Enantioselective Separation of 4,8-DHT and Phytotoxicity of the Enantiomers on Various Plant Species.

As a candidate for bioherbicide, 4,8-dihydroxy-1-tetralone (4,8-DHT) was isolated from Caryospora callicarpa epicarp and its two enantiomers, S-(+)-isosclerone and R-(-)-regiolone, were separated by chiral high-performance liquid chromatography (HPLC) on a Chiralcel OD column with chiral stationary phase (CSP)-coated cellulose-tris(3,5-dimethylphenylcarbamate). Then, the phytotoxicity of 4,8-DHT and its enantiomers toward the seeds germination and seedling growth of the five tested plant species, including lettuce (Latuca sativa), radish (Raphanus sativus), cucumber (Cucumis sativus), onion (Allium cepa), and wheat (Triticum aestivum), were investigated and the results indicated a hormesis at low concentration of 4,8-DHT and its enantiomers, but a retardant effect at high concentration. Between the two enantiomers of 4,8-DHT, the S-(+)-isosclerone was more toxic to seeds germination and seedling growth of the five tested plant species than the R-(-)-regiolone, and also the phytotoxicity of S-(+)-isosclerone varied with different plants. For example, S-(+)-isosclerone was the most active to seedling growth of lettuce, indicating that S-(+)-isosclerone had specific effects on different organisms. Thus, all of the chirality and concentration of 4,8-DHT, as well as the affected plant species, need to be taken into consideration in the development and utilization of 4,8-DHT.

Phytotoxicity of 4,8-dihydroxy-1-tetralone isolated from Carya cathayensis Sarg. to various plant species.

The aqueous extract from Carya cathayensis Sarg. exocarp was centrifuged, filtered, and separated into 11 elution fractions by X-5 macroporous resin chromatography. A phenolic compound, 4,8-dihydroxy-1-tetralone (4,8-DHT) was isolated from the fractions with the strongest phytotoxicity by bioassy-guided fractionation, and investigated for phytotoxicity on lettuce (Latuca sativa L.), radish (Raphanus sativus L.), cucumber (Cucumis sativus L.), onion (Allium cepa L.) and wheat (Triticum aestivum L.). The testing results showed that the treatment with 0.6 mM 4,8-DHT could significantly depress the germination vigor of lettuce and wheat, reduce the germination rate of lettuce and cucumber, and also inhibit radicle length, plumule length, and fresh weight of seedlings of lettuce and onion, but could significantly promote plumule length and fresh weight of seedlings of cucumber (p < 0.05). For the tested five plants, the 4,8-DHT was the most active to the seed germination and seedling growth of lettuce, indicating that the phytotoxicity of 4,8-DHT had the selectivity of dosage, action target (plant type) and content (seed germination or seedling growth).

Prospective teratology of retinoic acid metabolic blocking agents (RAMBAs) and loss of CYP26 activity.

All-trans retinoic acid (atRA) is the transcriptionally active product of vitamin A and induces gene expression via specific receptors at nM concentrations. Essential enzymes that regulate the local levels of atRA are the CYP26 members of the cytochrome P450 family, which catabolize atRA. Compounds that have been designed to inhibit these enzymes are known as Retinoic Acid Metabolic Blocking Agents (RAMBAs). Treatment with these compounds will raise endogenous atRA levels and may be therapeutic for the treatment of diseases that respond to high atRA concentrations, including several types of cancer as well as skin conditions such as psoriasis and acne. This review describes the mechanism of action of the RAMBAs and discusses the potential side effects of these compounds. atRA is highly teratogenic and the potential teratogenicity of the RAMBAs is described by comparison with the abnormalities resulting from null mutation of individual CYP26 genes. The possible effects of RAMBAs on the adult brain are also described that have the potential for harm but, in the right circumstances, may also be beneficial.

Cytotoxic and new tetralone derivatives from Berchemia floribunda (Wall.) Brongn.

