(+)/(−)-Yanhusuosines A and B, two dimeric benzylisoquinoline-protoberberine alkaloid atropo-enantiomers featuring polycyclic skeletons from Corydalis yanhusuo

(+)/(−)-Yanhusuosines A (1) and B (2), two pairs of trace benzylisoquinoline-protoberberine atropo-enantiomeric homodimers featuring an unprecedented 6/7/6/6/6/6 hexacyclic skeleton, were isolated from the tubers of Corydalis yanhusuo. The structures of (+)/(−)-1 and (+)/(−)-2 were elucidated using spectroscopic and quantum-chemical calculation approaches. (+)/(−)-Yanhusuosines A (1) and B (2) represent a new class of alkaloid dimers biogenetically constructed by a molecule of benzylisoquinoline with a unit of protoberberine via an intermolecular [4 + 3] cycloaddition. Their plausible biosynthetic pathways are discussed, and compound 2 exerted moderate inhibitory activity of NO formation in LPS induced RAW264.7 macrophages.