Drug Discovery Potential of Insect-Derived Compounds: A review.

Insects are the most numerous and diverse collection of organisms on earth. Around the world, human societies have utilised insects and the materials derived from them as medical resources. These arthropods use chemistry, like all other species. According to their survival needs, they make adaptations, including protecting themselves from infection as well as predation, being able to connect with a social life, and carrying out generations with survivability in the environment. The main focus of the study of chemical ecology is the abundance of chemical compounds found in arthropods that are used for these ecological adaptations. This thorough analysis summarises the huge potential for finding new natural compounds with medical benefits from the Arthropods. Insects and their derivatives have a wide range of uses, and their "raw products" have made significant strides in a wide range of industries, including pharmaceuticals, tissue engineering, dentistry, plant and agricultural science, veterinary medicine, cosmetics, and cosmeceuticals, food, and nutraceuticals, among others. Bioactive components derived from insects are emerging as potential therapeutic sources that are beneficial against a variety of disorders. Insects, which have a huge variety of species, are an intriguing and potential source of low molecular biologically active natural compounds that are either produced by the insect itself or by accompanying microbes. The present review work collated the updates of insect-derived compounds, the use of insects worldwide, and drug discovery potential of insect derivatives.

Evaluation of mosquito larvicidal activity of fruit extracts of Acacia auriculiformis against the Japanese encephalitis vector Culex vishnui.

The larvicidal potentiality of crude and ethyl acetate extracts of fruits of Acacia auriculiformis was investigated against all the larval instars of JE vector Culex vishnui. The crude extracts showed good results against all the larval instars with highest mortality at 0.09%. Highest mortality was found at 300 ppm of ethyl acetate extract. Lowest LC50 value was obtained at 72 h for third instar larvae. Non target organisms tested, showed no to very less mortality to ethyl acetate solvent extract. Presence of N-H stretching, a C=O stretching, C=C and C-N stretching vibrations of secondary amide or amine group were confirmed from IR analysis. GC-MS analysis revealed the presence of three compounds namely Ethane 2-chloro-1,1-dimethoxy, Acetic acid, 1-methyl ether ester and [4-[1-[3,5-Dimethyl-4[(trimethylsilyl)oxy)phenyl]-1,3-dimethylbutyl)-2,6dimethylphenoxy)(trimethyl) silane, responsible for mosquito larval death.

Larvicidal activity of phytosteroid compounds from leaf extract of Solanum nigrum against Culex vishnui group and Anopheles subpictus.

BACKGROUND: Vector control is facing a menace due to the appearance of resistance to synthetic insecticides. Insecticides of plant origin may provide appropriate substitute biocontrol techniques in the future. The present study was carried out to investigate the bio control potentiality of active ingredient isolated from chloroform: methanol (1:1 v/v) extract of mature leaves of Solanum nigrum L. (Solanaceae) against early 3rd instar larvae of Culex vishnui group (comprising of Cx. vishnui Theobald, Cx. pseudovishnui Colless and Cx. tritaeniorhynchus Giles) and Anopheles subpictus Grassi. S. nigrum is a common plant distributed in many parts of India with medicinal properties. METHODS: Bioactive compound isolated from chloroform: methanol (1:1 v/v) extract of mature leaves of S. nigrum was (25, 45, 60 mg/L) tested against early 3rd instar larvae of Cx. vishnui group and An. subpictus. The lethal concentration was determined by log probit analysis. The chemical nature of the active substance was also evaluated following gas chromatography-mass spectroscopy (GC-MS) and infrared (IR) analysis. The compound was also studied on non target organisms such as Daphnia sp. and Diplonychus annulatum. RESULTS: TLC spot having Rf value of 0.94 (Rf = 14.1/15 = 0.94) showed larvicidal activity. In a 72 h bioassay experiment, mortality rate at 60 mg/L was significantly higher (P < 0.05) than those at 25 and 45 mg/L against early 3rd instar. Result of log-probit analysis (at 95% confidence level) revealed that LC50 and LC90 values gradually decreased with the exposure period showing the lowest value at 72 h of exposure. A clear dose-dependent mortality was observed, as the rate of mortality (Y) was positively correlated with the concentration (X) having regression coefficient value close to one in each case. The compound was found to be eco-friendly as it did not show any adverse effect to the studied non target organisms. Chemical characterization (GC-MS and IR analyses) of the active ingredient revealed the presence of phytosteroid compounds responsible for mosquito larvicidal activity. CONCLUSION: Leaf extract of S. nigrum has great potential as bio control agent against Cx. vishnui group and An. subpictus. In near future the isolated bioactive phytochemical could be used as a source of an effective mosquitocidal agent.

