The Limonoids and Their Antitobacco Mosaic Virus (TMV) Activities from <i>Munronia unifoliolata</i> Oliv.

Five new limonoids, named munronoids K–O (<b>1</b>–<b>5</b>), together with three known limonoids were isolated from <i>Munronia unifoliola</i> Oliv. These limonoids were involved in the skeletons of evodulone, gedunin, and peieurianin types of limonoids, and their structures were established on the basis of spectroscopic data. Compound <b>5</b> featuring a γ-lactone ring instead of the β-substituted furan ring was found in the peieurianin type for the first time. The antitobacco mosaic virus (anti-TMV) activities of compounds <b>1</b>–<b>8</b> were also evaluated with half-leaf, enzyme-linked immunosorbent assay, and Western blot methods, and limonoids <b>1</b>, <b>5</b>, and <b>8</b> showed stronger anti-TMV treatment activities than the positive control ningnanmycin. Six compounds (<b>1</b>–<b>5</b> and <b>8</b>) exhibited infection inhibition activities against TMV.