Isolation and characterization of an allergy inhibitor from the Jelutong, Dyera costulata Hook. f.
Jelutong, the latex of D. costulata and D. lowii, is reported to inhibit allergic reactions in guinea pigs. The isolation of an allergy inhibitor, named compound A, from the latex of D. costulata is described. Using chemical and spectroscopic analyses, compound A was identified as dimethylmyoinositol. In an allergy test using male Heartley guinea-pigs, the inhibition rates of the passive cutaneous anaphylaxis reaction were 34.2% for compound A as compared with 55.0% for the butanol extract of D. costulata latex. It is suggested that the latex of D. costulata contains more than one allergy inhibitor.