Crotalaria spectabilis

We knew Utetheisa to feed on poisonous plants as a larva (Figure 1B). The plants, of the genus Crotalaria (family Leguminosae), were known to contain pyrrolizidine alkaloids (henceforth abbreviated as PAs), intensely bitter compounds potently hepatotoxic to mammals (7). Other species of Utetheisa were known to sequester PAs (8). We found this to be true for U. ornatrix as well. Adult Utetheisa raised on Crotalaria spectabilis, one of the principal foodplants available to the moth in the United States, contain on average about 700 p,g of monocrotaline (1), the principal PA in that plant (9, 10). 

CNS CS diet CsA CyP central nervous system Crotalaria spectabilis seed-supplemented diet cyclosporin A cyclophilin... 

Crotalaria spectabilis Roth Croton capitatus Michx. 

Digitaria ischaemum (Schreb. ex Schweig.) Schreb. ex Muhl. Crotalaria spectabilis Roth Croton capitatus Michx. 

Showy clotalaria Crotalaria spectabilis Rodriguez-Kabanaetal., 1992b... 

Rodriguez-Kdbana, R., Pinochet, J., Robertson, D.G, Weaver, C.F., King, P.S. Horsebean (Canavalia ensiformis) and crotalaria (Crotalaria spectabilis) for the management of Meloidogyne spp. Nematropica 1992b 22 29-35. 

Figure 12.5 Utetheisa ornatrix. A Male (above) stroking its everted coremata against female during courtship. B Larva feeding on seed pod of its natural, pyrrolizidine alkaloid-containing food plants (Crotalaria spectabilis). C Scanning electronmicrograph of abdominal tip of male, showing coremata in everted (left) and retracted condition. [Bar = 1 mm A and C from Eisner, 1980].

Alternaria cassiae Cassia obtusifolia (sicklepod) C. occidentalis (coffee senna) Crotalaria spectabilis (show crotalaria) 69-72... 

An alkaloid obtained from Crotalaria spectabilis and other species of Crotalaria (Leguminosae). 

Pyrrolizidine alkaloids have long been known to be antitumor active and, more recently, have become of interest as anti-cancer agents. They occur naturally in several plant species, but are often difficult to extract and isolate from the plant material without degradation or the use of toxic solvents. The extraction of a model pyrrolizidine alkaloid, monocrotaline, from the seeds of Crotalaria spectabilis was investigated in this work. 

The crushed seeds of Crotalaria spectabilis were first contacted with supercritical carbon dioxide and, as expected, the oils comprising the bulk of the seed material were preferentially extracted. The addition of ethanol and water as co-solvents in the fluid phase led to the appearance of monocrotaline in the extract. Monocrotaline contents as high as 24% of the total extract could be obtained with carbon dioxide-ethanol mixtures. 

The purpose of this study was to develop a general supercritical fluid based process for the separation and purification of pyrrolizidine alkaloids such as monocrotaline (CieHaaNOe, MW=325.3). Monocrotaline was selected as a model because of its role in the development of semisynthetic pyrrolizidine alkaloids (6) and because it occurs in several species of Crotalaria. The seeds of Crotalaria spectabilis served as the source of monocrotaline in this study. 

Purity and Preparation of Materials. The carbon dioxide used was Coleman instrument grade with a purity of >99.9%. Pure ethanol (>99.9%) was obtained by reactive distillation of HPLC grade ethanol with magnesium turnings catalyzed with iodine. Water was obtained by double distillation. Ethanol used for valve and collection vessel flushing was 95 wt.% ethanol - 5 wt.% water. All solvents and co-solvents were dried to confirm the absence of solids. Monocrotaline (>99%) was obtained from the seeds of Crotalaria spectabilis using the method described by Gelbaum et al. (6). 

The seeds of Crotalaria spectabilis were obtained in Clarke County, Georgia in November, 1984. These seeds were analyzed and found to contain 1.9 wt.% monocrotaline and 2.5 wt.% hexane-extractable lipid material. The seeds (5mm indiameter) were milled to 1 mm to break the hard outer coat and to expose the inner seed material containing the monocrotaline. The seed fragments were sieved to remove the 850-1- micron fraction (predominantly outer coat fragments) and the 850- micron fraction was packed in the equilibrium cell. 

Before investigating the extraction of monocrotaline from Crotalaria spectabilis, the solubility of pure monocrotaline was measured. This was done to determine the magnitude of the solubility, to evaluate the effect of co-solvents, and to confirm the integrity of the extracted monocrotaline. 

Due to the relative success of the pure component solubility studies, the same series of experiments were carried out using the complex seed material. Three systems were investigated to evaluate the ability of supercritical fluids to extract monocrotaline from the seeds of Crotalaria spectabilis. Pure carbon dioxide was studied with the expectation that the oils would be preferentially extracted. Ethanol was added as a co-solvent to increase the solubility of monocrotaline. Also, due to its success in the extraction of caffeine and nicotine, water was used as a co-solvent. 