Laboratory evaluation of molluscicidal & mosquito larvicidal activities of leaves of Solanum nigrum L.

BACKGROUND & OBJECTIVES: Indiscriminate use of synthetic pesticides has created serious problem for the aquatic flora and fauna, and also resulted in appearance of pesticide resistance in vector population. This study was designed to evaluate the biocontrol efficacy of aqueous and solvent extracts of mature leaves of Solanum nigrum L., against fresh water snail Lymnaea acuminata f. rufescens (Gray) (an intermediate host of parasites causing fasciolopsiasis) and larvae of Culex vishnui group (Reuben) (vector of Japanese encephalitis). METHODS: Aqueous and solvent extracts of fresh, mature, green/shed dried leaves of S. nigrum were tested against adult L. acuminata and larvae of Cx. vishnui group. The lethal concentration was determined and the appropriate lethal concentration at 24 h of benzene extract was also studied on non target organisms such as Daphnia sp, Diplonychus annulatum and Chironomus circumdatus. A qualitative phytochemical analysis was carried out in search of active ingredient and the chemical nature of the active substance was also evaluated by infrared (IR) analysis. RESULTS: In a 72 h bioassay experiment with the aqueous extract, the highest mortality was recorded in 0.5 and 3 per cent extract against larvae of Cx. vishnui group and L. acuminata, respectivela. In the benzene solvent extract, the maximum mortality was recorded at a concentration of 150 ppm against L. acuminata and at 50 ppm against larvae of Cx. vishnui group with LC 50 values of 55.45 and 11.59 ppm, respectively at 72 h. The log probit analysis (95% confidence level) recorded lowest value at 72 h of exposure. Qualitative phytochemical analysis reported the presence of some biochemical compounds, such as saponin, flavonoids, steroid and tannin. Among these, the toxic compound was detected by IR analysis having Rf=0.87 (showed 66.70% and 76.70% mortality of L. acuminata and larvae of Cx. vishnui group, respectively). IR analysis provided preliminary information about the aliphatic amide nature of the active ingredient. INTERPRETATION & CONCLUSIONS: The study results provide considerable scope in exploiting local indigenous plant resources for molluscicidal and mosquito larvicidal activities.

Glucosinolate from leaf of Solanum nigrum L. (Solanaceae) as a new mosquito larvicide.

The present study was carried out to investigate the biocontrol potentiality of active ingredient isolated from ethyl acetate extract of mature leaves of Solanum nigrum L. (Solanaceae) against the larval form of Culex quinquefasciatus Say. Mortality rate at a concentration of 25 mg/L of the active compound was highest (P < 0.05) amongst all tested concentrations. Result of log-probit analysis (at 95% confidence level) revealed that LC50 and LC90 values are inversely proportional to exposure period of bioassay. A clear dose-dependent mortality was observed, as the rate of mortality (Y) was positively correlated with the concentrations of the compound (X); having regression coefficient value close to 1. The compound was found to be ecofriendly as it did not show any adverse effect to the studied nontarget organisms. Chemical characterization of the active ingredient was also carried out by infrared spectroscopic analysis (IR), mass analyses (GC-MS) and carbon-hydrogen-nitrogen-sulphur analyses (CHNS), that revealed the presence of a glucosinolate compound [1-thio-ß-D-glucopyranose-1-[(R)-3-hydroxy-2-ethyl-N-hydroxysulfonyloxy propanimidate] having the molecular formula of C11H21NO10S2.

Mosquito larvicidal potential of four common medicinal plants of India.

