Yuko Takemura

Inhibitory effect of flavonoid derivatives on Epstein–Barr virus activation and two-stage carcinogenesis of skin tumors

To search for possible anti-tumor promoters, ten flavonoid derivatives (1-10) synthesized from morin and quercetin were examined for their inhibitory effects on the Epstein-Barr virus early antigen (EBV-EA) activation by a short-term in vitro assay. Of these compounds, pentaallyl ethers (9, 10) showed significant inhibitory effects on EBV-EA activation induced by the tumor promoter, 12-O-tetradecanoylphorbol 13-acetate. Further, quercetin pentaallyl ether (10) exhibited remarkable inhibitory effects on mouse skin tumor promotion in an in vivo two-stage carcinogenesis test.

Acridones as inducers of HL-60 cell differentiation.

Fifteen acridone alkaloids were examined for their activity of induction of human promyelocytic leukemia cell (HL-60) differentiation. HL-60 cells were differentiated into mature monocyte/macrophage by atalaphyllidine (9), atalaphyllinine (12), and des-N-methylnoracronycine (13). The activities of NBT reduction, nonspecific esterase, and phagocytosis, were induced by 2.5 microM of 9, 12, and 13. After a 4-day treatment, 9, 12, and 13 at 10 microM inhibited clonal proliferation of HL-60 cells by 28, 96, and 63%, respectively. The structure-activity relationship established from the results revealed that hydroxyl group at C-1 and prenyl group at C-2 had an important role.

Inhibitory effect of Epstein–Barr virus activation by Citrus fruits, a cancer chemopreventor

To search useful compounds in Citrus fruit for cancer chemoprevention, we carried out a primary screening of extracts of fruit peels and seeds from 78 species of the genus Citrus and those from two Fortunella and one Poncirus species, which were closely related to the genus Citrus. These Citrus extracts inhibited the Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol 13-acetate (TPA) as a useful screening method for anti-tumor promoters. Our results indicated that Citrus containing substances may be inhibit susceptibility factors involved in the events leading to the development of cancer.

New acridone alkaloids from Citrus plants

The spectroscopic structure elucidations of five new acridone alkaloids named yukocitrine (1), yukodine (3), Yukodinine (4), grandisine-III (6) and pummeline (7) from some Citrus plants were described

Two New Bicoumarins from Clausena excavata

Two novel type bicoumarins, named cladimarins A (1) and B (4), were isolated from the branch of Clausena excavata (Rutaceae) collected in Indonesia. The structures were elucidated on the basis of spectroscopical data especially by using HMBC method. Naturally occurring bicoumarin, connected two coumarin moieties by acetal ring as in 1 and by ester bond as in 4, is rare type. Inhibitory effects of new bicoumarins on EBV-EA activation induced by TPA in Raji cells were also demonstrated.

New Acrimarines from Citrus Plants

Five new acrimarines (acridone-coumarin dimers) were isolated from some Citrus plants (Rutaceae) and their structures were elucidated by spectroscopic method

New acridone alkaloids from Citrus yuko

From the root barks of Citrus yuko (Rutaceae), two new acridone alkaloids, named yukomine and citracridone-III, were isolated and their structures were elucidated as 1 and 2 on the basis of spectroscopic data

Three new acridone-coumarin dimers from a Citrus plant

Three new acridone-coumarin dimers, named dioxinoacrimarine-A (1), neo- acrimarine-E (2) and acrimarine-N (3) were isolated from the roots of Citrus plant and their structures were elucidated on the basis of spec- troscopic methods

Two novel acridone-coumarin dimers, neoacrimarines-A and -B, from citrus plants

Two novel acridone-coumarin dimers, named neoacrimarines-A (1) and -B (2), were isolated from the roots of Citrus plants and their structures were elucidated by spectroscopic method

Structure of bisclausarin, a new bicoumarins from Citrus plant

A new type bicoumarin, named bisclausarin, was isolated from the roots of Citru hassaku (Rutaceae) and the structure was elucidated as 1 on the basis of spectroscopic data