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Clausena excavata is a medicinal plant widely distributed in Southeast Asia. It is used for a variety of indications, including to treat malaria. In our present study, a phytochemical study of the methanol extract from the stem bark of C. excavata led to the isolation of five pyranocoumarins, nordentatin (1), dentatin (2), kinocoumarin (3), clausarin (4), and clausenidin (5), and a coumarin, 8-hydroxy-3″,4″-dihydrocapnolactone-2′,3′-diol (6). The isolation of compound 6 from C. excavata and the antiplasmodial activities against a multidrug-resistant K1 strain of Plasmodium falciparum of 1, 3 , and 5 were reported for the first time. Compounds 3 and 4 exhibited potent antiplasmodial activities with EC50 values of 1.10 and 0.58 µM, respectively, while 1 and 5 had EC50 values of 5.62 and 7.15 µM, respectively. A prenyl group attached to the C-3 or C-12 position on the pyranocoumarin ring probably plays an important role on the activity. A hydroxyl group at the C-10 position is also likely to enhance the activity. [ABSTRACT FROM AUTHOR]

Eight new compounds, fimbricalyxs B–D (1–3), fimbricalyxanhydrides A and B (4, 5), and fimbricalyxlactones A–C (6–8), together with three known compounds, trigonostemone (9), 3,6,9-trimethoxyphenanthropolone (10), and fimbricalyx A (11), were isolated from the roots of Strophioblachia fimbricalyx. The structures of the new compounds were elucidated on the basis of their spectroscopic data and, in the case of compounds 2, 4, and 7, confirmed by single-crystal X-ray crystallographic analysis. Compounds 1–4and 8were evaluated for their cytotoxicity (KB, MCF7, and NCI-H187 cancer cells) and antiplasmodial activity (Plasmodium falciparum, K1 multidrug-resistant strain). Fimbricalyx B (1) exhibited potent antiplasmodial activity with an IC50value of 0.019 μM, while 4was cytotoxic toward NCI-H187 cancer cells and showed antiplasmodial activities with IC50values of 5.7 and 3.9 μM, respectively. In addition, the X-ray structure of 10and the antiplasmodial activity of 11are reported herein for the first time.

Three new compounds, ferruginenes A (1) and B (2) and a mixture of C-5′(R) and C-5′(S) ferruginene C (3) diastereomers, have been isolated from a cytotoxic chloroform-soluble fraction of the leaves of Rhododendron ferrugineumtogether with 12 known compounds. The structures of these new compounds were elucidated by analyses of NMR spectroscopic and mass spectrometric data. Compounds 1−3were tested for their cytotoxicity against three human cancer cell lines, namely, HL-60, HeLa-S3, and MCF-7.

The known phenanthrenone trigonostemone (1), along with a new phenanthrenone, 9-O-demethyltrigonostemone (2), and two new phenanthropolones, 3,6,9-trimethoxyphenanthropolone (3) and 4,6,9-trimethoxyphenanthropolone (4), were isolated from the roots of Strophioblachia fimbricalyx. Compound 2showed cytotoxicity against NCI-H187, KB, and MCF7 cancer cells with IC50values of 0.8, 0.8, and 2.9 μg/mL, respectively, while 3and 4showed reduced cytotoxicity. Compounds 2and 3displayed antiplasmodial activity in vitro (IC50values of 2.7 and 3.2 μg/mL, respectively) against Plasmodium falciparum(K1, resistant strain). In addition, the antioxidant activity of 1−4toward DPPH radicals was determined, but only compound 2showed any discernible activity.

An unusually bridged epidithiodiketopiperazine, pretrichodermamide A (3), was isolated from the fungus Trichoderma sp. BCC 5926. During the extensive effort to crystallize 3for X-ray crystallographic analysis, conversion of this compound to trichodermamide A with coproduction of S8occurred.

Cordytropolone (1) and (−)-leptosphaerone A (2) were isolated from the culture broth of the fungus Polycephalomyces nipponicus. The structures of these two compounds were elucidated by spectroscopic methods and from a comparison of the spectroscopic data with those reported previously. The structure of 1was confirmed by X-ray crystallography for the first time while the leptosphaerone class (compound 2) was first isolated as its (+)-antipode from the fungus Polycephalomyces(Cordyceps). The fermentation process was monitored weekly by High performance liquid chromatography analysis for 10 weeks. The predominant compound (1) was produced at ~0.65 mg/mg of dry extract at week 9. Compound 1exhibited modest antipathogenic fungal activity against Collectrichum musae, Colletotrichum capsici, Colletotrichum gloeosporioides, Fusariumspp. TFPK301, F. spp. FOC1708, and Pestalotiaspp. with percentage of mycelial growth inhibition values of 3.74 ± 0.70%, 12.86 ± 1.43%, 0.91 ± 0.56%, 5.46 ± 0.56%, 7.93 ± 0.61%, and 18.75 ± 5.24%, respectively, at 25 μg/mL.

In the courses of our search for bioactive natural products on TRAIL resistance-overcoming activity, the active EtOAc extract from the bark of Celtis tetrandrawas chemically investigated. The fractionation of the extract resulted in the isolation of flavanols; (+)-afzelechin (1), (-)-epiafzelechin (2), (-)-catechin (3), and two new flavanol dimers; (-)-epiafzelechin-(4α→8)-(-)-catechin (4) and (-)-epiafzelechin-(4α→8)-(-)-epicatechin (5). All isolated compounds 1-5were tested for their TRAIL resistance-overcoming activity against AGS cells at the concentrations from 5–20 μM. It is likely that the flavanol dimers 4and 5exhibited weak activity in the range of the concentration of 10–20 μM as compared with the standard.

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