Biomimetic Synthesis of Macahydantoins A and B from <i>Lepidium meyenii</i>, and Structure Revision of Macahydantoin B as a Class of Thiohydantoin with a 4‑Methyl-hexahydropyrrolo[1,2‑<i>c</i>]imidazole Skeleton

Phytochemical investigation on <i>Lepidium meyenii</i> led to the discovery of macahydantoin C (<b>3</b>), a new thiohydantoin with a 1,3-diazabicyclo[3.3.1]­nonane core, the spectral properties of which indicate a potential structural misassignment of its previously reported analogue, macahydantoin B (<b>2a</b>). To probe this hypothesis, a concise, scalable, and biomimetic synthesis of the originally proposed <b>2a</b> and its revised structure (<b>2b</b>) was efficiently accomplished using the modified Edman degradation as the key step from commercially available materials in 65% (three steps) and 52% (three steps) overall yields, respectively. These synthetic endeavors undoubtedly reassigned the structure of macahydantoin B as an unreported type of thiohydantoin featuring a 4-methyl-hexahydropyrrolo­[1,2-<i>c</i>]­imidazole scaffold

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

(+)-Meyeniins A–C (<b>1</b>–<b>3</b>), a novel class of sulfur-containing hexahydroimidazo­[1,5-<i>c</i>]­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

Biomimetic Synthesis of Macahydantoins A and B from <i>Lepidium meyenii</i>, and Structure Revision of Macahydantoin B as a Class of Thiohydantoin with a 4‑Methyl-hexahydropyrrolo[1,2‑<i>c</i>]imidazole Skeleton

Phytochemical investigation on <i>Lepidium meyenii</i> led to the discovery of macahydantoin C (<b>3</b>), a new thiohydantoin with a 1,3-diazabicyclo[3.3.1]­nonane core, the spectral properties of which indicate a potential structural misassignment of its previously reported analogue, macahydantoin B (<b>2a</b>). To probe this hypothesis, a concise, scalable, and biomimetic synthesis of the originally proposed <b>2a</b> and its revised structure (<b>2b</b>) was efficiently accomplished using the modified Edman degradation as the key step from commercially available materials in 65% (three steps) and 52% (three steps) overall yields, respectively. These synthetic endeavors undoubtedly reassigned the structure of macahydantoin B as an unreported type of thiohydantoin featuring a 4-methyl-hexahydropyrrolo­[1,2-<i>c</i>]­imidazole scaffold

Three new isoquinoline alkaloids from the fermentation of <i>Aspergillus</i> sp. 0338 and their anti-MRSA activities

There is growing evidence that bioactive substances produced by microbial endophytes have applicability in medicine, agriculture and industry. To enrich the bioactive substances, in our search for new bioactive metabolites from fungi Aspergillus, the phytochemical reinvestigation on the Aspergillus sp. 0338 was carried out, and this led to the isolation of three new (1-3) and five known alkaloids (4-8). Their structures were elucidated by spectroscopic analysis, including extensive 1D and 2D NMR techniques, as well as comparison with literature values. Additionally, compounds 1-3 were evaluated for their anti-MRSA activities. The results revealed that compounds 1-3 exhibited good inhibitions with IZD of 15.2 ± 1.8, 14.6 ± 2.0, and 13.4 ± 2.2 mm, respectively.</p

Antiviral Chromones from the Stem of <i>Cassia siamea</i>

Seven new chromones, siamchromones A–G (<b>1</b>–<b>7</b>), and 12 known chromones (<b>8</b>–<b>19</b>) were isolated from the stems of <i>Cassia siamea</i>. Compounds <b>1</b>–<b>19</b> were evaluated for their antitobacco mosaic virus (anti-TMV) and anti-HIV-1 activities. Compound <b>6</b> showed antitobacco mosaic virus (anti-TMV) activity with an inhibition rate of 35.3% and IC₅₀ value of 31.2 μM, which is higher than that of the positive control, ningnamycin. Compounds <b>1</b>, <b>10</b>, <b>13</b>, and <b>16</b> showed anti-TMV activities with inhibition rates above 10%. Compounds <b>4</b>, <b>6</b>, <b>13</b>, and <b>19</b> showed anti-HIV-1 activities with therapeutic index values above 50

