PhytoecdysteroidThis service is more advanced with Phytoecdysteroidx available, learn more at http: Chemistry of Natural Compounds. The distribution of phytoecdysteroids in plants phytoefdysteroids the families Labiatae, Compositae, and Caryophyllaceae growing in Uzbekistan has been analyzed. It has been shown that some of them possess a capacity for lowering the levels of phytoecdysteroids in plants and residual nitrogen in the blood and for improving the functional state phytoecdysteroids in plants the kidneys in various pathological states. The dependence of biological activity on the structure of the compounds is discussed.
Role of Phytoecdysteroids in Insect Pest Management: A Review
Phytoecdysteroids are analogues of insect moulting steroid hormone, ecdysteroid. These are found in different plant groups and provide protection by deterring insects. Phytoecdysteroids have been synthesized in at least 27 families of Pteridophyta , 10 families of Gymnospermae and 74 families of Angiospermae. Chemically, phytoecdysteroids are triterpenoids, the group of compounds that includes triterpene saponins, phytosterols and phytoecdysteroids.
These are polar steroids with sugar-like solubility properties. Over phytoecdysteroids analogues have been identified so far and it has been speculated that there are over 1, possible structures in nature. These are synthesized from mevalonic acid and cholesterol. Phytoecdysteroids occur in relatively high concentration in many plants and comprise 0.
These have been isolated from all parts of plants in much higher amounts than those present in insects. Thus, plants are far better sources of ecdysteroids than insects.
Different plant parts contain different amounts of ecdysteroids and that ecdysteroid concentration varies with season and geographical distribution of the plant. Ecdysteroids control insect development at all stages of the life cycle.
Disruption of normal ecdysteroid level severely impairs insect development. Phytoecdysteroids mimic the insect ecdysteroid by binding to its receptors and eliciting a cascade of effects in insects. Phytoecdysteroids provide protection to plants by altering the normal levels of ecdysteroid hormone in adults and larvae in insects.
Therefore, phytoecdysteroids can be an excellent replacement of synthetic insecticides in insect pest management programme. With the beginning of agricultural practices and storage of food grains, insects started damaging standing crops and grains in storage both qualitatively and quantitatively.
Several synthetic pesticides have been developed and used to protect crops and grains from insect infestation. The continuous and extensive application of synthetic pesticides has developed the risk of ozone depletion, neurotoxicity, carcinogenicity, teratogenicity and mutagenicity in non-target animal species and cross- and multi-resistance in insects 1 - 4.
These adverse effects have increased public awareness regarding human safety and possible environmental damage diverting attention towards other alternatives especially the use of plant products in insect pest management. Plant botanicals include plant extracts. These are secondary plant metabolites synthesized by the plant for protective purposes. Some of these compounds are toxic to insects.
These plant derived chemicals are called botanical pesticides. These target a broad range of insect pests. Plant insecticides act as toxicants 5 - 8 , as repellents 9 - 11 , as antifeedants 12 - 15 , as oviposition deterrents 9 - 11 , 13 and developmental inhibitory activities 9 - 11 , 14 - Botanical insecticides do not affect the natural enemies of the pests adversely. Botanical pesticides are good alternatives to chemical pesticides as these are cheap, eco-friendly, cost-effective, target-specific and biodegradable.
This study work synergistically and it is difficult for insect pests to develop resistance. Ecdysteroid, insect moulting hormone, was first isolated from Bombyx mori This hormone governs all the aspects of transformation from larva to pupa to adult.
A number of ecdysteroid anologues called phytoecdysteroids have been reported from plants. Phytoecdysteroids are a class of chemicals that plants synthesize for defense against phytophagous insects. Ecdysteroids control insect development at all stages of the life cycle and disruption of normal ecdysteroid level or its action can be expected to impair insect development severely by mimicking the function of insect ecdysteroid After the discovery of Hydroxyecdysone, active form of ecdysone in the conifer, Podocarpus nakaii 23 , ecdysteroids have been detected in 27 families of the Pteridophyta , 10 families of Gymnospermae and 74 families of Angiospermae Since phyotecdysteroids are found in primitive plants such as ferns, it was assumed that these secondary compounds appeared very early in plant evolution.
In the angiosperms, 74 families possess ecdysteroid containing species. A majority of these families are within eleven orders: They are far better source of ecdysteroids than arthropods It is important to note that different plant parts contain different amounts of ecdysteroids and that ecdysteroid concentration varies with season and geographical distribution of the plant These phytoecdysteroids provide little protection against specialized herbivores, which have evolved efficient detoxification mechanisms but represent a consistent barrier against non-adapted herbivores.
Low concentrations ppm of phytoecdysteroids deter some insects, while other insects are resistant to very high concentrations ppm. The role of phyotecdysteroids in plants is not clearly understood, as there are conflicting data supporting ecdysteroids as plant hormones i.
Although initial reports show that ecdysteroids do not elicit any of the classical responses of known plant hormones, there are also data supporting ecdysteroids being physiologically active in plants Phytoecdysteroids may play a role in plant defense. Production of Hydroxyecdysteroids in spinach is elicited by both mechanical wounding and insect feeding.
Phytoecdysteroids protect spinach from plant-parasitic nematodes and may confer a mechanism for nematode resistance Application of these phytoecdysteroids on insects has been reported to result in marked growth and developmental disruption 30 - In this review, sources, structures and applications of phytoecdysteroids have been discussed. Phytoecdysteroids provide protection to plants by altering the normal levels of ecdysteroid hormone in adults and larvae of insects.
Therefore, phytoecdysteroids can be applied against insects causing economic injury and can be proved an excellent replacement of synthetic insecticides in insect pest management programme.
