Mosquito larvicidal activity of Aloe vera (Family: Liliaceae) leaf extract and Bacillus sphaericus,against Chikungunya vector,Aedes aegypti

The bio-efficacy of Aloe vera leaf extract and bacterial insecticide, Bacillus sphaericus larvicidal activity was assessed against the first to fourth instars larvae of Aedes aegypti, under the laboratory conditions. The plant material was shade dried at room temperature and powdered coarsely. A. vera and B. sphaericus show varied degrees of larvicidal activity against various instars larvae of A. aegypti. The LC₅₀ of A. vera against the first to fourth instars larvae were 162.74, 201.43, 253.30 and 300.05 ppm and the LC₉₀ 442.98, 518.86, 563.18 and 612.96 ppm, respectively. B. sphaericus against the first to fourth instars larvae the LC₅₀ values were 68.21, 79.13, 93.48, and 107.05 ppm and the LC₉₀ values 149.15, 164.67, 183.84, and 201.09 ppm, respectively. However, the combined treatment of A. vera + B. sphaericus (1:2) material shows highest larvicidal activity of the LC₅₀ values 54.80, 63.11, 74.66 and 95.10 ppm; The LC₉₀ values of 145.29, 160.14, 179.74 and 209.98 ppm, against A. aegypti in all the tested concentrations than the individuals and clearly established that there is a substantial amount of synergist act. The present investigation clearly exhibits that both A. vera and B. sphaericus materials could serve as a potential larvicidal agent. Since, A. aegypti is a container breeder vector mosquito this user and eco-friendly and low-cost vector control strategy could be a viable solution to the existing dengue disease burden. Therefore, this study provides first report on the mosquito larvicidal activity the combined effect of A. vera leaf extract and B. sphaericus against as target species of A. aegypti.     

Toxicity of Acalypha indica (Euphorbiaceae) and Achyranthes aspera (Amaranthaceae) leaf extracts to Aedes aegypti (Diptera: Culicidae)

Alternative control strategies for the dengue vector Aedes aegypti L. (Diptera: Culicidae) include botanical insecticides. They are believed to pose little threat to the environment or to human health and may provide practical substitutes for synthetic insecticides. In this study, we determined the biological activities of methanol extracts of Acalypha indica L. (Euphorbiaceae) and Achyranthes aspera L (Amaranthaceae) leaves individually and in combination as botanical insecticides against Ae. aegypti. Based on LC₅₀ values for 4th instar Ae. aegypti, the combined extracts showed the strongest larvicidal activity (277 ppm). A. aspera and A. indica extracts individually gave similar results (409 and 420 ppm, respectively). Respective LC₅₀ values for pupae were 326 ppm, 456 ppm, and 467 ppm. In studies of smoke toxicity, 64% of females exposed to negative control smoke (no extract) blood fed on chicken, whereas 17% blood fed when exposed to smoke containing A. aspera extract and to positive control smoke (0.2% d-allethrin). In the field, treatment of water storage tanks (≈ 0.5 m³) with combined plant extract reduced larval and pupal populations by 97% and 81%, respectively, after 5 days. Given the results of this study, further evaluation of the combined (A. indica + A. aspera) extract as a mosquito larvicide is warranted. Mosquito coils with A. aspera extract also show promise as a practical and potentially economical means for mitigating mosquito blood feeding.     

Acaricidal active fractions from acetone extract of <Emphasis Type="Italic">Aloe vera</Emphasis> L. against <Emphasis Type="Italic">Tetranychus cinnabarinus</Emphasis> and <Emphasis Type="Italic">Panonychus citri</Emphasis>

This study aimed to isolate acaricidal active fractions from acetone extract of Aloe vera L. and investigate the toxicity of these fractions against Tetranychus cinnabarinus (T. cinnabarinus) and Panonychus citri (P. citri). Acetone extract of A. vera L. was isolated by immersing in acetone for 72 h, and diverse fractions were fractionated by column chromatography. The acaricidal activity of each fractions was evaluated by corrected mortality of T. cinnabarinus through slide-dip bioassay. The 8th and 13th fractions of acetone extract with good acaricidal activity were indentified by LC/MS, and the toxicity of these two fractions to T. cinnabarinus and P. citri was identified by regression analysis. Acetone extract of A. vera L. exhibited obvious acaricidal activity, from which a total of 18 fractions were isolated. The 8th and 13th fractions with strong acaricidal activity against T. cinnabarinus were identified to be 3-O-alpha-d-mannopyranosyl-d-mannopyranose (OAMM) and aloe emodin. When compared with spirodiclofen, both OAMM and aloe emodin exhibited higher toxicity to T. cinnabarinus, while only OAMM exhibited a higher toxicity to P. citri (P < 0.05). OAMM and aloe emodin isolated from acetone extract of A. vera L. exhibited obvious acaricidal activities against T. cinnabarinus and P. citri.     

