Hr Kang

Termisoflavones A–C, Isoflavonoid Glycosides from Termite-Associated Streptomyces sp. RB1

Three new isoflavonoid glycosides, termisoflavones A-C (1-3), and eight isoflavonoids (4-11) were isolated from termite-associated Streptomyces sp. RB1 recovered from the cuticle of the South African termite, Macrotermes natalensis. The structures of new compounds were determined by spectroscopic methods including 1D and 2D NMR and HR-MS analysis, as well as comparison of their NMR data with those of related isoflavonoid glycoside derivatives. The absolute configurations of the sugar moieties were clarified by chemical reactions. None of the isolates (1-11) displayed antifungal or antimicrobial activities (MICs > 100 μg/mL), whereas compounds 6 and 11 ameliorated cisplatin-induced kidney cell damage to 80% of the control value at a cisplatin dose of 25 μM.

Bioactivity-guided isolation of antioxidant triterpenoids from Betula platyphylla var. japonica bark

The bark of Betula platyphylla var. japonica (Betulaceae) has been used to treat pneumonia, choloplania, nephritis, and chronic bronchitis. This study aimed to investigate the bioactive chemical constituents of the bark of B. platyphylla var. japonica. A bioassay-guided fractionation and chemical investigation of the bark of B. platyphylla var. japonica resulted in the isolation and identification of a new lupane-type triterpene, 27-hydroxybetunolic acid (1), along with 18 known triterpenoids (2-19). The structure of the new compound (1) was elucidated on the basis of 1D and 2D NMR spectroscopic data analysis as well as HR-ESIMS. Among the known compounds, chilianthin B (17), chilianthin C (18), and chilianthin A (19) were triterpene-lignan esters, which are rarely found in nature. Compounds 4, 6, 7, 17, 18, and 19 showed significant antioxidant activities with IC50 values in the range 4.48-43.02μM in a DPPH radical-scavenging assay. However, no compound showed significant inhibition of acetylcholine esterase (AChE). Unfortunately, the new compound (1) exhibited no significance in both biological activities. This study strongly suggests that B. platyphylla var. japonica bark is a potential source of natural antioxidants for use in pharmaceuticals and functional foods.

Cytotoxic Triterpenoids from the Barks of Betula platyphylla var. japonica.

Phytochemical investigation on the barks of Betula platyphylla var. japonica (Betulaceae) was carried out, resulting in the isolation and identification of three new triterpenoids, 27‐O‐cis‐caffeoylcylicodiscic acid (1), 27‐O‐cis‐feruloylcylicodiscic acid (2), and 27‐O‐cis‐caffeoylmyricerol (3), along with six known triterpenoids, obtusilinin (4), winchic acid (5), 27‐O‐trans‐caffeoylcylicodiscic acid (6), uncarinic acid E (7), myriceric acid B (8), and 3‐O‐trans‐caffeoyloleanolic acid (9). The structures of the new compounds were elucidated by extensive spectroscopic methods, including 1D‐ and 2D‐NMR, and HR‐ESI‐MS. All of the isolated compounds were evaluated for cytotoxicity against four human tumor cell lines (A549, SK‐OV‐3, SK‐MEL‐2, and Bt549). Compounds 2, 6, 8, and 9 exhibited potent cytotoxicity against all of the tumor cells tested (IC50 < 10.0 μm), while compounds 3, 4, 5, and 7 showed moderate cytotoxicity against all of the tumor cells tested (IC50 < 20.0 μm).

A new aliphatic alcohol and cytotoxic chemical constituents from Acorus gramineus rhizomes.

A new aliphatic alcohol, (2R,6R)-oct-7-ene-2,6-diol (1), and seven other known compounds (2-8) were isolated from Acorus gramineus rhizomes. The structure of 1 was elucidated by a combination of extensive spectroscopic analyses, including 2D NMR, HR-MS, and the modified Mosher’s method. Compounds 3-8 displayed consistent antiproliferative activities against the cell lines tested with IC50 values ranging from 7 to 48 μm.

A New Steroidal Saponin from the Tubers of Ophiopogon japonicus and Its Protective Effect Against Cisplatin-Induced Renal Cell Toxicity

A new furostanol saponin, ophiopogonin T, was isolated from the tubers of Ophiopogon japonicus. Its structure was established by extensive spectroscopic techniques including 1D (1H and 13C) and 2D nuclear magnetic resonance (NMR) experiments (correlation spectroscopy (COSY), heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond correlation (HMBC) and nuclear Overhauser effect spectroscopy (NOESY)), high-resolution electrospray ionization mass spectrometry (ESIMS), and chemical methods. Using cell-based assays, this compound was evaluated for its cytotoxic effect on cancer cell lines and its protective effect against anticancer drug-induced nephrotoxicity. Cisplatin-induced cytotoxicity in porcine kidney (LLC-PK1) cells was significantly reduced upon treatment with ophiopogonin T, without affecting human hepatoma (HepG2) cancer cell proliferation or tube formation in human umbilical vein endothelial cells (HUVECs). These results collectively reflect the beneficial effect of ophiopogonin T on the side effects of cisplatin.

Chemical Characterization of Novel Natural Products from the Roots of Asian Rice (Oryza sativa) that Control Adipocyte and Osteoblast Differentiation

Oryza sativa L. is consumed globally as a staple food, and its roots have been used as a Korean and Chinese medical supplement for protection of the stomach and lungs and for amelioration of vomiting and fever. In our continuing search for biologically effective metabolites from Korean natural materials, we found that an EtOH extract of O. sativa root reciprocally regulated adipocyte and osteoblast differentiation. Chemical analysis of the EtOH extract using a bioassay-guided fractionation protocol led to the isolation and determination of two novel lignans, oryzativols A and B, responsible for these regulatory activities. Using 1D and 2D nuclear magnetic resonance spectroscopic analyses, high-resolution mass spectrometry, and circular dichroism analysis, the structures of the novel compounds were elucidated. We examined their effects on the regulation of mesenchymal stem cell differentiation. Treatment with oryzativol A in the human mesenchymal cell line C3H10T1/2 suppressed gene expression of peroxisome proliferator activated receptor γ, which resulted in a reduction in adipogenesis. Oryzativol A also enhanced the expression of Runx2 and cellular differentiation into osteoblasts in the same mesenchymal stem cell line.