Min Zhou

(+)-Meyeniins A–C, Novel Hexahydroimidazo[1,5-c]thiazole Derivatives from the Tubers of Lepidium meyenii: Complete Structural Elucidation by Biomimetic Synthesis and Racemic Crystallization

(+)-Meyeniins A-C (1-3), a novel class of sulfur-containing hexahydroimidazo[1,5-c]thiazole derivatives, were isolated from the tubers of Lepidium meyenii (maca) cultivated in Lijiang, Yunnan province, China. Guided by their biosynthetic hypothesis, a stereocontrolled biomimetic synthesis of meyeniins A-C and their individual enantiomers was efficiently accomplished by a combination of a condensation reaction and Edman degradation. The formation of high-quality crystals for X-ray crystallography occurred much more readily from a racemic mixture of (±)-meyeniin A than with the single enantiomer alone in this case. These extensive strategies, combined with circular dichroism (CD) spectra, allowed the complete structural assignments of (+)-meyeniins A-C. Among them, (+)-meyeniin A showed moderate selective cytotoxicities against the HL-60, A549 and MCF-7 human cell lines with IC50 values of 14.41, 32.22, and 33.14 μM, respectively. To some extent, these findings support traditional applications of maca as healthy nutritional supplements or functional foods for cancer prevention.

Flavones from Cassia siamea and their anti-tobacco mosaic virus activity

Two new flavones, siameflavones A and B (1 and 2), together with five known flavones (3–7) were isolated from the stem of Cassia siamea. Their structures were elucidated by spectroscopic methods including extensive 1D and 2D NMR techniques. Compounds 1–5 were evaluated for their anti-tobacco mosaic virus (Anti-TMV) activity. The results showed that compounds 1–5 showed weak anti-TMV activity with inhibition rates in the range of 11.6–18.5%.

Three new anthraquinones from the twigs of Cassia fistula and their bioactivities

Abstract Three previously unreported anthraquinones, fistulaquinones A–C (1–3), together with three known ones (4–6) were isolated from the twigs of Cassia fistula. Their structures were determined by means of extensive NMR and MS spectroscopic analyses. All the isolated compounds were tested for their anti-tobacco mosaic virus (anti-TMV) activity, and compound 3 showed significant activity with inhibition rate of 34.5% at 20 μM concentration, even more potent than positive control. Additionally, compounds 1–6 exhibited moderate cytotoxicity with IC50 values ranging from 2.8 to 9.4 μM for some tested human tumor cell lines.

Isopentylated diphenyl ether derivatives from the fermentation products of an endophytic fungus Phomopsis fukushii

Three new isopentylated diphenyl ethers, (1–3), together with two known isopentylated diphenyl ethers derivatives (4 and 5) were isolated from the fermentation products of an endophytic fungus Phomopsis fukushii. Their structures were elucidated by spectroscopic methods, including extensive 1D- and 2D NMR techniques. Compounds 1–3 were evaluated for their anti-methicillin-resistant Staphylococcus aureus (anti-MRSA) activity. The results showed that compounds 1–3 showed strong activity with diameter of inhibition zone (IZD) of 21.8u2009±u20092.4u2009mm, 16.8u2009±u20092.2u2009mm, and 15.6u2009±u20092.0u2009mm, respectively.

Three new diphenyl ether derivatives from the fermentation products of an endophytic fungus Phomopsis fukushii

Abstract Three new diphenyl ethers (1-3), together with four known isopentylated diphenyl ethers derivatives (4-7), were isolated from the fermentation products of an endophytic fungus Phomopsis fukushii. Their structures were elucidated by spectroscopic methods, including extensive 1D and 2D NMR techniques. Compounds 1-3 were evaluated for their anti-methicillin-resistant Staphylococcus aureus (anti-MRSA) activity. The results revealed that compounds 1 and 2 showed strong inhibitions with inhibition zone diameters (IZD) of 20.2 ± 2.5 mm and 17.9 ± 2.2 mm, respectively. Compound 3 also showed good inhibition with IZD 15.2 ± 1.8 mm. The IZD data of compound 1 is close to that of positive control with IZD 21.9 ± 2.1 mm.

Two New Alkaloids from the Seeds of Cassia alata and Their Anti-Tobacco Mosaic Virus Activity

Two new alkaloids, 3-(hydroxymethyl)-6,9-dimethyl-7H-benzo[de]quinolin-7-one (1) and 3-(hydroxymethyl)-8-methoxy-6,9-dimethyl-7H-benzo[de]quinolin-7-one (2), together with two known alkaloids (3 and 4) were isolated from the seeds of Cassia alata. Their structures were determined by means of HR-ESI-MS and extensive 1D and 2D NMR spectroscopic studies. Compounds 1–4 were tested for their anti-tobacco mosaic virus (anti-TMV) activity. The results revealed that compounds 1–4 have potential anti-TMV activity with inhibition rates of 29.2, 38.5, 24.2, and 28.8% at the concentration of 20 μM, respectively. The inhibition rates of 1 and 2 are higher than that of the postive control.