Chong-Ren Yang

Antifungal Activity of C-27 Steroidal Saponins

ABSTRACT As part of our search for new antifungal agents from natural resources, 22 C-27 steroidal saponins and 6 steroidal sapogenins isolated from several monocotyledonous plants were tested for their antifungal activity against the opportunistic pathogens Candida albicans, Candida glabrata, Candida krusei, Cryptococcus neoformans, and Aspergillus fumigatus. The results showed that the antifungal activity of the steroidal saponins was associated with their aglycone moieties and the number and structure of monosaccharide units in their sugar chains. Within the 10 active saponins, four tigogenin saponins (compounds 1 to 4) with a sugar moiety of four or five monosaccharide units exhibited significant activity against C. neoformans and A. fumigatus, comparable to the positive control amphotericin B. The antifungal potency of these compounds was not associated with cytotoxicity to mammalian cells. This suggests that the C-27 steroidal saponins may be considered potential antifungal leads for further preclinical study.

Steroidal saponins from fresh stem of Dracaena cochinchinensis.

A further phytochemical investigation on the fresh stem of Dracaena cochinchinensis yielded 18 steroidal saponins. Fourteen of which are new compounds, designated as 25(R,S)-dracaenosides E-H, M, O-Q, dracaenosides I-L, R, and 25(S)-dracaenoside N. Their structures were determined by detailed spectroscopic analysis, including extensive 1D and 2D NMR data, and the result of hydrolytic reaction.

Triterpenoid saponins from Pulsatilla campanella

Abstract From the roots of Pulsatilla campanella , three new saponins of hederagenin, named pulsatilosides A-C were isolated by column chromatography and identified from their chemical and spectroscopic characteristics, along with the six known saponins leontosides A, B, D, caulosides D and F, and calcoside D. The chemotaxonomic significance of these closely related saponins in P. campanella is noted.

Minor dammarane saponins from Panax notoginseng

Further investigation of the roots of Panax notoginseng yielded two new minor dammarane saponins, notoginsenosides R(8) and R(9), whose structures were established by means of spectral evidence as (20S)-dammar-22-ene-3 beta, 6 alpha, 12 beta, 20, 25-pentol 6-O-beta-D-glucopyranoside and its (20R)-epimer analogue, respectively.

Steroidal saponins from Chlorophytum malayense

Abstract Four new steroidal saponins, chloromalosides A–D, were isolated from the rhizomes of Chlorophytum malayense. On the basis of detailed chemical and spectroscopic evidence, the structures of chloromalosides A–D were elucidated to be neohecogenin 3-O-β- d -glucopyranosyl(1→2)-[β- d -xylopyranosyl(1→3)]-β- d -glucopyranosyl(1→4)-β- d -galactopyranoside, 26-β- d -glucopyranosyl-22-hydroxy-25(S)-5α-furostane-3β,26-diol 3-O-β- d -glucopyranosyl(1→2)-[β- d -xylopyranosyl(1→3)]-β- d -glucopyranosyl(1→4)-β- d -galactopyranoside, neohecogenin 3-O-β- d -xylopyranosyl (1→3)-[α- l -arabinopyranosyl(1→2)]-β- d -glucopyranosyl(1→4)-[α- l -rhamnopyranosyl(1→2)]-β- d -galactopyranoside and neotigogenin 3-O-β- d -xylopyranosyl(1→3)-[α- l -arabinopyranosyl(1→2)]-β- d -glucopyranosyl(1→4)-[α- l -rhamnopyranosyl(1→2)]-β- d -galactopyranoside, respectively.

MONOTERPENOID AND PHENYLETHANOID GLYCOSIDES FROM LIGUSTRUM PEDUNCULARE

Two new phenylethanoid glycosides, lipedosides A-I and A-II as well as six new monoterpene glycosides, lipedosides B-I-B-VI were isolated together with three known constituents, osmanthuside B, anatolioside and linalool from Ligustrum pedunculare. Their structures have been elucidated by chemical and spectroscopic methods.