Acetylenic 2-phenylethylamides and new isobutylamides from Acmella oleracea (L.) R. K. Jansen,a Brazilian spice with larvicidal activity on Aedes aegypti

Ethanol extract obtained from dried leaves of Acmella oleracea afforded after a liquid/liquid partition procedure a larvicidal hexane fraction (LC₅₀ = 145.6 ppm) and a non larvicidal dichloromethane one. From the inactive fraction, three amides were identified, two new structures, named deca-6,9-dihydroxy-(2E,7E)-dienoic acid isobutylamide (1), deca-8,9-dihydroxy-(2E,6Z)-dienoic acid isobutylamide (2) and the known nona-2,3-dihydroxy-6,8-diynoic acid 2-phenylethylamide (3). Bioassay-guided chromatographic fractionation of the hexane partition led to the identification of an amide mixture, nona-(2Z)-en-6,8-diynoic acid 2-phenylethylamide (4) and deca-(2Z)-en-6,8-diynoic acid 2-phenylethlylamide (5). This mixture was active against Aedes aegypti larvae at LC₅₀ = 7.6 ppm. Low toxicity of crude extracts and derived fractions on Artemia salina nauplies showed the possibility of using them to control the A. aegypti mosquito larvae. This is the first report on larvicidal activity of acetylenic 2-phenylethylamides and their identification in A. oleracea leaves.     

Biological activity of Xanthium strumarium seed extracts on different cancer cell lines and Aedes caspius,Culex pipiens (Diptera: Culicidae)

Effects of methanol extracts of Xanthium strumarium on different cancer cell lines and on the mortality rates of Aedes caspius, Culex pipiens (Diptera: Culicidae) were investigated. Among the cell lines tested, the Jurkat cell line was the most sensitive to the methanol extract and ethyl acetate fraction, with reported LC₅₀ values of 50.18 and 48.73 μg/ml respectively. Conversely, methanol extracts were not that toxic to the A549 cell line though the toxicity increased on further purification. The percentage of growth inhibition was dose dependent for the methanol extract and ethyl acetate fraction. The ethyl acetate fraction showed higher toxicity to all cell lines tested when compared to the methanol extract. The results showed that methanol extracts of plant seeds caused 100% mortality of mosquito larvae at a concentration of 1000 μg/ml after 24 h of treatment. The LC₅₀ and LC₉₀ values of X. strumarium were found to be 531.07 and 905.95 μg/ml against Ae. caspius and 502.32 and 867.63 μg/ml against Cx. Pipiens, respectively. From the investigations, it was concluded that the crude extract of X. strumarium showed a weak potential for controlling the larval instars of Ae. caspius and Cx. pipiens. However, on further purification the extract lost the larvicidal activity. The ethyl acetate fraction showed higher toxicity to all cell lines tested when compared to the methanol extract. The ethyl acetate fraction investigated in this study appears to have a weak larvicidal activity but a promising cytotoxic activity. Future studies will include purification and investigation in further detail of the action of X. strumarium on Cancer Cell Lines and mosquitoes.     

