Natural compounds derived from plant sources are well characterized as possessing a wide variety of remarkable anti-tumour properties, for example modulating programmed cell death, primarily referring to apoptosis, and autophagy. Distinct from apoptosis, autophagy (an evolutionarily conserved, multi-step lysosomal degradation process in which a cell destroys long-lived proteins and damaged organelles) may play crucial regulatory roles in many pathological processes, most notably in cancer. In this review, we focus on highlighting several representative plant natural compounds such as curcumin, resveratrol, paclitaxel, oridonin, quercetin and plant lectin -that may lead to cancer cell death -for regulation of some core autophagic pathways, involved in Ras-Raf signalling, Beclin-1 interactome, BCR-ABL, PI3KCI/Akt/mTOR, FOXO1 signalling and p53. Taken together, these findings would provide a new perspective for exploiting more plant natural compounds as potential novel antitumour drugs, by targeting the pathways of autophagy, for future cancer therapeutics.
Two new triterpenoid saponins, ardisicrenoside K (1) and ardisicrenoside L (2), have been isolated from the roots of Ardisia crenata Sims. Their structures have been determined as 3beta-O-[alpha-L-rhamnopyranosyl-(1 --> 2)-beta-D-glucopyranosyl-(1 --> 4)-[beta-D-glucopyranosyl-(1 --> 2)]-alpha-L-arabinopyranosyl]-13beta,28-epoxy-16-oxo-30,30-dimethoxyoleanane and 3beta-O-[beta-D-xylopyranosyl-(1 --> 2)-beta-D-glucopyranosyl-(1 --> 4)-[beta-D-glucopyranosyl-(1 --> 2)]-alpha-L-arabinopyranosyl]-13beta,28-epoxy-16alpha,20-dihydroxyoleanane by means of chemical evidences and spectral analysis. Their weak anti-fungal activity against the plant pathogenic fungus Pyricularia oryzae was evaluated in vitro.
The pharmacokinetics behaviour of 20(S)-25-methoxyl-dammarane-3beta, 12beta, 20-triol (25-OCH3-PPD) and its active metabolite after oral and intravenous administration in rats were studied. Rats were administered 2.5, 5.0, and 10 mg kg(-1) 25-OCH3-PPD orally after an overnight fasting or by intravenous injection of 5 mg kg(-1) 25-OCH3-PPD via the tail vein. Plasma concentration-time profiles of 25-OCH3-PPD and its active metabolite 25-O-demethylated (25-OH-PPD) in rats were monitored by liquid chromatography-tandem mass spectroscopy (HPLC-MS-MS). The 25-O-demethylated metabolite appears to be a pathway in the phase I metabolism of 25-OCH3-PPD in rats. The plasma concentration of the metabolite was higher than that of the parent compound.
A new triterpenoid saponin, named stauntoside A (1) along with four known saponins (2,3,4,5) was isolated from Stauntonia chinensis DC., (Lardizabalaceae). Their structures were elucidated by spectroscopic analysis and chemical methods as 3-O-alpha-L-arabinopyranosyl-30-norhederagenin -28-O-beta-D-glucopyranosyl-(1 --> 6)-beta-D-glucopyranosyl ester (1), 3-O-alpha-L-arabinopyranosyl-30- norhederagenin-28-O-alpha-L-rhamnopyranosyl-(1 --> 4)-beta-D-glucopyranosyl-(1 --> 6)-beta-D-glucopyranosyl ester (2), 3-O-alpha-L-rhamnopyranosyl-(1 --> 2)-alpha-L-arabinopyranosyl-30-norhederagenin-28-O-alpha-L- rhamnopyranosyl-(1 --> 4)-beta-D-glucopyranosyl-(1 --> 6)-beta-D-glucopyranosyl ester (3), 3-O-alpha-L- arabinopyranosyl-hederagenin-28-O-alpha-L-rhamnopyranosyl-(1 --> 4)-beta-D-glucopyranosyl-(1 --> 6)-beta-D- glucopyranosyl ester (4), 3-O-alpha-L-rhamnopyranosyl-(1 --> 2)-alpha-L-arabinopyranosyl-hederagenin -28-O-alpha-L-rhamnopyranosyl-(1 --> 4)-beta-D-glucopyranosyl-(1 --> 6)-beta-D-glucopyranosyl ester (5). The (1)H and (13)C NMR data for Glycoside L-G1 or Sinofoside A are paradox in the reported before. Thus, the structure elucidation of saponin 2, known as Glycoside L-G1 or Sinofoside A, was discussed and the unambiguous assignments were given.
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