CHAPTER 5: TOXICOLOGY OF PLANT MATERIALS
Contents - Previous - NextThe presence of so-called secondary compounds, which have no known function in photosynthesis, growth or other aspects of plant physiology, give plant materials or their extracts their anti-insect activity. Secondary compounds include alkaloids, terpenoids, phenolics, flavonoids, chromenes and other minor chemicals. They can affect insects in several different ways: they may disrupt major metabolic pathways and cause rapid death, act as attractants, deterrents, phagostimulants, antifeedants or modify oviposition. They may retard or accelerate development or interfere with the life cycle of the insect in other ways (Bell , et al. 1990).
Table 1 lists the secondary metabolites most commonly found in the plant species examined. It is noteworthy that many compounds are common to the plant species tested. Plants, which provide large or economic yields of these key chemicals, may offer the best scope for using as botanicals in the future. Details of the mammalian toxicology of these compounds are listed in Table 2.
Table 1: List of commonly found secondary metabolites.
Acids
|
Esters
|
Nitrogen-containing compounds
|
||
Acetic | Allicin | Caffeine | ||
Hydrocyanic acid | Azadirachtin | Hydrogen cyanide | ||
Iso-butyric acid | Butyric | Methyl isothiocyanate | ||
Malic acid | Caprylic | Nicotine | ||
Oxalic acid | Formic | Sanguinarine | ||
Succinic acid | Iso-valeric | a -Tomatine | ||
Salicylic acid | Methyl salicylate | |||
Sebacic acid | Pyrethrins I/II |
Phenols |
||
Valeric | Pyrogallol | |||
Flavones |
Safrole | |||
Aldehydes |
Quercetin | |||
Acetaldehyde | Rutin |
Sterols |
||
Citral | Ergosterol | |||
Alcohols |
Fatty acids |
Terpenoids |
||
Benzyl alcohol | Ricinoleic acid | Ascaridole | ||
Carvacrol | Saturated fatty acids | Azadirachtin | ||
1,8 Cineol | Capric acid | 1-Borneol | ||
Citronellol | Lauric acid | Camphor | ||
Eugenol | Myristic acid | Carene | ||
Geraniol | Palmitic acid | Carvone | ||
Gossypol | Stearic acid | 1,8-Cineol | ||
Linalool | Unsaturated fatty acids | Cinnameldehyde | ||
Menthol | Linoleic acid | Citral | ||
Pentanol | Oleic acid | Citronellol | ||
Pyrogallol | Cumene | |||
Glycosides |
p-Cymene | |||
Alkaloids |
Oleandrin | Eugenol | ||
Anabasine | Solamine | Geraniol | ||
Capsaicin | Limonene | |||
Histamine |
Hydrocarbons |
Meliantriol | ||
Methyl anthranilate | Camphene | Menthol | ||
Methyl salicylate | Limonene | b -Ohellandrene | ||
Nicotine | a -Pinene | a -Pinene | ||
Nornicotine | Pulegone | |||
Piperine |
Lactones |
Saponin | ||
Ryania | Coumarin | Terpinen-4-ol | ||
Vinblastine | Thujone | |||
Vinblastine |
Sources: Southon and Buckingham, 1988; Glasby, 1982; Norris, 1990; Rauffauf, 1970.
Table 2: Toxicity data for some chemical components of different plant genera
(list of abbreviations given at end of table).