Comparative study of three herbal formulations against dengue vectors Aedes aegypti

The efficacy of three formulations (i.e., natural lavender crude, essential oil, and gel) extracted from Lavender angustifolia was tested against vectors of the epidemic dengue virus, Aedesaegypti, to evaluate their larvicidal activity effect. The ethanolic extract of the lavender crude was prepared using a rotary evaporator, while the other extracts, such as essential oil and gel, were obtained from iHerb, a supplier of medicinal herbs in the US. The mortality rate of larvae was evaluated 24 h after exposure. Larvicidal activity of the lavender crude was 91% mortality at 150 ppm, 94% for essential oil at a concentration of 3000 ppm, and 97% for lavender gel at a 1000 ppm. Natural lavender crude was one of the most promising extracts tested against Ae.aegypti larvae, with lethal concentrations at LC₅₀ and LC₉₀ of 76.4 and 174.5 ppm post-treatment. The essential oil had the least effect on mosquito larvae, with LC₅₀ and LC₉₀ reaching 1814.8 and 3381.9 ppm, respectively. The lavender gel was moderately effective against Ae. aegypti larvae, with LC₅₀ and LC₉₀ values reaching 416.3 and 987.7 ppm after exposure. The occurrence of morphological abnormalities in the larvae treated with the three compounds, in turn, resulted in an incomplete life cycle. Therefore, our results indicated that natural lavender crude displayed the highest larvicidal activity against larvae, followed by gel and essential oil. Thus, this study concluded that lavender crude is an effective, eco-friendly compound that can be used as an alternative to chemical products to control vector-borne epidemic diseases.     

Chemistry,antioxidant and antimicrobial potential of nutmeg (Myristica fragrans Houtt)

Antioxidant and antimicrobial activities of nutmeg (Myristica fragrans Houtt) seed extracts were evaluated. Seeds were extracted with acetone, ethanol, methanol, butanol and water. All the extracts have shown significant antioxidant and antimicrobial activities against the tested microorganisms. Among all extracts, acetone extract has shown the highest antioxidant activity. The acetone extract showed 93.12 ± 1.48 mg gallic acid equivalents (GAE)/100 g dry weight total phenolic content, DPPH scavenging activity of 63.04 ± 1.56%, chelating activity of 64.11 ± 2.21% and 74.36 ± 1.94% inhibition of β-carotene bleaching, at 1 mg/mL extract concentration. Out of all extracts, acetone extract was able to exert antimicrobial activity against all tested bacteria and fungi. Acetone extract has shown the strongest antibacterial and antifungal activity with Staphylococcus aureus (13.8 ± 0.42 mm) and Aspergillus niger (14.4 ± 0.37 mm), respectively. GC–MS analysis of acetone extract has revealed the presence of 32 compounds of extract representing 99.49%. Sabinene (28.61%) has shown the highest occurrence in the extract. β-Pinene (10.26), α-pinene (9.72), myristicin (4.30%), isoeugenol (2.72%), p-cymene (1.81%), carvacrol (1.54%), eugenol (0.89%) and β-caryophellene (0.82%) were reported as possible contributor for antioxidant and antimicrobial activity of nutmeg.     

In vitro cytotoxicity and genotoxicity of five Ochna species (Ochnaceae) with excellent antibacterial activity

Extracts and fractions of some Ochna species had excellent antibacterial activity. Before considering the potential therapeutic use of these extracts it is important to determine the safety of extracts. The cytotoxicity of Ochna natalitia, Ochna pretoriensis, Ochna pulchra, Ochna gamostigmata, and Ochna serrulata (Ochnaceae) was determined in monkey kidney (Vero) cells, human hepatocellular carcinoma (C3A) cells and bovine dermis cells using the mitochondrial viability MTT assay. Their potential mutagenic effects were also determined using the Ames test with strains Salmonella typhimurium TA98 and TA100 with and without metabolic activation. The LC₅₀ values (the lethal concentration at which 50% of the cells are killed) of the extracts on the various cell lines ranged from 26 to 99 μg/ml. None of the plant species was mutagenic (mutagenic index values ≤ 1.59 for TA98 and ≤ 0.92 for TA100). In a previous study, we determined the antibacterial activity of the five extracts against Staphylococcus aureus, Escherichia coli, Enterococcus faecalis and Pseudomonas aeruginosa. From this we calculated the selectivity index (SI) values by dividing the LC₅₀ value by the minimum inhibitory concentration (MIC) to obtain the ratio of toxicity to bioactivity of each extract. The plant extracts had low SI values ≤ 1.307. This is a clear indication of non-selective toxicity, i.e. extracts are almost equally toxic to the bacteria and mammalian cell lines used in the assays. As a result, the extracts may have limited application as ingestible or intravenous therapeutic agents based on the in vitro findings. However, it may be necessary to also evaluate in vivo toxicity of the extracts in animal models as in vitro toxicity does not always equate to in vivo toxicity because of the difference in physiological microenvironment in live animals and tissue culture. Additionally, if it is the case that the toxic compounds are not the same as the active compounds, it may be possible to potentiate the extracts by the removal of toxic compounds and concentration of active compounds. The extracts may then be useful for development into treatments for topical bacterial infections.     

