Identification of anti-TMV active flavonoid glycosides and their mode of action on virus particles from Clematis lasiandra Maxim.

BACKGROUND: Tobacco mosaic virus (TMV) is a disreputable plant pathogen that causes a decline in the quality and yield of various economic crops. Natural products are important potential sources of biopesticides to control TMV. This study focuses on the discovery of anti-TMV active flavonoid glycosides and their mode of action on TMV particles from Clematis lasiandra Maxim. RESULTS: A new benzoyl acylated flavonoid glycoside, kaempferol 3-O-(2''-benzoyl)-ß-d-glucopyranosyl-7-O-α-l-rhamnopyranoside (1), and nine known flavonoids (2-10) were identified first from C. lasiandra. The hydroxyl group at C-7, E-p-coumarate at C-6'' in the Glc of C-6, and the glucuronic acid at C-3 were functional groups for the antiviral flavonoid glycosides. Flavonoids 2, 5, and 6 showed higher inactivation efficacies of 64.62% to 82.54% compared with ningnanmycin at 500 µg ml-1 . The protective and curative efficacies for 2 and 5 were 57.44-59.00% and 41.17-43.92% at 500 µg ml-1 , respectively. Compound 5 showed higher TMV systemic resistance with control efficacies of 41.64%, 36.56% and 27.62% at concentrations of 500, 250 and 125 µg ml-1 compared with ningnanmycin in K326 tobaccos, respectively. Compound 5 can directly fracture TMV particles into small fragments combining with the fusion phenomena, and TMV-CP was an important target for 5 to break TMV particles. CONCLUSION: Flavonoid glycosides from C. lasiandra showed potent antiviral activities against TMV with multiple modes of action including inactivation, protective and curative effects, and inducing systemic resistance. TMV-CP was an important target for active flavonoid glycosides to fracture TMV particles. The results provided evidence that flavonoid glycosides from C. lasiandra have the potential to control TMV.

New cytotoxic triterpenoid saponins from the whole plant of Clematis lasiandra Maxim.

Four new oleanane type triterpenoid saponins (1-4) and three known saponins (5-7) were isolated from the whole plant of Clematis lasiandra Maxim. The structures of the four new compounds were elucidated as 3-O-ß-D-ribopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-[ß-D-glucopyranosyl-(1 → 4)]-ß-D-xylopyranosyl hederagenin (1), 3-O-ß-D-ribopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1→2)-ß-D-xylopyranosyl oleanolic acid 28-O-ß-D-glucopyranosyl ester (2), 3-O-ß-D-ribopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-ß-D-xylopyranosyl hederagenin (3) and 3-O-ß-D-ribopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-[ß-D-glucopyranosyl-(1→4)]-α-L-arabinopyranosyl hederagenin (4) on the basis of extensive spectroscopic analysis and chemical evidence. Compounds 1-7 were evaluated for their cytotoxicity against human tumor cell lines HL-60, Hep-G2 and SGC-7901, and all of the evaluated saponins showed significant cytotoxicity to those three tumor cell lines with IC50 in the range from 1.40 to 19.50 µmol/L except for compounds 2 and 6.