Chemical | Toxicity | Plant genera |
Acetaldehyde | oral rat LD50 1930 mg | Carum, Cinnamomum,
Citrus, Lycopersicon, Mentha, Nicotiana, Pimpinella, Rosmarinus |
Acetic acid | oral hmn TDLo 1470
mg oral rat LD50 3310 mg |
Widespread, including
Gossypium |
Acetone | oral rbt LD50 5300 mg | Coriandrum, Lycopersicon, Pogostemon |
Allicin | mice LD50 60 mg | Allium |
Amyl alcohol | oral rat LD50 3030 mg | Mentha, Origanum |
Anabasine | oral rat LDLo 10 mg | Nicotiana |
Anethole | oral rat LD50 2090 mgADI 0-0.6 mg | Anethum, Ocimum, Pimpinella, Piper |
Apiole scumus | LDLo 1000 mg | Apium, Piper |
Asarone | ipr gpg LD50
275 mgEC recommended hmits: 0.1 mg/kg in food and beverages |
Acorus, Piper |
Ascaridole | oral LDLo 250 mg | Chenopodium |
Azadirachta | lethal dose pig 6000 mg | Melia |
Benzyl alcohol | oral rat LD50
1230 mg ADI 0 5 mg |
Canaga, Canangium, Eugenia |
Borneol | oral rbt LDLo 2000 mg | Angelica, Blumea,
Cinnamomum, Citrus, Coriandrum, Cymbopogon, Eucalyptus, Lavendula, Myristica, Ocimum, Rosmarinus, Salvia, Thymus, Valeriana, Zingiber |
Butyraldehyde | ihl hmn TCLo 580 mg/m2 |
Artemisia, Eucalyptus, Lavendula, Raphanus |
Butyric acid | oral rat LD50 2940 mg | Eucalyptus, Gossypium, Sapindus |
iso-Butyric acid | oral rat LD50 280 mg | Artemisia, Cinnamomum, Croton, Eucalyptus, Laurus, Lavendula |
Calamus oil | oral rat LD50 777mg | Acorus |
d-Camphene | Rosmarinus, Zingiber | |
Camphor | ipr rat LDLo 900 mg | Acorus, Alpina, Artemisia, Chenopodium, Chrysanthemum, Cinnamomum, Curcuma, Lavendula, Lippia, Ocimum, Rosmarinus, Salvia |
Caproic acid |
oral rat LDLo 3000 mg | Chrysanthemum, Cinnamomum, Cocos, Laurus, Lavendula, Mentha |
Caprylic acid | ivn mus LD50 600 mg | Cinnamomum, Citrus, Cocos, Cymbopogon, Mentha, Myristica |
Capsaicin | ivn cat LDLo 1600 mg | Capsicum |
Caraway oil | oral rat LD50 3500 mg | Carum |
Carene | oral rat LD50 4800 mg | Chenopodium, Citrus, Eucalpyrus, Piper |
Carvacrol | oral LD50 810 mg | Anabasis, Carum, Cinnamomum, Mentha, Ocimum, Origanum, Thymus, Zea |
Carvone | oral LD50 1640 mg | Anethum, Carum, Chrysanthemum, Citrus, Cymbppogon,
Eucalpyrus, Lavendula, Lippia, Mentha, Syzygium |
Cassia oil | oral rat LD50 2800 mg | Cinnamomum |
Choline | ipr rat LD50 400 mg | Acorus, Artemisia, Eupatorium, Glycine, Gossypium, Helianthus, Linum, Olea, Pimpinella, Trigonella, Valeriana |
Cineole (1-8) | oral rat LD50 2480 mg | Alpina, Artemisia, Blumea, Cinnamomum, Curcuma, Eucalyptus, Eugenia, Laurus, Lavendula, Lippia, Mentha, Ocimum, Piper, Psidium, Rosmarinus, Salvia, Syzygium Zingiber |
Cinnamaldehyde | oral gpg LD50 1160 mg | Cassia, Cinnamomum, Lavendula, Pogostemon |
Citral | oral rat LD50 4960 mg ADI 0-0.5 mg | Citrus, Cymbopogon, Eucalyptus, Lavendula, Lippia, Ocimum, Piper, Thymus, Zingiber |
Citronella oil | oral mam LDLo 1000 mg | Cymbopogon |
Citronellol | ims mus LD50 4000 mg | Cinnamomum, Citrus, Cymbopogon, Lippia |
Clove oil | oral rat LD50 3720 mg | Syzygium |
Coriander oil | oral rat LD50 4130 mg | Coriandrum |
Coumarin | oral rat LD50 293 mg | Ageratum, Cinnamomum, Lavendula |
Cumene | oral rat LD501400 mg | Cuminum |
Cumin oil | oral rat LD50 2500 mg | Cuminum |
Cuminic alcohol | oral rat LD50 1020 mg | Cinnamomum, Cuminum, Eucalyptus, Lavendula |
Cuminic aldehyde | oral rat LD50 1390 mg | Aegele, Artemisia, Cinnamomum,
Cuminum, ADI 0-0.1 mg Lavendula, Zanthoxylum |
Curcumin | Curcuma | |
p-Cymene | oral hmn TDLo 86 mg CNS oral rat LD50 4750 mg |
Aegele, Chenopodium,
