2.5. Accumulation of 1 and 2 in major Poaceae species in response to CuCl 2 treatment

To examine the distribution of 1 and 2 accumulation in Poaceae, we treated leaves of rice, maize, oat, rye (Secale cereale), and barley with 1 mM CuCl 2. We extracted compounds in the leaves 72 h after treatment, and analyzed the amounts of 1 and 2 by HPLC. Compounds 1 and 2 accumulated in response to CuCl 2 treatment in barley leaves, and their amounts were 3.4 and 4.4 nmol/g fr. wt, respectively. Compounds 1 and 2 were not detected in rice, maize, oat, or rye.

2.6. Antimicrobial activities of 1 and 2

The antifungal activities of 1 and 2 against phytopathogenic fungi B. sorokiniana, F. graminearum, and Alternaria brassicicola were evaluated by inhibition of conidial germination and germ tube elongation. The concentration of 1 was not enough to examine a dose-response relationship; the assay was only performed at 1,000 μM. Compounds 1 and 2 showed inhibitory effects on the conidial germination of F. graminearum and A. brassicicola but not B. sorokiniana (Fig. 8A and B). Conversely, compounds 1 and 2 almost completely inhibited germ tube elongation in F. graminearum and A. brassicicola at 1,000 μM and inhibited that of B. sorokiniana by 39.5 and 48.0%, respectively (Fig. 8C). Compound 2 demonstrated a marked inhibitory effect on the germ tube elongation of F. graminearum and A. brassicicola, even at 10 μM (Fig. 8D).

The inhibitory activity of 2 against Pseudomonas syringae pv. japonica was assayed by monitoring growth in liquid culture. However, 2 did not inhibit growth, even at 1,000 μM (data not shown).