In recent years, a number of man-made chemicals have been shown to be able to mimic endogenous hormones, and it has been hypothesized that alterations in the normal pattern of reproductive development seen in some populations of wildlife are linked with exposure to these chemicals. Of particular importance are those compounds that mimic estrogens and androgens (and their antagonists), because of their central role in reproductive function. In fact, the evidence showing that such chemicals actually do mimic (or antagonize) the action of hormones in the intact animal is limited. In only a few cases have laboratory studies shown that chemicals that mimic hormones at the molecular level (in vitro) also cause reproductive dysfunction in vivo at environmentally relevant concentrations. In addition, the reported studies on wild populations of animals are limited to a very few animal species and they have often centered on localized 'hot-spots' of chemical discharges. Nevertheless, many of these xenobiotics are persistent and accumulate in the environment, and therefore a more widespread phenomenon of endocrine disruption in wildlife is possible. This article reviews the evidence, from both laboratory and field studies, that exposure to steroid hormone mimics may impair reproductive function and critically assesses the weight of evidence for endocrine disruption in wildlife.

Endocrine Disruption in Wildlife: A Critical Review of the Evidence

Repellent activity of essential oils: a review.

This opinion describes the assessment of the risks to public health associated with bisphenol A (BPA) exposure. Exposure was assessed for various groups of the human population in three different ways: (1) external (by diet, drinking water, inhalation, and dermal contact to cosmetics and thermal paper); (2) internal exposure to total BPA (absorbed dose of BPA, sum of conjugated and unconjugated BPA); and (3) aggregated (from diet, dust, cosmetics and thermal paper), expressed as oral human equivalent dose (HED) referring to unconjugated BPA only. The estimated BPA dietary intake was highest in infants and toddlers (up to 0.875 µg/kg bw per day). Women of childbearing age had dietary exposures comparable to men of the same age (up to 0.388 µg/kg bw per day). The highest aggregated exposure of 1.449 µg/kg bw per day was estimated for adolescents. Biomonitoring data were in line with estimated internal exposure to total BPA from all sources. BPA toxicity was evaluated by a weight of evidence approach. “Likely” adverse effects in animals on kidney and mammary gland underwent benchmark dose (BMDL10) response modelling. A BMDL10 of 8 960 µg/kg bw per day was calculated for changes in the mean relative kidney weight in a two generation toxicity study in mice. No BMDL10 could be calculated for mammary gland effects. Using data on toxicokinetics, this BMDL10 was converted to an HED of 609 µg/kg bw per day. The CEF Panel applied a total uncertainty factor of 150 (for inter- and intra-species differences and uncertainty in mammary gland, reproductive, neurobehavioural, immune and metabolic system effects) to establish a temporary Tolerable Daily Intake (t-TDI) of 4 µg/kg bw per day. By comparing this t-TDI with the exposure estimates, the CEF Panel concluded that there is no health concern for any age group from dietary exposure and low health concern from aggregated exposure. The CEF Panel noted considerable uncertainty in the exposure estimates for non-dietary sources, whilst the uncertainty around dietary estimates was relatively low.

Scientific Opinion on the risks to public health related to the presence of bisphenol A (BPA) in foodstuffs: Executive summary

Plant-based repellents have been used for generations in traditional practice as a personal protection measure against host-seeking mosquitoes. Knowledge on traditional repellent plants obtained through ethnobotanical studies is a valuable resource for the development of new natural products. Recently, commercial repellent products containing plant-based ingredients have gained increasing popularity among consumers, as these are commonly perceived as “safe” in comparison to long-established synthetic repellents although this is sometimes a misconception. To date insufficient studies have followed standard WHO Pesticide Evaluation Scheme guidelines for repellent testing. There is a need for further standardized studies in order to better evaluate repellent compounds and develop new products that offer high repellency as well as good consumer safety. This paper presents a summary of recent information on testing, efficacy and safety of plant-based repellents as well as promising new developments in the field.

/pdf/plant-based-insect-repellents-a-review-of-their-efficacy-zxnqflf1e6.pdf

Plant-based insect repellents: a review of their efficacy, development and testing

time, probably by stimulation of the hepatic microsomal enzyme system3. Similar properties were exhibited by its roots. However, the petroleum ether extract (PEE) of the roots enhanced pentobarbitone sleeping time, probably due to CNS depression4. The PEE of the seed of Pongomia pinnata was further tested for nootropic activity in an experimental model of Alzheimer’s disease (created by ibotenic acid induced lesioning of nuclear basalis magnocellularis). It reversed both, the cognitive deficits and the reduction in cholinergic markers after 2 weeks of treatment. Reversal of perturbed cholinergic function appears to be the possible mechanism5.

/pdf/pharmacology-of-medicinal-plants-and-natural-products-55vzicfceo.pdf

Pharmacology of medicinal plants and natural products

Anti-malarial activity of some xanthones isolated from the roots of Andrographis paniculata.

