Surachai Pornpakakul

Cytotoxic activity of four xanthones from Emericella variecolor, an endophytic fungus isolated from Croton oblongifolius.

Four xanthones were isolated from mycelia ofEmericella variecolor, an endophytic fungus isolated from the leaves ofCroton oblongifolius. Their structures were elucidated by spectroscopic analysis to be shamixanthone, 14-methoxytajixanthone-25-acetate, tajixanthone methanoate, and tajixanthone hydrate. All compounds were tested for cytotoxic activity against various human tumor cell lines including gastric carcinoma, colon carcinoma, breast carcinoma, human hepatocarcinoma, and lung carcinoma. The antitumor activities of these xanthones were compared with that of doxorubicin hydrochloride, a chemotherapeutic substance. All of them showed moderate activities and were selective against gastric carcinoma, colon carcinoma, and breast carcinoma. Only tajixanthone hydrate exhibited moderate activity against all cancer cell lines. Furthermore, under the test conditions it was found that 14-methoxytajixanthone-25-acetate and tajixanthone hydrate are almost as active as doxorubicin hydrochloride against gastric carcinoma (KATO3) and breast carcinoma (BT474).

Biotransformation of ent-kaur-16-en-19-oic acid by Psilocybe cubensis

Biotranformation of ent-kaur-16-en-19-oic acid (1) using Psilocybe cubensis resulted in hydroxylated products. After two days of incubation, ent-16β,17-dihydroxy-kauran-19-oic acid (2) was isolated. After further incubation for nine days, two novel metabolites, ent-12α,16β,17-trihydroxy-kauran-19-oic acid (3) and ent-11α,16β,17-trihydroxy-kauran-19-oic acid (4), were obtained. The metabolites were identified by spectroscopic methods and X-ray crystallography. Compounds 1–4 were evaluated for their cytotoxic properties against the human leukaemia K562 cell line; only compound 1 showed moderate activity.

A new sesquiterpenoid metabolite from Psilocybe samuiensis

A novel 2,3-secoaromadendrane-type sesquiterpenoid metabolite, psilosamuiensin A (1), was isolated from the broth of Psilocybe samuiensis. The structure of psilosamuiensin A was established by spectroscopic data and its configurations were confirmed by single crystal X-ray crystallographic analysis. This is the first report of psilosamuiensin A found in the genus Psilocybes.

New cleistanthane diterpenoids and 3,4- seco -cleistanthane diterpenoids from Croton oblongifolius

Two new cleistanthane-type diterpenoids, 3-hydroxycleistantha-13(17),15-diene (1) and 3,4-seco-cleistantha4(18),13(17),15-trien-3-oic acid (2), were isolated from the stem bark of Croton oblongifolius Roxb. Epoxidation of 2 gave two epoxides 3 and 4. Their structures were established on the basis of spectroscopic data. Compound 1 showed nonspecific strong cytotoxicity against human tumor cell lines, compound 2 showed weak activity, and compounds 3 and 4 were inactive.

Pregnane-type steroidal glycosides from Gymnema griffithii Craib.

Eight pregnane-type steroidal glycosides substituted with ortho-acetate groups were isolated from the methanolic extract of the pericarp of Gymnema griffithii fruits, and named gymnemogriffithosides A-H. Their structures were determined by spectroscopic analysis (one and two dimensional nuclear magnetic resonance, high resolution electrospray ionization mass spectrometry and attenuated total reflectance-Fourier transformed infrared spectroscopy), while the absolute structure of the steroidal skeleton of one of these was additionally determined using Moshers method. All compounds were evaluated for their in vitro (i) cytotoxic effects against five human tumor cell lines (BT 474, Chago, Hep-G2, KATO-III and SW620) and (ii) α-glucosidase inhibitory activity.

seco-Kaurane skeleton diterpenoids from Croton oblongifolius

A new seco-kaurane type diterpenoid, ent-3,4-seco-17-oxo-kaur-4(19),15(16)-dien-3-oic acid, and a known compound, ent-3,4-seco-kaur-4(19),16(17)-dien-3-oic acid, were isolated from the stem bark of Croton oblongifolius. The structures of these compounds were established on the basis of spectroscopic data.

(4S,5S,6S)-4-Hy­droxy-3-meth­oxy-5-methyl-5,6-ep­oxy­cyclo­hex-2-en-1-one

The title compound, C(8)H(10)O(4), was isolated from culture extracts of the endophytic fungus Xylaria sp. (PB-30). The cyclo-hexenone ring exhibits a flattened boat conformation. In the crystal structure, mol-ecules related by translation along the b axis are linked into chains through O-H⋯O hydrogen bonds. Weak non-classical C-H⋯O contacts are also observed in the structure.

In vitro and in vivo characterization of the anticancer activity of Thai stingless bee (Tetragonula laeviceps) cerumen.

Tetragonula laeviceps cerumen was sequentially extracted with 80% (v/v) methanol, dichloromethane, and hexane and also in the reverse order. By the MTT assay and the respective 50% inhibition concentration value, the most active fraction was further purified to apparent homogeneity by bioassay-guided silica gel column chromatography. α-Mangostin was identified by high-resolution electrospray ionization mass spectrometry and nuclear magnetic resonance analyses. It had a potent cytotoxicity against the BT474, Chago, Hep-G2, KATO-III, and SW620 cell lines (IC50 values of 1.22 ± 0.03, 2.25 ± 0.20, 0.94 ± 0.01, 0.88 ± 0.16, and 1.50 ± 0.39 µmol/L, respectively). The in vitro cytotoxicity of α-mangostin against the five human cancer cell lines and primary fibroblasts was further characterized by real-time impedance-based analysis. Interestingly, α-mangostin was more cytotoxic against the cancer-derived cell lines than against the primary fibroblasts. Later, the migration assay was performed by continuously measuring the attachment of cells to the plate electrodes at the bottom of the transwell membrane. The combined caspase-3 and -7 activities were assayed by the Caspase-Glo® 3/7 kit. It showed that the cytotoxic mechanism involved caspase-independent apoptosis, while at low (non-toxic) concentrations α-mangostin did not significantly alter cell migration. Furthermore, the in vivo cytotoxicity and angiogenesis were determined by alkaline phosphatase staining in zebrafish embryos along with monitoring changes in the transcript expression level of two genes involved in angiogenesis (vegfaa and vegfr2) by quantitative real-time reverse transcriptase- polymerase chain reaction. It was found that the in vivo cytotoxicity of α-mangostin against zebrafish embryos had a 50% lethal concentration of 9.4 µM, but no anti-angiogenic properties were observed in zebrafish embryos at 9 and 12 µM even though it downregulated the expression of vegfaa and vegfr2 transcripts. Thus, α-mangostin is a major active compound with a potential anticancer activity in T. laeviceps cerumen in Thailand.

8-[(3,3-Dimethyl-oxiran-2-yl)methoxy-meth-yl]-11-hydr-oxy-2-isopropenyl-5-methyl-12-oxo-1,2,3,12-tetra-hydro-pyrano[3,2-a]xanthen-1-yl acetate.

The title compound, commonly known as 14-methoxytajixanthone-25-acetate, C28H30O8, was isolated from Emericella variecolor. The central xanthone core is approximately planar (r.m.s. deviation = 0.084 Å). The dihydropyran ring adopts a distorted half-chair conformation. The oxirane plane is oriented at an angle of 63.3 (2)° with respect to the phenol group. An intramolecular O—H⋯O hydrogen bond forms an S(6) ring. In the crystal, molecules are linked into a two-dimensional network parallel to the ab plane by weak intermolecular C—H⋯O hydrogen bonds.