The use of spices and medicinals as bioactive protectants for grains. Chapter 5.

CHAPTER 5: TOXICOLOGY OF PLANT MATERIALS
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The 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
LD₅₀LDLo
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.

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