Larvicidal activities of the stem bark extract and rotenoids of Millettia usaramensis subspecies usaramensis on Aedes aegypti L. (Diptera: Culicidae)

The dichloromethane/methanol (1:1) extract of the stem bark of Millettia usaramensis subspecies usaramensis was tested for its larvicidal activity against the 4th instar Aedes aegypti larvae and demonstrated activity with LC₅₀ value of 50.8 ± 0.06 μg/mL at 48 h. Compounds isolated from the extract were also tested for their larvicidal activities, and the rotenoid usararotenoid-A (LC₅₀ 4.3 ± 0.8 μg/mL at 48 h) was identified as the most active principle. This compound appears to be the first rotenoid having a trans-B/C ring junction and methylenedioxy group at C-2/C-3 with high larvicidal activity. Related rotenoids with the same configuration at the B/C-ring junction did not show significant activity at 100 μg/mL.     

Isolation of antioxidant constituents from Combretum apiculatum subsp. apiculatum

Species of the family Combretaceae are used extensively in traditional medicine against inflammation and infections, and although antibacterial activity has been reported in non-polar extracts, further rationale for the widespread use of the Combretaceae is expected to exist. Methanol extracts of leaves of ten different Combretum species were evaluated for antioxidant activity by spraying TLC chromatograms of each leaf extract with 2,2-diphenyl-1-picrylhydrazyl (DPPH). Compounds with antioxidant activity were detected by bleaching of the purple DPPH colour. Leaf extracts of Combretum apiculatum subsp. apiculatum had the most antioxidant compounds. This species was consequently selected for phytochemical investigation. A DPPH assay-directed fractionation of the leaf extracts of C. apiculatum led to the isolation of four antioxidant compounds from the ethyl acetate and butanol soluble fractions. The structures of the compounds were determined by spectroscopic analyses (¹H-NMR, ¹³C-NMR and MS) and identified as: cardamonin (1), pinocembrin (2), quercetrin (3) and kaempferol (4). In a quantitative antioxidant assay, the more polar fractions (ethyl acetate and butanol) obtained by solvent–solvent fractionation had the highest antioxidant activity among the solvent fractions obtained from C. apiculatum, with EC₅₀ values of 3.91 ± 0.02 and 2.44 ± 0.02 μg/ml respectively. Of the four isolated compounds, quercetrin (4) and kaempferol (3) had the strongest antioxidant activity, with EC₅₀ values of 11.81 ± 85 and 47.36 ± 0.03 μM respectively. Cardamonin (1) and pinocembrin (2) did not demonstrate strong activity. L-ascorbic acid was used as standard antioxidant agent (EC₅₀ = 13.37 ± 0.20 μM or 2.35 μg/ml). The cytotoxicity of cardamonin and pinocembrin was evaluated on Vero kidney cells using the MTT (3-(4,5-dimethylthiazol)-2,5-diphenyl tetrazolium bromide) assay with berberine as positive control. At concentrations higher than 50 μg/ml of cardamonin or pinocembrin, the cells were not viable. Cardamonin was more toxic (LC₅₀ = 1.97 μg/ml) than pinocembrin (LC₅₀ = 29.47 μg/ml) and even the positive control, berberine (LC₅₀ = 12.35 μg/ml).     

Chemical composition and larvicidal activity of Piper capense essential oil against the malaria vector,Anopheles gambiae

