Methylenebisnicotiflorin: a rare methylene-bridged bisflavonoid glycoside from ripe Pu-er tea

<p>A new methylene-bridged dimeric flavonol glycoside, methylenebisnicotiflorin (<b>1</b>), was isolated from ripe Pu-er tea, along with 10 known flavonoids (<b>2</b>–<b>11</b>) and seven known phenolic compounds (<b>12</b>–<b>18</b>). The structure elucidation was based on spectroscopic analysis. Among them, 1,3-dihydroxyphenyl-2-<i>O</i>-sulfate (<b>13</b>), 2,3,4-trihydroxybenzoic acid (<b>16</b>) and 3,3′,4,4′-tetrahydroxybiphenyl (<b>18</b>) are reported from tea plants for the first time.</p>