Celery, furanocoumarins

Diawara M M, Trumble J T, Quiros C F and Hansen R (1995), Implications of distributions of linear furanocoumarins within celery , J Agric Food Chem, 43, 723-727. 

Nigg H N, Strandberg J O, Beier R C, Petersen H D and Harrison J M (1997), Furanocoumarins in Florida celery varieties increased by fungicide treatment , J Agric Food Chem, 45, 1430-1436. 

S. F. Berkley et al., Dermatitis in Grocery Workers Associated with High Natural Concentrations of Furanocoumarins in Celery, Ann. Intern. Med. 105 (1986) 551-55. 

Linear furanocoumarins are polenl photosensitizing agents in celery, parsley, parsnips, limes, and figs. The most commonly reported symptoms include contact dermatitis and photodermatitis. particularly on the hands and forearms. 

As well as these beneficial (either for the plant or for humankind) uses of photoactivation of plant compounds, there are equally numerous and varied examples of harmful phototoxic responses to plant compounds. Many plants potentially ingested by livestock can initiate photosensitizing responses [38]. In particular, plants that produce sufficient concentrations of furanocoumarins, hypericin, and cercosporin have been documented to affect livestock in this manner [39]. A specific example of non-target species photosensitization by plant compounds is the dramatic erythemic response of agricultural workers exposed to the sap of celery (Apium graveolens) plants during harvest [40]. 

L.D. Scheel, V.B. Perone, R.L. Larkin, R.E. Kupel (1963). The isolation and characterization of two phototoxic furanocoumarins (psoralens) from diseased celery. Biochemistry, 2,1127-1131. 

Other classes of compounds that inactivate human and rat liver microsomal P450 enzymes via protein modification are known. One such class is represented by the fiiranocoumarins, natural constituents of foods such as celery, parsley, figs, parsnips, and grapefruit juice . Among these compormds, the photoactive linear furanocoumarin, 8-MOP (methoxsalen) is a particularly potent P450 inactivator. Evidence that... 

The food sources of furanocoumarins include figs (contains xanthotoxin), parsley [has bergapten (39)], and fruits of Ammi majus and Ficus carica (include imperatorin) [122]. They have also been reported in limes, mustard, carrots and celery [123]. 

The coumarins, scopoletin and aesculetin, were present in celery roots in amounts smaller than 0.5 mg/kg f.w. [51]. The coumarin concentration was five to ten times higher in the peel of the tuber than in the edible portion. When celery tubers were coated with pectin gels and stored for 6 months at 4°C and 95% relative humidity, the furanocoumarin concentration increased considerably [53]. 

The furanocoumarins, psoralen, bergapten, xanthotoxin and isopimpinellin, were detected in celery leaves and stalk. The total furanocoumarin content ranged from about 12 to 50 mg/kg in Florida cultivars [54]. Treatment with fungicides increased the bergapten content 2-4 times in leaves and stalk, xanthotoxin 2-3 times in stalk, and isopimpinellin about 2-3 times in leaves, while psoralen levels remained constant. This fact is of some importance since linear furanocoumarins are the cause of photosensitive reactions in humans. 

Psoralens in Healthy Celery. Healthy celery contains at least four linear furanocoumarins (Figure 1), psoralen, bergapten, xanthotoxin, and isopimpinellin (14). The observed quantities of linear furanocoumarins in healthy samples of three different celery cultivars grown at different locations in the U.S. are shown in Table I. 

Table I. Summary of the Linear Furanocoumarin Content in Fresh Celery Grown in California, Florida, and Michigan ...

Figure 1. The four linear furanocoumarins observed in celery.

During the measurement of linear furanocoumarins in fresh celery (14), relatively high levels of psoralens were randomly observed in some samples. It was then hypothesized that psoralens may function as phytoalexins in celery. The linear furanocoumarin, xanthotoxin, has been previously reported as being a phytoalexin in parsnip root (Pastnaca sativa) (24). 

Linear Furanocoumarins in Diseased Celery. There are a number of reports of linear furanocoumarins (12,13) in diseased celery, and the effects of diseased celery (10,30,31) on celery... 

Phytoalexins in Celery. Past studies support the hypothesis that linear furanocoumarins act as phytoalexins in celery. The infection of celery with Sclerotlnla sclerotlorum has been correlated with elevated levels of psoralens, and with the onset of celery dermatitis (12,13). Spurious elevated levels of linear furanocoumarins also are found during analysis of... 

CuSOTreatment. Celery petioles were immersed in a CUSO solution (9 X 10 M) for 0.5 hr at room temperature. Some treated plant material was kept at 26 C and some at 2 C. Figure 3 shows some HPLC tracings of CuSO treated celery and controls after 72 hrs at 26 C and 2 C with comparison to standard psoralens. At 26 C, the psoralen level was the lowest and bergapten the highest of the observed linear furanocoumarins. However, at 2 C the psoralen level was... 

All of the treatments in Table 3 caused an increase in the quantities of linear furanocoumarins to some degree, with some samples containing as much as 29 ppm of total psoralens. It is also interesting that a sample of harvested celery allowed to age 4 days in the laboratory prior to CuSO treatment exhibited a 23 fold decrease in the total linear furanocoumarin production when compared to non-aged CuSO -treated celery (Table 3). This result may reflect a deterioration of the cellular condition in these samples. 

Figure 6. HPLC tracings of the detector response vs. retention time for sodium hypochlorite-treated celery cv. 5270-R after 72 hat 2 °C and 26 °C in comparison to the linear furanocoumarin standards psoralen (p), bergapten (b), xanthotoxin (x), and isopimpinellin (i).

Studies to date indicate that celery purchased at local markets should contain low levels of linear furanocoumarins (14) Increased levels of psoralens as a result of a phytoalexin... 

Clearly, certain chemicals and stress situations can cause up to 100 fold increases in the linear furanocoumarin content of previously excised celery petioles. Therefore, it seems possible that certain stress situations and/or chemical... 

The actual role of linear furanocoumarins in the disease resistance of celery is unknown however, it has been concluded that the phytoalexins studied to date play an important role in resistance (47). 

Along with our celery studies, we treated carrot slices with CuSO (9 X lO M) for 0.5 hr, and made analyses by HPLC after 72 hrs. Even with this attempted stimulation, no linear furanocoumarins were detected. 

Parsnips and perhaps celery and parsley contain appreciable levels of the linear furanocoumarins psoralen (17), xan-thotoxin (19), and bergapten (18). Consumption of 100 g of parsnip root would expose an individual to 4-5 mg of these compounds, which are known to be phytotoxic, mutagenic, and photocarcinogenic. Furanocoumarins are not destroyed by normal cooking (Ivie, 1981). 

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