Hydro-distilled essential oil from Kenyan Piper capense (Piperaceae) was analysed by gas chromatography mass spectrometry (GC–MS) and evaluated for larvicidal activity against the malaria vector, Anopheles gambiae. The oil consisted mainly of sesquiterpene hydrocarbons which accounted for 43.9% of the oil. The major sesquiterpenes were δ-cadinene (16.82%), β-bisabolene (5.65%), and bicyclogermacrene (3.30%). The oil also had appreciable amounts of monoterpene hydrocarbons (30.64%), including β-pinene (7.24%) and α-phellandrene (4.76%), and arylpropanoids (8.64%), including myristicin (4.26%). The oil showed larvicidal activity against third instar larvae of A. gambiae, with LC₅₀ and LC₉₀ values of 34.9 and 85.0 ppm, respectively. Most of the larvae died within the first few hours. The high larvicidal activity of this oil was indicated by the fact that over 80% mortality was observed at a concentration of 100 ppm after 24 h. These results compared favourably with the commercial larvicide pylarvex® which had LC₅₀ and LC₉₀ values of 3.7 and 7.8 ppm, respectively. Application of this oil or of products derived from it to larval habitats may lead to promising results in malaria and mosquito management programmes.     

Target and non-target effects of Foeniculum vulgare and Matricaria chamomilla combined extract on Culex pipiens mosquitoes

The present study focused on extracting green larvicides from extracts of the combination of Foeniculum vulgare and Matricaria chamomilla using different solvents of increasing polarity in a Soxhlet extractor and evaluating their ovicidal, larvicidal, and cytotoxic activities. The most promising among all tested extracts was hexane extract. The ovicidal activity of the hexane PH2 extract resulted in a significant (p < 0.05) decrease in egg hatchability from 95.00 ± 6.16% to 15 ± 9.04% at doses ranging from 62.5 to 500 µg/mL. The larval mortality with the hexane extract ranged from 13.33 ± 3.3% to 93.33 ± 3.3% at doses ranging from 31.25 to 250 µg/mL, respectively. The LC₅₀ and LC₉₀ values of the larvicidal activity of the hexane extract were estimated to be 148.3 and 242.17 µg/mL, respectively, after 24 h of exposure. Similarly, the LC₅₀ values after 48 and 72 h of exposure were 124.93 and 100.3 µg/mL, respectively, against the third instar of Cx. pipiens. PH2 treatment of larvae resulted in histopathological changes such as degenerated epithelial cells and destruction of microvilli on the epithelial cells. The PH2 extract achieved a dose-dependent decrease in the rate of cell survival. The IC₅₀ value of PH2-treated HUVECs was 192.07 µg/mL after 24 h of incubation. The cells showed changes in cellular and nuclear morphology. In conclusion, the hexane extract of PH2 could be used in mosquito management programs.     

Acetylcholinesterase inhibitory effects of the bulb of Ammocharis coranica (Amaryllidaceae) and its active constituent lycorine

Ammocharis coranica (Ker-Gawl.) Herb. (Amaryllidaceae) is used in southern Africa for the treatment of mental illnesses. The ethanol extracts of the bulb of A. coranica and its total alkaloids rich fractions were screened for inhibition of acetylcholinesterase enzyme (AChE), which is implicated in the pathophysiology of Alzheimer's disease. The ethanolic extracts significantly inhibited AChE with IC₅₀ value of 14.3 ± 0.50 μg/ml. The basic ethyl acetate and butanol fractions of the crude extracts were the most active against AChE with IC₅₀ values of 43.1 ± 1.22 and 0.05 ± 0.02 μg/ml respectively. Bioassay-guided fractionation of the basic fractions led to the isolation of lycorine and 24-methylenecycloartan-3β-ol. Lycorine which was isolated from both butanol and ethyl acetate fractions had IC₅₀ of 29.3 ± 3.15 μg/ml, while 24-methylenecycloartan-3β-ol was not active.     

Antifouling activity exhibited by secondary metabolites of the marine sponge,Haliclona exigua (Kirkpatrick)

Bioassay guided purification of the acetone extract of the marine sponge, Haliclona exigua, (Gulf of Mannar, India) yielded a fraction rich in bis-1-oxaquinolizidine alkaloids, active against seven strains of fouling bacteria as well as cyprids of the cosmopolitan barnacle, Balanus amphitrite. The major alkaloids in the mixture have been tentatively identified as nor-araguspongine C (33.76%), araguspongine C (6.49%), dihydroxy araguspongine (36.36%), methyl and dimethyl derivatives of the latter (12.98 and 10.38%, respectively) from HRMS studies. The lower EC₅₀ (6.6 μg/ml as against the US Navy standard of 25 μg/ml for NPAs) and low toxicity (LC₅₀ 18 μg/ml as compared to 0.00001 μg/ml for TBT) values, coupled with its favourable therapeutic ratio (2.7 as against the requirement of >1) makes these compounds ideal NPAs in environmentally compatible antifouling coatings.     

