Suwanna Deachathai

Bioactive Carbazole Alkaloids from Clausena wallichii Roots

Four new carbazole alkaloids, clausenawallines C-F (1-4), along with 18 known compounds (5-22) were isolated from the roots of Clausena wallichii. Compounds 3, 9, and 22 exhibited significant antibacterial activity against methicillin-resistant Staphylococcus aureus SK1 (MRSA SK1) and Staph. aureus TISTR 1466 with MIC values in the range 4-16 μg/mL, whereas compound 4 showed the highest cytotoxicity against oral cavity cancer (KB) and small-cell lung cancer (NCI-H187) with IC(50) values of 10.2 and 4.5 μM, respectively.

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.

Rapid antioxidant capacity screening in herbal extracts using a simple flow injection-spectrophotometric system

A simple flow injection (FI)-spectrophotometric system for the screening of antioxidant capacity in herbal extracts was developed. The analysis was based on the color disappearance due to the scavenging of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical by antioxidant compounds. DPPH and ascorbic acid were used as reagent and antioxidant standard, respectively. Effects of the DPPH concentration, DPPH flow rate, and reaction coil length on sensitivity were studied. The optimized condition provided the linear range of 0.010-0.300mM ascorbic acid with less than 5%RSD(n=10). Detection limit and quantitation limit were 0.004 and 0.013mM, respectively. Comparison of antioxidant capacity in some herbal extracts determined by the FI system and a standard method was carried out and no significant difference was obtained.

Antibacterial compounds from Zanthoxylum rhetsa

A new amide, zanthorhetsamide (1), along with nine known compounds (2–10) was isolated from the roots and stem barks of Zanthoxylum rhetsa. The structure was characterized by spectroscopic methods. In addition, the antibacterial activity of the isolates was evaluated. Dihydrochelerythrine (4) exhibited strong activity against methicillin-resistant Staphylococcus aureus SK1 and moderate activity against Escherichia coli TISTR 780 with MIC values of 8 and 16 μg/mL, respectively.

Phenolic compounds from the seeds of Garcinia dulcis

Dulcisxanthone G, 1,3,6-trihydroxy-2-(2,3-dihydroxy-3-methylbutyl)-7-methoxy-8-(3-methyl-2-butenyl)xanthone, together with 13 known compounds were isolated from the seeds of Garcinia dulcis. Their structures were determined by analysis of 1D and 2D NMR spectroscopic data. The activities on antibacterial and antioxidation of the isolated compounds were examined.

Antibacterial and Antioxidative Compounds from Oroxylum indicum

Plants are the largest reservoir of secondary metabolites that contribute to combating different diseases from ancient times [1]. Oroxylum indicum (L.) Benth. ex Kurz, a plant belonging to the Bignoniaceae family, is known as an Asian medical plant and is used in folk medicine for the treatment of rheumatism, diarrhea, and dysentery [2, 3]. Considering its wide traditional uses, we have carried out phytochemical studies of O. indicum and evaluated the antibacterial and antioxidative activities of its crude extracts and isolated compounds. Studies of the chemical constituents of the leaves, roots, stems, and twigs of O. indicum show that it possesses flavonoids, xanthones, coumarin, quinine, one cyclohexylethanoid, benzaldehyde, and one phenylpropanoid. Their structures were elucidated by spectroscopic analysis including UV, IR, and NMR. To the best of our knowledge, the 11 compounds (6–16) in O. indicum are reported for the first time. The antibacterial and antioxidative activities of the extracts and isolated compounds were also evaluated using 2-fold serial dilutions and flow injection analysis (FIA) methods, respectively. Isolation and purification of O. indicum extracts led to 16 compounds (1–16), including flavonoids: 5,7-dihydroxy6-methoxyflavone (1) [4], 5,7-dihydroxyflavone (2) [4], 5,7,4 -trihydroxy-6-methoxyflavone (3) [5], 5,7,4 -trihydroxyflavone (4) [6], 5,6,7,4 -tetrahydroxyflavone (5) [7], 5,7,4 -trihydroxy-3 -methoxyflavone (6) [8], and 5,4 -dihydroxy-7-methoxyflavone (7) [9]; four xanthones: 5 -demethoxycadensin G (8) [10], 1,7-dihydroxyxanthone (9) [11], 1,3,6-trihydroxy-7-methoxy-2(3,7-dimethyl-2,6-octadienyl)xanthone (10) [12], and 3,7-dihydroxy-1-methoxyxanthone (11); one coumarin: heraclenin (12) [13]; one quinone: 2-methoxystypandrone (13) [14]; one cyclohexylethanoid: rengyolone (14) [15]; one benzaldehyde: 4-hydroxy-3-methoxybenzaldehyde (15) [16]; and one phenylpropanoid: 1-(4-hydroxyphenyl)propan-1-one (16) [17]. The antibacterial activity of the crude extracts against gram-positive bacteria (B. cereus, S. aureus, and MRSA SK1) and gram-negative bacteria (E. coli, P. aeruginosa, and S. typhimurium) were investigated; and they showed weak to moderate activity against gram-positive bacteria (160–1280 g·mL–1) and gram-negative bacteria (640–1280 g·mL–1). Compounds 8 and 3 exhibited moderate antibacterial activity against B. cereus and MRSA SK1 with MIC values of 16 and 32 g·mL–1, respectively. The other isolated compounds showed weak antibacterial activity with a MIC range of 64–128 g·mL–1. In addition, we studied the antioxidative activity of the compounds by the FIA method; the acetone extracts of the leaves and roots of the plant and compound 5 exhibited strong antioxidative activity with IC50 values of 8.01 0.29 and 9.81 0.09 g·mL –1 and 11.88 0.06 M, respectively. In addition, the acetone extracts of the stems and twigs, the dichloromethane extracts of the roots and twigs, and compound 6 exhibited moderated radical scavenging activity with IC50 values of 28.06 1.66, 34.24 1.77, 31.57 1.08, 32.72 0.41 g·mL–1 and 33.45 1.45 M, respectively. The hexane extract of the leaves, the dichloromethane extract of the leaves, methanolic extracts of the stems and twigs, and isolated compounds 1–4 and 8–16 showed a % inhibition lower than 50% and were not further tested for IC50. Plant Materials. The leaves, roots, stems, and twigs of O. indicum were collected from Lamphun Province, Thailand in April 2011.