3-Pentanol glycosides from root nodules of the actinorhizal plant Alnus cremastogyne.

Alnus cremastogyne Burkill (Betulaceae), an actinorhizal plant, can enter a mutualistic symbiosis with Frankia species that leads to the formation of nitrogen fixing root nodules. Some primary metabolites (carbohydrates, dicarboxylic acids, amino acids, citrulline and amides) involved in carbon and nitrogen metabolism in actinorhizal nodules have been identified, while specialized metabolites in A. cremastogyne root nodules are yet to be characterized. In this study, we isolated and identified three undescribed 3-pentanol glycosides, i.e., 3-pentyl α-l-arabinofuranosyl-(1''→6')-ß-d-glucopyranoside, 3-pentyl α-l-rhamnopyranosyl-(1''→6')-ß-d-glucopyranoside, and 3-pentyl 6'-(3-hydroxy3-methylglutaryl)-ß-d-glucopyranoside, as well as seventeen known compounds from A. cremastogyne root nodules. 3-Pentanol glycosides are abundantly distributed in root nodules, while they are distributed in stems, roots, leaves and fruits at low/zero levels. A. cremastogyne plants treated by root nodule suspension emit 3-pentanol. This study enriches the knowledge about specialized metabolites in the actinorhizal host, and provides preliminarily information on the signal exchange in the actinorhizal symbiosis between A. cremastogyne and Frankia.

Discovery of Cyclic Diarylheptanoids as Inhibitors against Influenza A Virus from the Roots of Casuarina equisetifolia.

Four new cyclic diarylheptanoids, casuarinols A-C (1-3) and casuarinolide A (4), together with six known ones (5-10), were isolated from the roots of Casuarina equisetifolia. Structures were elucidated by extensive spectroscopic analysis, theoretical conformational, and electronic circular dichroism analyses. Casuarinol C (3) is a novel cyclic diarylheptanoid-aldehyde adduct. Casuarinolide A (4) represents the first structure of a seco-cyclic diarylheptanoid. Compounds 1-9 were evaluated for their anti-influenza A virus (IAV) activity against A/WSN/33 (H1N1). (-)-(M)-11-Oxo-3,12R,17-trihydroxy-9-ene-[7,0]-metacyclophane (5) displayed significant anti-IAV activity with an IC50 value of 8.64 ± 2.49 µM and a CC50 higher than 100 µM.