Permethrin resistance in Aedes aegypti (Linnaeus) collected from Kuala Lumpur,Malaysia

Permethrin resistance status of a laboratory strain, a permethrin-selected strain and three field strains of Aedes aegypti collected in Kuala Lumpur, Malaysia were evaluated using three standard laboratory bioassays: WHO larval bioassay, WHO adult mosquito bioassay, and mixed function oxidase (MFO) enzyme microassay. The LC₅₀ values of field strains from the WHO larval bioassay did not differ significantly. The highest LC₅₀ value was from the Taman Melati field strain (0.39 mg/L). The resistance ratio for the permethrin-selected strain and the field strains ranged from 1.86 fold to 5.57 fold. Pre-exposure to piperonyl butoxide (PBO) in the WHO adult bioassay and MFOs enzyme microassay reduced the LT₅₀ values and reduced the mean optical density of elevated oxidase activity (0.28–0.42) at 630 nm. The LC₅₀ or LT₅₀ values and the level of oxidases were significantly correlated (r = 0.825; p< 0.05). This study confirmed the presence of permethrin resistance in these mosquito populations.     

Biological activities of two macroalgae from Adriatic coast of Montenegro

In the present investigation the acetone extracts of macroalgae Ulva lactuca and Enteromorpha intestinalis were tested for antioxidant, antimicrobial and cytotoxic potential. Antioxidant activity was evaluated by measuring the scavenging capacity of tested samples on DPPH and superoxide anion radicals, reducing the power of samples and determination of total phenolic and flavonoid compounds in extracts. As a result of the study, U. lactuca extract was found to have a better free radical scavenging activity (IC₅₀ = 623.58 μg/ml) than E. intestinalis extract (IC₅₀ = 732.12 μg/ml). Moreover, the tested extracts had effective ferric reducing power and superoxide anion radical scavenging. The total content of phenol in extracts of U. lactuca and E. intestinalis was 58.15 and 40.68 μg PE/mg, while concentrations of flavonoids were 39.58 and 21.74 μg RE/mg, respectively. Furthermore, among the tested species, extracts of U. lactuca showed a better antimicrobial activity with minimum inhibitory concentration values ranging from 0.156 to 5 mg/ml, but it was relatively weak in comparison with standard antibiotics. Bacillus mycoides and Bacillus subtilis were the most susceptible to the tested extracts. Contrary to this Aspergillus flavus, Aspergillus fumigatus and Penicillium purpurescens were the most resistant. Finally, cytotoxic activity of tested extracts was evaluated on four human cancer cell lines. Extract of E. intestinalis expressed the stronger cytotoxic activity towards all tested cell lines with IC₅₀ values ranging from 74.73 to 155.39 μg/ml.     

Bioactivity and structure–activity relationship of cinnamic acid derivatives and its heteroaromatic ring analogues as potential high-efficient acaricides against Psoroptes cuniculi

A series of cinnamic acid derivatives and its heteroaromatic ring analogues were synthesized and evaluated for acaricidal activity in vitro against Psoroptes cuniculi, a mange mite. Among them, eight compounds showed the higher activity with median lethal concentrations (LC₅₀) of 0.36–1.07 mM (60.4–192.1 µg/mL) and great potential for the development of novel acaricidal agent. Compound 40 showed both the lowest LC₅₀ value of 0.36 mM (60.4 µg/mL) and the smallest median lethal time (LT₅₀) of 2.6 h at 4.5 mM, comparable with ivermectin [LC₅₀ = 0.28 mM (247.4 µg/mL), LT₅₀ = 8.9 h], an acaricidal drug standard. SAR analysis showed that the carbonyl group is crucial for the activity. The type and chain length of the alkoxy in the ester moiety and the steric hindrance near the ester group significantly influence the activity. The esters were more active than the corresponding thiol esters, amides, ketones or acids. Replacement of the phenyl group of cinnamic esters with α-pyridyl or α-furanyl significantly increase the activity. Thus, a series of cinnamic esters and its heteroaromatic ring analogues with excellent acaricidal activity emerged.     

