- Croton L.
About 750 species are found in tropical and sub-tropical regions. Crotons of horticulture belong to the genus Codiaeum A.Juss.
Croton cascarilla Bennett and Croton eluteria Bennett yield cascarilla bark, used as a tonic and to scent tobacco (Nicotiana tabacum L., fam. Solanaceae). Croton lacciferus L. yields a lac used in varnish making.
- Croton astroites Dryander
- Maran, Black Balsam, Wild Marrow
The plant possesses toxic properties similar to those of Croton tiglium L. (Oakes & Butcher 1962). They stated that croton oils are concentrated in the seeds but also occur in the stems and leaves.
- Croton capitatus Michaux
The plant can produce dermatitis (Shelmire 1940) and is described as an infrequent sensitiser. An extract of the plant produced a positive patch test reaction in 1 of 50 patients who had "weed dermatitis" (Shelmire 1939a).
- Croton ciliato-glanduliferus Ortega
The plant is said to irritate the eyes, causing inflammation and blindness (von Reis Altschul 1973). The sticky hairs that clings to the hands after touching the plant causes severe inflammation on contact with the eyes (Dahlgren & Standley 1944, Morton 1981).
Cattle are said to have been blinded as a result of grazing among these bushes (Dahlgren & Standley 1944).
- Croton cortesianus Kunth
- (syn. Croton trichocarpus Torr.)
The juice is used as a caustic for the treatment of skin diseases (Uphof 1959, Martinez 1969).
- Croton elliottianus Baillon
The seed is a drastic purgative in man; the seed oil does not have vesicant properties but is purgative though less so than the seed (Watt & Breyer-Brandwijk 1962).
- Croton eluteria Bennett
- Cascarilla, Sweetwood Bark
A fragrance raw material, cascarilla oil, is prepared from the steam distillate of the bark of this species (Arctander 1960). No irritant, sensitising, nor phototoxic effects could be demonstrated with the undiluted oil in various test animals including man (Opdyke 1976, p. 707).
- Croton flavens L.
- (syn. Croton rhamnifolius Standl.)
- Rock Balsam, Yellow Balsam
The plant is extensively used for medicinal and food purposes in Central America and the West Indies (Morton 1981).
Highly skin irritant and cocarcinogenic 16-hydroxyphorbol and 4-deoxy-16-hydroxyphorbol esters have been isolated from this species (Weber & Hecker 1978).
- Croton gratissimus Burchell
The plant is used by the Zulu as a cathartic and as an eruptive irritant. The bark is applied for its irritant action on the chest wall in any painful respiratory condition and in intercostal neuralgia (Watt & Breyer-Brandwijk 1962).
- Croton gubouga S.Moore
A burning sensation in the mouth is produced by chewing the seeds (Watt & Breyer-Brandwijk 1962).
- Croton hentyi Airy Shaw
- (syn. Croton hirtus L'Hér.)
Hairs on the stem are said to be "stinging", but perhaps irritant rather that urticating (Airy Shaw 1980).
- Croton humilis L.
- Ikaban, Pepper-Bush, Pepper Rod, Small Seaside Balsam
In Yucatan, the sap of this species is said to cause blindness in cattle (Morton 1981).
- Croton impressus Urban
- Palo de Verraco
This species is among the 14 commoner causes of plant contact dermatitis in the Dominican Republic (Brache & Aquino 1978).
- Croton megalocarpus Hutch.
- (syn. Croton elliottianus Pax & Engl.)
The wood has been used for flooring in England. The fresh wood has an objectionable smell, and the sawdust irritates the nose and throat of some workmen (Anon 1957).
- Croton monanthogynus Michaux
- Prairie Tea
Shelmire (1940) observed that an extract of the plant produced negative patch test reactions in 50 patients who had "weed dermatitis", and stated that the plant was an infrequent sensitiser.
- Croton mubango Müll.Arg.
Watt & Breyer-Brandwijk (1962) record that this species is a drastic purgative.
- Croton niveus Jacq.
The leaf juice is applied on dermatitis caused by Hippomane mancinella L. (Morton 1981).
- Croton origanifolius Lam.
This species is one of the 14 commoner causes of plant contact dermatitis in the Dominican Republic (Brache & Aquino 1978).
