Λεξικό .. Buckwheat [(L.) Fagopyrum esculentum]

A cereal belonging to the Polygonaceae family of the weed group, frequently used as a substitute for common cereals, especially in Asia, where it was described as a cause of severe respiratory and food allergy. Buckwheat (Fagopyrum schulentum) is not taxonomically related to wheat and other cereal grains. Buckwheat flour is used as a wheat substitute in breads, biscuits, pancakes, and crepes.

In a clinical study [1] involving both allergic (showing symptoms after ingestion of buckwheat) and sensitized (without symptoms to buckwheat, but positive RAST) patients, several allergens were identified at different molecular weights, ranging from 9 to 67kDa. Three of them were characterized and sequenced: the 9 kDa allergen, identical to the buckwheat trypsin inhibitor; the 16 kDa allergen, homologous to the α-amylase/trypsin inhibitor of millet; the 19 kDa allergen, homologous to the -globulin of rice, one of the 2S albumins.

The last was the only one specifically recognized more by buckwheat allergic individuals (78%) than by the sensitized ones (7%) [1]. The 19-kD BW allergen may be the major allergen from BW. For the diagnosis of clinical reactivity to BW, the r19-kD protein sIgE ELISA test was more discriminative than the coated allergen particle sIgE measurement using whole BW extract[2]. No immunological cross-reactivity was seen between this allergen and the two recombinant 2S albumins Bra j 1 and Sin a 1 It is not taxonomically related to wheat and used as a wheat substitute in breads, biscuits, pancakes, and crepes. Occupational exposure to buckwheat flour has been associated with rhinitis, conjunctivitis, contact urticaria, and occupational asthma. Buckwheat ingestion is a potential cause of food-related anaphylaxis. The first allergenic 2S albumin ever described in cereals was found in buckwheat (Fagopyrum esculentum), There does not appear to be cross-reactivity between buckwheat and wheat allergy. Buckwheat is generally regarded as a nutritionally rich food source. However, earlier studies prove that it also causes allergies to subjects. Allergenic proteins with a strong IgE-binding activity have been identified in common buckwheat (CB) and a 24 kDa allergen (rTBa) in tartary buckwheat (TB) [3].

In a food allergic population, 38% showed raised specific IgE antibodies to buckwheat. Buckwheat is considered also a potent occupational allergen. In patients sensitized to buckwheat or fig, cross-reactivity to natural rubber latex (NRL) has been described and confirmed by RAST inhibition in only a few patients. Development of buckwheat allergy due to cross-sensitization with NRL is highly probable in our patient since she was not heavily exposed to buckwheat products (e.g., at work), which are the usual source of buckwheat sensitization in Europe Patients with NRL allergy should be aware of possible associated food hypersensitivities to buckwheat or fig [4]. f11 is the symbol of buckwheat in RAST.

References

1. Park JW, Kang DB, Kim CW, et al. Identification and characterization of the major allergens of buckwheat. Allergy 2000;55:1035-1041.

2.Choi SY, Sohn JH, Lee YW, Lee EK, Hong CS, Park JW.  Characterization of buckwheat 19-kD allergen and its application for diagnosing clinical reactivity. Int Arch Allergy Immunol.

3. Cui XD, Wang ZH. Molecular cloning, recombinant expression, and immunological characterization of a novel allergen from tartary buckwheat. J Agric Food Chem. 2008 Nov 26;56(22):10947-53.

4. Schiffner, R.. Anaphylaxis to buckwheat. Allergy 2001: 56(10):1020.

5. Davidson AE, Passero MA, Settipane GA. Buckwheat-induced anaphylaxis: a case report. Ann Allergy. 1992 Nov;69(5):439-40.