Polyprenylated Xanthones Isolated from Garcinia Resins and Their Beneficial Effects on Rice Blast Disease

Five undescribed polyprenylated xanthones (1, 3, 4, 22, and 23) and 27 known compounds were isolated from Garcinia resins, and the antifungal activities of 15 of them were investigated. Compound 7 exhibited notable in vitro antifungal effects against Magnaporthe grisea with an IC₅₀ value of 3.54 μg/mL, superior to isoprothiolane (10.30 μg/mL), and showed an excellent protective efficiency of 78.4% at 200 μg/mL against RB (rice blast), equivalent to isoprothiolane (87.2%). Its antifungal activity may be related to the destruction of the cell membrane and the effect of absorption and utilization of sugar by the mycelium, which was proven by the transcriptome sequencing and preliminary mechanism, showing a good application prospect for replacing agrochemical fungicides in the control of RB disease.