Cytotoxic Deoxybenzoins and Diphenylethylenes from <i>Arundina graminifolia</i>

Eight new C-4-alkylated deoxybenzoins (<b>1</b>–<b>8</b>), three new diphenylethylenes (<b>9</b>–<b>11</b>), and five known diphenylethylenes were isolated from A<i>rundina graminifolia</i>. The structures of <b>1</b>–<b>11</b> were elucidated by spectroscopic methods including extensive 1D and 2D NMR techniques. Compounds <b>9</b>–<b>11</b> are the first naturally occurring diphenylethylenes possessing a hydroxyethyl unit. Compounds <b>1</b>–<b>11</b> were evaluated for cytotoxicity against five human tumor cell lines. Compounds <b>4</b>, <b>5</b>, and <b>9</b>–<b>11</b> showed significant cytotoxicity against five cancer cell lines, with IC₅₀ values ranging from 1.8 to 8.7 μM

Cytotoxic Oxepinochromenone and Flavonoids from the Flower Buds of <i>Rosa rugosa</i>

A new oxepinochromenone, rugosachromenone A (<b>1</b>), seven new flavonoids, rugosaflavonoids A–G (<b>2</b>–<b>8</b>), and 11 known compounds (<b>9</b>–<b>19</b>) were isolated from the flower buds of <i>Rosa rugosa</i>. Compound <b>1</b> is found from Nature for the first time. Compound <b>2</b> displayed cytotoxicity against NB4, SHSY5Y, and MCF7 cells with IC₅₀ values of 2.2, 2.5, and 2.3 μM, respectively, and <b>3</b> was toxic to A549 and MCF7 cells with IC₅₀ values of 1.2 and 2.8 μM, respectively

Aspergillines A–E, Highly Oxygenated Hexacyclic Indole–Tetrahydrofuran–Tetramic Acid Derivatives from <i>Aspergillus versicolor</i>

Aspergillines A–E (<b>1</b>–<b>5</b>) are highly oxygenated cyclopiazonic acid (CPA)-derived alkaloids bearing a rigid and sterically congested hexacyclic indole–tetrahydrofuran–tetramate scaffold, isolated from the endophytic fungus <i>Aspergillus vesicolor</i>. Apergillines A–C represent a new subclass of CPA-derived alkaloids, and aspergillines B and E possess a butanoic acid methyl ester moiety. The structures, including absolute configuration, were elucidated by interpretation of the NMR, X-ray crystallographic, and circular dichroism data. All compounds displayed anti-TMV and cytotoxic activities

Bioactive Dibenzocyclooctadiene Lignans from the Stems of <i>Schisandra neglecta</i>

Seven new unusual dibenzocyclooctadiene lignans, neglignans A–G (<b>1</b>–<b>7</b>), together with 16 known dibenzocyclooctadiene lignans, were isolated from the stems of <i>Schisandra neglecta</i>. Compounds <b>1</b> and <b>2</b> are the first dibenzocyclooctadiene lignans bearing a carboxyl group at C-4, and compounds <b>3</b> and <b>4</b> are the first 7,8-<i>seco</i>-dibenzocyclooctadiene lignans found from Nature. The new compounds (<b>1</b>–<b>7</b>) and several of the known compounds were evaluated for their anti-HIV activity and cytotoxicity. Compounds <b>2</b> and <b>6</b> showed anti-HIV-1 activities with therapeutic index values greater than 50, and compound <b>4</b> showed cytotoxicity against the NB4 and SHSY5Y cancer cell lines with IC₅₀ values of 2.9 and 3.3 μM, respectively

Flavones from <i>Cassia siamea</i> and their anti-tobacco mosaic virus activity

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