High-precision measurement of 234U/238U isotopic abundance ratio was carried out for three uranium samples, separated from a lake sediment and two zircon specimens. The thermal ionization mass spectrometer used has nine new bucket-type Faraday collectors and a Daly ion-counting system detector positioned behind axial Farady and WARP filter (a kind of energy filter). The WARP filter is designed to suppress the tailing effect of adjacent strong ion. The aberration of the measured ratio from the theoretical ratio was as small as 0.02%, for a zircon from Finland. A 0.20% excess of 234U in the lake sediment is judged to be reasonably significant. The amount of uranium used is of the order of 200-300ng, and the measuring time required is 80 minutes as a whole. Half-life of 234U is evaluated to be 2, 44416×105y.
“Man-made (artificial) urushi”has been prepared by laccase-catalyzed curing of new urushiol analogues, which were facilely synthesized by lipase-catalyzed regioselective acylation of catechol derivatives having a primary alcohol with unsaturated fatty acids derived from plant oils, one of the most important renewable resources. The curing of the catechol derivative having two or three unsaturated group proceeded under mild reaction conditions to produce the crosslinked film (“man-made urushi”) with high hardness and gloss surface, which are comparable with those of natural urushi coating. Similar urushiol analogues from 4-hydroxyphenetyl alcohol and unsaturated fatty acids were subjected to an oxidative polymerization by Fe-salen catalyst, yielding soluble polyphenols having the unsaturated group in the side chain. Cardanol, a phenol derivative mainly having a C15 unsaturated hydrocarbon chain with 1-3 double bonds at m-position, is obtained from cashew nut shell liquid. Oxidative polymerization of cardanol by peroxidase or Fe-salen catalyst gave the crosslinkable polyphenol. These prepolymers were subjected to hardening by thermal treatment or cobalt naphthenate catalyst to give a crosslinked film (also, “man-made urushi”) with good hardness.
We have noticed the presence of cytotoxic activity in the body fluid of a butterfly, Ideopsissimilis, in family Danaidae. The cytotoxic principles were purified and identified to be phenanthroindolizidine alkaloids. In addition, the cytotoxic activity was observed in the leaves of Tylophora tanakae, which is a host plant for caterpillars of I. similis. In the present study, cytotoxic principles in methanol extracts of the leaves against human gastric carcinoma TMK-1 cells were purified by acid-base partition, repeated HPLC and preparative TLC, and two cytotoxic compounds were isolated. From spectroscopic analysis of their structures, they were identified as phenanthroindolizidine alkaloids, trans-(+)-3, 14α dihydroxy-4, 6, 7-trimethoxyphenanthroindolizidine N-oxide and (-)-7-hydroxy-2, 3, 6-trimethoxyphenanthroindolizidine. The amounts of two compounds isolated from 200g of dried leaves were 3.5 and 4.0mg, respectively. These alkaloids are different from those in the fluid of I. similis. When TMK-1 cells were treated with these phenanthroindolizidine alkaloids, strong cytotoxic effects were observed, doses of 6ng/ml for trans-(+)-3, 14α-dihydroxy-4, 6, 7-trimethoxyphenanthroindolizidine N-oxide and 3ng/ml for (-)-7-hydroxy-2, 3, 6-trimethoxyphenanthroindolizidine inducing 50% cell growth inhibition (IC50).