Isolation and HPLC Quantitative Determination of 5α-Reductase Inhibitors from Tectona grandis L.f. Leaf Extract.

Steroid 5α-reductase plays a crucial role in catalyzing the conversion of testosterone to dihydrotestosterone, which is involved in many androgen-dependent disorders. Leaf-hexane extract from Tectona grandis L.f. has shown promise as a 5α-reductase inhibitor. The objectives of this current study were to isolate and identify 5α-reductase inhibitors from T. grandis leaves and to use them as the bioactive markers for standardization of the extract. Three terpenoid compounds, (+)-eperua-8,13-dien-15-oic acid (1), (+)-eperua-7,13-dien-15-oic acid (2), and lupeol (3), were isolated and evaluated for 5α-reductase inhibitory activity. Compounds 1 and 2 exhibited potent 5α-reductase inhibitory activity, while 3 showed weak inhibitory activity. An HPLC method for the quantitative determination of the two potent inhibitors (1 and 2), applicable for quality control of T. grandis leaf extracts, was also developed. The ethanolic extract showed a significantly higher content of 1 and 2 than found in the hexane extract, suggesting that ethanol is a preferable extraction solvent. This study is the first reported isolation of 5α-reductase inhibitors (1 and 2) from T. grandis leaves. The extraction and quality control methods that are safe and useful for further development of T. grandis leaf extract as an active ingredient for hair loss treatment products are also reported.

Chemical constituents and antibacterial activity from the stems and leaves of Piper wallichii.

A phytochemical investigation of the stems and leaves of Piper wallichii led to the isolation of two new compounds, an aryl alkanone, piwalkanone (1) and a dioxoaporphine alkaloid, piwallidione (2), together with nine known compounds, a dioxoaporphine alkaloid, cepharadione A (3); two aristolactams, piperolactam A (4) and stigmalactam (5); a piperidine, piperine (6); four isobutylamides, piperlonguminine (7), pellitorine (8), N-isobutyl-2E,4E-octadecadienamide (9), and guineensine (10); and a tyramine, N-trans-feruloyltyramine (11). Their structures were elucidated on the basis of spectroscopic evidence (IR, 1H NMR, 13C NMR and 2 D NMR) and MS. Compounds 2 and 3 showed inhibitory activities against pathogenic bacteria, Bacillus cereus, Bacillus subtilis and Staphylococcus aureus.

A new antibacterial tirucallane from Walsura trichostemon roots.

Phytochemical investigation of the roots of Walsura trichostemon, a Thai medicinal plant, provided a new tirucallane, 3-epimesendanin S 12-acetate (1), together with four known compounds, 3-epimesendanin S (2), meliasenin G (3), ß-sitosterol (4) and ß-sitosterol glucoside (5). Their structures were characterized by intensive spectroscopy including 1 D and 2 D NMR, UV, IR and MS spectrometric analysis. The isolated compounds were evaluated for antibacterial and acetylcholinesterase inhibitory activities. Compounds 1-2 showed antibacterial activity against Bacillus cereus and Bacillus subtilis with MIC values ranging from 16-128 µg/mL. In addition, compound 3 was active against Pseudomonas aeruginosa and Escherichia coli with MIC values of 64 and 128 µg/mL, respectively.

Spirosteroids and α-glucosidase inhibitory norlignans from Asparagus racemosus Willd. roots.

Three undescribed spirosteroids, asparacemosones A-C, an undescribed spiro-21-norsteroid, asparacemosone D, along with seven known compounds were isolated from Thai herbal plant Asparagus racemosus Willd. roots. Their structures were elucidated by spectroscopic analysis including NMR, UV, IR and mass spectrometry. The absolute configurations of asparacemosones A, B, and D were determined by single crystal X-ray diffraction using CuKα radiation. Among the isolated compounds, the norlignan nyasol and three acetylenic norlignans demonstrated potent α-glucosidase inhibition, with IC50 values ranging from 0.003 to 0.004 µM which is 5 × 104 fold more potent than the standard acarbose.

Bioactive homogentisic acid derivatives from fruits and flowers of Miliusa velutina.

Chromatographic separation of fruits and flowers of the Thai medicinal plant, Miliusa velutina, resulted in the isolation of five new rare homogentisic acid derivatives, miliusanal (1) and miliusanones A-D (2-5), together with fifteen known secondary metabolites (6-20). Their structures were determined through the use of extensive spectroscopic data. The absolute configurations of homogentisic acid derivatives 2-7 were identified using NOESY data and a comparison of experimental and calculated ECD spectral data. Compounds 2, 3, 6, and 7 showed antimalarial activity with IC50 values in the range of 3.3-5.2 µg/mL. Compound 6 also showed activity against Mycobacterium tuberculosis with an MIC value of 50 µg/mL. Compounds 1-3, 6 and 7 exhibited cytotoxicity againt KB, MCF-7, NCI-H187 and Vero cell lines with IC50 values in the range of 5.8-40.4 µg/mL. In addition, compounds 1, 2 and 6 showed moderate antibacterial activities against three Gram-positive bacteria (Bacillus cereus, Staphylococcus aureus, and Methicillin resistant S. aureus) with MICs in the range of 32-64 µg/mL.

Antibacterial carbazole alkaloids from Clausena harmandiana twigs.

Three new carbazole alkaloids, harmandianamines A-C (1-3), together with fifteen known compounds (4-18) were isolated from the twigs of Clausena harmandiana. The structures were elucidated by spectroscopic methods, including UV, IR, NMR, and MS. The antibacterial activity against Escherichia coli TISTR 780, Salmonella typhimurium TISTR 292, Staphylococcus aureus TISTR 1466 and methicillin-resistant S. aureus (MRSA) SK1 of some isolated compounds was also evaluated. Compound 6 exhibited significant antibacterial activity against MRSA SK1 with an MIC value of 0.25 µg/mL which higher than that of standard drug, vancomycin (MIC value=1 µg/mL) whereas compounds 14 and 5 showed strong activity with MIC values of 4 and 8 µg/mL, respectively. Only compound 14 showed strong antibacterial activity against S. aureus TISTR 1466 with an MIC value of 4 µg/mL.

Antibacterial dihydrobenzopyran and xanthone derivatives from Garcinia cowa stem barks.

Two new compounds, garciniacowol (1) and garciniacowone (2) along with 15 knowncompounds were isolated from the stem barks of Garcinia cowa. Their structures weredetermined by intensive spectroscopic methods. The structure of 1 was a symmetrical dimericdihydrobenzopyran derivative, whereas the framework of 2 was a triprenyl caged-xanthoneprecursor. The antibacterial activities against Escherichia coli TISTR 780, Salmonellatyphimurium TISTR 292, Staphylococcus aureus TISTR 1466, and methicillin-resistant S. aureus(MRSA) SK1 of the isolated compounds were also evaluated. Compounds 2 and 9 exhibitedgood antibacterial activity against MRSA SK1 with the same minimum inhibitory concentration(MIC) value of 2 µg/mL. Moreover, compound 2 also showed good antibacterial activityagainst S. aureus with an MIC value of 2 µg/mL.