Scalemic Caged Xanthones Isolated from the Stem Bark Extract of Garcinia propinqua

Abstract

Seven new caged xanthones, doitunggarcinones E-K (1-7), all as scalemic mixtures and 10 known compounds (8-17), were isolated from the stem bark extract of Garcinia propinqua. The structures were elucidated on the basis of spectroscopic methods. The separation of the enantiomers of 1-6 was achieved by semipreparative chiral HPLC. The absolute configuration of compound (+)-1 was determined by single-crystal X-ray crystallographic analysis using Cu Kα radiation. The absolute configurations of the other related compounds were determined from comparisons of their ECD spectra with that of compound (+)-1. Compounds (-)-6 and 7 showed cytotoxicity against a colon cancer cell line with IC values of 14.23 and 23.95 μM, respectively.

Structural diversity and biological activities of caged Garcinia xanthones: recent updates

“…The structural diversity of these compounds lies mainly in the different substitutions at the C-2, C-4 and C-5 positions. Doitunggarcinone K (30) [27,28], 3-O-geranylforbesione (31) [15], 3-O-methylbractatin (32) [29][30][31] and garcibractatin A (35) [21] are alkoxylated at C-3. Compounds 32 and 35 possess exactly the same chemical structure, except that the C-1 hydroxyl is replaced by -OMe in 35.…”

“…The other compounds, 23-25 from G. hanburyi, present a fused bicyclic ring attached to the caged xanthone skeleton in which gambogefic acid A (23) [24] and 12-hydroxygambogefic acid A (24) [25] are the hydrated and dihydroxylated version of gambogefic acid (25) [15], respectively. Beyond gambogellic acid, which was discovered and isolated in 1996 [62], another three compounds (26)(27)(28)(29) bearing a rare bridged bicyclic A ring system have been found. The compound 7-methoxygambogellic acid (26) has a methoxy moiety substituted at C-7 [18]; gambogellic acid A ( 27) is 12-hydroxylated [24] and gambogollic acid (28) and its epimer (29) are oxidized at C-38, with 28 bearing β-H at C-37 and 29 bearing a-H [26].…”

Natural Enantiomers: Occurrence, Biogenesis and Biological Properties

“…As shown in Scheme 4, the generation of enantiomeric 300a/300b−302a/302b is plausibly derived from diallylxanthone through a key process of nonstereospecific Claisen rearrangement [158]. In addition to 300−302, eleven pairs of caged prenylxanthone enantiomers 303a/303b−307a/307b and 308a/308b−313a/313b were reported from Garcinia bracteata in 2018 [159] and from Garcinia propinqua in 2017 [160], respectively, with the abs. config.…”

“…The xanthones 297a/297b were able to inhibit the proliferation of human HL-60 and MDA-MB-231 cancer cells, and the (−)-enantiomer 297b showed much stronger inhibitory activity than its (+)-enantiomer 297a against MDA-MB-231 cells [156]. The levorotatory enantiomer 312b was found to inhibit the proliferation of colorectal HCT-116 cell line with an IC 50 of 14.23 µM, but its antipodal enantiomer 312a was considered to be inactive [160].…”

A tocotrienol quinone dimer and xanthones from the leaf extract of Garcinia nigrolineata

“…xanthones and benzophenones were the most common compounds isolated from this genus [5][6][7][8][9][10][11]. These types of compounds have displayed a wide range of biological activities such as anti-bacterial, cytotoxic, anti-HIV, α-glucosidase inhibitory, antioxidant, antiinflammatory, antimalarial, and anti-pyretic activities [12][13][14][15][16][17][18][19].…”