Carbon Dioxide - Crotalaria Spectabilis System. The fluid phase concentration was found to be time-dependent (Figure 3). At the start of the extraction, the concentration was constant indicating that it was equal to the equilibrium concentration. After approximately one mass percent of the initial mass of the bed had been removed, however, the exit concentration began to decrease. 

Carbon Dioxide - Ethanol - Crotalaria Spectabilis System. The solubility of the seed material increased by as much as 20 fold in the presence of ethanol (Figure 5). The presence of monocrotaline in the extracts became detectable at 2-4 mol% ethanol and increased markedly as ethanol concentration increased. The solubility of monocrotaline when extracted from the seed material was from 50% to 93% less than the comparable solubility (same ethanol concentration, temperature, and pressure) of monocrotaline. This is in contrast to the observations of Dobbs (10) and Kurnik et al. (11) who found that the solubility of a component is generally enhanced in the presence of other components. As the extraction proceeded and the seed bed became depleted of soluble components, the overall exit fluid phase concentration again decreased. However, the... 

Figure 3 Amount extracted and concentration of Crotalaria spectabilis in carbon dioxide as a function of time of extraction at 308.15 K, 27.41 MPa.

Figure 4 Overall solubility of Crotalaria spectabilis extract in carbon dioxide. No monocrotaline was detected in die extract...

Carbon Dioxide - Water - Crotalaria Spectabilis System. Water has been used as a CO-solvent in the extraction of caffeine from coffee and nicotine from tobacco. To extract caffeine from coffee beans, Zosel (3) recommended the pre-saturation of the carbon dioxide with water before passing the fluid through the coffee bean bed. In the case of nicotine from tobacco, Hubert and Vitzthum (2) first soaked the tobacco with up to 25 wt.% water and subsequently passed carbon dioxide through the tobacco bed. The water acted as a co-solvent as it saturated the fluid phase. Both of these processes have proven highly selective toward the alkaloids present in the plant material. Therefore, water was used as a co-solvent in the present study. 

Figure 6 History of an extraction of Crotalaria spectabilis with 95 mole% carbon dioxide + 5 mole% ethanol at 318.15 K, 11.81 MPa.

Ion Exchange Adsorption Process. Supercritical fluid extracts of Crotalaria spectabilis contain monocrotaline, a basic alkaloid, and non-polar lipid material. In the separation of caffeine from coffee, Zosel (3) recommended separation of the caffeine from the fluid phase by either adsorption onto activated carbon or absorption into liquid water. Activated carbon adsorption would be undesirable in the present case because the lipids would also be adsorbed and because desorption from activated carbon is quite difficult. Liquid water would absorb... 

Host plants play a key role in the production and use of sex pheromones by herbivorous insects through larval or adult sequestration of chemically active compounds and pheromone precursors [210]. One of the best examples of sequestration of plant chemicals by larvae and their subsequent use by adult males in sex attraction or courtship interactions is shown in Utetheisa ornatrix (Arctiidae), whose courtship pheromone derives from pyrrolizidine alkaloids (PAs) ingested at the larval stage from the host plant Crotalaria spectabilis [211]. U. omatrix larvae sequester PAs (e.g. monocrotaline) and retain the alkaloids through metamorphosis into the adult stage to provide egg protection for the next generation. 

Monocrotaline (63) from Crotalaria spectabilis (Legumy is responsible for the activity of Crotalaria extracts against adenocarcinoma-755 in mice. Similar alkaloids have been screened for anti-tumour activity by other researchers in general, however, pyrrolizidine alkaloids have liver toxicity and it is questionable whether they can be used in chemotherapy. Furthermore, cissampareine (64) from Cissampelos pareira (Menisperm.) and coronaridine (65) from Ervata-mia dichotoma (Apocyn.) have been investigated by the Kupchan group. 

Also mentioned in the aforecited book are colchicine and colchidnamide, derived from the common autumn crocus (Colchicum autumnale), also called meadow saffron. (Colchicine, incidentally, is used in plant gaieties to artificially produce mutations.) The notable use cited is against breast cancer, but gout and arthritis also yield to treatment. It is emphasized that both these alkaloids are potent, and their use requires expert medical supervision. Another plant mentioned is cro-talaria (Crotalaria spectabilis), from which a toxic alkaloid called monocrotaline may be obtained. This substance also has antitumor properties, but acts against the liver. 

Crotalaria laburnifolia (anacrotine), 244 Crotalaria spectabilis (supinidine), 241... 

Monocrotaline, a pyrrolizidine alkaloid of chemotherapeutic interest, has been extracted from the seeds of Crotalaria spectabilis using supercritical carbon dioxide and carbon dioxide-ethanol mixtures (29). Other alkaloids that have been extracted using SFE include nicotine and caffeine. Environmental applications of supercritical fluids include regeneration of activated carbon, extraction of organic contaminants like polynuclear aromatic hydrocarbons and polychlorinated biphenyls from water and soils, and the newly emerging field of supercritical water oxidation. 

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