Isolation and antifungal action of naturally occurring 2-methoxy-1,4-naphthoquinone.

Several antibiotic compounds have been isolated from green plants. Those which have been structurally identified, are citrinin (l-4), dicumarol (5-7), and protoanemonin (8, 9). Other less well defined factors are an oil from AZZium sativum (lo-12), a colorless crystalline compound from Arci&rz minus (13), Products A and B from Asarum cunadense (14), cassic acid from the leaves of Custiu reticdutu (15)) crepin from the buds and flowers of Crepis turu~acz@Ziu (16), a low melting compound from the leaves and flowers of @raea uruncus (17), and tomatin, occurring in Lycoperticon esmulentum (garden tomato) (18). An antibacterial substance has also been extracted from Tillandsia usneoides (Spanish moss) (19), and the milky juice of crushed water chestnuts has been shown to inhibit the growth of Staphylococcus uureus, Escherkhiu coli, and Aerobacter uerogenes (20). Many of these materials have been tested for activity exclusively against strains of the common test bacteria used in most laboratories to determine effectiveness against zoopathogenic organisms. For the most part these compounds have been found to be of little use to date because of low potency, toxicity to animals, and low stability. Work in this laboratory has been directed toward the discovery, purification, and characterization of compounds occurring in plants which may be useful against phytopathogens causing destructive plant diseases. Such compounds should be less toxic to plant cells and might therefore be used advantageously for the control of plant pathogens. This report deals with the discovery, isolation, and identification of 2methoxy-1 , 4-naphthoquinone occurring in garden balsam (Imputiens baZaarnina L). A short description of its antifungal activity is included. A semiquantitative assay procedure with an alcohol-tolerant strain of yeast as the susceptible test organism was used to facilitate the isolation. The utilization of this yeast permitted the testing of 100 per cent ethyl alcohol extracts of the plant material. This assay procedure is described.