Absolute configuration of spiro-flavostilbenoids from Yucca schidigera Roezl ex Ortgies: First indication of (2R)-naringenin as the key building block.

The absolute configurations of the known but unusual spiro-flavostilbenoids found in the bark of Yucca schidigera Roezl ex Ortgies, were determined by applying time-dependent density functional theory simulation of electronic circular dichroism spectra. The absolute configurations obtained were as follows: (2S,3R) for yuccaol A, yuccaol D and yuccalide A; (2S,3S) for yuccaol B, yuccaol C and yuccaol E; (2S,3S,2'S,3'S) for gloriosaol A; (2S,3R,2'S,3'R) for gloriosaol C; (2S,3S,2'S,3'R) for gloriosaol D; (2S,3R,2'S,3'S) for gloriosaol E. These findings indicate that the compounds are all biosynthetic derivatives either of (2R)-naringenin and trans-resveratrol or of trans-3,3',5,5'-tetrahydroxy-4'-methoxystilbene. In contrast, gloriosaols are direct derivatives of yuccaols (note that substituting by stilbenoid changes the absolute configuration of C-2 naringenin carbon to 2S). A putative mechanism for their biosynthesis is proposed taking into account key aspects of regio- and stereoselectivity. Yuccaol B and gloriosaol A showed in vitro moderate inhibitory effects against acetyl-/butyrylcholinesterases (AChE/BChE) with IC50 values of 43/81 and 45/65 µM respectively. The selectivity index values calculated from the IC50 values of BChE and AChE were 1.9 and 1.4. Molecular docking simulations showed their interaction with the peripheral anionic site of human AChE and the catalytic site of the human BChE.

Antiproliferative and cytotoxic activity of Geraniaceae plant extracts against five tumor cell lines.

AIM: To determine the antiproliferative and cytotoxic activities of Geranium and Erodium species against human cancer and noncancer cell lines, respectively. METHODS: Twenty-one species of Geranium and Erodium were extracted and screened against cancerous and noncancerous human cell lines. RESULTS: In a dose-response manner, G. glaberrimum, G. asphodeloides, E. brandianum and E. leucanthum were able, with variable potency, to inhibit cellular proliferation. Except for E. brandianum, all extracts induced cellular autophagy in tumor cells with similar levels to that of rapamycin; but, only E. brandianum induced cellular apoptosis, likely through Bcl2 and BAX protein expressions. DISCUSSION: This is the first study to report the potential antiproliferative effects of ethanol extracts of several Geraniaceae species.