ent-Clerodane diterpenoids from the stems of Croton krabas.

The first phytochemical investigation from the stems of Croton krabas resulted in the isolation of three new ent-clerodane diterpenoids, crotonkrabases A-C (1-3), along with two known compounds, 12-oxohardwickiic acid (4) and crotonpyrone B (5). Their structures were elucidated using extensive spectroscopic methods. The structure of 3 was unambiguously proven by X-ray crystallography. Furthermore, the absolute configurations of compounds 1-3 were identified by NOESY and the comparison of their experimental ECD spectra with those of calculated ECD spectra reported in the literature. Compounds 1, 2, and 5 showed antibacterial activities against two Gram-positive bacteria (Bacillus cereus and Bacillus subtilis); whereas compound 4 exhibited weak antibacterial against B. cereus. In addition, compound 4 showed potent α-glucosidase inhibitory activity, which was lower than the reference standard acarbose.

Bioactive galloyl flavans from the stems of Helixanthera parasitica.

Three new flavans, (2S)-7-O-galloyl-5,3',4'-trihydroxyflavan (1), (2S)-7,3'-O-digalloyl-5,4'-dihydroxyflavan (2), and (2S)-7,4'-O-digalloyl-5,3'-dihydroxyflavan (3), together with four known compounds, (2S)-5,7,3',4'-tetrahydroxyflavan (4), (-)-epicatechin (5), (-)-syringaresinol (6), and methyl gallate (7) have been isolated from the EtOAc extract of the stems of Helixanthera parasitica. Compounds 2 and 3 were obtained as a mixture of positional isomers. The structures of the isolated compounds were established using extensive spectroscopic data. Compound 1 and the mixture of 2 and 3 exhibited significant antimalarial activity against Plasmodium falciparum, with IC50 values of 0.59 and 1.38 µM, respectively. In addition, flavans 1-3 showed cytotoxicity against KB, MCF-7, and NCI-H187 cancer cell lines, with IC50 values in the range of 11.1-30.0 µM.

Mycotoxins from the Fungus Botryotrichum piluliferum.

Two new sterigmatocystin derivatives, oxisterigmatocystins E and F (1 and 2, respectively), along with nine known compounds, oxisterigmatocystins G and H (3 and 4, respectively), sterigmatocystin (5), N-0532B (6), O-methylsterigmatocystin (7), N-0532A (8), 6-O-methylversicolorin A (9), 6,8-O-dimethylversicolorin A (10), and 8-O-methylaverufin (11), were isolated from the fungus Botryotrichum piluliferum. The structures of these mycotoxins were elucidated by spectroscopic evidence. Among these, compounds 3, 4, and 9 were discovered as natural products for the first time. Compounds 1, 3, and 4 displayed antimalarial activity toward Plasmodium falciparum (IC50 = 7.9-23.9 µM). In addition, compounds 1-6 and 8-11 exhibited cytotoxicity against KB, MCF-7, and NCI-H187 cell lines (IC50 = 0.38-78.6 µM). However, compounds 1-9 showed cytotoxic effects against the Vero cell line (IC50 = 0.65-12.3 µM). This finding should promote awareness of the contamination of B. piluliferum in the food chain and agricultural soil.

Chevalone C analogues and globoscinic acid derivatives from the fungus Neosartorya spinosa KKU-1NK1.

Four meroterpenoids, 1-hydroxychevalone C, 1-acetoxychevalone C, 1,11-dihydroxychevalone C, and 11-hydroxychevalone C and two ester epimers, 2S,4S-spinosate and 2S,4R-spinosate, together with seven known compounds, chevalones B, C, and E, tryptoquivaline, nortryptoquivaline, tryptoquivaline L, and quinadoline A were isolated from the fungus Neosartorya spinosa. Their structures were established based on spectroscopic data analyses. The theoretical ECD spectra of epimers, 2S,4S-spinosate and 2S,4R-spinosate were calculated to support the experimental results of their CD spectra. 1-hydroxychevalone C exhibited antimycobacterial activity against Mycobacterium tuberculosis with a MIC value of 26.4 µM. 1-Acetoxychevalone C and tryptoquivaline showed antimalarial activity against Plasmodium falciparum with IC50 values of 6.67 and 2.65 µM, respectively. In addition, 1-hydroxychevalone C, 1-acetoxychevalone C, 1,11-dihydroxychevalone C and quinadoline A showed cytotoxicity against KB and NCI-H187 cancer cell lines with IC50 values in the range of 32.7-103.3 µM.

Bioactive depsidones from the fungus Pilobolus heterosporus.

A new aromatic ester, pilobolusate (1), four new depsidones, pilobolusones A-D (2-5), five known depsidones, (6-10), and ergosterol were isolated from the fungus Pilobolus heterosporus. Their structures were established on the basis of spectroscopic data. Compounds 2 and 4-9 showed cytotoxicity against three cancer cell lines (KB, MCF-7, and NCI-H187) with IC50 values in the range of 9.94-97.42 µM. In addition, compounds 2, 5, 9, and 10 exhibited antimalarial activity against Plasmodium falciparum with IC50 values ranging from 3.67-23.56 µM.

Chemical constituents and biological activities from roots of Enkleia siamensis.

Chemical investigation from roots of Enkleia siamensis (Kurz) Nervling resulted in the isolation of 10 compounds. Their structures were established on the basis of 1D and 2D NMR spectroscopic data as linobiflavonoid (1), chamaejasmin (2), 7-O-ß-D-glucopyranosylchamaejasmin (3), ormocarpin (4), (-)-wikstromol (5), matairesinol (6), (+)-lariciresinol (7), umbelliferone (8), daphnoretin (9) and carthamidin (10). Compounds 2 and 8 showed cytotoxicity against KB, MCF-7 and NCI-H187 cancer cell lines. Compounds 1, 2 and 5 showed weak minimum inhibitory requirements to acetylcholinesterase with values ranging from 50 to 1000 ng. In addition, compound 2 exhibited antimalarial activity against Plasmodium falciparum with an IC50 value of 2.32 µg/mL.