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

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>