia annua leaf extracts and artemisinin against larvae of Culex quinquefasciatus and Culex tritaeniorhynchus.

Using in vitro bioassays, we evaluated the crude methanol, ethanol, chloroform, and acetone leaf extracts of Artemisia annua as well as pure artemisinin against late 3rd and early 4th instars of Culex quinquefasciatus and Cx. tritaeniorhynchus. Based on the lethal concentration for 50% mortality (LC50) and lethal concentration for 90% mortality (LC90) values, the chloroform leaf extract was the most toxic, followed by methanol, ethanol, and acetone. The LC50 and LC90 values for chloroform extract were 0.18 and 9.65 ppm against Cx. quinquefasciatus and 0.91 and 8.73 ppm against Cx. tritaeniorhynchus, respectively. The LC50 and LC90 values for artemisinin, dissolved in chloroform, were significantly higher, 14.31 and 296.39 ppm for Cx. quinquefasciatus and 4.13 and 50.36 ppm for Cx. tritaeniorhynchus, respectively.

In vitro isolation, elicitation of psoralen in callus cultures of Psoralea corylifolia and cloning of psoralen synthase gene.

Psoralen, an important furanocoumarin occurring abundantly in seeds of Psoralea corylifolia is used as an anticancerous compound against leukemia and other cancer cell lines. Evaluation and isolation of psoralen from the calluses derived from different plant parts, viz. cotyledons, nodes, leaves and roots have been done in the present case for the first time. Amongst all, a maximum of 1934.75 µg/g f.w. of psoralen was recorded in callus derived from cotyledons, followed by 1875.50 and 1465.75 µg/g f.w. of psoralen in node and leaf derived calluses, respectively. Amount of psoralen enhanced further when cotyledonary calluses were exposed to different concentrations of organic elicitors (yeast extract, proline, inositol, casein hydrolyzate (CH), glycine, glutamine and sucrose) and precursors of psoralen (umbelliferone, cinnamic acid and NADPH). Isolation of psoralen was done using methanol as solvent through column chromatography and TLC. FT-IR and NMR further characterized and confirmed the structure of psoralen. In addition, the putative gene, psoralen synthase involved in psoralen synthesis pathway has been isolated, cloned and sequenced which comprised 1237 bp length. BLAST analysis of the gene sequence of psoralen synthase revealed that its nucleotide sequence showed 93% homology with psoralen synthase isolated from Ammi majus. This is the first report of isolation, cloning and characterization of psoralen synthase from Psoralea corylifolia.

In vitro isolation and characterization of biolarvicidal compounds from micropropagated plants of Spilanthes acmella.

Spilanthes acmella (Family: Asteraceae) commonly known as "toothache plant" is known to possess strong insecticidal and larvicidal properties. Experiments have been conducted to isolate and characterise the biolarvicidal compounds from the flower head extract of micropropagated S. acmella plants employing various tools like FT-IR, TLC, CC, NMR. FT-IR spectroscopy of the crude hexane extract sample revealed the presence of amide (secondary metabolite) as functional group in S. acmella flower heads. The crude extract was separated into 85 fractions (100 ml each) through silica gel column chromatography using hexane-ethyl acetate mobile phase. All fractions were tested for their larvicidal activity against late III/early IV instar Anopheles stephensi larvae and fraction showing maximum bioefficacy against aforesaid larvae was further resolved into three separate bands on Preparative TLC plate, the respective R (f) values being (a) 0.18, (b) 0.23 and (c) 0.27. Based on Proton NMR spectrum of the eluted compounds and their comparison with published results, three different compounds were identified: N-isobutyl-2,6,8-decatrienamide (compound 1), undeca-2E,7Z,9E-trienoic acid isobutylamide (compound 2) from band a and (2E)-N-(2-methylbutyl)-2-undecene-8,10-diynamide (compound 3) from band b. The amount of the compounds obtained were 338 mg (compounds 1 and 2) and 188.4 mg (compound 3), respectively. This is the first report of biolarvicidal compounds isolation and characterisation from micropropagated S. acmella plants.

Strong larvicidal activity of three species of Spilanthes (Akarkara) against malaria (Anopheles stephensi Liston, Anopheles culicifacies, species C) and filaria vector (Culex quinquefasciatus Say).

A system for biocontrol of malaria and filarial mosquito vectors has been developed using herbal extracts of three Spilanthes species, S. acmella L.var oleraceae Clarke, S. calva L. and S. paniculata Wall ex DC. Cent percent mortalities was achieved against the late third/early fourth instar larvae of A. stephensi Liston, A. culicifacies species C and C. quinquefasciatus Say using crude hexane extract obtained from flower heads of Spilanthes spp. Of the three plant species, S. acmella extract proved to be the most effective in inducing complete lethality at minimum doses, the respective LC50 and LC90 values being 4.57 and 7.83 (A. stephensi), 0.87 and 1.92 (A. culicifacies) and 3.11 and 8.89 ppm (C. quinquefasciatus). This was followed by S. calva and S. paniculata extracts, respectively. This is the first report of achieving cent percent lethality against these mosquito larvae using minimal doses of plant extracts from this or any other plant species.