Two new steroidal alkaloids from the rhizomes of Veratrum nigrum L. and their anti-TYLCV activity

Two new steroidal alkaloids (1–2), together with seven known related steroidal alkaloids (3–9), were isolated from the rhizomes of Veratrum nigrum L. Their structures were elucidated by extensive spectroscopic analysis, and by comparison with literature data. Compound 1 possessed a rare 1, 3-oxazolidine unit within varazine-type alkaloids, and 2 was a 9-hydroxy-4-one derivative of 3-veratroylgermine. All isolates were evaluated inhibit tomato yellow leaf curl virus (TYLCV) activity. Compounds 5 and 7 (40 μg/mL) showed a significant anti-TYLCV activity in the host Nicotiana benthamiana with inhibition rates 74.6% and 63.4%, respectively, which are higher than that of the positive control ningnanmycin (51.4%).