Iridoid Constituents of Viburnum brachybotryum

Abstract

Eleven new iridoids, brachybones A–K (1–11), were isolated from the twigs of Viburnum brachybotryum. Their structures including absolute configurations were determined by spectroscopic data analysis and from the electronic circular dichroism (ECD) spectra. All of the compounds 1–11 possess one or two acetoxysenecioate substituents. Furthermore, compounds 5–7 and 11 feature a Cl atom in the molecule, while compounds 9–11 exhibit a cagelike rigid skeleton through an unusual oxo bridge from C-3 to C-8 or C-10. The isolates were evaluated for cytotoxic activity against the HCT-116, A549, and Hela cell lines, and the results showed compounds 10 and 11 to be active against HCT-116 cells.

Computational methods and points for attention in absolute configuration determination

“…A popular method of analysis is to calculate ECD and compare it with the experimental spectrum. Many examples have been studied and the predicted ECD curves agreed well with the experimental results (Junior et al, 2014;Wang et al, 2014b;Fleming et al, 2015;Pescitelli and Bruhn, 2016;Masnyk et al, 2016;Lee et al, 2018;Zhu et al, 2018;Liu et al, 2019a;Liu et al, 2019b;Guo et al, 2021a;Arreaga-González et al, 2021;Guo et al, 2021b;Wang et al, 2021b;Rao et al, 2021;Tan et al, 2021;Xie et al, 2021); this includes the compounds in which the ECD were compared with the compound's configuration that was assigned using quantum theory methods (Socolsky et al, 2016). Some examples (66-84) are summarized in Figure 12 (Zhang et al, 2008;Pazderkova et al, 2014;Zhang et al, 2014;Bultinck et al, 2015;Sherer et al, 2015;Liu et al, 2016b;Xu et al, 2016b;Evidente et al, 2016;Nakashima et al, 2016;Yu et al, 2016;Endo et al, 2017;Maslovskaya et al, 2017;Xu et al, 2019;Zhou et al, 2019;He et al, 2021a;Sun et al, 2021b;Lu et al, 2021;Xue et al, 2021;Yang et al, 2021).…”

A Survey of Recently Discovered Naturally Occurring Organohalogen Compounds

“…Prunolides D and E significantly inhibit the aggregation (>89%) of α-synuclein in a ThT amyloid dye assay. 53 A Queensland collection of the ascidian Polycarpa procera provides the new procerolide E (141), methyl procerolate A (142), and the new natural product 3-bromo-4methoxyphenylacetamide (143), previously known as a synthetic compound. 54 Procerolides C, D and procerone A are described in ref 4.…”

“…Brachybone K (312) is active toward HCT-116 cells (IC 50 5.2 μM). 143 An examination of the roots and rhizomes of Valeriana of f icinalis revealed 26 iridoids, including the two new chlorinated iridoidvols D (313) and E (314). 144 An example of a rare crotofolane diterpenoid is 315 from the Kenyan plant Croton megalocarpus, which the authors suspect is an "extraction artifact" (using CH 2 Cl 2 /MeOH).…”

“…Four new chlorine-containing iridoids, brachybones, E ( 309 ), F ( 310 ), G ( 311 ), and K ( 312 ) were characterized in the Chinese evergreen shrub Viburnum brachybotryum . Brachybone K ( 312 ) is active toward HCT-116 cells (IC 50 5.2 μM) . An examination of the roots and rhizomes of Valeriana officinalis revealed 26 iridoids, including the two new chlorinated iridoidvols D ( 313 ) and E ( 314 ) .…”