Pharmacology of Ch‘ang Shan (Dichroa febrifuga), a Chinese Antimalarial Herb

Abstract

FOR centuries in China the roots (Chang Shan) and the leaves (Shuu Chi) of Dichroa febrifuga, Lour, have been used against malarial fevers. In our first report¹ in 1943, it was recorded that a crude extract of this root had been effectively used on clinical cases of tertian malaria. Then in 1945, when Plasmodium gallinaceum became available to us, we found that the crude extracts of both the root and the leaves of the herb were also effective for chicks infected with P. gallinaceum, the leaves being about five times as active as the roots. An alkaloidal fraction of the root exhibited a marked anti-malarial activity, but of the three alkaloids, F (later called dichroine A), O and I, and two neutral principles, E (later dichrin A) and H (later dichrin B), none was found active². In the following year we announced the isolation of an active alkaloid, dichroine B, melting at 237–238° C. with decomposition (considered as hydrochloride at first, later identified as dihydrochloride). It was effective against chicken malaria in intramuscular doses of 2–4 mgm./kgm. twice or thrice a day³. The empirical formula of dichroine B was first reported as C₁₆H₁₉O₃N₃⁴, and later as C₁₆H·₂₁O₃N₃ when purer batches were examined⁵. As reported to the general conference of the Chinese Physiological Society on May 14, 1947, we had thus far isolated from Ch‘ang Shan altogether five alkaloids and two neutral principles. Among the five alkaloids, dichroine A, dichroine B, dichroine C, dichroidine and quinazolone (4-keto-dihydroquinazoline), the first three members were soon found to be isomers mutually convertible under certain conditions. In conformity with the conventional nomenclature of isomers, they have been, thenceforth, called dichroine-α, dichroine-Î, and dichroine-Î respectively⁵. With the probable exception of dichroine-a, all these alkaloids are more or less effective against P. gallinaceum infection in chicks, their antimalarial activity being in the descending order as follows: dichroine-Î, dichroine-Î, dichroidine and quinazolone. From analytical studies of the oxidation products of dichroine-α, it is apparent that the dichroine isomers are quinazoline derivatives. Of the two neutral principles, dichrin A and dichrin B, the first has been identified as umbelliferone. In the accompanying table, the chemical and pharmacological properties of these seven substances from Dichroa febrifuga are summarized.