Rongwei Teng

Biotransformation of podophyllotoxin by Hordeum vulgare cell suspension cultures

Hordeum vulgare cell suspension cultures were used to modify podophyllotoxin (1) One major product (1a) and one minor product (1b) were detected in both the culture medium and cells. To optimize the yield of compound 1a, we showed that: (1) the optimal concentration of added podophyllotoxin (1) was 33 mg L−1; higher concentrations caused cell toxicity; (2) the stage of the cell cycle (lag/log/stationary) at which podophyllotoxin was added only marginally affected the yield of compound 1a; the optimal addition time was after lag phase, in which the yield of compound 1a reached ca. 76%, and (3) biotransformation of podophyllotoxin (1) was relatively slow; podophyllotoxin fed at 4 days after subculture resulted in yields of compound 1a of ca. 56, 64 and 76% after an additional 3, 6 and 10 days of incubation, respectively. Product 1a was purified and identified as isopicropodophyllone (1a) based on MS and NMR data.

Regioselective acylation of several polyhydroxylated natural compounds by Candida antarctica lipase B

Regioselective acylation of four polyhydroxylated natural compounds, deacetyl asperulosidic acid (1), asperulosidic acid (2), puerarin (3) and resveratrol (4) by Candida antarctica Lipase B in the presence of various acyl donors (vinyl acetate, vinyl decanoate or vinyl cinnamoate) was studied. Compounds 1, 2 and 4 were regioselectively acetylated with vinyl acetate to afford products, 3′-O-acetyl-10-O-deacetylasperulosidic acid (1a), 3′,6′-O-diacetyl-10-O-deacetylasperulosidic acid (1b), 3′-O-acetylasperulosidic acid (2a), 3′,6′-O-diacetylasperulosidic acid (2b), 4′-O-acetylresveratrol (4a), respectively, with yields of 22 to 50%, while reactions with vinyl decanoate and vinyl cinnamoate were slow with lower yields. Compound 3 was readily acylated with all three acyl donors and quantitatively converted to products 6″-O-acetylpuerarin (3a), 6″-O-decanoylpuerarin (3b), 6″-O-cinnamoylpuerarin (3c), respectively. The structures of these acylated products were determined by spectroscopic methods (MS and NMR).

New tirucallane-type triterpenoid saponins from Sapindus mukorossi Gaetn

Two new tirucallane-type triterpenoid saponins, sapimukoside C (1) and sapimukoside D (2), have been isolated from the roots of Sapindus mukorossi Gaetn. Their structures have been determined, on the basis of spectral and chemical analysis, as 3-O-α-L-rhamnopyranosyl-(1→2)-[α-L-arabinopyranosyl-(1→3)]-β-D-glucopyranosyl (21,23R)-epoxyl tirucalla-7,24-diene-(21S)-ethoxyl-3β-ol (1) and 3-O-α-L-rhamnopyranosyl-(1→2)-[α-L-arabinopyranosyl-(1→3)]-β-D-glucopyranosyl (21,23R)-epoxyl tirucall-7, 24-diene-(21S)-methoxyl-3β-ol (2).

Two new epimeric isopavine N-oxides from Meconopsis horridula var. racemosa

Two new epimeric isopavine N-oxides, amuresinine N-oxide A (1) and B (2), were isolated from Meconopsis horridula var. racemosa. Their structures were elucidated by spectroscopic methods.

Four new oleanane type Saponins from Morina nepalensis var. alba

Four new oleanane type saponins, monepalosides G–J (1–4), were isolated from the water-soluble part of the whole plant of Morina nepalensis var. alba Hand-Mazz. On the basis of chemical and spectroscopic evidence, their structures were determined as 3-O-α-L-arabinopyranosyl-(1→3)-α-L-arabinopyranosyl oleanolic acid 28-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside (monepaloside G, 1), 3-O-α-L-arabinopyranosyl-(1→3)-β-D-xylopyranosyl oleanolic acid 28-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside (monepaloside H, 2), 3-O-α-L-arabinopyranosyl-(1→3)-[β-D-glucopyranosyl-(1→2)]-α-L-arabinopyranosyl oleanolic acid 28-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside (monepaloside I, 3), 3-O-β-D-glucopyranosyl-(1→4)-β-D-glucopyranosy-(1→3)]-α-L-arabinopyranosyl oleanolic acid 28-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside (monepaloside J, 4), respectively. Two-dimensional NMR spectra, including H–H COSY, HMQC, 2D HMQC–TOCSY, HMBC and ROESY were utilized in the structure elucidation and complete assignments of 1H and 13C NMR spectra.

Regioselective acylation of 3-O-angeloylingenol by Candida antarctica Lipase B

Acylation of 3-O-angeloylingenol (1) with vinyl acetate, vinyl decanoate and vinyl cinnamate, catalyzed by Candida antarctica Lipase B, was investigated. In each case, compound 1 was quantitatively and regioselectively acylated to afford a single product, 3-O-angeloyl-20-O-acetylingenol (1a), 3-O-angeloyl-20-O-decanoylingenol (1b) and 3-O-angeloyl-20-O-cinnamoylingenol (1c), respectively. The structures of the novel compounds 1b-1c were determined by MS and NMR, and product 1a by comparison of RP-HPLC and TLC with a standard. Compounds 1b-1c induced a bipolar morphology of MM96L melanoma cells at a similar concentration as compound 1, as well as having activity in inhibiting the growth of MM96L melanoma cells.

Biotransformation of ingenol-3-angelate in four plant cell suspension cultures

Four plant species, Hordeum vulgare, Oryza sativa, Panax quinquefolium and Nicotiana tabacum, grown as cell suspension cultures, were used for the biotransformation of an anticancer compound, ingenol-3-angelate (1). Three compounds (1a–1c) were detected predominantly in the cultured medium and their structures were determined as 16-hydroxy-ingenol-3-angelate (1a), ingenol (1b) and ingenol-5-angelate (1c), based on MS and NMR spectroscopic evidence. 16-Hydroxy-ingenol-3-angelate (1a) was the only compound produced by H. vulgare cell cultures except that, at high substrate concentration (266 mg L−1), 1c was produced with a low yield both in the medium and within cells. In contrast, compounds 1a and 1b were produced in different yields and proportions in the other three cell cultures. The effect of substrate concentration, addition and incubation time on the production of 1a by H. vulgare cell cultures was investigated, and compounds 1a and 1b were assayed to be active in inhibiting the growth and inducing a bipolar morphology of MM96L melanoma cells.