Mitsuru Hirota

Epstein-Barr virus activation by tung oil, extracts of Aleurites fordii and its diterpene ester 12-O-hexadecanoyl-16-hydroxyphorbol-13-acetate

During the screening of plant oils for their Epstein-Barr virus (EBV)-activating potency, we found that tung oil possesses an activity comparable to croton oil. Tung oil from various sources and the extracts from its parental plant Aleurites fordii (Chinese tung oil tree), when used in combination with n-butyrate, were shown to efficiently activate EBV persisting in human lymphoblastoid Raji cells (non-producer). The major diterpene ester in the plant extract, 12-O-hexadecanoyl-16-hydroxyphorbol-13-acetate (HHPA), also exerted a similar activity. In producer P3HR-1 cells, both tung oil and HHPA increased the yield of infectious EBV by approximately five-fold. Since tung oil is used for the manufacture of oil paints, varnishes, waterproof substance, anticorrosives and other products, the implication of using such an agent with EBV-activating potency in our daily life is assessed and discussed.

Bitter cyanoglucosides from Lophira alata

Abstract Four bitter compounds, lophiroside A1, A2, B1 and B2, were isolated from the bark of Lophira alata , and their structures were determined by chemica

Formation of a new toxic compound, citrinin H1, from citrinin on mild heating in water

Citrinin, a relatively weak mycotoxin, can be detoxified by heating; however, a compound having high toxicity was formed on heating at 140 °C in the presence of water. The toxic compound was isolated from heated citrinin and its structure was determined. Its toxicity, evaluated by cytotoxicity assay, was 10-fold higher on a weight basis than that of citrinin. This new compound was named citrinin H1, which was also formed by heating citrinin at 100 °C for 30 min.

Possible anti-tumour promoters: bi- and tetraflavonoids from Lophira alata

Abstract Three possible flavonoid-type anti-tumour promoters were isolated from the bark of Lophira alata using an in vitro short-term assay, Epstein-Barr virus (EBV) early antigen (EA) induction test. One of the flavonoids was identified as lophirone F. The other two, named azobechalcone A and isolophirachalcone, were a new biflavonoid and a tetraflavonoid, respectively. Azobechalcone A (5 μM) and isolophirachalcone (5 μM) showed potent inhibitory activities (83% and 65%, respectively) against EBV-EA induction by a tumour promoter, teleocidin B-4 (50 nM). Lophirone F was less active (18% at the same dose) than azobechalcone A and isolophirachalcone.

Relationship between ornithine decarboxylase-inducing activity and configuration at C-4 in phorbol ester derivatives

SummaryMeasurements were made of induction of ornithine decarboxylase activity after painting mouse skin with 12-O-hexadecanoyl-16-hydroxyphorbol-13-acetate and its two epimeric 4-deoxy-analogs, 12-O-hexadecanoyl-4-deoxy-16-hydroxyphorbol-13-acetate and 12-O-hexadecanoyl-4-deoxy-4α-16-hydroxyphorbol-13-acetate. The inductive activities of HHPA and 4-deoxy-HHPA were similar, but 4-deoxy-4α-HHPA had no inductive activity. These findings on natural phorbol esters confirm that both the 4β-hydrogen and the 4β-hydroxyl in phorbol esters are essential for ODC-inducing activity. The interactions of 4-deoxy-HHPA and 4-deoxy-4α-HHPA with a possible receptor are discussed.