BACKGROUND & OBJECTIVES: Mosquitoes transmit serious human health diseases, causing millions of deaths every year. Plants may be sources of alternative mosquito control agents. The present study was carried out to assess the role of larvicidal activities of the crude extracts of four plants viz. Alternanthera sessilis L. (Amaranthaceae), Trema orientalis L. (Cannabaceae), Gardenia carinata Smith. (Rubiaceae) and Ruellia tuberosa L. (Acanthaceae) against Culex quinquefasciatus Say in laboratory bioassay. METHODS: Selective concentrations (0.5, 1 and 1.5%) of crude extract of all four plant leaves were tested against I st to IV th instar larvae of Cx. quinquefasciatus. Log probit analysis (at 95% confidence level) revealed the LC50 values. Preliminary qualitative phytochemical analyses of crude extracts were also done. The lethal concentrations (%) of crude extracts at 24 h against III rd instar larvae were also studied on non-target organisms. RESULT: In a 72 h bioassay experiment with crude extract, the highest mortality was recorded in 1.5 per cent extract. A. sessilis showed the highest mortality (76.7%) at 1.5 per cent crude extract against II nd instar larvae having LC50 value of 0.35 per cent, followed by R. tuberosa (LC50 = 1.84%), G. carinata (LC50 = 2.11) and T. orientalis (LC50 = 2.95%). The regression equation showed a dose-dependent mortality, as the rate of mortality (Y) was positively correlated with the concentration (X). Phytochemical analysis of the crude extract showed the presence of many bioactive phytochemicals such as steroids, alkaloids, terpenes, saponins, etc. No changes in the swimming behaviour and survivality of non-target organism were noticed at the studied concentrations. INTERPRETATION & CONCLUSIONS: Crude extract of the four selected plants showed larvicidal activity against Cx. quinquefasciatus. The extracts at the studied concentrations did not produce any harmful effect on non-target organisms.

Mosquito larvicidal and antimicrobial activity of synthesized nano-crystalline silver particles using leaves and green berry extract of Solanum nigrum L. (Solanaceae: Solanales).

Silver nanoparticles (AgNPs) that are synthesized by using aqueous extracts of Solanum nigrum L., is a simple, non-toxic and ecofriendly green material. The present study is based on assessments of the larvicidal and antimicrobial activities of the synthesized AgNPs from fresh leaves, dry leaves and green berries of S. nigrum against larvae of Culex quinquefasciatus and Anopheles stephensi and four human pathogenic and five fish pathogenic bacteria respectively. The synthesized nanoparticles are characterized with UV-vis spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscope (TEM) analysis. The nanoparticles are spherical to polyhedral in shape with size of 50-100nm (average size of 56.6nm). In larvicidal bioassay with synthesized AgNPs, highest mortality are observed at 10ppm against An. stephensi with LC50 values of 1.33, 1.59, 1.56ppm and LC90 values of 3.97, 7.31, 4.76ppm for dry leaves, fresh leaves and berries respectively. Antibacterial activity test reveals better results against fish pathogenic bacteria than human pathogenic bacteria. Non target organism like Toxorhynchites larvae (mosquito predator), Diplonychus annulatum (predatory water-bug) and Chironomus circumdatus larvae (chironomid) are also exposed to respective lethal concentrations (to mosquito larvae) of dry nanoparticles and no abnormality in the non target organisms are recorded. These results suggest that the synthesized AgNPs of S. nigrum have the potential to be used as an ideal eco-friendly compound for the control of the mosquito larvae and harmful bacteria.

Mosquito larvicidal activity of Solanum nigrum berry extracts.

Phytochemicals are widely used as biocontrol agent against vector mosquitoes. The present study was undertaken to isolate and evaluate the mosquitocidal activity of various extracts of berries of S. nigrum against Culex quinquefasciatus. Crude and chloroform: methanol (1:1, v/v) extracts of fresh, mature, green berries of S. nigrum were tested against Cx. quinquefasciatus. The lethal concentration was determined and the chemical nature of the active substance was evaluated. A qualitative phytochemical analysis of chloroform: methanol (1:1, v/v) extract was performed in search of the active ingredient. The appropriate lethal concentrations at 24 h for chloroform: methanol (1:1, v/v) extract was also studied on non-target organisms. In a 72 h bioassay experiment with crude extract, the highest mortality was recorded in 3 per cent extract. In the chloroform: methanol (1:1, v/v) solvent extract, the maximum mortality was recorded at a concentration of 120 µg/ml. The log probit analysis (95% confidence level) recorded lowest LC 50 value at 72 h of exposure. Both crude and chloroform: methanol (1:1, v/v) extracts showed good larvicidal activity against Cx. quinquefasciatus. The isolated active ingredient may be tested as a potential larvicide after determination of its structure.

