Samuel S. M. Sun

A rice bran polyphenol, cycloartenyl ferulate, elicits apoptosis in human colorectal adenocarcinoma SW480 and sensitizes metastatic SW620 cells to TRAIL-induced apoptosis.

High intake of whole grain food has been suggested as an important factor for reducing the risk of colon cancer, owing to the abundance of indigestible fibers. Our findings demonstrated that, among various rice bran phenolic compounds tested, cycloartenyl ferulate (CF) showed the most prominent in vitro growth inhibition on human colorectal adenocarcinoma SW480, but had low toxicity on normal colon CCD-18-Co cells. The anticancer activity of CF was further illustrated by its ability to induce significant regression of SW480 xenograft in nude mice. CF elevated the death receptors DR4 and DR5 and triggered both the death receptor and the mitochondrial apoptosis pathways. Depletion of anti-apoptotic Bcl-2 and up-regulation of pro-apoptotic Bak were observed, accompanied by dissipation of the mitochondrial membrane potential and release of cyto c and SMAC/DIABLO from mitochondria into the cytosol. Bid was found to be cleaved by caspase-8, so that the death receptor pathway might be exaggerated by the mitochondrial pathway. Strikingly, we showed for the first time that CF also sensitized the metastatic and resistant colon cancer SW620 to TRAIL-induced apoptosis and the mechanisms involved at least enhanced activation of caspase-8 and -3. This study provides a clear evidence that the health-beneficial properties of whole grain consumption are not only limited by the presence of dietary fibers but also other molecules that can either act as a chemopreventive agent to directly induce tumor regression or as a sensitizer to enhance TRAIL-induced apoptosis in metastatic cancer cells.

Antiviral activity of daphnoretin isolated from Wikstroemia indica.

The ethanol extract of Wikstroemia indica was fractionated with organic solvents of different polarities, and various fractions were screened for their antiviral activity against respiratory syncytial virus (RSV) using a cytopathic effect (CPE) reduction assay. The ethyl acetate fraction was most active against RSV with 50% inhibition concentration (IC50) value < 3.9 μg/mL and a selectivity index (SI) > 64.1. Further isolation and purification of the fraction led to a purified compound, daphnoretin. Daphnoretin was tested for its anti‐RSV activity using a plaque reduction assay and found active against RSV, with an IC50 value of 5.87 μg/mL and SI value of 28.17. The mode of antiviral action study revealed that daphnoretin could slightly inhibit the early events of the viral infection but its effect was mainly on the later phase of the replication cycle. Copyright

Purification and characterization of non-specific lipid transfer proteins from the leaves of Pandanus amaryllifolius (Pandanaceae).

Two proteins were isolated from the saline extract of mature leaves of Pandanus amaryllifolius, using affinity chromatography on fetuin-agarose and Affi-gel Blue gel, anion exchange chromatography as well as gel filtration. The proteins were demonstrated as non-glycoproteins, with molecular mass of 18 and 13 kDa, respectively, comprising of peptide subunits from 6.5 to 9 kDa in the forms of heterodimer and homodimer. All of them have similar N-terminal amino acid sequences with only minor variations and are matched to non-specific lipid transfer proteins (nsLTPs) of the other plants such as wheat LTP using NCBI Blast searching for short, nearly exact matches. Furthermore, they explicated each other as isoforms originated putatively from a multigene family with various molecular weight, binding affinity, ionic strength, and subunits. However, the potencies for antiproliferation of HL-60 cell line and inhibition of the growth of the bacteria Pseudomonas aeruginosa are different in that those of the fetuin-binding protein are greater than non-fetuin binding proteins. The non-specific lipid transfer proteins of P. amaryllifolius exhibit weak to moderate hemagglutinating activity toward rabbit erythrocytes, but, this activity could not be reversed by mannose. They thus could be easily differentiated from the previously reported mannose-binding lectin isolated from this plant, which has subunits with similar molecular weight.

Molecular Cloning and the cDNA-Derived Amino Acid Sequence of Narcissus tazetta Isolectins

Recently several complete cDNAs encoding the Narcissus tazetta lectins (NTL) were cloned. The sequence analyses of the cloned DNAs reveal that there are at least three unidentical positive clones for NTLs. The primary structure of the three NTL clones contains a mature polypeptide consisting of 105 amino acids and a C-terminal peptide extension beyond the C-terminal amino acids Thr-Gly. There are two fixed-position cysteines within the protein domain (amino acids 29 and 52), which are probably involved in the disulfide-bond linkage within the molecules to confer the secondary structure of the mature lectin. One third of the deduced amino acid composition consisted of glycine, leucine, and asparagine. From the cDNA-derived amino acid sequences the three NTL clones are not identical and are suggested to be isolectins present in N. tazetta var. chinensis. This study further confirms the previous isolation of mannose-specific isolectins from Chinese daffodil leaves [Ooi et al. (2000), J. Protein Chem.19, 163-168].

Mannose-Specific Isolectins with Different Hemagglutinating Potencies Isolated from Chinese Daffodil (Narcissus tazetta var. chinensis) Leaves

Three mannose-specific lectins exhibiting considerable similarities in NH2-terminal amino acid sequence were isolated from leaves of the Chinese daffodil Narcissus tazetta (Family Amaryllidaceae). The purification protocol involved extraction with an aqueous buffer, anion exchange chromatography on DEAE-cellulose using stepwise elution with increasing salt concentrations, affinity chromatography on mannose-agarose, and FPLC-gel filtration on Superose 12. From the peak unadsorbed on DEAE-cellulose, and two peaks adsorbed on the ion exchanger and eluted respectively with 0.2 M Tris-HCl buffer and 0.5 M NaCl, were prepared fractions which yielded isolectins 1, 2, and 3 after adsorption on mannose-agarose and FPLC-gel filtraton. All three isolectins were homodimers with a molecular weight of 26 kDa. The lectin unadsorbed on DEAE-cellulose had the lowest, while the most strongly adsorbed lectin had the highest hemagglutinating activity.