Cinnamomum, Citrus, Coriandrum, Croton, Cuminum, Cupressus, Eucalyptus, Eupatorium, Myristica, Origanum, Pimpinella, Salvia, Thymus |
Decanal | oral rat LD50 3730 mg | Cassia, Cinnamomum, Citrus,
Coriandrum, Lavendula |
Ergosterol | oral dog LDLo 4 mg | Citrus, Nicotiana |
Esdragole (estragole) | oral rat LD501820 mg | Antemisia, Ocimum, Pimpinella |
Ethyl alcohol
|
oral man LDLo 50 mg |
Citrus, Eucalyptus, Lycopersicon, Mentha, Nicotiana |
Eucalyptus oil
|
oral rat LD50 4440 mg
|
Eucalpyrus
|
Eugenol
|
oral rat LDLo 500 mg
|
Acorus, Ageratum, Alpina, ADI 0.1-2.5 mg/kg
Cinnamomum, Citrus, Cymbopogon, Eugenia, Lantana, Laurus, Lavendula,
Myristica, Nicotiana, Ocimum, Pimpinella, Piper, Pogostemon, Syzygium
|
iso-Eugenol
|
oral LD50 1560 mg
|
Canaga, Canangium, Cinnamomum, Myristica
|
Formic acid
|
oral rat LD50 1210 mg
|
Artemisia, Cinnamomum, Citrus, Mentha,
|
ADI 0-3 mg
|
Myristica, Nicotiana, Ricinus, Valeriana
|
|
Furfural
|
oral rat LD50 127 mg
|
Angelica, Carum, Cinnamomum, Citrus,
Cupressus, Cymbopogon, Gossypium, Lavendula, Mentha, Myristica, Syzygium, Zea |
Gaultheria oil
|
oral hmn TDLo 170 mg
oral rat LD,o 887 mg |
Gaultheria
|
Geraniol
|
oral LD50 3600 mg
|
Cinnamomum, Citrus, Eucalyptus, Eugenia, Laurus,
Lavendula, Lippia, Myristica, Thymus, Zingiber
|
Gossypol
|
oral rat LD50 2315 mg
|
Gossypium
|
Histamine
|
ivn dog LDLo 50 mg
|
Chenopodium, Citrus, Lycopersicon
|
Hydrocyanic acid | oral hmn LDLo 570 mg ADI not to be used |
Ageratum, Allium, Annona, Boscia, Cassia,
Chenopodium, Cinnamomum, Citrus, Combretum, Crotalaria, Cymbopogon, Erythrophleum, Eucalyptus, Euphorbia, Gliricidia, Glycine, Ipomaea, Jatropha, Lantana, Linum, Nerium, Nicotiana, Ocimum, Piper, Psidium, Ricinus, Tagetes, Tephrosia |
Isovaleraldehyde | Cinnamomum, Citrus, Cymbopogon,Eucalyptus, Glycine, Lavendula, Mentha, Raphanus | |
Lauric acid | ivn mus LD50 131 mg | Cinnamomum, Citrus, Cocos, Elaois, Laurus |
Limonene | oral rat LDLo 4600 mg ADI not specified |
Anethum, Apium, Carum, Chenopodium, Cinnamomum, Citrus, Coriandrum, Croton, Cuminum, Cymbopogon, Eucalyptus, Hyptis, Lavendula, Lippia, Mentha, Myristica, Nicotiana, Ocimum, Origanum, Pimpinella, Piper, Rosmarinus, Salvia, Syzygium, Valeriana |
Linalool | oral rat LD50 2790 mg ADI 0-0.5 m |
Artemisia, Cinnamomum, Citrus, Coriandrum, g Cymbopogon, Eucalyptus, Laurus, Lavendula, Mentha, Myristica, Ocimum, Origanum, Rosmarinus, Salvia, Syzygium, Thymus, Zingiber |
Linoleic acid | Helianthus, Ricinus | |
Malic acid | oral rat LDLo 1600 mg ADI not specified |
Artemisia, Capsicum, Coriandrum, Helianthus, Juniperus, Lycopersicon, Nicotiana, Ricinus |
Menthol | oral rat LD50 3180 mg ADI 0-0.2 mg |
Mentha, Thymus |
Methanol | oral hmn LDLo 340 mg | Carum, Gossypium, Lycospericon, Mentha, Syzygium |
Methyl anthranilate | oral rat LD50 2910 mg ADI 0-1.5 mg |
Cananga, Canangium, Citrus |
Methyl chavicol | oral rat LD50 1820 mg | Artemisia, Ocimum, Pimpinella |
(esdragole) | ||
(estragole) | ||
Methyl eugenol | Syzygium | |
Methyl salicylate | oral hmn LDLo 170 mg oral rat LD50 887 mg ADI 0-0.5 mg |
Chenopodium, Erythroxylum, Eugenia, Gaultheria, Myristica, Syzygium, Xanthophyllum |
Myristic acid | ivn mus LD50 43 mg | Cinnamomum, Citrus, Cocos, Croton, Elaeis, Helianthus, Myristica, Pimpinella |
Myristicin | oral cat LDLo 570 mg | Anethum, Carum, Cinnamomum, Myristica |
Nicotine | oral hmn LDLo 1 mg | Erythroxylum, Nicotiana |
Nornicotine (D and L) |
ipr rat 6-23.5 mg | Nicotiana |
Noscapine | ivn mus LD50 83 mg | Lycopersicon |