Larvicidal activity of Dregea volubilis and Bombax malabaricum leaf extracts against the filarial vector Culex quinquefasciatus.

OBJECTIVE: To analyze the larvicidal activity of two plant leaf powder and leaf-extracts, Dregea volubilis and Bombax malabaricum against Culex quinquefasciatus. METHODS: The larvicidal bioassay was done for powdered leaves of Dregea volubilis and Bombax malabaricum individually and their methanol extracts against first-, second-, third- and fourth-instar larval forms of Culex quinquefasciatus. Mortality rate was recorded after 24, 48 and 72 h of post-exposure. LC(50) and LC(90) values were calculated at different time intervals for third instar larvae. RESULTS: All the graded concentration (0.1%, 0.2%, 0.3%, 0.4%, 0.5%) of powdered leaves showed significant (P <0.05) larval mortality. The mortality rate was higher in 50 ppm doses of methanolic extracts of both the plants against Culex quinquefaciatus. The corresponding LC(50) values were 56.97 ppm and 48.85 ppm, respectively after 24 h of exposure. There is no mortality of non-target organism such as Chironomous circumdatus, Oreochromis niloticus niloticus and Diplonichus annulatum within 72 h of post exposure to 0.1%, 0.2%, 0.3% crude powdered leaves and methanolic extracts of both the two individual plants under the laboratory condition. The results of preliminary qualitative phytochemical analysis of both the plants revealed the presence of many bioactive principles such as steroids, tannins, flavonoids, triterpenoids, saponins, etc. that may be responsible for their bio-control potentiality. CONCLUSIONS: The results have shown potential and eco-friendly use of both plant extracts against larva of Culex quinquefasciatus for the first time.

Mosquito larvicidal activities of Solanum nigrum L. leaf extract against Culex quinquefasciatus Say.

The present study was carried out to establish the larvicidal activities of crude and solvent extracts of Solanum nigrum L. leaves against Culex quinquefasciatus Say as target species. The results indicated that the mortality rates at 0.5% concentration were highest amongst all concentrations of the crude extracts tested against all the larval instars at 24, 48 and 72 h of exposure. Result of log probit analysis (at 95% confidence level) revealed that lethal concentration LC(50) and LC(90) values gradually decreased with the exposure periods in bioassay experiment with the crude plant extract. The results of regression analysis of crude extract of S. nigrum revealed that the mortality rate is positively correlated with the concentration of the extracts. Mature leaves of S. nigrum were also extracted with six different solvents [viz. petroleum ether, benzene, ethyl acetate, chloroform: methanol (1:1 v/v), acetone and absolute alcohol] to determine the best extractant for subsequent isolation and characterization of active ingredient. Mortality rate with ethyl acetate extract was significantly higher (p < 0.05) than other extracts when 50-ppm doses were used. The corresponding LC(50) value of acetone, absolute alcohol, petroleum ether, chloroform: methanol (1:1 v/v), benzene and ethyl acetate extracts were 72.91 ppm, 59.81 ppm, 54.11 ppm, 32.69 ppm, 27.95 ppm and 17.04 ppm, respectively, after 24 h of exposure period. Results of this study show that the ethyl acetate extract of S. nigrum may be considered as a potent source of a mosquito larvicidal agent.

Larvicidal activities of three plants against filarial vector Culex quinquefasciatus Say (Diptera: Culicidae).

The present study was carried out to establish the larvicidal properties of crude extracts of three plants, viz. Carica papaya, Murraya paniculata and Cleistanthus collinus against Culex quinquefasciatus as target species. The relative efficacy of the plant extracts in vector control was as follows: C. papaya seed extract > M. paniculata fruit extract > M. paniculata leaf extract > C. collinus leaf extract. Result of log-probit analysis (at 95% confidence level) revealed that LC(50) and LC(95) values gradually decreased with the exposure periods similar to the result in bioassay experiment for each of the plant extract. The results of preliminary qualitative phytochemical analysis of all the plants revealed the presence of many bioactive principles such as steroids, alkaloids, terpenes, saponins, etc. that may be responsible for their biocontrol potentiality. The appropriate lethal concentrations at 24 h for each of the extracts were also studied on non-target organisms such as Diplonychus annulatum and Chironomus circumdatus, and no change in the swimming behaviour and survivality was noticed, which indicates that all the extracts are safe for the aquatic ecosystem.