- Croton roxburghii Balakr.
- (syn. Croton oblongifolius Roxb.)
The seed oil is a drastic purgative (Chopra & Badhwar 1940).
- Croton sparsiflorus Morong
Phorbol esters have been isolated from the seeds of this species (Upadhyay & Hecker 1976).
- Croton sylvaticus Hochst.
A burning sensation in the mouth and throat is produced by chewing the seeds (Watt & Breyer-Brandwijk 1962).
- Croton texensis Müll.Arg.
- Texas Croton
Pammel (1911) notes that this species sometimes causes irritation of the skin.
- Croton tiglium L.
- Purging Croton, Chenkian, Chemekian
The seeds are the source of croton oil (Oleum Tiglii), the vesicant nature of which is well recognised (Uphof 1959, Smitinand & Scheible 1966, Nadkarni 1976). The oil has been rubbed on the scalp as an irritant "hair-producing" application (White 1887). Its use as a counter irritant by application and by pricking into the skin for pulmonary disease, a process called "Baunscheitismus", fell into disuse (White 1887). Taken orally, it is a drastic purgative; its use in human and veterinary medicine has been largely abandoned because of its toxicity and violent action.
The bark exudes a kino (astringent tannin). The smoke from the burning wood irritates the eyes (Burkill 1935). Croton oil has been used for illumination, but only outdoors since the fumes of the burning oil are irritant to the eyes, and intolerable (Burkill 1935). The seeds have been employed for self-mutilation by malingerers (Duke-Elder & MacFaul 1972b). The oil blisters the mucous membrane of the mouth; absorption of the irritant principle through the skin can produce a purgative action. The plant seems to vary in toxicity from region to region. The oil becomes less irritating with ageing by the action of a ferment within the seeds (Burkill 1935). Croton oil may be detected in vomit by exhaustive extraction with acidulated ether, and then recognising it by its vesicating action on the skin (Gimlette 1929).
Harrison (1906) included croton oil in a list of drugs, applied externally or taken internally, which may cause dermatitis. Depending on the amount applied and the duration of application, croton oil produces an erythematous or vesico-papular reaction when applied to the skin (White 1887); folliculitis may also occur (De Carvalho 1956). The action of croton oil was compared with that of some other irritants by Björnberg (1968); 0.2% croton oil in vaseline was found to produce erythema. In contact with the eye, croton oil causes severe keratoconjunctivitis with pain, swelling, and purulent discharge (Grant 1974).
Swingle et al. (1981) compared the irritant effects of croton oil and cantharidin on mouse ears. Topically applied triamcinolone acetonide effectively inhibited the inflammation produced by the croton oil. Topically applied isoproterenol sulfate (in a pyridine/ether/water solution) also produced marked inhibition of the inflammation, whilst indomethacin (applied in acetone solution) produced some inhibition of inflammation and was the most effective of the non-steroidal anti-inflammatory compounds tested. The inflammation and epidermal hyperproliferation caused by TPA (see below) may be inhibited in guinea pigs by indomethacin (Bourin et al. 1982).
A detailed histopathological study of the effects of croton oil on the skin was made by Bandmann (1960). Electron microscopic studies of croton oil dermatitis were made by Metz (1972). Early changes in the epidermis following application of croton oil were described by Takigawa et al. (1978). Techniques for testing irritant effects of croton oil in man, using a Duhring chamber, were described by Frosch & Kligman (1979). A procedure for the comparative irritancy testing of purified croton oil constituents and related "euphorbia irritants" utilising mouse ears has been described by Evans & Schmidt (1979a).
The phorbol-12,13-diesters in the seed oil are responsible for its irritant and purgative activity. Most of these esters are also potent cocarcinogens when applied to mouse skin (Hecker 1968, Hecker & Schmidt 1974). Irritant contact dermatitis in humans from esters of phorbol and related diterpene polyols was reported by Hickey et al. (1981).
The biochemical research tool known as TPA, PMA, or compound A1 is 12-O-tetradecanoylphorbol-13-acetate. It is derived commercially from croton oil. TPA is used in the study of co-carcinogenicity or tumour promotion, and a variety of other phenomena such as the production of inflammation and platelet aggregation (Evans & Soper 1978, Evans & Taylor 1983).