Serotonin transporter protein (SERT) and P-glycoprotein (P-gp) binding activity of montanine and coccinine from three species of Haemanthus L. (Amaryllidaceae)

The alkaloid rich extracts from an acid/base extraction of bulb material of Haemanthus coccineus L., H. montanus Baker and H. sanguineus Jacq. revealed that two montanine type Amaryllidaceae alkaloids, montanine (1) and coccinine (2) were the major alkaloid constituents. Together these two alkaloids constituted 88, 91 and 98% of the total alkaloid extract from each species respectively. GC–MS analysis revealed that H. coccineus and H. sanguineus had a relative abundance of coccinine (74 and 91% respectively) to montanine (14 and 7% respectively); whereas H. montanus had 20% coccinine and 71% montanine. The three extracts and two isolated alkaloids were evaluated for binding to the serotonin transporter protein (SERT) in vitro. Affinity to SERT was highest in H. coccineus (IC₅₀ = 2.0 ± 1.1 μg/ml) followed by H. montanus (IC₅₀ = 6.8 ± 1.0 μg/ml) and H. sanguineus (IC₅₀ = 28.7 ± 1.1 μg/ml). Montanine (IC₅₀ = 121.3 ± 3.6 μM or 36.56 ± 1.14 μg/ml; K_i = 66.01 μM) was more active than coccinine (IC₅₀ = 196.3 ± 3.8 μM or 59.15 ± 1.08 μg/ml; K_i = 106.8 μM), both of which were less active than the total alkaloid extracts of each species investigated. The possible synergistic effects of two coccinine/montanine mixtures (80:20 and 20:80) were investigated, however the mixtures gave similar activities as the pure compounds and did not show any increase in activity or activity similar to the total alkaloid extracts. Thus the considerably higher activity observed in the total alkaloid extracts is not correlated to the relative proportions of coccinine and montanine in the extracts and thus are likely to be due to more potent unidentified minor constituents. Both alkaloids exhibited low binding affinity to P-glycoprotein (P-gp) as demonstrated by low inhibition of calcein-AM efflux in the MDCK-MDR1 cell line. This indicates that P-gp efflux will not be limiting for blood–brain-barrier passage of the alkaloids.     

Chemical composition and larvicidal activity of leaf essential oil from Clausena dentata (Willd) M. Roam. (Rutaceae) against the chikungunya vector,Aedes aegypti Linn. (Diptera: Culicidae)

Larvicidal activity of essential oil and isolated compounds from Clausena dentata leaves were tested against early fourth instar Aedes aegypti larvae. GC–MS analysis of essential oil revealed the presence of fourteen compounds of which the major compounds were sabinene (21.27%), biofloratriene (19.61%), borneol (18.34%) and β-bisabolol (17.68%). The essential oil of C. dentata exhibited significant larvicidal activity, with 24 h LC₅₀ and LC₉₀ values of 140.2 and 341.6 mg/l, respectively. Larvicidal activities of the four major compounds of essential oil were also tested. The LC₅₀ values of sabinene, biofloratriene, borneol and β-bisabolol were 27.3, 47.4, 43.5 and 33.2 mg/l, respectively. Results of this study show that the leaf essential oil of C. dentata and its four major compounds may be a potent source of natural larvicides.     

Chemical composition,oviposition deterrent and larvicidal activities against Aedes aegypti of essential oils from Piper marginatum Jacq. (Piperaceae)

The essential oils of leaves, stems and inflorescences of Piper marginatum, harvested in the Atlantic forest in the State of Pernambuco, Brazil, were obtained by hydrodistillation. GC and GC–MS analyses revealed the presence of 40 components accounting, respectively, for 99.6%, 99.7% and 99.1% of the leaf, stem and inflorescence oil, the most abundant being (Z)- or (E)-asarone and patchouli alcohol. The essential oil of the inflorescences exhibited potent activity against the 4th instar of Aedes aegypti with LC₁₀ and LC₅₀ values of 13.8 and 20.0 ppm, respectively. Furthermore, the inflorescence oil did not interfere in the oviposition of A. aegypti females when assayed at 50 ppm. These properties suggest that P. marginatum oil is a potential source of valuable larvicidal compounds for direct use or in conjunction with baits in traps constructed to capture eggs and larvae.