Diarylheptanoids from Alnus glutinosa bark and their chemoprotective effect on human lymphocytes DNA

A study of secondary metabolites from the bark of Alnus glutinosa led to the isolation of fourteen diarylheptanoids: oregonin (1), platyphylloside (2), rubranoside A (3), rubranoside B (4), hirsutanonol (5), hirsutenone (6), hirsutanonol-5-O-β-D-glucopyranoside (7), platyphyllonol-5-O-β-D-xylopyranoside (8), aceroside VII (9), alnuside A (10), alnuside B (11), 1,7-bis-(3,4-dihydoxyphenyl)-5-hydroxy-heptane-3-O-β-D-xylopyranoside (12), (5S)-1-(4-hydroxyphenyl)-7-(3,4-dihydroxyphenyl)-5-O-β-D-glucopyranosyl-heptan-3-one (13), and (5S)-1,7-bis-(3,4-dihydroxyphenyl)-5-O-β-D-[6-(3,4-dimethoxycinnamoylglucopyranosyl)]-heptan-3-one (14). All of the diarylheptanoids, except 1 and 5, were found in A. glutinosa for the first time, while 13 and 14 were new compounds. The structures were determined by spectroscopic techniques: 1D and 2D NMR, HR-ESI-MS, FTIR, UV, and CD. All isolated compounds were analyzed for an in vitro protective effect on chromosome aberrations in peripheral human lymphocytes using the cytokinesis-block micronucleus assay. The majority of them, including the new compounds 13 and 14, exerted a pronounced effect in decreasing DNA damage in human lymphocytes. Diarylheptanoids 1, 2, 5, 13, and 14 at a concentration of 1 µg/mL decreased the frequency of micronuclei by 52.8 %, 43.8 %, 63.6 %, 44.4 %, and 56.0 %, respectively, exerting a much stronger effect than the synthetic protector amifostine (17.2 %, c = 1 µg/mL).