New aporphine alkaloids from the aerial parts of <i>Piper semiimmersum</i>^§

<p>Two new aporphine alkaloids, semiimmersumines A (<b>1</b>) and B (<b>2</b>), along with 20 known compounds, were isolated from the aerial parts of <i>Piper semiimmersum</i> (Piperaceae). The structures of the new compounds were elucidated based on the analysis of 1D and 2D NMR, MS, and CD data. The absolute configuration of semiimmersumine A (<b>1</b>) was determined by single crystal X-ray diffraction analysis using anomalous dispersion with copper radiation. The effects of all compounds from the plant on rabbit platelet aggregation induced by thrombin (IIa) or PAF were also evaluated.</p

Nudibaccatumone, a Trimer Comprising a Phenylpropanoid and Two Sesquiterpene Moieties from <i>Piper nudibaccatum</i>

A new complex natural product with a C₃₉ skeleton, named nudibaccatumone, and the known sesquiterpenes (+)-spathulenol, (−)-4β,10α-aromadendranediol, and <i>ent</i>-T-muurolol, as well as the phenylpropanoid hydroxychavicol, were isolated from the aerial parts of <i>Piper nudibaccatum</i>. The structure and absolute configuration of nudibaccatumone were elucidated using spectroscopic methods and ECD calculations. A 1,8-Michael addition reaction and an intermolecular, inverse electron demand Diels–Alder reaction are proposed as the key steps in the biosynthesis of nudibaccatumone

Tabercorymines A and B, Two Vobasinyl–Ibogan-Type Bisindole Alkaloids from Tabernaemontana corymbosa

Tabercorymines A (<b>1</b>) and B (<b>2</b>), two new vobasinyl–ibogan-type bisindole alkaloids with an unprecedented skeleton, were isolated from Tabernaemontana corymbosa. Their structures were established by a combination of spectroscopic data, chemical transformation, single-crystal X-ray diffraction, and ECD calculation. Compound <b>1</b> represents a novel bisindole alkaloid, characterized by a caged heteropentacyclic ring system incorporating an unprecedented C-7/C-20 bond in the vobasinyl unit. Alkaloids <b>1</b> and <b>2</b> showed potent antiproliferative activity against several human cancer cell lines, including vincristine-resistant KB

Indole Alkaloid Glycosides from the Aerial Parts of <i>Strobilanthes cusia</i>

Three indole alkaloid glycosides, strobilanthosides A–C (<b>1</b>–<b>3</b>), two known indole alkaloid glucosides (<b>4</b> and <b>5</b>), and five phenylethanoid glycosides (<b>8</b>–<b>10</b>) were isolated from the aerial parts of <i>Strobilanthes cusia</i>. The structures of the new compounds were elucidated by spectrometric analysis, and the absolute configurations of <b>1</b> and <b>2</b> were established by ECD spectrocsopy. <i>N</i>′-β-d-Glucopyranosylindirubin (<b>5</b>) showed weak antibacterial activity (MIC 62.5–125 μM) against <i>Staphylococcus aureus</i>

Trigoflavidols A–C, Degraded Diterpenoids with Antimicrobial Activity, from <i>Trigonostemon flavidus</i>

Trigoflavidols A (<b>1</b>) and B (<b>2</b>), tetranorditerpenoid dimers possessing a rearrangement skeleton with a spiroketal core moiety, and trigoflavidol C (<b>3</b>), a hexanorditerpenoid, have been isolated from <i>Trigonostemon flavidus</i> along with two known compounds. Compounds <b>1</b> and <b>2</b> showed moderate antimicrobial activities (MIC values: 3.12–6.25 μg/mL) against <i>Staphylococcus aureus</i>, 8^#MRSA, and 82^#MRSA, and <b>1</b>, <b>2</b>, and <b>5</b> showed weak activities (IC₅₀ values: 3.75–28.99 μM) against various human tumor cell lines

Trigohowilols A–G, Degraded Diterpenoids from the Stems of <i>Trigonostemon howii</i>

Two new degraded diterpenoids, trigohowilols A (<b>1</b>) and B (<b>2</b>), four new heterodimers, trigohowilols C–F (<b>3</b>–<b>6</b>), one new homodimer, trigohowilol G (<b>7</b>), and three known degraded diterpenoids (<b>8</b>–<b>10</b>) were isolated from the methanol extract of the stems of <i>Trigonostemon howii</i>. Compounds <b>1</b>–<b>7</b> were evaluated for their cytotoxic activity against five human tumor cell lines by an MTT assay, and trigohowilols E (<b>5</b>) and F (<b>6</b>) exhibited inhibitory activity with IC₅₀ values ranging from 2.33 to 12.57 μM. Moreover, compounds <b>1</b>–<b>6</b> showed weak antimicrobial activities (MIC values: 6.25–25 μg/mL) against <i>Staphylococcus aureus</i>, <i>Pseudomonas aeruginosa</i>, MRSA 92^#, and MRSA 98^# using a 2-fold dilution method