Background
Mosquitoes transmit serious human diseases, causing millions of deaths every year. Use of synthetic insecticides to control vector mosquitoes has caused physiological resistance and adverse environmental effects in addition to high operational cost. Insecticides of botanical origin have been reported as useful for control of mosquitoes. Azadirachta indica (Meliaceae) and its derived products have shown a variety of insecticidal properties. The present paper discusses the larvicidal activity of neem-based biopesticide for the control of mosquitoes.

https://link.springer.com/content/pdf/10.1186%2F1475-2875-8-124.pdf

Larvicidal activity of neem oil (Azadirachta indica) formulation against mosquitoes

Background & objectives Development of insect resistance to synthetic pesticides, high operational cost and environmental pollution have created the need for developing alternative approaches to control vector-borne diseases. In the present study we have investigated the insecticidal activity of essential oil isolated from the leaves of Lantana camara against mosquito vectors. Methods Essential oil was isolated from the leaves of L. camara using hydro-distillation method. Bioassay test was carried out by WHO method for determination of adulticidal activity against mosquitoes. Different compounds were identified by gas chromatography-mass spectrometry analysis. Results LD(50) values of the oil were 0.06, 0.05, 0.05, 0.05 and 0.06 mg/cm(2) while LD(90) values were 0.10, 0.10, 0.09, 0.09 and 0.10 mg/cm(2) against Ae. aegypti, Cx. quinquefasciatus, An. culicifacies, An. fluvialitis and An. stephensi respectively. KDT(50) of the oil were 20, 18, 15, 12, and 14 min and KDT(90) values were 35, 28 25, 18, 23 min against Ae. aegypti, Cx. quinquefasciatus, An. culicifacies, An. fluviatilis and An. stephensi, respectively on 0.208 mg/cm(2) impregnated paper. Studies on persistence of essential oil of L. camara on impregnated paper revealed that it has more adulticidal activity for longer period at low storage temperature. Gas chromatographic-mass spectrometric analysis of essential oil showed 45 peaks. Caryophyllene (16.37%), eucalyptol (10.75%), alpha-humelene (8.22%) and germacrene (7.41%) were present in major amounts and contributed 42.75 per cent of the total constituents. Interpretation & conclusions Essential oil from the leaves of L. camara possesses adulticidal activity against different mosquito species that could be utilized for development of oil-based insecticide as supplementary to synthetic insecticides.

Adulticidal activity of essential oil of Lantana camara leaves against mosquitoes.

The repellent effect of Lantana camara flowers was evaluated against Aedes mosquitoes. Lantana flower extract in coconut oil provided 94.5% protection from Aedes albopictus and Ae. aegypti. The mean protection time was 1.9 h. One application of Lantana flower can provide more than 50% protection up to 4 h against the possible bites of Aedes mosquitoes. No adverse effects of the human volunteers were observed through 3 months after the application.

Repellency of Lantana camara (Verbenaceae) flowers against Aedes mosquitoes.

A root extract of Valeriana jatamansi (code BAL-O) exhibited larvicidal and adulticidal activity against different mosquito species. The median lethal concentration (LC50) of BAL-O against larvae of Anopheles stephensi, Anopheles culicifacies, Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus were 68.1, 42.8, 51.2, 53.8, and 80.6 mg/liter, respectively. The LC50 and the 90% lethal concentration against adult An. stephensi, An. culicifacies, Ae. aegypti, Ae. albopictus, and Cx. quinquefasciatus were 0.14, 0.16, 0.09, 0.08, and 0.17 and 0.24, 0.34, 0.25, 0.21, and 0.28 mg/cm2, respectively. The median knock-down time and 90% knock-down time of the fraction were 13, 13, 12, 13, and 18 and 24, 25, 21, 20, and 42 min against An. stephensi, An. culicifacies, Ae. aegypti, An. albopictus and Cx. quinquefasciatus, respectively, using 0.28 mg/cm2 impregnated papers. The median effective time and 90% effective time against An. stephensi at 4°C were 46.6 and 8.7 days, and at 29°C, 25.5 and 5.6 days...

https://bioone.org/journals/journal-of-the-american-mosquito-control-association/volume-24/issue-2/5642.1/Insecticidal-Activity-of-Valeriana-Jatamansi-Valerianaceae-Against-Mosquitoes/10.2987/5642.1.pdf

Virendra K. Dua

Papers

Anti-malarial activity of some xanthones isolated from the roots of Andrographis paniculata.

Larvicidal activity of neem oil (Azadirachta indica) formulation against mosquitoes

Adulticidal activity of essential oil of Lantana camara leaves against mosquitoes.

Repellency of Lantana camara (Verbenaceae) flowers against Aedes mosquitoes.

Insecticidal activity of Valeriana jatamansi (Valerianaceae) against mosquitoes.