Chemically, phytoecdysteroids are triterpenoids, a group of compounds that includes triterpene saponins, phytosterols and phytoecdysteroids. Ecdysteroids are polar steroids with sugar-like solubility properties Animals and humans also synthesize some of the same products from the mevalonate pathway, such as ubiquinone and sterols. They can not, however, synthesize ecdysteroids. Phytoecdysteroids universally lack the polyhydroxylated side chain characteristic of ecdysteroids and are, therefore, more lipophilic Unlike invertebrates, which are unable to synthesize ecdysteroids and must consume dietary phytosterols that are then converted into ecdysteroids, plants can synthesize ecdysteroids from mevalonic acid and cholesterol Plants synthesize phytoecdysteroids from mevalonic acid in the mevalonate pathway in cell using acetyl-CoA as a precursor.
Most phytoecdysteroids possess a cyclopentano-perhydrophenanthrene carbon skeleton cholestenone carbon skeleton C27 , derived biosynthetically from cholesterol and phytosterols, often with a hydroxyl group in the position The carbon number can vary between CC29 The anellations of the rings are characteristic: Phytoecdysteroids are highly hydroxylated with hydroxyl groups. The structural variations among different phytoecdysteroids include number, position and orientation of hydroxyl groups.
Further common characteristic is the Chydroxylation in addition to C, C, C and Chydroxylations , which is usually frequent at ecdysteroids as well as for cardenolides and bufadienolides.
Although the most common ecdysteroid found in plants is Hydroxyecdysone, over ecdysteroid analogues have been identified so far in plant kingdom and it has been speculated that there are over 1, possible structures in nature 19 , 20 Fig. The various analogues differ in the number and site of hydroxylations, as well as the length and structure of the carbon side chain. Glycosylated and acetylated ecdysteroids have been described both in nature and in the laboratory The term phytoecdysteroid can also apply to ecdysteroids found in fungi, even though fungi are not plants.
Fungi that produce phytoecdysteroids include Achyranthes bidentata 38 , Tinospora cordifolia 39 , Pfaffia paniculata 40 , Leuzea carthamoides 41 , Rhaponticum uniflorum 42 , Serratula coronate 43 , Cordyceps and Asparagus During discovery for anti-cancer compounds in plant extracts, Nakanishi et al. Soon after the isolation of ponasterone A, Hydroxyecdysone, the major ecdysteroid of arthropods was reported in a conifer, Podocarpus elatus 44 , Polypodium vulgare fern 45 and the angiosperm, Achyranthes fauriei Later, both ecdysone and Hydroxyecdysone were isolated from the ferns, Pteridium aquilinum 47 and Polypodium vulgare Phytoecdysteroids obtained from plants are ajugasterone in Ajuga Lamiaceae and Vitex Verbenaceae ; leuzeasterone in Leuzea carthamoides Asteraceae , 2-Deoxyhydroxyecdysone 3-Glucoside and 3-Epideoxyhydroxyecdysone in Tinospora cordifolia Menispermaceae 39 , ecdysterone and inokosterone in Achyranthes bidentata Amaranthaceae , polypodine B in Leuzea carthamoides Asteraceae 41 and ecdysterone, ajugasterone C, ajugasterone C, monoacetonide in Rhaponticum uniflorum Asteraceae To date, different phytoecdysteroids have been identified Phytoecdysteroids differ in the number of C-atoms present 24CC , the number, position and location of hydroxyl and keto groups on the steroid skeleton.
The most commonly occurring phytoecdysteroid is Hydroxyecdysone, followed by polypodine B. Hydroxyecdysone is a naturally occurring ecdysteroid which controls the ecdysis and metamorphosis in insects. Ecdysteroid is derived from enzymatic modification of cholesterol by p enzymes. The primary sources of Hydroxyecdysone in larvae are the prothoracic gland, ring gland, gut and fat bodies in larvae.
These tissues convert dietary cholesterol into Hydroxyecdysone In the adult female, ovary is a source of Hydroxyecdysone production In adult males, fat body is the source of hydroxyecdysone.
Its anologues called phytoecdysteroids are produced by various plants where these disrupt the development and reproduction of insect pests. This hormone is hydrophobic in nature, thus, it traverses lipid membranes and permeates the tissues of an organism.
In insects, Hydroxyecdysone acts through the ecdysone receptor. The ecdysone receptor is a nuclear receptor a ligand-activated transcription factor , which controls development and contributes to other processes such as reproduction 54 , The ecdysone receptor is a non-covalent heterodimer of two proteins viz. The binding of ecdysone to receptor leads to the activation of ecdysone responsive genes and many other genes causing puffing of polytene chromosomes at over a hundred sites.
Sites of puffing represent the position of genes to be extressed and thus, position of transcription. The first gene to be activated are called early response genes. This is a code for proteins that are themselves gene regulatory factors either alone or in combination with hormones.
They activate late-response genes that code for the proteins that actually cause structural changes, cell differentiation or apoptosis programmed cell death. Ultimately, the activation cascade causes physiological changes that result in ecdysis moulting The ecdysone receptor also binds to and is activated by phytoecdysteroids.
Thus, phytoecdysteroids can mimic Hydroxyecdysteroid of insects, bind insect ecdysone receptors and can elicit the same responses.
These phytoecdysteroids induced responses at inappropriate time and stage causes feeding detterency, abnormal development, altered pattern of ecdysis and finally death. Jones and Firn 59 reported that ecdysone and Hydroxyecdysone deter feeding in P.
Chilo partellus , Phyllobius pyri and P. Hydroxyecdysone and polypodine B regulate the length of feeding periods in larval instars and silk production when added to the diet of B.