Two new alpha-tetralone (=3,4-dihydronaphthalen-1(2H)-one) derivatives, berchemiaside A and B (1 and 2, resp.), and one new flavonoid, quercetin-3-O-(2-acetyl-alpha-L-arabinofuranoside (3), together with ten known flavonoids compounds, eriodictyol (4), aromadendrin (5), trans-dihydroquercetin (6), cis-dihydroquercetin (7), kaempferol (8), kaempferol-3-O-alpha-L-arabinofuranoside (9), quercetin (10), quercetin-3-O-alpha-L-arabinofuranoside or avicularin (11), quercetin 3'-methyl ether, 3-O-alpha-L-arabinofuranoside (12), and maesopsin (13), were isolated from the bark of Berchemia floribunda. Their structures were determined by various NMR techniques and chemical studies. Compounds 3-13 were tested for their cytotoxic activity against human leukemia cells. Among them, kaempferol (8) and maesopsin (13) showed significant inhibitory activities against human leukemia cells CCRF-CEM and its multidrug-resistant sub-line, CEM/ADR5000, with IC(50) values of 14.0, 5.3, 10.2, and 12.3 microM, respectively.

Monocyclic and dicyclic hydrocarbons: structural requirements for proximal giant axonopathy.

The chromogenic and neurotoxic gamma-diketone 1,2-diacetylbenzene (1,2-DAB), but not its isomer 1,3-DAB, induces blue discoloration of tissues and urine, clustering of axonal microtubules and proximal neurofilament-filled axonal swellings in rodents. The remarkable chromogenic property of 1,2-DAB, a monocyclic aromatic hydrocarbon, arises from reaction with lysine residues of proteins and formation of dimeric and polymeric derivatives. Tetralin, a dicyclic solvent structurally related to acetyl ethyl tetramethyl tetralin, a chromogenic and neurotoxic agent, reportedly induces excretion of green urine, and causes neurological disturbances in humans. Monocyclic aromatic 1,2,4-triethylbenzene (1,2,4-TEB), but not its isomer 1,3,5-TEB, is also reportedly chromogenic and induces neurophysiological deficits in rodents consistent with axonal neuropathy, but without neuropathological confirmation. We treated 12-week-old C57Bl/6 mice by gavage with 300, 600, or 900 mg/kg/day 1,2,4-TEB, or equivalent doses of 1,3,5-TEB, 3 days/week, for up to 12 weeks, or intraperitoneally with 400 mg/kg/day tetralin, or 50 or 100 mg/kg/day of its alpha-tetralol analogue, 5 days/week, for up to 5 weeks. Animals treated with 1,2,4-TEB, but not 1,3,5-TEB, tetralin or alpha-tetralol, developed hind limb weakness, excreted greenish urine, and showed 1,2-DAB-like neuropathology. These findings support the hypothesis that 1,2-spaced ethyl (or acetyl) moieties on a benzene ring of hydrocarbons are required for hydrocarbons to induce chromogenic changes and proximal giant neurofilamentous axonopathy. Key molecular targets of these compounds likely reside in the axon where they serve to maintain normal cytoskeletal organization.

Cytotoxic mannich bases of 1-arylidene-2-tetralones.

Various 1-arylidene-2-tetralones 1 had been shown previously to possess moderate cytotoxic properties unaccompanied by murine toxicity. The objective of the present investigation was to undertake different molecular modifications of representative members of series 1 with a view to discerning those structural features leading to increased potencies. All compounds were evaluated using human Molt 4/C8 and CEM T-lymphocytes as well as murine P388 and L1210 leukemic cells. The Mannich bases 2, 4, 5 and 7 possessed increased potencies compared to the corresponding unsaturated ketones 1 and in general were potent cytotoxics having IC50 values in the 0.2-10 microM range. QSAR using the cytotoxicity data for 2a-e suggested that potency was positively correlated with the size of the substituents in the arylidene aryl ring. Compounds 2a-f were evaluated using a panel of approximately 53 human tumour cell lines and, when all cell lines were considered, were more potent than the reference drug melphalan. In particular, marked antileukemic activity was displayed. Molecular modeling was utilized in order to evaluate whether the shapes of the different compounds contributed to the varying potencies observed. Representative compounds demonstrated minimal or no inhibiting properties towards human N-myristoyltransferase (NMT) and did not bind to calf thymus DNA. This study has revealed a number of unique lead molecules as candidate anti-neoplastic agents serving as prototypes for future development.