1,3,5,6-Tetrahydroxyxanthone

Plant Cell Rep. 2015 Jul 21.

Xanthones from roots, hairy roots and cell suspension cultures of selected Hypericum species and their antifungal activity against Candida albicans.[Pubmed: 26194328]

Highest xanthone contents were found in Hypericum pulchrum and H. annulatum untransformed roots. The best anti- Candida activity was obtained for hairy roots extracts of H. tetrapterum clone 2 ATCC 15834.
METHODS AND RESULTS:
Extracts of root cultures, hairy roots and cell suspensions of selected Hypericum spp. were screened for the presence of xanthones and tested for their antifungal activity against Candida albicans strain ATCC 10231. At least one of the following xanthones, 5-methoxy-2-deprenylrheediaxanthone; 1,3,6,7-tetrahydroxyxanthone; 1,3,5,6-Tetrahydroxyxanthone; paxanthone; kielcorin or mangiferin was identified in methanolic extracts of the untransformed root cultures. The highest total xanthone content, with five xanthones, was found in untransformed H. pulchrum and H. annulatum root cultures. Hairy roots and the controls of H. tetrapterum contained 1,7-dihydroxyxanthone, while hairy root cultures and the corresponding controls of H. tomentosum contained toxyloxanthone B, 1,3,6,7- and 1,3,5,6-Tetrahydroxyxanthone. Two xanthones, cadensin G and paxanthone, were identified in cell suspension cultures of H. perforatum. Their content increased about two-fold following elicitation with salicylic acid. The anti-Candida activity of the obtained extracts ranged from MIC 64 to >256 µg ml(-1).
CONCLUSIONS:
Among the extracts of Hypericum untransformed roots, the best antifungal activity was obtained for extracts of H. annulatum grown under CD conditions. Extracts of hairy roots clones A4 and 7 ATCC15834 of H. tomentosum and clone 2 ATCC15834 of H. tetrapterum displayed inhibition of 90% of Candida growth with 256 μg ml(-1). Extracts from chitosan-elicitated cells did not show antifungal activity.

Arch Pharm Res. 2009 Oct;32(10):1393-7

Chromone glycosides and hepatoprotective constituents of Hypericum erectum.[Pubmed: 19898802]

METHODS AND RESULTS:
Two chromone glycosides, hyperimone A [7-(beta-D-glucopyranosyloxy)-5-hydroxy-2-(1-methylethyl)-4H-1-benzopyran-4-one (1)] and hyperimone B [7-(beta-D-glucopyranosyloxy)-5-hydroxy-3-methyl-4H-1-benzopyran-4-one (2)], together with six known compounds were isolated from the methanolic extract of the whole plant of Hypericum erectum.
CONCLUSIONS:
1,3,5,6-Tetrahydroxyxanthone (5) and I3, II8-biapigenin (6) showed moderate hepatoprotective activity with EC(50) values of 160.2 +/- 0.6 microM and 217.7 +/- 1.3 microM, respectively, against tacrine-induced cytotoxicity in HepG2 cells.

J Nat Prod. 1992 May;55(5):691-5.

Inhibition of angiotensin-I-converting enzyme by tetrahydroxyxanthones isolated from Tripterospermum lanceolatum.[Pubmed: 1517742]

METHODS AND RESULTS:
Five tetrahydroxyxanthones, 3,4,6,7-tetrahydroxyxanthone [1], 1,3,5,6-Tetrahydroxyxanthone [2], 3,4,5,6-tetrahydroxyxanthone [3], 1,3,6,7-tetrahydroxyxanthone [4], and 2,3,6,7-tetrahydroxyxanthone [5] isolated from Tripterospermum lanceolatum inhibited angiotensin-I-converting-enzyme activity in a dose-dependent manner.
CONCLUSIONS:
The mode of inhibition of the tetrahydroxyxanthones (THXs) was found to be competitive inhibition. When the tetrahydroxy groups of THXs were blocked with acetyl groups, the angiotensin-I-converting-enzyme inhibitory activity was abolished, suggesting that the tetrahydroxy groups are indispensible for the inhibitory activity.