Nutmeg oil (expressed) |
oral rat LD50 3640 mg | Myristica |
Nutmeg oil (volatile) |
oral rat LD50 2620 mg | Myristica |
Oleic acid i | vn mus LD50 230 mg | Major component of oilseeds |
Origanum oil | oral rat LD50 1850 mg | Origanum |
Oxalic acid | oral hmn LDLo 700 mg | Allium, Anacardium, Capsicum, Chenopodium, Citrus, Coriandrum, Glycine, Ipomaea, Juniperus, Lycopersicon, Mentha, Momordica, Nicotiana, Raphanus |
Palmitic acid | ivn mus LD50 57 mg | Common in oilseeds, Apium, Gossypium, Ricinus |
Pennyroyal oil | oral rat LD50 400 mg | Mentha |
Peppermint oil | oral rat LD50 4441 mg | Mentha |
Phellandrene | Aegele, Anethum, Angelica, Artemisia, Cinnamomum, Citrus, Coriandrum, Cuminum, Curcuma, Cymbopogon, Eucalyptus, Lantana, Laurus, Lavendula, Mentha, Pimpinella, Piper, Zingiber | |
a-Pinene | Coriandrum, Cuminum, Eucalyptus, Laurus, Myristica, Origanum, Pimpinella, Piper, Rosmarinus, Syzygium | |
Pipericide | Piper | |
Propionic acid | oral rat LD50 1510 mg | Widespread, including Cinnamomum, Lavendula, Pimpinella |
Pulegone | ipr mus LD50 150 mg | Bystropogon, Mentha, Origanum |
Pyrethrin I | oral rat LD50 1200 mg | Chrysanthemum |
Pyrethrin II | oral rat LD50 1200 mg | Chrysanthemum |
Pyrethrum | oral rat LD50 200 mg | Chrysanthemum |
Pyrocatechol | oral rat LD50 3890 mg | Allium, Citrus, Eucalyptus, Psidium, Raphanus |
Pyrogallol | unk man LDLo 120 mg oral rat LD50 787 mg |
Carum |
Quercitin | oral rat LD50 161 mg | Allium, Euphoria, Euphorbia, Gossypium, Psidium, Shorea, Zea |
Ricinoleic acid | scu rbt TDLo 3120 mg | Cassia, Ricinus |
Rotenone | oral rat LD50 132 mg | Derris, Lonchocarpus, Tephrosia |
Rutin |
ivn mus LD50 950 mg | Widespread, including Artemisia, Calotropis, |
(sophorin) | Eucalyptus, Gossypium, Lycopersicon, Nerium,(vitamin P), Nicotiana, Tephrosia, | |
Safrole |
oral rat LD50 1950 mg |
Chenopodium, Cinnamomum, Myristica, |
(shikimol) | No ADI allocated | Ocimum, Pimpinella, Piper |
Sage oil | oral rat LD50 2600 mg | Salvia |
Salicylic acid | oral rat LD50 891 mg No ADI allocated |
Cinnamomum, Gaultheria, Gossypium, Mentha |
Sanguinarine | ipr rat LD50 18 mg | Sapindus, Zanthoxylum |
Saponin | oral mus LDLo 3000 mg | Very widespread, including Acorus, Aegele, Allium, Anabasis, Bassia, Cassia, Chenopodium, Citrus, Eucalyptus, Eugenia, Euphorbia, Glycine, Helianthus, Lippia, Momordica, Nicotiana, Ocimum, Olea, Raphanus, Ricinus, Salvia, Sapindus, Thymus |
Sebacic acid | ipr mus LD50 500 mg | Ipomaea |
Solanine | ipr mus LD50 32 mg | Capsicum, Lycopersicon |
Stearic acid (Octadecanoic acid) | ivn rat LD50 22 mg | Citrus, Croton |
Succinic acid | scu frg LDLo 2000 mg | Artemisia, Gossypium, Helianthus |
Tannic acid | oral mus LDLo 2000 mg | Widespread, including Acorus, Artemisia, Catharanthus, Cinnamomum, Coriandrum, Cuminum, Eucalyptus, Eugenia, Eupatorium, Euphoria, Helianthus, Ipomaea, Lavendula, Melia, Myristica, Pimpinella, Rosmarinus, Salvia, Syzygium |
Terpinen-4-ol | oral rat LD50 4300 mg | Artemisia, Cinnamomum, Citrus, Cuminum, Cupressus, Cymbopogon, Lantana, Laurus, Lippia, Myrisfica, Origanum, Pimpinella, Rosmarinus, Salvia, Thymus |
Thujone | ipr rat LDLo 120 mg | Artemisia, Lavendula, Lippia, Salvia |
Thyme oil | oral rat LD50 2840 mg | Thymus |
Thymol | oral LD50 980 mg | Anabasis, Carum, Lavendu/a, Ocimum, Origanum, Thymus |
Tomatine | oral rat LDLo 800 mg | Lycopersicon |
Trimethylamine | ipr mus LDLo 75 mg | Acorus, Chenopodium, Gossypium, Nicotiana |
Tryptothane | oral rat TDLo 1100 mg/DC NEO |