Antiviral activity and possible mechanisms of action of pentagalloylglucose (PGG) against influenza A virus

Influenza A virus (IAV) infection is a major public health threat leading to significant morbidity and mortality. The emergence of drug-resistant virus strains highlights the urgent need to develop novel antiviral drugs with alternative modes of action. Pentagalloylglucose (PGG), a naturally occurring polyphenolic compound, possesses a broad spectrum of biological activities. In this study, we found that PGG has anti-influenza-virus activity, and investigated its possible mechanism(s) of action in vitro. Both pre-incubation of virus prior to infection and post-exposure of infected cells with PGG significantly inhibited virus yields. Influenza-virus-induced hemagglutination of chicken red blood cells was inhibited by PGG treatment, suggesting that PGG can inhibit IAV infection by interacting with the viral hemagglutinin. PGG did not affect viral protein synthesis or nuclear transport of viral nucleoprotein (NP) but greatly reduced plasma membrane accumulation of NP protein at the late stage of the replication cycle. Furthermore, PGG significantly reduced virus budding and progeny virus release from infected cells. This study revealed for the first time that PGG can inhibit IAV replication with a dual mode of action and offers new insights into its underlying mechanisms of antiviral action.

Steroid saponins from Polygonatum kingianum.

Four new steroid saponins, kingianosides A-D, were isolated from the rhizome of Polygonatum kingianum, together with two known steroid saponins. On the basis of chemical and spectral evidence, the structures of kingianosides A-D were established as gentrogenin 3-O-beta-D-glucopyranosyl (1-->4)-beta-D-galactopyranoside, gentrogenin 3-O-beta-D-glucopyranosyl(1-->4)-beta-D-fucopyranoside, 26-O-beta-D-glucopyranosyl-22-hydroxy-25(R)-furost-5-en-12-on-3 beta, 22-diol 3-O-beta-D-glucopyranosyl(1-->4)-beta-D-galactopyranoside and 26-O-beta-D-glucopyranosyl-22-hydroxy-25(R)-furost-5-en-12-on-3 beta,22-diol 3-O-beta-D-glucopyranosyl(1-->4)-beta-D-fucopyranoside, respectively.

Triterpenoid saponins from Ilex latifolia

Three new triterpenoid saponins, latifolosides F, G, H were isolated from the leaves of Ilex latifolia. Their structures were elucidated on the basis of chemical and spectral evidence. Latifoloside F was determined to be 3-O-[alpha-L-rhamnopyranosyl(1-2)]-[beta-D-glucopyranosyl(1-3)-]- alpha-L-arabinopyranosyl ilexgenin B 28-O-[alpha-L-rhamnopyranosyl(1-2)]-beta-D-glucopyranoside. Latifoloside G was 3-O-[alpha-L-rhamnopyranosyl(1-2)]-[beta-D-glucopyranosyl(1-3)-]- alpha-L-arabinopyranosyl pomolic acid 28-O-[alpha-L-rhamnopyranosyl(1-2)]-beta-D-glucopyranoside. Latifolioside H(3) was 3-O-[alpha-L-rhamnopyranosyl(1-2)]-[beta-D-glucopyranosyl(1-3)-]- alpha-L-arabinopyranosyl siaresinolic acid 28-O-[alpha-L-rhamnopyranosyl(1-2)]-beta-D-glucopyranoside.

Dammarane saponins from Panax ginseng

From the dried roots of Panax ginseng two new minor dammarane saponins named koryoginsenoside-R1 and -R2 were isolated, along with fourteen known saponins. On the basis of spectral and chemical evidence, the structure of the new saponins were elucidated as 6-O-[trans butenoyl-(1-->6)-beta-D-glucopyranosyl]-20-O-beta-D- glucopyranosyl dammar-24-en-3 beta,6 alpha,12 beta,20(S)-tetrol and 3-O-[beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranosyl]-20-O-[beta-D- glucopyranosyl-(1-->6)-beta-D-glucopyranosyl] dammar-22-en-3 beta,12 beta, 20(S),- 25-tetrol, respectively.