Synthesis of glabridin derivatives as tyrosinase inhibitors.

A novel 3'',4''-dihydroglabridin was successfully prepared for studying on tyrosinase inhibitory activity. The result demonstrated that 3'',4''-dihydroglabridin exhibited higher activity than glabridin (IC(50) value = 11.40 microM), which is probably due to the 4-substituted resorcinol skeleton and the lacking of double bond between carbon atom 3'' and 4'' on its structure giving more conformational flexibily to interact with the enzyme more effectively. In addition, various acylated derivatives were synthesized as glabridin prodrugs. The chemical and enzymatic hydrolysis of prodrugs revealed that the diacetate ester was rapidly hydrolyzed by porcine liver esterase with the half-life of 2.36 minute, while those of the dihexanoate was 14.8 hour. Both of them were sufficiently stable in phosphate buffer, both pH 5.5 and 7.4, at 37 degrees C with more than 15 days half-life.

Flavaglines and triterpenoids from the leaves of Aglaia forbesii.

Three structurally complex flavaglines of the cyclopenta[bc]benzopyran type, named desacetylpyramidaglains A, C, D (1-3), and the triterpene 23, 24, 25-trihydroxycycloartan-3-one (4) were isolated from the leaves of Aglaia forbesii together with the two rare pregnane steroids 2beta,3beta-dihydroxy-5alpha-pregn-17(Z)-en-16-one and 2beta,3beta-dihydroxy-5alpha-pregn-17(E)-en-16-one, as well as the bisamide pyramidatine, the sesquiterpene spathulenol, and the widespread triterpenoids lupeol, lupenone, and a mixture of beta-sitosterol and stigmasterol. Their structures were elucidated by 1D and 2D NMR spectroscopy and mass spectrometry. Compounds 3, 4, 5, and 6 were tested for antituberculosis and antiviral activity.

A new sesquiterpene and other terpenoid constituents of Chisocheton penduliflorus.

A new aromadendrane sesquiterpene, allo-aromadendrane-10alpha, 14-diol (3), was isolated from Chisocheton penduliflorus (Meliaceae), along with two known sesquiterpenes: allo-aromadendrane-10beta, 14-diol (2) and allo-aromadendrane-10beta, 13, 14-triol (7). Six dammarane triterpenoids, including cabraleadiol (1), eichlerialactone (4), cabraleahydroxylactone (5), cabralealactone (6), hollongdione (8) and dammaradienone (9), the coumarins scoparone and scopoletin, and vanillic acid were also isolated from the wood and leaves of this plant. Compounds 1-7 displayed antimycobacterial activity against Mycobacterium tuberculosis. Compounds 1, 4, 5 and 6 were weakly cytotoxic to a breast cancer (BC) cell line; whereas, compound 6 was moderately active against a small-cell lung cancer (NCI-H187) cell line.

Biologically active constituents of Aglaia erythrosperma.

From the fruits and leaves of Aglaia erythrosperma (Meliaceae), 10 chemical constituents were isolated and identified, i.e. the dammarane triterpenoids cabraleadiol (1), cabraleahydroxylactone (2), ethyl eichlerianoate (3), eichlerialactone (4), aglinin A (5), cabralealactone (6), the aglaialactone 5,6-desmethylenedioxy-5-methoxy-aglalactone (7), the flavagline 4'-demethoxy-3',4'-methylenedioxy-methyl rocaglate (8) and two coumarins: scoparone and scopoletin. Flavagline 8 exhibited antimalarial activity with an IC(50) value of 7.30 µg mL(-1) and was strongly cytotoxic against small cell lung cancer (NCI-H187), epidermoid carcinoma (KB) and breast cancer (BC) cell lines, with IC(50) values of 2.17, 2.10 and 0.11 µg mL(-1), respectively. Aglinin A (5) displayed moderate cytotoxicity against all the three cancer cell lines, whereas ethyl eichlerianoate (3), cabralealactone (6) and the aglaialactone 7 were exclusively cytotoxic to NCI-H187 cell line. Cabraleahydroxylactone (2) showed antiviral activity against herpes simplex virus type-1 with an IC(50) value of 3.20 µg mL(-1), in comparison with the standard acyclovir (IC(50) = 1.90 µg mL(-1)). When tested for antimycobacterial activity against Mycobacterium tuberculosis H(37)Ra, compounds 1-4 and 6-8 displayed minimum inhibitory concentration in the range of 25-50 µg mL(-1).

In vitro antimalarial activity of prenylated flavonoids from Erythrina fusca.

Ethyl acetate (EtOAc) extract from the stem bark of Erythrina fusca showed a antimalarial activity against the multi-drug-resistant strain (K1) of Plasmodium falciparum, and six flavonoids, lupinifolin (1), citflavanone (2), erythrisenegalone (3), lonchocarpol A (4), liquiritigenin (5), and 8-prenyldaidzein (6), were isolated from the extract. Diprenylated flavanone 4 showed a notable antimalarial activity (IC(50); 1.6 microg/mL); however 1 and 3 did not show the activity, even though these compounds possessed prenylated substitution.