Glycine, Helianthus, Ipomaea, Linum, Lycopersicon, Nicotiana |
Turmurone | Curcuma | |
Undecanoic acid | ivn mus LD50 140 mg | Artemisia, Cocos, Thymus |
Valeric acid | ivn mus LD50 1290 mg | Cananga, Canangium, Croton, Laurus Lavendula, Mentha, Valeriana |
iso-Valeric acid | oral rat LDLo 3200 mg | Artemisia, Calotropis, Cinnamomum, Citrus, Croton, Eucalyptus, Lavendula, Lippia, Mentha, Nicotiana, Rosmarinus, Valeriana |
Note: Toxicity data quoted in Duke, 1985. Derived from NIOSH, 1975. Unless otherwise indicated all g, mg and m g entries are expressed as per kg body weight. ADI quoted from JECFA, 1994.
Abbreviations used:
ADI CNS C D EC frg GIT gpg hmn ihl ipr ivn& LCLo LD50 LDLo mam mus NEO scu TCLo TDLo unk |
acceptable daily intake central nervous system continuous day Economic Community frog gastrointestinal tract effects guinea pig human inhalation intraperitoneal intravenous lowest published lethal concentration lethal dosage 50 percent kill lowest published lethal dose mammal mouse neoplastic effects subcutaneous lowest published toxic concentration lowest published toxic dose unreported |
The six plant genera most frequently investigated, namely Acorus, Chenopodium, Eucalyptus, Mentha, Ocimum and Piper possess many chemical constituents in common and these are listed below in Table 3. Eight constituents are found in at least three of the six listed. These include five terpenoids: carene, cineole, citral, eugenol and phellandrene; the alcohol, linalool and the phenol, safrole. The terpenoid, limonene, is found in five of the plants, whilst hydrocyanic acid is found in four. Acorus, which is not reported to possess either toxicant, contains the phenyl propene, asarone (Lander and Schreier, 1990).
It is often assumed that natural plant extracts are safer than synthetic chemicals, but this is not always true. Plant fragments or extracts should not be recommended for admixture with stored foodstuffs until appropriate tests have shown them to be safe.
Table 3: Toxins found in frequently examined plant genera
Plant species | Toxins |
Acorus | asarone, calamus oil, camphor, choline, eugenol, eugenol ethyl ether, heptanoic acid, methylamine, saponin, tannic acid, trimethylamine. |
Chenopodium | Ascaridole, carene, cymene, histamine, hydrocyanic acid, limonene, methyl salicylate, oxalic acid, safrole, saponin, trimethylamine. |
Eucalyptus | Benzaldehyde, borneol, butyraldehyde, butyric acid, carene, carvone, cineole, citral, cuminic acid, cymene, ethyl alcohol, eucalyptus oil, gallic acid, geraniol, hydrocyanic acid, isoamyl alcohol, isobutyric acid, isoprene, isovaleraldehyde, isovaleric acid, limonene, linalool, mandelonitirle, phellandrene, pyrocetechol, quercitrin, quinic acid, rutin, saponin, shikimic acid, tannic acid, valeraldehyde. |
Mentha | Acetaldehyde, amyl alcohol, caproic acid, caprylic acid, carvacrol, carvone, cineole, ethyl alcohol, formic acid, furfural, isoamyl alcohol, isovaleraldehyde, isovaleric acid, limonene, linalool, menthol, methanol, methylamine, nonanoic acid, oxalic acid, pennyroyal oil, peppermint oil, phellandrene, pulegone, salicylic acid, valeric acid. |
Ocimum | Anethole, camphor, carvacrol, cineole, citral, esdragole, eugenol, hydrocyanic acid, limonene, linalool, safrole, saponin, thymol. |
Piper | Anethole, apiole, asarone, carene, cineole, citral, dihyrokawain, eugenol, eugenol methyl ether, hydrocyanic acid, limonene, phellandrene, piperidine, piperonal, safrole, stearyl alchol. |