Diterpene alkaloids and diterpenes from Spiraea japonica and their anti-tobacco mosaic virus activity

Abstract Five new naturally occurring natural products, including two atisine-type diterpene alkaloids ( 1 and 2 ), two atisane-type diterpenes ( 3 and 4 ), and a new natural product spiramine C2 ( 5 ), along with nine known ones ( 6 – 14 ), were isolated from the ethanolic extracts of the whole plant of Spiraea japonica var. acuminata Franch. Their structures were elucidated by extensive spectroscopic analysis. The anti-tobacco mosaic virus (TMV) activities of all the compounds were evaluated by the conventional half-leaf method. Six compounds ( 2 , 3 , 6 , 7 , 11 , and 12 ) exhibited moderate activities at 100 μg/mL with inhibition rates in the range of 69.4–92.9%, which were higher than that of the positive control, ningnanmycin. Their preliminary structure–activity relationships were also discussed.