The already known benzoquinone, embelin (mixed with rapanone), and two new benzoquinones, myrsinone and myrsinaquinone, were isolated from the Myrsinaceae plant, Rapanea melanphloes (L), Mez. All the three compounds showed antifeedant activity when bioassayed on nymphs of the desert locust, Schistocerca gregaria (Forsk). They also inhibited growth of second-instar larvae of mosquito Aedes aegypti at low doses, and had acute lethal effects at higher doses.

Leaf extractables/fractions obtained from the leaves of soybean PI 227687 showed greater antifeedant activity towards the third-instar larvae of the cabbage looper, Trichoplusia ni (Hub.). Extraction of leaves with ethyl acetate followed by 60% methanol, and counter-current partitioning of leaf extractables between ethyl acetate, water and hexane was not convenient for isolation of antifeedants. Methanol (60%) in water extracted most of the antifeedants from leaves, and this extract when partitioned between ethyl acetate and water (the latter repeatedly extracted with the former), concentrated the antifeedants from soybean leaves for further processing on thin layer chromatography or high performance liquid chromatography.

There were quantitative differences in ethyl acetate fraction of PI 227687 (6%) and Davis (3.2%), and in flavonoids resolved at Rf 0.10–0.20 in benzene: ethyl acetate: methanol (4:3:3). Most of the flavonoids with antifeedant activity resolved at Rf 0.10–0.80. The antifeedant activity of flavonoid bands from PI 227687 was greater than the corresponding bands of Davis.

Extracts of five plants, namely Argemone mexicana, Artemisia absinthium, Cassia occidentalis, Cymbopogon citratus and Siegesbeckia orientalis were tested for their antifeedant and insecticidal effects on third-instar larvae of the cabbage webworm, Crocidolomia binotalis, which is presently one of the most important pests of cruciferous crops in Mauritius. All the five plant species investigated showed significant antifeedant properties, with A. mexicana showing the highest control potential of the five plant species studied against C. binotalis.

The crude n-hexane and methanol extracts of the aerial parts of plant, Pimpinella monoica Dalz. (Umbelliferae) showed significant feeding deterrency to Spodoptera litura F. larvae. Phytochemical investigation of these extracts has resulted into the isolation of one furanocoumarin and five biogenetically related furanochromones. Furanocoumarin, isopimpinellin was found to be most active. Furochromones, visnagin and khellin exhibited significant activity while their hydroxymethyl analogues, khellol and ammiol showed moderate activity. α-Hydroxyisopropyldihydrofurochromone, visamminol was found to be least active.

Use of plant derivatives for insect pest control was common in the tropics before the advent of synthetic pesticides. Plants such as neem, Azadirachta indica A. Juss, chinaberry, Melia azedarach L., and Warburgia spp., have been known for insect repellent and antifeedant properties in addition to other plants possessing insecticidal and growth regulating properties. Practical usefulness of antifeedants derived from plants for management of insect pests in selected field crops and stored grains is discussed. These products would, however, require some definitions of quality control and standardization of biological properties for large-scale use.

Two antifeedants, isopongaflavone and tephrosin have been isolated from Tephrosia elata. Tephrosin displayed high activity against Spodoptera exempta, while isopongaflavone was shown to be very active against Maruca testulalis and Eldana saccharina. Rotenone was found to be active as an antifeedant against S. exempta, E. saccharina and M. testulalis. Insects in the orders Coleoptera, Hymenoptera, Lepidoptera and Diptera, all associated with T. elata seed pods, were identified.

Various alkaloids from Adhatoda vasica (Acanthaceae) were found to be responsible for the antifertility and antifeedant activity of the extracts of the plant against insects. Among the major alkaloids vasicine, vasicinol and vasicinone severe antifertility effects were exhibited by vasicinol against Dysdercus skoenigii and Tribolium castaneum due to blocking of oocytes in the oviduct. Feeding deterrence was observed against Aulacophora foveicollis and Epilachna vijintioctopunctata at 0.05 and 0.1% levels of these compounds. These allelochemics appear to show a dual activity vis-à-vis a species specificity.

Limonin, deoxylimonin, citrolin, obacunone, harrisonin and acetoxyharrisonin were assayed as potential antifeedanfe against the African crop pests, Spodoptera exempta, Eldana saccharina and Manica testulalis. Even at the highest applied concentration, limonin, deoxylimonin, citrolin and acetoxyharrison were not active against S. exempta. At high concentrations, obacunone and harrisonin were mildly active in S. exempta assays. Harrisonin and obacunone displayed potent activity against E. saccharina and M. testulalis.

A two-choice type bioassay has been used to screen extracts from a number of plants of the sagebrush community for their antifeeding properties against the Colorado potato beetle, Leptinotarsa decemlineata Say. The extracts of Artemisia tridentata, Purshia tridentata and Chrysothamnus nauseosus have been fractionated for their antifeeding constituents. Known constituents of these plants (deacetalmatricarin, coumarins, cucurbitacins, polyphenols, polyacetylenes, and essential oils) were also screened. The results indicate that several chemical classes of compounds are responsible for antifeeding activity in each plant. Water soluble substances present in the waste marc after steam distillation of peppermint oil were highly active, too.