Various plant tissue cultures have been reported to show antimicrobial activities (1-6) as well as activity against plant viruses (7,8). In the present study, we have carried out a screening test of culture lines derived from five species of boraginaceous plants in an attempt to isolate antidermatophytic as well as antibacterial substances. This paper chiefly deals with the isolation of deoxyshikonin from cell cultures of Lithospermum erythrorhizon Sieb. et Zucc. as a compound showing the strongest antidermatophytic activity.Of the extracts of 36 cell lines tested, 22 (61%) showed growth inhibitory activities against one or more of the test microorganisms (Table 1). None of these extracts, however, was active against Escherichia coli NIHI IFO 12734, and only the extract of Echium lycopsis was active against Candida albicans IFO 0197. The red cell lines of L. erythrorhizon producing shikonin derivatives were active against Staphylococcus aureus 209P IFO 12732 and Trichophyton rubrum IFO 5808, whereas all 10 of the non-pigmented cell lines of this species were inactive.It has been reported that the pigmented cultured cells of L. erythrorhizon contain the same red naphthoquinone pigments (shikonin derivatives) as those found in the root bark of the original plant (10). It is also known that several naphthoquinones and benzoquinone derivatives from L. erythrorhizon as well as E. lycopsis cultures have antibacterial activities (13), but these compounds have not been examined with respect to the antidermatophytic activity. The present study has demonstrated for the first time that deoxyshikonin is the main MeOHsoluble antidermatophytic principle of Lithospermum cells.As shown in Table 2, deoxyshikonin proved to inhibit the growth of four dermatophytes (MIC 6.25-25 µg/ml), Saccharomyces sake IFO 0305 (MIC 6.25 µg/ ml), and for four Gram-positive bacteria deoxyshikonin showed weak activities (MIC 50-200 µg/ml). Except against S. sake, the activity of shikonin was somewhat weaker or equal to deoxyshikonin. It is possible, therefore, that the antifungal activity is decreased by the presence of a hydroxy group at the 1' position of the side chain. Neither deoxyshikonin nor shikonin inhibited the following Gram-negative bacteria and yeasts even at the highest concentration tested (200 µg/ml): E. coli NIHJ IFO 12734, Pseudomonas aeruginosa IFO 12689, Serratia marcescens IFO 12648, C. albicans IFO 0197, Candida guilliermondii IFO 0454, Candida mycoderma IFO 0162, Candida tropicalis IFO 0006, and Candida utilis IFO 0454. In the experiment employing the agar streak method followed by the liquid dilution method, the survival of Trichophyton mentagrophytes IFO 5809 was confirmed even at the deoxyshikonin concentration of 100 µg/ml. Therefore, it is considered that the activity of deoxyshikonin against dermatophytes is not fungicidal but fungistatic.